Cummins ISL 350 hp caps system compression test

[Raybo]

How much compression should each cylinder have

[mackwrench]

I don't recall a spec for it, what I do is remove valve cover and then take off rocker arms on the cylinder I'm testing... using a compression adapter tool, looks like a injector, you remove injector on suspect cylinder and use the tool ...
The adapter has a quick connect air hose fitting on it and I plug in my shop air hose. Basically putting 120 psi in the cylinder. If the cylinder is leaking, you'll hear air rapidly leaking, either out the exhaust pipe, the turbo intake, or dipstick tube

Inquiring minds want to know why you need to check compression?
Oil consumption? Lots of blow by?

[Raybo]

Originally Posted by mackwrench

I don't recall a spec for it, what I do is remove valve cover and then take off rocker arms on the cylinder I'm testing... using a compression adapter tool, looks like a injector, you remove injector on suspect cylinder and use the tool ...
The adapter has a quick connect air hose fitting on it and I plug in my shop air hose. Basically putting 120 psi in the cylinder. If the cylinder is leaking, you'll hear air rapidly leaking, either out the exhaust pipe, the turbo intake, or dipstick tube

Inquiring minds want to know why you need to check compression?
Oil consumption? Lots of blow by?

Engine won’t start has fuel going to injector’s mechanic was thinking it might be compression. This morning he hocked up commons insite again an going to commons web site. Says the codes given should not keep it from not starting.

[jacwjames]

What codes did he see in the Cummins Insite?


One of the best resources out there is the Cummins Quickserve site
https://quickserve.cummins.com/info/index.html


You can create an account and then register the engine using the SN. Once the engine is registered you have access to lots of info, parts, maintenance, troubleshooting etc. There are also maintenance manuals specific to your engine/sn.

There is a fault code look up. Put the fault code in and it will come up with what the code is but will also provide troubleshooting steps. In most cases the document will have links to other steps and will provide all the information you need to get to the root cause.



I would suggest creating an account and finding the documentation on the fault codes.





I would not do a compression test unless the quickserve site suggests doing this. Follow the steps.

[mackwrench]

I've seen engines run with broken pistons, rings, etc...not run good, but will start.
I doubt compression is your issue.

But with out knowing your DTC's anything suggested here is only a guess.