Air Compressor needs repair


Old 05-23-07, 03:39 AM
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Smile Air Compressor needs repair

I have a DeVilbiss Air Compressor 5 hp 20 gallon oilless. It has two air guages and is on wheels. I think the model number is A5020.
I runs, but it appears that no air goes into the tank, either that or the pressure gage is not working.

Is there a troubleshooting technique that one can follow to determine what the problem might be? The air regulator valve never seems to close. Is it a faulty valve or faulty switch?

Logically, I guess one of two things is happening, either air isn't going into the tank or isn't staying in the tank. I don't want the danged thing to blow up on me, so how can I determine the problem?

Thanks for your help in advance.
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Old 05-23-07, 06:25 PM
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Sorry, I don't have knowledge of the compressor end of an air compressor, only the engine end. Stay tuned for Cheese, or others who may.
Old 05-24-07, 12:31 AM
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These compressor pumps are destined to fail when they're built. No oil means no lubrication. The piston seal is likely torn, bent, or worn through, keeping the pump from moving any air. You can remove the plastic cover from the underside of the cylinder and look up and see the piston. The piston is fixed to the end of the motor shaft with a little torx or allen head screw. Remove it and have a look at the plastic seal. Also note the condition of the cylinder. The rod is fixed rigid to the piston (cast as part of the piston) and the entire piston rocks back and forth a bit, especially at the top of the cylinder, since the rod doesn't move. Check this area well, and the rest of the cylinder for damage before replacing the piston. This is general info based on memory from the work I've done on other devilbiss and other brand name compressors. I believe they have all been nearly the same in construction, so I'm assuming yours is built in this manner.

This is the cause of failure on almost every oilless compressor I've seen. If your piston happens to check out ok, then there is a check valve in the head that could be bad.
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