Diesel Fuel Injector Pressure (Pop) Tester Not Holding Pressure

There are some things you should do or not do for long service life

The tester is very robust and should last for many years of use, but it should not be abused or neglected or it may not work properly. Here are some do’s and don’t along with instructions on cleaning the pump chamber and check valve should the pump fail to hold pressure.• Do not leave in a high moisture cold environment for long periods without use.

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Problem & Solution

  • When storing, keep it full of diesel fuel - mix in a small amount of transmission fluid for rust prevention
  • ALWAYS use clean diesel fuel. Do not reuse fuel that has already been run through the tester
  • Never use vegetable oil or vegetable oil/diesel fuel mix in the tester
  • When bringing out of storage, pump at least a cup of clean diesel through the line before connecting injector

If the pump should fail to hold pressure, it is likely the ball check valve at the base of the unit is either stuck or dirty. In order to clean the check valve and passages, just remove the on/off locking valve at the bottom of the tester. Turn it all the way out counter clockwise. Turn the tester on its side and lightly tap the base on your workbench. A steel ball bearing will come out so be ready to catch it. 

Thoroughly clean the ball bearing and the chamber it sits it. Use a very small nylon bottle type brush if you have it.  Do not use Q-tips or anything that could leave lint or other contaminants in the check valve. Due to the high pressure, it is critical that the ball seat perfectly on the seat of the valve to prevent loss of pressure. Blow through some compressed air if at all possible. Reassembly the check valve and pump a cup or two of clean diesel through the tester before using. 

Watch the video to the right for more tips.