Hard starting and Over Run fix of Generac 16kW model 0052540

[khnitz]

I wanted to be sure to document this somewhere for the next person having these troubles, and Garage Journal seemed like a good fit.

Our house came equipped with a 16kW natural gas powered Generac stand-by generator (model 0052540 and serial 4643547) - for a Garage Journal tie-in, this generator also powers my shop garage when the power goes out It is equipped with the 992cc engine model 0F9145 and serial number 8022413.

In the last year and a half or so, our generator has been struggling to start. The weekly exercise wouldn't always successfully get going, and sometimes the power changeover during an outage wouldn't happen automatically, either. I would need to use a little starting fluid to help get the generator to finally kick over and run. BUT, then sometimes the generator would shut off while running, and the Overspeed / No RPM Sense if Flashing error light would be blinking.

I have replaced my plugs, oil and filter on a yearly basis since taking over maintenance on the generator after we bought our house (the previous owner had a service company come out annually - they were less handy). The only bigger issue we encountered over the years was an oil leak from the old oil cooler lines (those were then replaced). This past summer, tried replacing the starter in hopes of getting the generator to start easier, but that didn't solve the problem. I installed another new battery in July and things seemed to be working (the generator starting) better. But lately the generator was not starting again.

At this point, I was either going to find a fix for the generator, or wind up buying a new one. I did a lot of research trying to find a solution. I again reviewed the parts and owners manuals for our generator (I've had those .pdf's for a few years already) and kept trying to find a solution to the hard-starting - that seemed to me to be the most troubling issue. Then I finally found this forum, and there were a few more insights here that led me to identify a couple of potential fixes for my issues.

In the end, I think there were two issues that were causing us trouble and that I was able to resolve:
1) Hard Starting - after reviewing a number of posts here, I was able to to identify that my choke plate was not providing a good enough seal of the intake barrel when engaged. There was play in the plate the plate with the spring in the wrong position, and it was greatly reduced after I corrected the position of its spring arm. Here's a video demonstrating what I found:

16kW NG Generac 16kW stand-by generator (model 0052540, serial 4643547) Choke Plate sealing issues

This video shows what I did to correct a hard-starting condition on our Generac generator. In the end, one arm of the spring for the choke plate was in the wrong position. As a result, it was not p...

rumble.com

And, here are some pictures of the spring arm out of position (purple arrow) and then put in its correct position (green arrow):




2) Engine Shutdown and Overspeed / No RPM Sense if Flashing LED - the posts I found here were able to narrow down the issue's likely root cause to the behavior of the Stepper Motor / Controller. It seemed that the engine was being allowed to exceed the maximum speed, driving up the output frequency and tripping the engine safety shutdown. I removed the motor and measured the coils, but I surprisingly found that they all measured between 10-11 Ohms (within expected normal range). I moved the Stepper Motor through its range by hand, and it seemed a little difficult, but it did move through the range. My only indication that there may still be in issue is that I felt a slight "hitch" in the movement about halfway through its travel, and it was more pronounced in one direction than another.
I went ahead and ordered a new motor. It arrived and I installed it and the engine no longer over-revs and shuts down. Additionally, with the old stepper motor / controller, there seemed to be more surges or dips in the engine speed when running. With the new motor, the engine speed held spot-on. Here's a video or the engine starting, and it shows the full range of motion of the stepper motor and choke solenoid / plate:

Generac 16kW generator - Stepper Motor and Choke Plate fix and operation

This video shows the stepper motor / controller for the throttle and the solenoid for the choke plate going through their movements during engine startup on a 16kW NG Generac 16kW generator (model 005

rumble.com

I put everything back together and let the engine go through one last manual startup cycle to insure everything was 100% again. As part of this repair, I also installed a fresh battery. Here's a final video of the full startup:

Generac 16kW generator - startup after Stepper Motor and Choke Plate repairs

This video shows a normal startup of our generator after replacing the stepper motor / controller for the throttle and the solenoid for the choke plate on a 16kW NG Generac generator (model 0052540, s

rumble.com

Just to compile all my findings to help the next person, here are some of the other causes I considered for my hard-starting issues:

• Hardening or Cracking of the fuel pump diaphragm: this was mentioned as an issue for hard-starting that would result in the the engine not getting enough fuel/gas. The Diaphragm Regulator 0F9426 is no longer available. Had the problem traced to this part, I would have had to see if a newer regulator might work with our generator. Also, to trace the problem to this issue I would have needed a manometer to read the gas supply pressure into and out of the regulator. I'm always up for buying a new tool, though!
• Valves out of Adjustment: I have never adjusted the valves on our unit. I will add that to my next annual maintenance. I do not know if the previous homeowner had the valves adjusted as part of the service they used to maintain the generator, either. From what I read hear, if the valves are out of adjustment and not sealing correctly, then this could cause issues with poor compression or lack of strong-enough vacuum to pull in fuel and cause hard staring and poor running.
• Poor Compression: I did not check the compression on our engine this time. I think I looked at it in the past at one point, but do not recall the readings. The poor compression could cause hard starting and poor running. I do know that our engine has "a lot" of hours on it, though it is older and not equipped with an hour meter. We've had outages here that have lasted almost a week, and we have at least 1 or 2 multi-day outages per year. It's woodsy where we live

Hopefully all this info will help another down the road

 

[theoldwizard1]

I would have needed a manometer to read the gas supply pressure

Forget the manometer. You just need a low pressure/vacuum gauge. Maybe OTC 5613 Vacuum/Pressure Gauge Kit or similar.

IIRC, gas line pressure is between 5-10 psi.

 

[KenC]

Forget the manometer. You just need a low pressure/vacuum gauge. Maybe OTC 5613 Vacuum/Pressure Gauge Kit or similar.

IIRC, gas line pressure is between 5-10 psi.

It may vary place to place, but mine is much lower than that. Measured in inches of water, so less than 2 psi.

 

[Chuckster in NJ]

Forget the manometer. You just need a low pressure/vacuum gauge. Maybe OTC 5613 Vacuum/Pressure Gauge Kit or similar.

IIRC, gas line pressure is between 5-10 psi.

That gauge kit ^ reads PSI…..Gas pressure (after regulator) is usually measured in "Inches of Water"

BTW! There are 27.7 inches of water per 1 PSI.……. EG: 27.7 inches of water = 1 PSI

 

[mm08822]

Forget the manometer. You just need a low pressure/vacuum gauge. Maybe OTC 5613 Vacuum/Pressure Gauge Kit or similar.

IIRC, gas line pressure is between 5-10 psi.

Nope, if ng .....5-7 " wc (~0.25psi), if LP....., 10 - 12" wc

A 0 - 30" wc pressure gauge works. Liquid filled even better.

Edit:
Some ng is 2 psi at gas meter output but steps down with another regulator inside close to appliances. I think it was in Minn. that a poster mentioned this.

 

[khnitz]

FYI - I'm getting good advice in a forum that is supported by generator techs to really look into the valve clearance. More detail on that is here in the "Ziller Electric forum". I found a lot of helpful generator info in searching those forums vs. others I tried when looking to identify a fix for my issues.

 

[The Cobbler]

IIRC, gas line pressure is between 5-10 psi.

no way in a residential service.

 

[mm08822]

I wanted to be sure to document this somewhere for the next person having these troubles, and Garage Journal seemed like a good fit.

Our house came equipped with a 16kW natural gas powered Generac stand-by generator (model 0052540 and serial 4643547) - for a Garage Journal tie-in, this generator also powers my shop garage when the power goes out It is equipped with the 992cc engine model 0F9145 and serial number 8022413.

In the last year and a half or so, our generator has been struggling to start. The weekly exercise wouldn't always successfully get going, and sometimes the power changeover during an outage wouldn't happen automatically, either. I would need to use a little starting fluid to help get the generator to finally kick over and run. BUT, then sometimes the generator would shut off while running, and the Overspeed / No RPM Sense if Flashing error light would be blinking.

I have replaced my plugs, oil and filter on a yearly basis since taking over maintenance on the generator after we bought our house (the previous owner had a service company come out annually - they were less handy). The only bigger issue we encountered over the years was an oil leak from the old oil cooler lines (those were then replaced). This past summer, tried replacing the starter in hopes of getting the generator to start easier, but that didn't solve the problem. I installed another new battery in July and things seemed to be working (the generator starting) better. But lately the generator was not starting again.

At this point, I was either going to find a fix for the generator, or wind up buying a new one. I did a lot of research trying to find a solution. I again reviewed the parts and owners manuals for our generator (I've had those .pdf's for a few years already) and kept trying to find a solution to the hard-starting - that seemed to me to be the most troubling issue. Then I finally found this forum, and there were a few more insights here that led me to identify a couple of potential fixes for my issues.

In the end, I think there were two issues that were causing us trouble and that I was able to resolve:
1) Hard Starting - after reviewing a number of posts here, I was able to to identify that my choke plate was not providing a good enough seal of the intake barrel when engaged. There was play in the plate the plate with the spring in the wrong position, and it was greatly reduced after I corrected the position of its spring arm. Here's a video demonstrating what I found:

16kW NG Generac 16kW stand-by generator (model 0052540, serial 4643547) Choke Plate sealing issues

This video shows what I did to correct a hard-starting condition on our Generac generator. In the end, one arm of the spring for the choke plate was in the wrong position. As a result, it was not p...

rumble.com

And, here are some pictures of the spring arm out of position (purple arrow) and then put in its correct position (green arrow):




2) Engine Shutdown and Overspeed / No RPM Sense if Flashing LED - the posts I found here were able to narrow down the issue's likely root cause to the behavior of the Stepper Motor / Controller. It seemed that the engine was being allowed to exceed the maximum speed, driving up the output frequency and tripping the engine safety shutdown. I removed the motor and measured the coils, but I surprisingly found that they all measured between 10-11 Ohms (within expected normal range). I moved the Stepper Motor through its range by hand, and it seemed a little difficult, but it did move through the range. My only indication that there may still be in issue is that I felt a slight "hitch" in the movement about halfway through its travel, and it was more pronounced in one direction than another.
I went ahead and ordered a new motor. It arrived and I installed it and the engine no longer over-revs and shuts down. Additionally, with the old stepper motor / controller, there seemed to be more surges or dips in the engine speed when running. With the new motor, the engine speed held spot-on. Here's a video or the engine starting, and it shows the full range of motion of the stepper motor and choke solenoid / plate:

Generac 16kW generator - Stepper Motor and Choke Plate fix and operation

This video shows the stepper motor / controller for the throttle and the solenoid for the choke plate going through their movements during engine startup on a 16kW NG Generac 16kW generator (model 005

rumble.com

I put everything back together and let the engine go through one last manual startup cycle to insure everything was 100% again. As part of this repair, I also installed a fresh battery. Here's a final video of the full startup:

Generac 16kW generator - startup after Stepper Motor and Choke Plate repairs

This video shows a normal startup of our generator after replacing the stepper motor / controller for the throttle and the solenoid for the choke plate on a 16kW NG Generac generator (model 0052540, s

rumble.com

Just to compile all my findings to help the next person, here are some of the other causes I considered for my hard-starting issues:

• Hardening or Cracking of the fuel pump diaphragm: this was mentioned as an issue for hard-starting that would result in the the engine not getting enough fuel/gas. The Diaphragm Regulator 0F9426 is no longer available. Had the problem traced to this part, I would have had to see if a newer regulator might work with our generator. Also, to trace the problem to this issue I would have needed a manometer to read the gas supply pressure into and out of the regulator. I'm always up for buying a new tool, though!
• Valves out of Adjustment: I have never adjusted the valves on our unit. I will add that to my next annual maintenance. I do not know if the previous homeowner had the valves adjusted as part of the service they used to maintain the generator, either. From what I read hear, if the valves are out of adjustment and not sealing correctly, then this could cause issues with poor compression or lack of strong-enough vacuum to pull in fuel and cause hard staring and poor running.
• Poor Compression: I did not check the compression on our engine this time. I think I looked at it in the past at one point, but do not recall the readings. The poor compression could cause hard starting and poor running. I do know that our engine has "a lot" of hours on it, though it is older and not equipped with an hour meter. We've had outages here that have lasted almost a week, and we have at least 1 or 2 multi-day outages per year. It's woodsy where we live

Hopefully all this info will help another down the road

I hook up two spark indicators first. (helps to assess magnetos, clearance)
Connect gas pressure gauge. (gas pressure ok, gas valve stuck closed, low flow)
Read battery voltage before attempting to start. ( gives baseline for charging ability.)
Go to manual start (check choke, servo operation, starter strength/voltage to it.)

If it doesn't start with the above all ok, then pull plugs and check valve clearances.

The black "reservoir" have been known to rust out and cause excess air to combine leaning out the fuel to engine.
Make sure the fuel hoses arent loose or pinched.

 

[khnitz]

I hook up two spark indicators first. (helps to assess magnetos, clearance)
Connect gas pressure gauge. (gas pressure ok, gas valve stuck closed, low flow)
Read battery voltage before attempting to start. ( gives baseline for charging ability.)
Go to manual start (check choke, servo operation, starter strength/voltage to it.)

If it doesn't start with the above all ok, then pull plugs and check valve clearances.

The black "reservoir" have been known to rust out and cause excess air to combine leaning out the fuel to engine.
Make sure the fuel hoses arent loose or pinched.

Awesome! Thanks for those steps/tips!

 

[khnitz]

So, I found time to adjust the valves ( this video was helpful as a tutorial). Adjusting the valves was good practice, as I have a '73 Fiat Sport Spider 850 that I'll need to adjust the valves on as I get it ready to go back on the road

Here is the first start-up after the valve adjustment:

Generac 16kW generator - startup after Stepper Motor and Choke Plate repairs

This video shows a normal startup of our generator after replacing the stepper motor / controller for the throttle and the solenoid for the choke plate on a 16kW NG Generac generator (model 0052540, s

rumble.com

And here is a 2nd start-up:

Generac 16kW generator - second start after valve adjustment

This video shows the second startup of our 16kW NG Generac generator (model 0052540, serial 4643547) after adjusting the valves. The exhaust valves were tight (no lash clearance, basically), so I adju

rumble.com

To my ear, it is starting much easier The exhaust valves were tight on both cylinders - they had no clearance at all. I set them to 0.003" and checked and adjusted the intake valves to 0.003", as well. I did tear the valve cover gaskets in removing the covers (they are pretty old, and may even be original to the generator). I have new gaskets on order and they'll arrive in the middle of the week.

While I had the spark plugs out to make turning the engine over to find TDC easier, I gapped them to 0.040" - they were in pretty good shape and pretty close to the correct gap. Oh, and I used another tip from here to remove the small shield over the exhaust (on the left of the generator) in order to turn the engine over by hand via grabbing the fan at the end of the generator.

 

[mm08822]

That model is easier to access at the exhaust end.

When you replace the valve cover gaskets, be careful not to overtighten. Tightening the lower righthand bolt can break the tab off of the head. Then it leaks and you are replacing the valve head!

It's a design flaw that generac fixed on recent models and the replacement heads.

 

[khnitz]

That model is easier to access at the exhaust end.

When you replace the valve cover gaskets, be careful not to overtighten. Tightening the lower righthand bolt can break the tab off of the head. Then it leaks and you are replacing the valve head!

It's a design flaw that generac fixed on recent models and the replacement heads.

Any idea what the recommended bolt torque is for those?

 

[Chuckster in NJ]

Do you have a "on board" battery maintainer?……. If so, did you check the battery voltage to make sure the charger (maintainer) is working?

 

[mm08822]

Any idea what the recommended bolt torque is for those?

60 inch Lbs. You want to consider permatex gasket sealer and blue (mild) locktite if 60 inch Lbs doesn't seem tight enough.

 

[Snip's]

Any idea what the recommended bolt torque is for those?

I have the 24kW Generac that has the G-Force 1000 series engine @ 999 cc
The manual lists the torque for the valve cover as 10kW at 80 in-lbs and 20-24kW at 60 in-lbs.
The manual only covers three engine sizes 460 cc, 816 cc and 999 cc, so yours wasn't listed at 992 cc???

To be sure, you can download the manual for your particular engine from the Generac website..

The manual does a good job of listing several other torque values... rocker arm, spark plugs, etc..

 

[khnitz]

Do you have a "on board" battery maintainer?……. If so, did you check the battery voltage to make sure the charger (maintainer) is working?

There is an on-board battery maintainer. I'll need to verify that it is still working correctly, though.

 

[khnitz]

I got back to town yesterday after a week in Vegas at SEMA for work, and I was able to install the new intake valve cover gaskets. 60 inch-lbs worked great on the bolt torque (I had recently picked up a smaller torque wrench for just these kinds of values).

I also double-checked the operation of the onboard battery charger, per the check pre-scribed here. At the connector I label as "1" in the photo (coming off of the transformer), I measured 19.3 VAC. At the output to charge the battery (which I label as "2" in the photo), I got 12.5 VDC with it connected, and 14 VDC across the pins at the board with it disconnected - I think this means my charger is still good.



I set the exercise time on the unit and it started, ran and shut off just fine. The new stepper motor controller is working well, making speed adjustments if I move it out of position.

I think I'm all set for Winter. Thanks for all the help here!

 

[mm08822]

Sounds good. Cycle the main cb in the coldest part of the day to simulate an outage. It should start-up and transfer flawlessly.

If your oil is milky (caramel color) run it under load for 45-60 min to burn off the moisture. Change oil if that doesn't clear it up.

 

[cgrutt]

Wow timely thread. I just bought a new battery for a 16kW generator tonight and am looking into servicing info will be sure to check out info and links above.

So it turns out the battery was original from 2015. I'd say 9 years was a good run! It's my MILs generator recently stopped working. I asked her if she would like me to take a look at it. She said she wanted to call the HVAC place that installed it. OK no problem. I told my wife about a week ago if I had to guess it needed a new battery. This was sight unseen. HVAC guy came a couple days ago. Needs a new battery (no surprise there) and a service (filters, spark plug and oil change). Pretty sure it's never been serviced so definitely past due. $175 for the diagnosis and about $1000 for the service and replace the battery. To the guys credit he saw my engine lift and stand in driveway and asked my MIL who they belonged to. He said if I can work on cars I can probably do the service and save my MIL a lot of money. After the $1000 quote she asked me if I could do it for her. Absolutely i just wish she let me look at it before he charged her $175 for the diagnostics.

Not sure if i would have been able to spot the problem...



Surprised how expensive the battery was $221 including taxes. Got to order the maintenance kit (about $30) and pick up two quarts of oil ($20). So $271 vs $1000. Plus the $175 which was a complete waste of money IMO. Hey at least I saved her $700+ and will now stay on top of maintenance for her...

 

[TurnipTruck]

Also timely thread! I had to jump the 2yo battery in my 16kw Generac two weeks ago in the dark in the middle of a windstorm. Last week I got around to pulling the battery out and load testing it. Fail! Pried open the vent caps and found it was 3cups low. Filled with distilled water and ran a charge/load/desulfate cycle on my new 4 bank maintainer. Failed another load test. Bought new.
The Generac charger is giving it 13.94v, so that isn’t what boiled it dry, so the problem must be the cold weather kit overheated the battery. Installed the spare and need to figure out some other way to keep the battery warmer but not too warm.

But not too cold, either!

 

[mm08822]

Also timely thread! I had to jump the 2yo battery in my 16kw Generac two weeks ago in the dark in the middle of a windstorm. Last week I got around to pulling the battery out and load testing it. Fail! Pried open the vent caps and found it was 3cups low. Filled with distilled water and ran a charge/load/desulfate cycle on my new 4 bank maintainer. Failed another load test. Bought new.
The Generac charger is giving it 13.94v, so that isn’t what boiled it dry, so the problem must be the cold weather kit overheated the battery. Installed the spare and need to figure out some other way to keep the battery warmer but not too warm.

But not too cold, either!

The battery heating pads cook the battery all year long. Every one I have installed as part of a new gen install has caused the battery to fail within 3 years.

The oil filter heater alone has proven to be trouble free. I have never tried it, but maybe hook the battery heater up to 120vac only. That would give 1/4 of the power from the blanket into the battery.

Or disconnect the battery pad for 9 mos of the year.

 

[khnitz]

Just a further update:
The first week's exercise cycle completed successfully, but at week two's, it came back with a low battery error light.

I wound up charging the battery and replacing the battery charger board. Before being replaced, with the old board, the voltage at the charging output was 12.56VDC. With the new charging board, it measured 13.36VDC (that was right after replacement).

I'll watch it over the next several weeks, but I think this gets it done

 

[My Old Tools]

I gave up on the Generac built in battery maintainer long ago and just plugged in a standard maintainer/trickle charger. Works great. Cost almost nothing.

 

[theoldwizard1]

The Generac charger is giving it 13.94v, so that isn’t what boiled it dry, ...

If that is continuous (24/7 X 365), YES, it will boil the battery dry. You need to clean the outside and check/top off the electrolyte (water) every 6 months.

IMHO, no battery, regardless of it chemistry, should be left connected to any type of charger 24/7 ! If it is a separate charger, hook it to an old fashioned mechanic lamp timer set to charge for no more than 4 hours per day.

 

[wyliesdiesels]

If that is continuous (24/7 X 365), YES, it will boil the battery dry. You need to clean the outside and check/top off the electrolyte (water) every 6 months.

IMHO, no battery, regardless of it chemistry, should be left connected to any type of charger 24/7 ! If it is a separate charger, hook it to an old fashioned mechanic lamp timer set to charge for no more than 4 hours per day.

unless its a smart charger that knows when the battery is fully charged like the one i got from o'reilly. once the battery is fully charged it lights a green LED and shuts off.

 

[theoldwizard1]

unless its a smart charger that knows when the battery is fully charged like the one i got from o'reilly. once the battery is fully charged it lights a green LED and shuts off.

I always question if they really "shut off" ! The only way to confirm is checking for current flow.

Anecdotally - I read (here) from a guy who was responsible for maintaining sewage pumps in his small community. They had back up generators installed with the pumps. Average lead-acid battery life was 1-2 years. He installed lamp timers so that the charger would only run about 4 hrs/day. Battery life became 4-6 years.

 

[dscheidt]

I always question if they really "shut off" ! The only way to confirm is checking for current flow.

Anecdotally - I read (here) from a guy who was responsible for maintaining sewage pumps in his small community. They had back up generators installed with the pumps. Average lead-acid battery life was 1-2 years. He installed lamp timers so that the charger would only run about 4 hrs/day. Battery life became 4-6 years.

cooked batteries from trickle charging is very common. Designers used to spend a great deal of effort matching the output to the self discharge of the battery they supplied. If the battery installed isn't the one designed against (because it's been replaced, or their supplier changed design, or...), this doesn't work.

But it's the 21st century; building trickle chargers/maintainers that charge only when the battery voltage is low enough to warrant it is a trivial bit of electronics design, and adds very little to the cost or complexity of the part. The fully automatic charger I have -- I think it's a black&decker one, it came from a big box store because I needed one when that was the only place open -- does this just fine. I have verified there is no current flowing when it says it's done, with a clamp meter.

 

[wyliesdiesels]

I always question if they really "shut off" ! The only way to confirm is checking for current flow.

Anecdotally - I read (here) from a guy who was responsible for maintaining sewage pumps in his small community. They had back up generators installed with the pumps. Average lead-acid battery life was 1-2 years. He installed lamp timers so that the charger would only run about 4 hrs/day. Battery life became 4-6 years.

Considering the on light turns off and the off light turns on and you can put the 2 clamps together and not get any arcing, id say yes its definitely really off…

 

[LopezBart]

unless its a smart charger that knows when the battery is fully charged like the one i got from o'reilly. once the battery is fully charged it lights a green LED and shuts off.

Bingo... I have several Battery Tenders on everything from my CPAP battery (full time power supply) to my Kubota and Super Tenere motorcycle.

 

[dave*99]

If that is continuous (24/7 X 365), YES, it will boil the battery dry. You need to clean the outside and check/top off the electrolyte (water) every 6 months.

IMHO, no battery, regardless of it chemistry, should be left connected to any type of charger 24/7 ! If it is a separate charger, hook it to an old fashioned mechanic lamp timer set to charge for no more than 4 hours per day.

Here is the problem with a blanket statement as above:

If you connect a smart battery maintainer to a timer as one might based on your suggestion, when the timer turns on the charger usually starts a charge cycle and then turns off once it is satisfied the battery is charged. You might force a charge cycle every day and this may be unnecessary.

If left to it's own resources, the smart charger will turn on when the battery NEEDS a charge. And that's likely not every day. Mixing old tech and new tech can lead to undesirable results. YMMV.

FWIW, I have used a timer and old style trickle charger. But I have never used a timer with my Battery Tender. The indicator lights inform me of the status.

 

[JBD10]

I wanted to be sure to document this somewhere for the next person having these troubles, and Garage Journal seemed like a good fit.

Our house came equipped with a 16kW natural gas powered Generac stand-by generator (model 0052540 and serial 4643547) - for a Garage Journal tie-in, this generator also powers my shop garage when the power goes out It is equipped with the 992cc engine model 0F9145 and serial number 8022413.

In the last year and a half or so, our generator has been struggling to start. The weekly exercise wouldn't always successfully get going, and sometimes the power changeover during an outage wouldn't happen automatically, either. I would need to use a little starting fluid to help get the generator to finally kick over and run. BUT, then sometimes the generator would shut off while running, and the Overspeed / No RPM Sense if Flashing error light would be blinking.

I have replaced my plugs, oil and filter on a yearly basis since taking over maintenance on the generator after we bought our house (the previous owner had a service company come out annually - they were less handy). The only bigger issue we encountered over the years was an oil leak from the old oil cooler lines (those were then replaced). This past summer, tried replacing the starter in hopes of getting the generator to start easier, but that didn't solve the problem. I installed another new battery in July and things seemed to be working (the generator starting) better. But lately the generator was not starting again.

At this point, I was either going to find a fix for the generator, or wind up buying a new one. I did a lot of research trying to find a solution. I again reviewed the parts and owners manuals for our generator (I've had those .pdf's for a few years already) and kept trying to find a solution to the hard-starting - that seemed to me to be the most troubling issue. Then I finally found this forum, and there were a few more insights here that led me to identify a couple of potential fixes for my issues.

In the end, I think there were two issues that were causing us trouble and that I was able to resolve:
1) Hard Starting - after reviewing a number of posts here, I was able to to identify that my choke plate was not providing a good enough seal of the intake barrel when engaged. There was play in the plate the plate with the spring in the wrong position, and it was greatly reduced after I corrected the position of its spring arm. Here's a video demonstrating what I found:

16kW NG Generac 16kW stand-by generator (model 0052540, serial 4643547) Choke Plate sealing issues

This video shows what I did to correct a hard-starting condition on our Generac generator. In the end, one arm of the spring for the choke plate was in the wrong position. As a result, it was not p...

rumble.com

And, here are some pictures of the spring arm out of position (purple arrow) and then put in its correct position (green arrow):




2) Engine Shutdown and Overspeed / No RPM Sense if Flashing LED - the posts I found here were able to narrow down the issue's likely root cause to the behavior of the Stepper Motor / Controller. It seemed that the engine was being allowed to exceed the maximum speed, driving up the output frequency and tripping the engine safety shutdown. I removed the motor and measured the coils, but I surprisingly found that they all measured between 10-11 Ohms (within expected normal range). I moved the Stepper Motor through its range by hand, and it seemed a little difficult, but it did move through the range. My only indication that there may still be in issue is that I felt a slight "hitch" in the movement about halfway through its travel, and it was more pronounced in one direction than another.
I went ahead and ordered a new motor. It arrived and I installed it and the engine no longer over-revs and shuts down. Additionally, with the old stepper motor / controller, there seemed to be more surges or dips in the engine speed when running. With the new motor, the engine speed held spot-on. Here's a video or the engine starting, and it shows the full range of motion of the stepper motor and choke solenoid / plate:

Generac 16kW generator - Stepper Motor and Choke Plate fix and operation

This video shows the stepper motor / controller for the throttle and the solenoid for the choke plate going through their movements during engine startup on a 16kW NG Generac 16kW generator (model 005

rumble.com

I put everything back together and let the engine go through one last manual startup cycle to insure everything was 100% again. As part of this repair, I also installed a fresh battery. Here's a final video of the full startup:

Generac 16kW generator - startup after Stepper Motor and Choke Plate repairs

This video shows a normal startup of our generator after replacing the stepper motor / controller for the throttle and the solenoid for the choke plate on a 16kW NG Generac generator (model 0052540, s

rumble.com

Just to compile all my findings to help the next person, here are some of the other causes I considered for my hard-starting issues:

• Hardening or Cracking of the fuel pump diaphragm: this was mentioned as an issue for hard-starting that would result in the the engine not getting enough fuel/gas. The Diaphragm Regulator 0F9426 is no longer available. Had the problem traced to this part, I would have had to see if a newer regulator might work with our generator. Also, to trace the problem to this issue I would have needed a manometer to read the gas supply pressure into and out of the regulator. I'm always up for buying a new tool, though!
• Valves out of Adjustment: I have never adjusted the valves on our unit. I will add that to my next annual maintenance. I do not know if the previous homeowner had the valves adjusted as part of the service they used to maintain the generator, either. From what I read hear, if the valves are out of adjustment and not sealing correctly, then this could cause issues with poor compression or lack of strong-enough vacuum to pull in fuel and cause hard staring and poor running.
• Poor Compression: I did not check the compression on our engine this time. I think I looked at it in the past at one point, but do not recall the readings. The poor compression could cause hard starting and poor running. I do know that our engine has "a lot" of hours on it, though it is older and not equipped with an hour meter. We've had outages here that have lasted almost a week, and we have at least 1 or 2 multi-day outages per year. It's woodsy where we live

Hopefully all this info will help another down the road

Would you have a pdf of the owners manual for the 0052540 model? The Generac site does not have it and I can't find it anywhere on the web. If so, please email it to me at [email protected] and I would appreciate it!

 

[mm08822]

Would you have a pdf of the owners manual for the 0052540 model? The Generac site does not have it and I can't find it anywhere on the web. If so, please email it to me at [email protected] and I would appreciate it!

I found this by tweaking the model # to 5254-0. Still hard to find, but I did. This manual is very, very similar to others of the same timeframe available but you never know the differences between them. Generac website should have been able to produce it, but it has been flakey with some of the "special ways" to input certain model info.

https://inspectapedia.com/electric/Generac-Generator-Manual-005series.pdf

 

[khnitz]

Just a further update:
The first week's exercise cycle completed successfully, but at week two's, it came back with a low battery error light.

I wound up charging the battery and replacing the battery charger board. Before being replaced, with the old board, the voltage at the charging output was 12.56VDC. With the new charging board, it measured 13.36VDC (that was right after replacement).

I'll watch it over the next several weeks, but I think this gets it done

A couple of updates:
1) The battery has been working fine with the new charging board since Nov-2024. I should probably replace the battery before this Winter, however.

2) The next challenge faced with this generator came with the recent spate of storms this week. After running for about 12hrs (10pm-10am), the generator shut off due to a low oil level warning. The level was at the low hash of the dipstick, so a topped it up and started it without issue and it ran fine. I had a look around but didn't see any obvious point of a leak, though there was some oil to clean up on the floor of the generator case.

About 12hrs later (somewhere around 11pm), it shut-off again, and with the low oil pressure warning again. Same routing - I topped up the oil and started it and let it run. This time I stuck around trying to figure out the source of the leak (there was oil on the floor of the generator case, again). After 30s or so, the leak appeared - it was a slow weep and drip from the oil pressure sensor housing, drop-by-drop, onto the oil filter housing and then the floor of the case.



I found a small plastic tub to fit under the oil filter to catch to weeping oil, and then I got up every 2 hours after that to check the oil level and top it up.

At the start of the 2hrs:


After about 2-2.5hrs (about a 1/2cup was in the tub):

There are lots of reflections in this picture, so I will state that I did not notice any metal sheen or flakes in the leaked oil when I examined it.

The original switch is Generac PN 0C3025 . It has a 1/4-18 thread and is "normally closed" (NC) but trips open at 10psi. I think the generator confirms that the switch is shorted (NC) before starting, and then once it has started it needs to stay open (indicating good oil pressure) to keep running. At some point in the night on one of the checks to top up the oil, the generator began to shut off right after starting. To me, this indicated a second issue where the switch was remaining shorted/closed and tripping the generator to shut down. I decided to bypass the oil pressure sensor to keep the generator running until I could get the new oil pressure. NOTE: THIS IS RISKY, as with the switch bypassed, if there is some other reason for oil loss - a oil cooler pipe bursting, etc. - the system will not be able to detect it and shut the engine down.

Thankfully, this morning I was able to procure a new switch from a Generac installer here in town. I bought the new-style oil pressure switch, Generac PN 0L2917C, which has an updated design that is less-prone to leaking oil. The Generac tech I dealt with said that the old style could leak from the rubber tip (yellow arrow in the above picture), while I also think mine was weeping at the plastic/metal crimp (purple arrow, above). I had to change the wires to the switch from ring terminals to female blade style to accommodate the new switch (no big deal, I had those terminals in my shop). The generator started right back up and when I checked 2.5hrs later or so, there was no sign of further oil leaking and the oil level was fine in the engine.

Our power went out Thursday evening around 10pm...we're not supposed to get it back until some time on Sunday

 

[khnitz]

FYI - this is the old switch, PN 0C3025:


And this is the new switch, PN 0L2917C:

 

[The Cobbler]

speaking of oil switches, and not to derail this thread... I had a 69 GM Camper special pick up , the 350 leaked oil quite bad, it was diagnosed as a bad rear main seal by other than me. Pulled the engine out to replace it, and found it was the oil sender unit leaking and not the rear main...

 

[dave*99]

speaking of oil switches, and not to derail this thread... I had a 69 GM Camper special pick up , the 350 leaked oil quite bad, it was diagnosed as a bad rear main seal by other than me. Pulled the engine out to replace it, and found it was the oil sender unit leaking and not the rear main...

Subarus in the 1980s had OPSU leaks frequently. I’m helping your derailment effort.

 

[mm08822]

FYI - this is the old switch, PN 0C3025:


And this is the new switch, PN 0L2917C:

My neighbor's gen leaked out from the same problem last week. Original ps looked like it had a rubber plug in it and it gave out....as in blew out! Generac has since obsoleted the original style.

Yesterday I just got the new ps and may change out tomorrow. Biggest time spent will be cleaning all of the old oil up.

I have the same switch, just p/n tweaked.

 

[Firebrick43]

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