Generator won't start, back fires instead. Valves?

[skeer]

I've got a Champion 3500 watt I bought from Lowes back in 2005 in preparation for Katrina. It's been a champ (no pun intended).. so anyway last time it was ran was back in Sept-ish last year and it ran for almost 2 days due to a power outage. Anyway FF to now we've got 1-3" of snow/ice/wintry mix going to hit us tonight/tomorrow so I should probably stop procrastinating and see if I can get this guy working.

So far: fuel is good, fuel delivery is good. Carb's been apart, everything's clean and orifices are open. Fuel is making it to the spark plug and plug is getting a good spark.
When you choke it and crank you can tell it's wanting to catch and fire up but instead some very light puffs of white smoke. After maybe half a dozen cord pulls it'll back fire. Pretty consistently.

I'm wondering how accurate you guys this this dude is:

Valve covers been off, turning the engine over the push rods and rockers are doing their things but perhaps that's not entirely indicative of things being proper?

There's no broken springs, push rods and everything else you can see in there is intact.. nothings like bent or anything. I have not checked valve lash yet.. haven't really had the time but Im gonna have to this afternoon.

Thoughts?

 

[Badhabit]

Start with a new good quality spark plug. Not a Champion. I have learned this from experience. If it works, great, if it doesn't it didn't cost much

H

 

[jmarkwolf]

How do you know the fuel is good?

If you haven't, I would put some fresh fuel in it (also cheap to try).

White smoke? Possible fuel got mixed with rain last usage somehow?

 

[mm08822]

What did you do to put it away after the last run? Drain fuel, run dry, gas stabilizer?

New plug, proper gap, fuel filter, fuel flowing, drain bowl, fuel valve on, verify spark.

Make sure carb needle port is not blocked/ partially blocked.

Use some ether to help get it started. Once it starts with ether, report back with what you need to do to keep it running.

 

[skeer]

How do you know the fuel is good?

If you haven't, I would put some fresh fuel in it (also cheap to try).

White smoke? Possible fuel got mixed with rain last usage somehow?

because it's new

No seriously, I drained the tank and put in new so.. always stored and ran under a roof.

 

[skeer]

What did you do to put it away after the last run? Drain fuel, run dry, gas stabilizer?

New plug, proper gap, fuel filter, fuel flowing, drain bowl, fuel valve on, verify spark.

Make sure carb needle port is not blocked/ partially blocked.

Use some ether to help get it started. Once it starts with ether, report back with what you need to do to keep it running.

Oh no I'm flat out horrible with proper small engine storage. Fuel valve gets shut and I roll it into the shed.
You missed some of what I mentioned in the OP, all of what you suggested is a yes except a new plug.

 

[mm08822]

Oh no I'm flat out horrible with proper small engine storage. Fuel valve gets shut and I roll it into the shed.
You missed some of what I mentioned in the OP, all of what you suggested is a yes except a new plug.

Putting an engine properly into storage is very easy to do. When you don't do it, you get what you got! If done right, next time needed, it can start anywhere from 1st - 4th pull with fresh gas.

I've tried to recover a few inherited engines in the past that were put away wrong. Pulled carb and left soaking in a heated vibratory parts cleaner for a few days....no good. Had to buy a new carb to get it running.

I didn't miss what you stated, I just did a brain dump.

Ether?

Unless you have the manual and clearance spec's for the engine, don't mess with it.

 

[skeer]

Yes I know, I'm aware of the negatives of not putting them away properly.

No ether.. haven't tried starting fluid.

0.008 for exhaust and 0.006 for intake.

My point I think was mostly missed, I'm just wondering if valve lash being out could cause these symptoms.

 

[mm08822]

It could, but is generally checked after the basics are confirmed.

Go buy some starting fluid first.

Careful pulling off the valve cover. Don't want to tear gasket.

 

[racecougar]

My point I think was mostly missed, I'm just wondering if valve lash being out could cause these symptoms.

Yes, but based on how the engine was put away, it's more likely crud/gummed up carb than valve lash.

 

[drmarkr]

Yes I know, I'm aware of the negatives of not putting them away properly.

No ether.. haven't tried starting fluid.

0.008 for exhaust and 0.006 for intake.

My point I think was mostly missed, I'm just wondering if valve lash being out could cause these symptoms.

It's possible, but not likely in this situation. Are you saying the valve clearances are what you stated above? If so then you do not have a valve stuck open. By far the most likely situation here is that the fuel you left in the carburetor has a passage blocked, despite all of your cleaning efforts.

 

[skeer]

You'll forgive me for asking this but.. since the nearest place that sells starter fluid is a 40 minute round trip, I need to make sure. The idea of using starting fluid is to eliminate the possibility of bad gas or a stifled fuel supply (clogged filter, host) right?

We've established that the gas is new, there is no supply issue as the line is new and fuel is reaching the cylinder.

 

[drmarkr]

We use brake cleaner as a starting fluid, FYI. Works fine. Your purpose is to establish that the reason the engine isn't running is a fuel delivery problem. If some brake cleaner will allow the engine to run for a few seconds then it's unlikely you have valve train issues.

 

[skeer]

Yes, but based on how the engine was put away, it's more likely crud/gummed up carb than valve lash.

So far: fuel is good, fuel delivery is good. Carb's been apart, everything's clean and orifices are open. Fuel is making it to the spark plug and plug is getting a good spark.

 

[Old Man Roger]

Ya, I've had to clean a carb I just cleaned before.lol In response to not wanting to drive for the starter fluid, pour a little gas on a rag and choke the carb with the rag.

 

[Firebrick43]

Yes I know, I'm aware of the negatives of not putting them away properly.

No ether.. haven't tried starting fluid.

0.008 for exhaust and 0.006 for intake.

My point I think was mostly missed, I'm just wondering if valve lash being out could cause these symptoms.

Excessive exhaust backlash usually causes hard starting because the decompression mechanism won’t work properly with excessive lash.

But it’s more hard to pull rope the recoil starter, not getting enough speed, and the pull handle being yanked out your hand.

Yours doesn’t appear to match those symptoms.

If you indeed have good spark and fuel I would look at timing. Flywheel key could be sheared or fly wheel magnets damaged.

 

[firebirdparts]

I'm going to say no to valve lash.

Sheared key is a lot more interesting.

I am confused about the 40 minute round trip away. I commute 9 miles daily. I feel like you've just said "dang, 9 miles, I can't just drive that far." 40 minutes is about right.

 

[drmarkr]

I do not believe you've established that the carburetor is delivering the proper air fuel mixture to the engine. Not at all have you established that, in my opinion. Even if you soak the carburetor with cleaner overnight and used an ultrasonic as well, you can't be certain there's not a blocked or partially blocked passageway somewhere affecting fuel mixture.

 

[mm08822]

I have cleaned carbs with parts cleaner, poked the ports as deep as possible, re-soaked in heated parts cleaner, redone it all again, and again and still couldnt get the carb to work properly. Threw on a new one and it worked.

Go get ether, brake cleaner, whatever.

 

[skeer]

We use brake cleaner as a starting fluid, FYI. Works fine. Your purpose is to establish that the reason the engine isn't running is a fuel delivery problem. If some brake cleaner will allow the engine to run for a few seconds then it's unlikely you have valve train issues.

Thanks, just wanted to make sure.

 

[adsinnott1]

Spray gas straight into the carb intake if you do not have ether or brake clean.

 

[skeer]

Ok so brake clean right into the carb had no discernible effect. This is the first time I'd had it backfire with the air filter cover off, and it came back thru the intake. Very white and smoky but I imagine a lot of that was burning brake clean?

 

[Old Man Roger]

Ya, I've had to clean a carb I just cleaned before.lol In response to not wanting to drive for the starter fluid, pour a little gas on a rag and choke the carb with the rag.

Spray gas straight into the carb intake if you do not have ether or brake clean.

The rag trick works good too, it not only feeds fuel, it acts like a choke, and in some cases will clear out a clogged passage.

 

[The Cobbler]

squirt a bit of fresh clean fuel in to the carb & see what it does . flywheel shear key or valve adjustment are 2 possible causes .

 

[skeer]

squirt a bit of fresh clean fuel in to the carb & see what it does . flywheel shear key or valve adjustment are 2 possible causes .

Yeah pulling the flywheel might be next.

 

[skeer]

Wondering.. is there a difference between backfiring through exhaust and thru intake? Like different causes?

 

[Chilliwack Murray]

I agree with the others who mentioned timing, I've seen this exact symptom on a number of small engines of various brands over the years. If you can find a service manual there should be some kind of check you can do with a multimeter while slowly turning the engine over with the plug removed.

 

[dcg9381]

Oh no I'm flat out horrible with proper small engine storage. Fuel valve gets shut and I roll it into the shed.

I have that same generator. It's on carb #2 and I'm much better about storage than you are.
I know you think the carb is good, but I'd see if it'll fire on starter fluid... I know people are saying "brake clean" works - but didn't they just reformulate all that stuff to something more eco-friendly?

I gave up on cleaning the carb. Tried a few times. Bought a "generic" carb off Amazon with reviews that said it worked great out of the box on that particular generator.

And I stopped storing it with ANY fuel in it. Drain the bowl too.

It's possible it's not fuel delivery, watching the thread...

 

[BurtEggley]

Wondering.. is there a difference between backfiring through exhaust and thru intake? Like different causes?

yes. Generally a backfire thru the intake is wrong spark timing, wrong valve timing due to say a plastic camshaft slipping on the steel core, a stuck open intake valve or some wasps have filled your exhaust with mud so the gasses can't go out the exhaust. Sometimes a really lean mixture can also spit back out the exhaust. I use Berryman's carb cleaner as a carb spray to test start it. Not all brake cleaners are flammable and some have chlorine that the compounds from burning can damage health.

 

[Old Man Roger]

Wondering.. is there a difference between backfiring through exhaust and thru intake? Like different causes?

Detonation can cause it.

 

[Old Man Roger]

And timing like others have mentioned.

 

[KenC]

Were the valve clearances set by the manual? If it is an OHV, There is a specific location in the rotation to set them, And it is not TDC.
1/4" down the cylinder after TDC I think, but check.

Backfire from the intake must be either an intake open slightly, way early timing or exhaust not opening and the combustion is relieved at intake opening. Sheared key is not normally a problem on constant loads like a generator, usually on lawn mowers after hitting something.
It must be getting spark if it ignites at all so I think we can rule out ignition issues.

And be very careful with using a rag w/gas on the intake when dealing with you symptoms. I've be close to and observed a guy being badly burned with that process. At least keep the gas source really far away from the work. A flaming rag can be a bad thing!

 

[Old Man Roger]

Ive had a carbon trail on a distributor cap cause a backfire out the throttle body. No cap on this thing though.

 

[carlaisle]

Valves rarely go out of adjustment while not in use. Starting fluid is a diagnostic tool you need to acquire.

 

[Wakefield]

Do some modern "Briggs" engines have a poorly designed composite camshaft assembly whose lobes can rotate out of phase on the shaft part ?

 

[firebirdparts]

Wondering.. is there a difference between backfiring through exhaust and thru intake? Like different causes?

Backfiring through the intake is always caused by ignition at the spark plug with the intake valve open. There just aren't any sources of heat there to start a fire.

 

[firebirdparts]

I'm wondering how accurate you guys this this dude is:

I didn't watch that, (10 minutes) but a list of his "reasons" could have been posted and a man could read that in about 2 seconds. You tube is my least favorite source of everything. Anyway, this would be my small engine list:

1. Compression:
   1. Engine threw a rod
   2. Valve stuck open
   3. Valve train failure/adjustment
   4. Blown head gasket
   5. Cam timing
   6. Holed piston
2. Spark
   1. ignition module failure (assuming here one piece does it all
   2. Ignition timing (sheared pin)
   3. "Bad" spark plug
   4. Ignition defeated (whatever shutdown switches/components exist, could be many)
3. Fuel
   1. Out of gas
   2. Fuel valve closed
   3. Water
   4. Fuel filter stopped up
   5. Carb needle and seat problem
   6. Carb fuel passages stopped up
   7. Fuel shutoff solenoid exists and off

 

[Mikes61]

Was it running good when you shut it off last time? I’m assuming that is was. If so, it’s not the valves.

Ive learned something in messing with engines and cars and …. Whats wrong is usually the simplest thing. Fix that first. I’m willing to bet that the carburetor is fubar with old fuel. You can’t clean all the tiny passages, ever. Get a new carburetor.

When you get the starting fluid, my guess is that it’s only going to run when you’re spraying the starting fluid into the carburetor. When you stop spraying, the engine will stop too. Classic example of a clogged carburetor.

After you get it running good, put a double dose of Stabil in the gas and let it run. You won’t have these issues again.

 

[BurtEggley]

a stuck open intake valve could cause it. Normally that would be detected with a valve adjustment, compression test, or leak down test. Inspecting the exhaust opening for mud dauber nests should be something one might look at. Also if the mouse is small enough, they can get into an exhaust if there is no screen over it. Just holding ones hand over the exhaust while cranking it should tell if the exhaust is open or not. Pulling the rope over should tell one if there is good compression in the engine.

 

[larry4406]

a stuck open intake valve could cause it. Normally that would be detected with a valve adjustment, compression test, or leak down test. Inspecting the exhaust opening for mud dauber nests should be something one might look at. Also if the mouse is small enough, they can get into an exhaust if there is no screen over it. Just holding ones hand over the exhaust while cranking it should tell if the exhaust is open or not. Pulling the rope over should tell one if there is good compression in the engine.

I would use a compression tester to make this assessment.