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Troubleshooting Notes

No or low vacuum?

  • Check for leaks, pressurize the engine and listen. Engine must be TOTALLY SEALED.
  • Check pump by removing hose from engine and running at up to 5000 rpm. Check for suction. If you have a vacuum gage hook it up directly to the inlet of the pump and check at an engine rpm adequate to match the test rpm. If it measures 4" or more less than test value, the pump may need refurbishing.
  • Check your pump drive belt, pulleys etc. to make sure that the belt isn't slipping.
  • Unhook pump and see how much blow by the motor has, your rings may be going away.
  • Check for obstructions in the pump exhaust hose and puke tank. Sometimes the filter on the puke tank may be plugged up. Also sometimes people have put things in the puke tank itself to try and reduce the amount of oil blowing out, which actually hurts airflow - which in turn reduces vacuum. The proper way to reduce the amount of oil going through the pump is in getting the best location of the pump suction hose on the valve cover. If you're having problems with this, give us a call and we can review a number of different ideas that should help.
  • GZMS vacuum pumps have two small holes in the back, these holes are filled, at GZMS when we build the pump, with silicon. Filling these holes yields about 2" of vacuum and will lose 2" if the silicon falls out. If it is noticed that there is a drop in vacuum, check these holes and clean and refill carefully (turn pump immediately to wipe of extra silicon on the interior).

Too much oil in Puke Tank

  • If you're getting too much oil in the puke tank after a pass, you may need to relocate the vacuum hose inlet location. Avoid placing the inlet directly over a rocker arm or in a location that has a large amount of oil spray, such as the oil pump block off on a SBC. An ideal amount of oil in the puke tank after a 1/4 mile pass is about a thimble full.
  • The amount of oil the pump gets from the motor is related to the amount of oil laden air it is passing - with a large pump and a vacuum control valve that is bypassing often to control vacuum levels you may need to slow the Pump rpm down to lower the over all volume of air moving through the motor.

Not Enough oil in the Puke Tank

  • This is seldom an issue with a racing application, but for street/strip use it may occur at low rpm. If you are going to use your vacuum pump in a low rpm or street application contact us for information on a street oiling kit.