Technical Specific issue with 2.8JTD - any pointers?

[Laikadog]

I bought my 2003 2.8JTD a few months ago. It’s a motorhome, and I suspect it’s been sat for a few years without much use at some point, judging by a few things. On the drive home it was fine until it misfired and spat out a bit of black smoke. The engine light came on red. I was able to restart it 3 times and it ran fine, and on the third time the engine light went out.

Over 1,000 miles later it did this once more but this time it actually stalled on the misfire. The engine light came on and I couldn’t restart it. It would turn over but not catch. On the third go the light went out, it fired up and carried on fine.

I stuck a tank of injector cleaner through it. It was fine for the next 1,000 miles. Then it did it again, on the way to the garage for unrelated brake issues. The garage diagnosed a fault boost sensor, which they replaced. They also said it had errors relating to the fuel system, and recommended I take it to a fuel specialist.

As it was running fine again, I hoped the boost sensor had brought it under control. But on a long run it initially did the puff of black smoke and stalling thing, then ran fine for the next 300 miles. Then it suddenly chucked out a lot of grey smoke and stalled again. This time it wouldn’t initially fire up, but I could again restart it after the third attempt when the check engine light went off, but it was idling a bit rough. Any time I got it over about 1,700rpm it would chuck out grey smoke and stall again. I had it relayed back to the garage.

All of the relay drivers were puzzled by these symptoms: rough idle, grey smoke when revved, stalls, red engine light on, light clears after third attempt to restart, then it fires up again. I’m hoping the garage it’s gone back to will be able to have a look at it, but if not I’ll have to have it relayed to the specialist diesel fuel garage once they have space to take it. But meanwhile, has anybody seen these very specific symptoms and solved the problem already? I’m thinking faulty injector, but people who know more about these things than me say that normally leads to black smoke, not grey.

 

[Communicator]

My 2.8jtd has so far not exhbited such behaviour, so I must rely on logic, and guesswork.

As the engine light has illuminated, there will be stored fault codes. These should be read with a Fiat compatible code reader. The forum favourite is the software, multiecuscan running on a windows computer.

The control system for the 2.8jtd is relatively simple. The Electronic Control Unit (ECU) of a running engine receives inputs from the accelerator, fuel pressure, inlet manifold pressure, and crankshaft position. The fuel pressure and injection are controlled to deliver the required power.
(There are other sensors and outputs, but these are secondary.)

Black smoke suggests too much fuel, while grey smoke represents unburnt fuel.
I stress that in the absence of fault codes the following is only a guess, and others may have alternative, better suggestions.
I am thinking that perhaps the crankshaft sensor is starting to fail when hot.
This could lead to the ECU commanding injection at the wrong part of the engine cycle. If the ECU is unable to read the crankshaft sensor, then the engine will not start.