94 GMC turbo diesel won't run cold

I posted this on pirate4x4.com but haven't gotten any replies yet.

I'm borrowing my dad's truck for a few weeks while I tool on my Regal. He doesn't drive it much because it has a problem running until it's up to operating temp. When I first start it, it blows out a huge cloud of white smoke but doesn't smoke anymore afterwards. When I drive it cold, I have to keep the tranny in L1 for about a mile because if it shifts to L2, the engine dies or sputters and bucks real bad. After it warms up it's fine.

I went to Advanced Auto Parts and had the computer codes pulled. The result was "A problem with the turbo wastegate".

So what do I do now? Their Haynes manuals didn't have enough good info about the turbo diesels. How do I test or troubleshoot this?
Thanks,
MARK

 

Does not sound like a wastegate issue to me. Sounds like a fuel issue. Unfortunately, it may be the injection pump itself, but I would make sure that the fuel filter is not plugged and that the lift pump is operating before leaning towards the pump. Could also be injection pump timing. Make sure the three mounting nuts are tight on the pump and it does not look like it has slipped.

 

Where would that pump be located?
My dad has been adding a fuel additive for a few weeks now. Could that be the white smoke? Maybe he's putting too much in?

This morning, I wanted to "take a look" to see if I could figure anything out. I found a clamp loose over near the air filter area. There is a hose that comes straight up just in front of the turbo then clamps to a pipe that goes to another device behind the turbo. I'm sorry, I'm not very familiar with turbos or diesels. Maybe I'll take a picture tonight.

 

It's a small electric in-line pump that should be along the left frame rail. It will only run for a few seconds when you first turn the key on, or after the engine builds oil pressure while cranking. I don't think he could have added enough stabilizer or conditioner to cause the problem you are having.

The clamp you are talking about sounds like the breather tube that puts the blow-by from the crankcase back in to the turbo so it will be burned. The only trouble that could cause is ingesting dirty air instead of filtered air if the tube was loose or fell out of the rubber intake boot.

As far as the wastegate code is concerned, there is a solenoid at the rear of the left valve cover that opens and closes pulling vacuum on the wastegate dashpot, and I suspect that the vacuum pump has failed, or you have a broken vacuum line between the pump and the wastegate.

 

Just so I get my lefts and rights correct...
The fuel pump is on the left frame rail - Is that the passenger side?
And the left valve cover - also passenger side?

And while I'm under there - where is the fuel filter and fuel/water separator?

This is good info. Thanks.

 

I'm sorry. By "left" side, I mean as you are sitting in the truck, or Driver's side. The fuel filter is at the rear of the engine dead center bolted to the intake manifold, right where the distributor would be if it was gas (non-buick, of course).