I have never done a compression test on my truck ('74 Jimmy) and would like to do so. I watched a few YouTube videos and most of the process seems pretty straight forward. Test while the motor is warm, pull all the plugs, disconnect the coil wire, test with the throttle wedged wide open. The one thing that is not clear, many of the videos I saw said to disable the flow of fuel to the engine so it isn't injecting gas into the engine while cranking during the test. In those cases, the videos were being done on later model trucks so they had a fuel pump relay that could be disconnected during the test. I have a mechanical fuel pump so how to I do this? Thanks in advance for your help.
CK5
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Compression Test Question
- Thread starter pwjimmy
- Start date
Meh, it's so minute with a carb and a non-running engine. Just make sure the choke flap isn't closed while you're trying to run WOT.
With a carb the needle and seat shut off the flow. Any gas drawn into the intake while doing the test will evaporate before it has a chance to harm the test.
If you are still worried you can either plug or pinch the gas supply line at the fuel pump, then start the engine. Run till stalls. Perform test. Unblock fuel delivery hose.
If you are still worried you can either plug or pinch the gas supply line at the fuel pump, then start the engine. Run till stalls. Perform test. Unblock fuel delivery hose.
