How To Compression Test?

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Mar 12, 2009 | 12:00 PM

#11

Silvy6.0

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From: Arkansas

Quote:

Originally Posted by AKlowriderZ71

Remove all spark plugs, remove fuel pump relay, unplug both coil pack connectors. Screw hose with correct end(it will match spark plug threads) into spark plug hole and connect the gauge. Read the gauge while somebody cranks the engine for you. While they are cranking, they should have the throttle slightly cracked open. Let the engine spin three times(the gauge will jump 3 increments) and that is your reading.

Quote:

Originally Posted by Wilde Racing

I do all of that listed above, but throttle is at 100% open and I crank until the gauge stops moving.. max peak compression... once you find the low, faulty cylinder, I would do a cylinder leak down to verify the actual cause of the low compression...

I noticed both of you guys say that the throttle needs to be open. I have fly by wire. Do I just need to press the pedal a little since I can't do it under the hood?

Mar 12, 2009 | 01:05 PM

#12

budhayes3

PT's Slowest Truck

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From: Hackensack, NJ

You should be able to open the throttle blade by hand, then wedge it open with a screwdriver or something that will not damage the throttle body or get sucked in.