buy or not?

[rmtme]

Hi I'm Michael. I'm looking at buying a 93 Delica Exceed 2.5 or 2.8 Turbo Diesel.
The head gasket and timing belt were changed and shortly after that it's been running rough and blowing smoke constantly.
A mechanic thinks it's either the injectors or the fuel pump. Smoke is reported as being blu-ish.
Anyone with experience is welcome to offer their opinion on what it could possibly be and if its worth buying/fixing.
Thx!

[Growlerbearnz]

Hi Michael,

If it's a '93 then it's a 4D56 2.5 diesel. 2.8's are in the '94 and later L400/space gear models.

I see two possible explanations for the smoke, one of them is easily fixed and would make the van a good buy, the other is far more expensive to fix:

1) if the timing is wrong (which can happen when the timing belt is replaced one tooth out) but everything else is fine, a diesel engine can make white smoke which might be described as pale blue. It would also run extremely roughly. I'd check that the timing is correct. You say "shortly after" the timing belt was changed, which implies it was running fine for a while. If the belt wasn't correctly tensioned it might have slipped a tooth.

2) if the head or block is cracked from overheating there might be oil getting into the cylinders. I would expect the engine to run pretty well at first, with the smoke getting bluer and engine running rougher as it warms up. Oil leak smoke is pretty obviously blue/grey. Why was the head gasket changed? Did they test the head for flatness and cracks before reinstalling?

A leaky fuel injector can cause whitish/blue smoke, but the engine usually only runs a tiny bit rough.

[rmtme]

The mechanic swears it couldn't be out a tooth on timing. He's also the only guy in the area that is willing to work on it. I'm in The Yukon. Most mechanics won't touch them up here. No idea why gasket n belt were done. It only has 140k on it. No idea if the head was checked before it went back on. Are the iron or aluminum? Thx for your insight. I'm completely new to these vans n diesels in general. I used to work on cars yrs ago but don't anymore really. Is it possible to drive it as is without causing damage to the engine? I think it's possible timing belt did slip. Current owner just wants to sell without putting anymore $ into it. Thx!

[Growlerbearnz]

Diesels are easy, once you're past the learning curve . Everything that causes poor running comes down to the precise moment that the fuel actually ignites.

Sorry if you already understand the basics, but here they are: like in a gas engine, the rising piston compresses the air which heats the air up. Just before the piston reaches the top of its travel the injector pump squirts the fuel into the chamber, the heat of the compressed air ignites the fuel, which pushes the piston down again.

Many, many things can change the time the fuel ignites. If it's injected early (timing belt out a tooth), it'll ignite too soon and smack the rising piston. If it's too late, it'll burn slowly and poorly as the piston drops down the cylinder. If the cylinder has a poor seal (rings, head gasket, crack) it won't compress the air enough, and the fuel will ignite late because the air is cold (even if it's injected at the right time). If there's coolant getting into the cylinder, it'll vaporise and *increase* cylinder pressure, causing the fuel to explode rather than burn nicely.

So- your engine's issue. It could be many things, but I'd check in this order:

The timing is the easiest thing to check : http://www.delica.ca/forum/viewtopic.php?f=94&t=17654

Then the injectors: Any diesel mechanic will be able to test the injectors, but they'll need to be removed first. You want to confirm spray pattern and cracking pressure (check the Technical Reference Library here for a shop manual download)

And lastly, the head (alloy head on cast iron block, BTW). It sort of sounds like a cracked head- same symptoms as a blown head gasket, but changing the gasket won't fix the problem. I don't know of any reliable way to test for a cracked head without removing it. New heads are easy to find, but you'll need to remove yours to see if it's a protruding- or flush-valve head. '93 is the year of the changeover, so it's a bad idea to just guess.

I wouldn't drive it very far. A rough running diesel can punch holes in pistons, ruin the crank, crack the head, or melt the turbo. You *might* be ok, but you also might wreck the entire engine for the sake of a minor repair.

[rmtme]

Thanks for the insight. Another buyer took the vehicle.