NE frmhnd

He doesn't have the stock turbo, missed that.

MotDab

Thank you for all the help. Yes I bought the truck with everything already on it. I know the PO and he has been very helpful, and is very knowledgeable. I bought the truck as is. He was towing with it and when he let off the throttle it began what he described as skipping. I wouldn't be surprised if it has a melted piston. I just want to make sure it is nothing else before I have to pull the engine, replace it, and rebuild it. The end goal is to take the engine I am currently working on, build it up and put it in my 86 Blazer CUCV.
For now, this is the only time I can really trouble shoot it, before I tear into it. I just want to make sure that there is nothing else going on. Also it would be helpful if I could use the truck (light load) while I move to a new house. Its not imperative, but it would be helpful.
Now, I checked. I was wrong the "retrofitted lift pump". It is working when the engine is running.
I checked the Holset HE351cw turbo's waste gate, and it appeared to be frozen. I couldn't even wiggle it. To be honest I don't know if I should even be able to. Should I be able to produce any amount of boost while going 5mph with it floored?

I have tried shifting the transmission from 1,2,3 to D. But nothing. I don't think that the TC has much of a life left. But I do think it has some.
Again thank you for all the help.

Edit: I also forgot to mention, There is an exhaust leak where the down pipe from the turbo meets the turbo. It does subside after the turbo warms up though.

Edit #2: I'm assuming I have to take the turbo off to check it. So I'm considering putting a stock turbo on. Think I can reuse the gasket temporarily?

MotDab

Alright, decided to try and take it down the road today. Unlocked the hubs put it in low range and I built boost and dumped black smoke. Transmission shifted ok. TC is definitely slipping.

Time to swap the engine out. I'm convinced it is compression. Started to take the front end apart. Any recommendations for a good resource going from an automatic transmission to a manual? In other words a good check list?

j_martin

Compression is easy to test. Is that how you became convinced?

If compression were that bad, it'd be blowing oil all over the place out the breather.

MotDab

Good point, no it wasn't blowing oil all over the place out the breather, but after I took it down the road it stuttered and died. And i was dumping black clouds everywhere. One guy even flipped me off when I pulled over on the side of the road lol. Had plenty of boost too, the waste gate looked fine.

I did do a compression test. 200psi in all the cylinders except one was 100 psi and another was about 75psi. Crankcase pressure seems like a fair amount. But oil isn't coming out the breather that I can tell. And the dip stick isn't being pushed out of its tube either.

And it doesn't idle right once it comes up to temperature. It will die out if I leave it in gear. I put it in neutral and feather the throttle a moment and it fixes itself.

Angry Johnny

Did you check the valve adjustment?

j_martin

What you describe sounds like badly leaking injectors, or even grossly over-sized injectors.

Diesels ain't rocket science, but some folks seem to think they can just change something, like injectors, and get instant performance. Also, there's a lot of "performance" junk being sold out there. (Don't ask, it hurts)

Low compression without blow-by (much) or coolant problems is usually valves. Could be as simple as out of adjustment.

bobva

Read post 5

cougar

Things not mentioned,
Boost leaks
Your fuel pressure is too low
Fuel pin stuck or the spring removed

Angry Johnny

If there is low compression on two cylinders and the valves aren't too tight or the cam isn't flat then there is a mechanical condition that needs to be addressed first.

NE frmhnd

Couldn't you also get low compression from the valves not opening long enough and not letting air in to be compressed?

j_martin

That's what a flattened cam does.