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Single-Stage Compressor Pumps
www.chpower.com
Symptom Possible Cause(s) Corrective Action
Low discharge pressure 1. Air leaks 1. Listen for escaping air. Apply soap solution to all fittings
and connections. Bubbles will appear at points of leakage.
Tighten or replace leaking fittings or connections
2. Slipping belts 2. Loosen motor clamping bolts and move the motor in
a direction away from the compressor, being sure that
the motor pulley is perfectly aligned with the flywheel.
Tighten motor clamping bolts. The belt should deflect
about 1/2 inch under 5-lbs of pressure. Do not “roll” belts
over pulleys
3. Air demand exceeds pump
capacity
3. Reduce air demand or use a compressor with more
capacity
4. Blown gaskets 4. Replace any gaskets proven faulty on inspection
5. Leaking valves 5. Remove head and inspect for valve breakage, misaligned
valves, damaged valve seats, etc. Replace defective parts
and reassemble
Install a new head gasket each time the
head is removed
6. Restricted air intake 6. Clean the air filter element
7. Low compression 7. Low pressure can be due to worn rings and cylinder walls.
Correction is made by replacing the rings, cylinders, and
pistons as required
Pump overheating causes
air filter to melt
1. Broken valves/blown gasket 1. Replace valve or install new gasket
Excessive noise
(knocking)
1. Loose motor or compressor
pulley
1. Loose motor or compressor pulleys are a very common
cause of compressors knocking. Tighten pulley clamp bolts
and set-screws
2. Lack of oil in crankcase 2. Check for proper oil level; if low, check for possible
damage to bearings. Dirty oil can cause excessive wear
3. Worn connecting rod 3. Replace connecting rod; maintain oil level and change oil
more frequently
4. Worn piston pin bores 4. Remove piston assemblies from the compressor and
inspect for excess wear. Replace excessively worn piston
pin or pistons, as required; maintain oil level and change
oil more frequently
5. Worn bearings 5. Replace worn bearings and change oil
6. Piston hitting the valve plate 6. Remove the compressor head and valve plate and inspect
for carbon deposits or other foreign matter on top of
piston. Replace head and valve plate using new gasket
7. Noisy check valve in compressor
system
7. Replace
Large quantity of oil in
the discharge air
NOTE: Oil lubricated
compressors will always
have a small amount of
oil in the air stream.
1. Worn piston rings 1. Replace with new rings. Maintain oil level and change oil
more frequently.
2. Compressor air intake restricted 2. Clean filter. Check for other restrictions in the intake
system.
3. Excessive oil in compressor 3. Drain down to full level.
4. Wrong oil viscosity 4. Use Mobil 1
®
10W-30
Water in discharge air/
tank
1. Normal operation. The amount
of water increases with humid
weather
1. Drain tank more often. At least daily.
2. Add a filter to reduce the amount of water in the air line.
Troubleshooting Chart