Air Compressor Speed Change/Stall

[tigercreek]

I have an old 5hp/240v Campbell Hausfeld air compressor that is starting to have issues and I'm not sure how to pinpoint what is causing the problem.

First off let me list all of the things that are NOT causing the problems to get them out of the way -
Belt tightness
Pressure switch
Poor power
Leaking fittings/lines
Bad motor
Dirty filters
Low/dirty oil
Unloader valve

One of the issues seems to be happening all of the time. It changes speed constantly while it is running - sort of like it begins to bog and then surges.
This happens throughout the entire cycle of refilling the pressure to the tank - which I have set to only 120 lbs. It cuts in and out as it should, fills the tank and unloads after reaching pressure.
The new problem that just happened is the pump would only fill as far as 90lbs (no tools running) and stay there running - slower than it should. I manually switched it off for a few minutes, switched it back on and it filled to 120lbs and unloaded as it normally would. It did this to me a couple of times yesterday.

I believe it is a pump problem with the old twin cylinder/single stage Cambpell Hausfeld DP500002AV - but I am not sure what direction for repair these problems point me in. I don't want to pull and disassemble the pump only to find that there aren't any available parts to fix the problem. I also don't want to replace the pump only to find it was a simple fix.

Any ideas or suggestions would be greatly appreciated.

 

[sld961]

Air compressor pumps are pretty simple machines. You can have it torn down in a half hour. The 90 psi thing sounds like it could be rings. The surging thing might be something in the pump that's binding up intermittently?

I'd tear the pump down and see what you see. If you find the broken/worn part and you can't get a replacement, then get a new pump.

 

[metlmunchr]

I'd pull the heads off and check for any kind of trash that may be holding one or more of the valves open intermittently. A valve held open part of the time would explain both the variable load and problems coming up to pressure.

There's few parts available for the C-H V type pumps, and the ones that are available carry some high prices.

https://mastertoolrepair.com/air-compressor-pump-parts-dp500002av-dp210100av-p-22526.html

If its not a valve problem that can be repaired by cleaning or replacing the valve plates then the next move would be a new pump. Northern Tool has a 2 cyl single stage V type pump for $279 that's rated at about 14 cfm @ 90 psi. 1 yr warranty and parts available unlike a lot of the other cheap pumps that have no parts available. And $35 additional will extend the warranty to 2 years.

 

[tigercreek]

Thanks. Sounds like a good plan.

I'd pull the heads off and check for any kind of trash that may be holding one or more of the valves open intermittently. A valve held open part of the time would explain both the variable load and problems coming up to pressure.

There's few parts available for the C-H V type pumps, and the ones that are available carry some high prices.

https://mastertoolrepair.com/air-compressor-pump-parts-dp500002av-dp210100av-p-22526.html

If its not a valve problem that can be repaired by cleaning or replacing the valve plates then the next move would be a new pump. Northern Tool has a 2 cyl single stage V type pump for $279 that's rated at about 14 cfm @ 90 psi. 1 yr warranty and parts available unlike a lot of the other cheap pumps that have no parts available. And $35 additional will extend the warranty to 2 years.

 

[TRWham]

I know you said the belt is tight, but if it's old and hard it might still be slipping. Rubber and electric motors are not really good neighbors. The ozone generated by the motor will accelerate the aging of rubber.

 

[Dominick8295]

I'm wondering if there was any resolution to this fluctuating speed/surging issue? My IR twin single stage compressor is doing the same thing. It builds pressure, but it alternates between bogging down and speeding up after reaching about 90psi. I replaced the start and run capacitors on the motor, and pulled the head to check the reed valves but didn't find anything other than a potentially damaged head gasket between the cylinders. After replacing the gaskets and putting it back together...still having the same issue.

 

[MacMcMacmac]

Sounds like a loose or bad belt.

 

[whateg01]

Check the voltage?

 

[Dominick8295]

Sounds like a loose or bad belt.

Makes sense...I'll check that tonight.

 

[gimpyrobb]

The check valves sometimes stick open which would keep pressure on the pump. I've seen a compressor stall like this.