how to do a compression test?

[t-ray]

Does anyone have any specific instructions on how to perform a compression test?

What fuses need to be pulled? How do I disconnect the fuel pump? And how do I actually turn the motor over with the auto-starter?

Thanks for the help.

 

[corepwn]

Disconnect the FPDM by going into your trunk and in the spare tire well you'll find a plug, disconnect this.
Start the car and run it until it runs out of fuel and dies
You can also if you want to, disconnect your injectors.
Remove all of your spark plugs
Put the tester in each cylinder, press throttle to the floor, and turn the ignition. Let it try to turn over 5-6 times, and then turn off the key.
Go read the value, note it down for each cyl.

 

[Blazer707@TBR]

Corepwn hit the nail on the head. Only other thing i would suggest is throwing a jump box or charger on thr battery also.

 

[nissenc1337]

what levels should a factory coyote engine be at?

 

[Blazer707@TBR]

There is no actual spec on compression due to different sea levels and elevations that people live at. All you are checking for is a 25% difference between the highest and lowest reading.

 

[CobraRed_96_GT]

Disconnect the FPDM by going into your trunk and in the spare tire well you'll find a plug, disconnect this.
Start the car and run it until it runs out of fuel and dies
You can also if you want to, disconnect your injectors.
Remove all of your spark plugs
Put the tester in each cylinder, press throttle to the floor, and turn the ignition. Let it try to turn over 5-6 times, and then turn off the key.
Go read the value, note it down for each cyl.

Grounding the coils with SP's in them or disconnecting the source for the coils would be best, just did a compression test on my girl's car and turning over the engine multiple times with the COP's not attached or grounded to anything fried 2 of the COP's. Apparently this acts as sort of a stress test.

Engine only had 6.5% between highest and lowest which is good, but needing 2 new COP's sucks.

 

[bdcardinal]

Connect IDS, bring up "relative compression test" on the screen, hold throttle down and turn key when prompted, done. Ford generally will not have techs do a physical compression test because the IDS test is all that is needed for warranty replacement in most cases. When you crank the engine with the throttle all the way down, it disables the injectors.

 

[Blazer707@TBR]

Connect IDS, bring up "relative compression test" on the screen, hold throttle down and turn key when prompted, done. Ford generally will not have techs do a physical compression test because the IDS test is all that is needed for warranty replacement in most cases. When you crank the engine with the throttle all the way down, it disables the injectors.

Somewhat correct, Relative compression check is done first and if there is an issue then a manual comp test will have to be performed. Also 99% of the time hotline will want a physical compression check to be done before a tear down along with a CLT test.