8
 QS5 Operating Manual
9.0   Trouble-Shooting
Problem Possible Cause Remedy
Does not achieve 
good vacuum
1. Loose/open fittings
2. Not enough oil
3. Dirty/contaminated oil
4. Old/dirty/non-vacuum 
rated hoses
5. Gas ballast open in 
deep vacuum operation
6. Pump has reached the 
end of its useful life
1. Make sure all 
connections are tight, gas 
ballast & oil fill cap are 
closed and unused inlet is 
not open.
2. Add oil to level indicated
3. Change oil
4. Use new hoses rated for 
deep vacuum
5. Close gas ballast
6. Service or replace pump
Oil discolored 1. Excess moisture in oil, 
or oil burnt
1. Change oil
Oil leakage 1. Loose 
fittings/connections
2. Over-filled with oil
1. Ensure oil drain and 
related fittings are tight
2. Check oil level, drain 
extra if necessary
Failure to start 1. Power disconnected
2. Thermal protection 
has shut pump down
3. Cold start condition
4. Operating voltage too 
low
5. Power supply cord too 
long
6. Foreign matter has 
entered pump
7. Blown fuse
1. Connect power
2. Allow pump to cool, will 
re-start on its own
3. Subject pump to heat to 
raise the ambient 
temperature
4. Check operating voltage
5. Use shorter power supply 
cord
6. Check and clean pump
7. Check fuse (near power 
receptacle) and replace if 
necessary.