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Turbo diesel help

Shaggy123

NAXJA Forum User
Location
Kettering
Hi Everyone, my 1999 turbo diesel XJ Jeep has started blowing black smoke and lacking power. It starts and idles fine with no smoke and providing I keep the revs up and don’t put it under any load it seems to run fine, however when I load it up say under 2000 revs and put my foot down it won’t go and blows black smoke, which indicates it is fuel rich. I have cleaned the EGR valve and checked the turbo hoses and the turbo fan is solid with no play. I am at a bit of a loss as to why it does this anyone have any ideas. Thanks in advance.
 
I'm jealous. Ive worked on a lot diesels but never seen a diesel xj especially that new, as probably most everyone else here. Does it have any codes? It sounds like you have no boost. Does it have a boost pressure actuated wastegate? Map sensor is reading correctly? Air intake not clogged? If it runs smooth but no power it's likely not egr related. Fuel filter not clogged?

Any additional info you can give would be a big help
 
Thanks Trippled, I do love it. Only code is airbag, it does boost up, not sure about a wastegate? Still trying to find a factory workshop manual for it. Will confirm the map sensor, air intake is clean, never thought of fuel filter will check it as well. Thanks again for the ideas, I really appreciate it.

I will let you know if I come up with anything else that may help diagnose the issue.
 
If you haven't done a fuel filter in a while it's a good spot to start. They ideally should be done every 10-15k miles. That's about a year for most drivers here. I tried to find some info on that engine. Sounds like it should be a 2.5 vm motori engine? It looks really similar to the 2.8 we have here in the liberty. If so, it uses the Bosch cp3 high pressure fuel pump. They have no lift pump so it doesn't take much of a clogged filter to really affect performance. How have you verified boost pressure?
 
Does the turbo have an oiler (oil system)? You may want to check the air intake tubing for oil. May be the turbo oil seal is leaking. Usually the first sign of turbo failure in general.
 
Diesel mpg out of curiosity

Not to derail the thread, but what is you mpg with the diesel engine? I have often thought that the lightweight XJ would get great gas mileage with the right diesel engine.
 
Sounds like you're not making boost. How many miles on this thing, and have you had it scanned for codes?

Simple things first - what shape is the air filter in?

I don't know this engine at all, but if there's a vacuum or electrical connection to the turbo it's probably a VNT (Variable-Nozzle Turbo, also known as Variable-Geometry Turbo) like on my VW TDI.

if there's a vacuum line running to the turbo (not to be confused with the oil feed/return line), read on for some ideas:

If the turbo has a vacuum line hooked to it, the ECU is using engine vacuum to change the angle of the vanes on the exhaust side of the turbo to change boost, by way of the vacuum moving a linkage on the turbo.

If you hook a hand-operated vac pump (google "mityvac" for an example) to that vac line in place of wherever it goes normally and pump it while watching the linkage, you can see if it moves. If it doesn't move at all and the gauge on the mityvac doesn't build any vac, then your actuator or the line to it is probably shot (often the actuator can be replaced by itself, but it does depend on the exact turbo). The factory shop manual should have information on how much vacuum at which you should see the actuator linkage start and stop moving.

if you do build vac and don't see the linkage moving, then the VNT mechanism in the turbo could be gummed up (usually, this happens if you drive too easy too often) with soot. Sometimes you can clear that with the so-called "italian tuneup" (full-throttle run to redline), but before you do that, 8Mud made a very important point about the intercooler/boost piping:

If there's more than a couple ounces of oil in the intercooler/boost piping, the seals in the turbo are probably shot, and it's not safe for the engine to be driven that way - if you get on it hard and it sucks that oil into the engine, you're looking at a runaway condition that could just bend rods or even hydrolock the whole thing. Have you noticed any extra oil consumption of late?

Now, if there's no major oil in the intercooler/pipes and the turbo actuator checks out, the next thing is to see if the vacuum system in general has any leaks. Depending on age/mileage, it might be worth buying hose and just refreshing all the vac lines.

That's probably enough to digest for now, hopefully this will give you some stuff to look at to help narrow down your focus.
 
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