Vacuum Pump Troubleshooting

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.

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 directly related to the volume 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.

Too much oil in the pan can cause excessive windage, in turn increasing the amount of oil suspended within the air inside the engine..

If you have a valve cover (engine side) vacuum relief valve, You may also reduce the amount of oil being pulled by increasing the vacuum level as less air will flow thru the engine.

For installations that have the vacuum relief valve in the inlet line or pump (pump side), reducing the vacuum setting will reduce the amount of air (and oil) drawn into the pump.

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.

Loss of oil pressure

At high crankcase vacuum levels occasionally odd things can occur, for example we have had one instance where the crankcase vacuum was deflecting the bottom of an oil pan, drawing it too close to the oil pump pickup, which caused a drop in oil pressure. Problems like this can be hard to diagnose, just be aware of what changes in the engine may occur when the crankcase has a strong vacuum on it. Deflection in other components such as timing chain gear covers, valve covers, etc. may be observed in rare circumstances.

Low oil pressure can be caused by inadequate oil return holes to the pan. This causes higher vacuum in the upper part of the engine than in the pan, which will reduce oil pressure as oil is "pushed" by the pressure differential. Oil held up in the upper portion of the engine due to small oil returns will cause oil starvation. One recommened method to solve this is to add an air line from valve cover to lower portion of engine.