My 92 7.3L Turbo has got low compression on cylinders 1&3, 1-250psi 3-200psi while the other 6 cylinders are between 380-390psi. The truck misses when started cold no matter what the outdoor temp, has a slight rough idle and chuffing from the exhaust, while it is running it seems to have more then plenty of crankcase pressure holding my thumb over the CDR valve to air box cover pipe. Once up to operating temp it does run fine and still has decent power. What I'm curious is what is common on these to give these symptoms, without doing a leak down test. Should I be preparing to pull it out and give it rings, or just pull the heads and have them sent to a machine shop? Any suggestions thoughts or opinions are appreciated!!

 

If your oil consumsion is OK, my guess would be a sticky exhaust valve guide. A leak test when cold will tell the tale, Maybe someone else will have an opinion re doing an engine flush treatment to remove excess carbon deposits from your valve guides as a easy fix solution, or have the heads pulled and cleaned up. I would definately do a leak test first though to determine for sure where the problem is- rings or valves.

 

If its not using alot of oil or any coolant you could probabaly run it for a long time the way it is? until you have the extra $ to rebuild it. Its impossible to pin point the problem until you do the leak down test.
On my 84 people would say how do you make the diesel run so quiet, I just said its a secret, I never said its just wipped, tired, it would not start unless plugged in below 70 degrees. But it kept running once you got it started. I never bothered to check compression but when I finally tore it down, the ring gap on a couple cylinders was almost 100 thousand it should be around 10.

 

Oil consumption is about a quart every 3,500 miles. I didn't use an leak down tester, I just used compressed directly, most of the leakage was coming out the exhaust but a small amount of air did exit through the crankcase. I think I will just pull the heads and send them off, the oil consumption does not bother me, the rough idle and cold engine starts does though... Are these heads known for exhaust valve guide issues? Are they integral or pressed in? I just hope their not cracked, cause if they are I will be wishing I just left it alone!!!

 

Oil consumption is about normal. Have the injectors been pulled? You could have a few very worn ones which are not giving a good spray pattern.

 

you should loosen up the rack if your going to compress it directly since it may be partially opening a valve. also i like to test with the engine warmed up to see if anything shows a pattern
also if you do have poor injectors those cyl won't show the same as a good running cylinder.

 

I did the compression test with the engine warm but it wasn't when I used compressed air on the cylinders, injectors haven't been pulled I should check there as well, and while I still have all the glow plugs out I thing I will loosen up the rocker arm shafts, diesels sure are not the easiest to do leak down tests on even with a timing mark!