Does anybody know what are some good numbers for a compression test? I hear 400 and 350. If there are any Cummins techs on here, would you please let me know? Its a 03 with the HO and it has 138K on it. Thanks for your help.

 

The compression figure is some what elusive. If could measure would be nearer 400 on good engine. Believe the procedure for compression is loading on a dyno and measuring the CFM of blowby.. Another test haven't seen lately is a comparative starter current draw for each cylinder, while cranking with injection disabled.

 

It might be best to say why you are looking for that info ?
There is a lot more to it than just one number , like how many cycles during test , what the pressure is on the 1 full cycle , all with a warmed up engine .
But generally about 400 lbs , all cylinders within 10% of each other , I forget what the min. pressure before repair .

 

the min. is 350 psi. cylinder pressure should be within 20% from cylinder to cylinder.