Compression test

S

Sean Lauver

New member
I need help on the best way to do a compression test. I searched the threads and need a definate answer. Last night I pulled one of the plugs and put in my compression tester and then turned the truck over. The compression was 104-106? That seems low from what the forums had in the search bank. :tdown: Please let me know if that is the way to do it. The truck has 125,000 miles on it. Maybe I need a rebuild. Help with your :2cents: . Thankyou, Sean
 
TYHOGG

TYHOGG

Active member
Re: Compression test

Disconnect the power from you fuel pump(harness or fuse), remove one spark plug, insert compressions tester, crank motor, read pressure, replace spark plug, continue to next cylinder. I believe it is supposed to read between 130-140.
 
turbodig

turbodig

Active member
Re: Compression test

Don't forget to open the throttle while you're cranking.

I always remove all the plugs, less cranking load.

What were the other cyls measuring? I'd be more worried about a difference between cylinders than an arbitrary number. (Unless that number was *really* low....)
 
ShuggsRR

ShuggsRR

Donating Member
Re: Compression test

Ok let me see if I have this correct...
1) Pull out all the plugs (or one at a time)
2) Connect the compression tester
3) Pull the fuel pump fuse (under the dash?)
4) Crank the motor while flooring the gas
5) Take reading

Repeat for all other cylinders
 
turbodig

turbodig

Active member
Re: Compression test

ShuggsRR said:
Ok let me see if I have this correct...
1) Pull out all the plugs (or one at a time)
Click to expand...

All of 'em.

2) Connect the compression tester
3) Pull the fuel pump fuse (under the dash?)
Click to expand...

ECMB should suffice.

4) Crank the motor while flooring the gas
5) Take reading

Repeat for all other cylinders
Click to expand...

That's it, yep. I generally take a couple readings on each cyl just to make sure the results are consistent.
 
ShuggsRR

ShuggsRR

Donating Member
Re: Compression test

Thanks Dig! I wish I could do it now... but my intake is even off. Hmmm... I suppose i could do it with no fuel rail or intake....
 
turbodig

turbodig

Active member
Re: Compression test

ShuggsRR said:
Thanks Dig! I wish I could do it now... but my intake is even off. Hmmm... I suppose i could do it with no fuel rail or intake....
Click to expand...

Yep. As long as there's a valvetrain there and no rotational issues, you should be ok.
Might get a bit sloppy in your freshly cleaned engine compartment....
 
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