why would shutting off an injector tell you which piston is cracked. Even with the injector shut off, the cylinder still makes compression..............does it not?
Well I guess it's time
- Thread starter hondarider552
- Start date
why would shutting off an injector tell you which piston is cracked. Even with the injector shut off, the cylinder still makes compression..............does it not?
Well, stock tires are on and its backed in the single car garage. Time to get my butt in gear and see if Ive been paying attention all these years 
why??? Sorry, you're wrong. FYI, diesel engines are COMPRESSION IGNITION. You should know that from all the dinghy's you play around with, im sure most of them have diesel engines.
No compression (because cracked piston) = no combustion, even if fuel is still being sprayed in (via injector).
Was thinking the same thing. So a motor that is not running has no compression since injectors are not firing? hmm
No, no, no...
That's is not what I was trying to imply at all guys. I was simply thinking that if a piston had a small fracture in it you could shut off the injection event and the resulting loss of cylinder pressure would not push thru the fracture and stop the blow by thus indicating which cylinder to start with...
I know what you are/were thinking. And the answer is still no. Even with just a crack, the cylinder will have *zero* compression, and thus no combustion, even when fuel is present.
The only way you might be able to tell by shutting off the injector is by listening/feeling the engine. If it doesnt get "worse" sounding when you shut off X injector, then the problem could be with X cylinder
Compression test will tell the tale, Brian. My thinking is cracked piston, but you may have a couple things going on at the same time, mucking up the diagnoses. Headgasket lifting would cause your pressure issue.
I do hope I am wrong for your sake. Good luck.
I do hope I am wrong for your sake. Good luck.
We will have an answer tonight, tony is comin over and were gunna do a compression test. Is it best to pull every glow plug and then test one at a time or leave all glow plugs in a d remove/test one at a time?
On my gmc I removed/tested one at a time but just wanted to make sure so I do it the correct way.
Remove them all imho. Motor will spin a bit quicker and its easier to go down the line testing them. Gassers your suppose to hold the trottle wide open too but no need for it on a diesel as there is no butterfly valve
LMM's have a throttle plate, aka butterfly valve...
Just fawkin with you dude...
No hard feelings...:hug: