I just bought this 85 GMC 2500 with the 6.2 the other day and finally got it running today. It has been sitting for the last 5 years or so. I had to crank the piss out of it and i noticed one of the injectors was leaking, so i tightened it back up and it barely started. It sounded like a rod knock and was puffing white smoke out of the intake and would smoke black out the exhaust and the engine was shaking more than what i would call normal. The thing also wouldnt move under its own power and would die if you tried to put it in gear. It also smelled really bad (old fuel?) and it seemed to be running on about 5 cylinders. Im thinking its one or more of the injectors. Whats the best way to tell if thats the problem? :confused:

the symptoms are very similar to this.

http://www.youtube.com/watch?v=Jn0RRaUtQ-c&feature=related

Rod knock??!!! That video sounds like a broken crank to me, even though ive never heard one.....

you sure that wasnt a C4C video?

definetly more serious than an injector knock.

Well i went to start the thing today and it wasnt having any of it. I decided to check the glow plugs and found two were bad. I replaced them and now it wants to start but still wont quite pop off (odd since it started yesterday).

Should i replace the fuel filter or is there something i can check for as to why its not starting now? Maybe take out the injectors and take em to the diesel shop and have them pop tested? :confused: Any help would be greatly apperciated.

yea remove the injectors and change the fuel filter and im sure new fuel couldnt hurt.

Well I took out all the injectors and had them tested today and 4 were bad and the other 4 were below spec but acceptable. So ive installed four new ones and reinstalled other other 4. I also put on a new fuel filter on it and added some new fuel. It runs for about 2 secinds now so i plugged it in and hopefully i can get it started today. :( Not looking so promising though...

I finally got a chance to bring the truck inside to test the compression. All were about 280-300 and i got 400 on a few of them as well. Put it all back together and decided id try to start it one more time and to my surprise it popped right off. Ive put about 300 miles on it so far seems to be running great, no smoke and no leaks and im getting about 20mpg.

I wouldn't expect it to last long. That low of compression combined with such compression imbalance means you can expect bad things to happen in short order.

OR, you should try and retest compression, and maybe your rings just weren't seating right and all is good now.

I did to the test when it was cold still and the spec on ALLDATA was 300 psi. I think the higher readings came from slight combustion since those cylinders were the last ones that I tested and I'm not sure if I disabled the fuel system.

The spec for these engines, fresh after rebuild, is 400+ psi. You should be within 25 PSI or so between each cylinder. For an older engine, 350+ psi is considered acceptable.

If those compression readings are accurate and true, your engine is worn out.

I have run worn out engines for years though...lol....if it starts and goes and gets 20 mpg id hunt around for a motor and rebuild it at my convenience and when that one lets go youll have one ready...I almost got a used one with a working db2 that had 350-360lbs on all cyl for 250 bucks last week and another dude beat me there so I lost out but they are around.

Its alot easier to get one when now when youve got some time and a rod cap havent shot out the oil pan already and you have to be at work mon....damn that sucked..lol..

I never said he couldn't drive with that worn out engine, just that the VERY uneven compression, plus the low compression (hardly enough to get the fuel to diesel), would cause issues over time.

Based on how well he says it drives, I'm guessing if he redid his compression test right now, it'd be a much different story.

don't disagree with Trios,, lmao :cool:

The spec for these engines, fresh after rebuild, is 400+ psi. You should be within 25 PSI or so between each cylinder. For an older engine, 350+ psi is considered acceptable.

If those compression readings are accurate and true, your engine is worn out.

So in my case i should be looking for 375-400 psi right? I was told that it had to be about 75% of the highest on a gas engines, is it all that different on the diesels? When should I test the compression? (normal operating temp or just after its been sitting out all night ~10*F right now at night)

Also if it necessary to test it at normal operating temp how should I disable the fuel system so it doesn't start running while I'm doing the test.

pull the pink wire off the ip, that will keep the fuel from coming to the injectors, then do the compression test

So I should do it at operating temp then?

So I should do it at operating temp then?

Yes