Runaway Diesel

[dchsw]

The diesel gremlins have struck again.

What would cause my 2.5 Diesel Turbo (not Tdi) to race as if it had too much fuel?

Happend to me me several times today.

First time it revved like crazy, scared the bejesus out of me, spewed tons of black smoke then died away by itself in a couple of seconds and the smoke turned blue similar to when engine is cold. Engine was actually warm and the blue smoke disappeared back to its normal hot running no-smoke-at-all state in 10 seconds or so.

On subsequent occasions I caught it by quickly letting out the clutch to almost stall the engine which was easy as I had about 2,000 lbs of cargo (the rated payload of this 130 is 1,300 kg, by the way) in the back at the time. Once the revs dropped I depressed the clutch and everything went back to normal.

On all occasions I was in first high, clutch disengaged, gently letting it out and moving from stopped to forward motion. I typically don't drive that gently, but the load was tall and heavy, so I didn't want to make any sudden moves.

As luck would have it, I was on my way to see Don at Rovertech anyway today so he spent an hour poking around but could find nothing obviously wrong with the engine. Glow plugs sooty, but ok. No oil fouling in the turbo. Plenty of compression. Throttle cable not sticking. Plenty of strength in the injector pump return spring for the throttle.

Only slight issue was the oil level was a litre down.

Now, the missing oil is interesting. The truck does not leak engine oil to speak of or burn it day to day. However, when it was in the UK having its tipper body fitted I left it with an independent Land Rover dealer for a few weeks and on one occasion when he moved it it did the same thing.

In his words "it pickup up some oil from the sump and ran away". He quickly stalled it to stop the engine.

Ok, the plumes of black smoke when the incident occurs does suggest oil being burnt, but if there was a damaged ring or something, would it not burn oil and smoke like heck all the time?

For some reason, I keep coming back to the idea of opening the throttle very gently. I don't normally do that, but today I did because of the heavy load. The guy in the UK that it happened to would have been driving it for the first time, so may well have been taking it easy too.

Last thing - when running at speed the old boy runs sweet as a nut, no smoke and for an old land rover diesel with almost a tonne in the back, pulls very well.

By the way, when it happens, it sounds like the whole engine is going to break into a million pieces, it's not pretty.

Ok, over to you guys. Anyone seen this kind of thing before? Not necessarily on a Land Rover, but certainly on a diesel.

Thanks in advance, David

[DaveB]

Is it a dry paper filter or an oil bath? I think those were paper.

Check the filter that it isn't saturated with oil. On my Peugeot 2.5 turbo diesel in my 88", I occasionally get a little burst as well. I've concluded that the blow-by, while not particularly significant, is enough to slowly fill the bottom of the air filter box (via the two breathers) with motor oil, and the result is if it slops over into the intake it dumps a burst of oil through causing revving and black smoke for a few moments. I think the turbo chops up the dump of oil enough that it is a fairly fine mist otherwise I'd be worried about hydraulic lockup. It doesn't happen very often, and this is just my theory, but if I remove one of the turbo or intercooler hoses shortly afterwards it is quite oily compared to normal.

My plan to resolve it is to install a collection jar in the breather path to allow the oil to liquify there rather than in the air box, and occasionally feed the collected oil back to the crankcase.

Hope you find the problem.

Dave

[Roverworks]

Leaky turbo oil seal…very likely
Leaky valve stem seals/ worn valve guides…moderately likely
Previously over filled sump flooding engine venting…not so likely…. (wrong dip stick?)
Oil Dilution….you would notice other running problems... unlikely

Carry a CO2 extinguisher with you to drown the engine air intake if it takes off and will not shut down. Likely the damage will be done before you shut it down….

Alan
Rover Works B.C. Ltd
7620 Hwy 8
250-458-2447

[dchsw]

Dave, the turbo hoses were clean as a whistle when Don took them off today, no trace of fouling at all. I'll certainly take a look at the filter just in case - it's a paper one. If it happens again in a situation where I can stop and get the bonnet up I'll check if there's any gunk in the pipes.

Alan, Oil seal on the turbo. Interesting. At the revs the problem occured at I don't think the turbo would have been spinning very fast (it's quite loud on this engine so you tend to be concious of it) is that significant? i.e. is the seal more likely to allow oil past it when the turbo is spinning fast or slow? Thinking about it, is the fact the turbo is noisy indicative of anything?

Thanks for the input, David

[Greg S]

If it's worth anything, my two bits are on the oil seal for the turbo. It wouldn't matter that it is running slow, your getting extra hydrocarbons in the intake.

[Roverworks]

The bearings in the turbo, when it gets noisy and the bearings fail, will allow the shaft to move and disturb the seal causing leakage. This will often happen at low RPM while the turbo turns slowly and “floats”….at higher RPM the shaft is pushed back into position with the seal and normal running is achieved. Not uncommon.


Alan
Rover Works B.C. Ltd
7620 Hwy 8
250-458-2447

[DaveB]

Yes, Alan may have nailed it with the turbo seal. If your turbo is noisier than usual, is it still a single note sssss— noise or has it turned into more of a shshshsh— a soloist or a choir? My turbo wore out about 6 months ago and there was a definite change in its sound as it degraded, and that's what the guy at the turbo shop asked me. He also asked me to listen carefully at engine shutdown... You can hear a turbo spinning away fairly quietly for up to 30 seconds if its in good shape, but in bad shape you only hear it for 5-10 seconds, but much louder. In my case, because it wasn't too badly worn when I caught it, the turbo shop was able to rebuild it for about $450.

cheers, Dave

[dchsw]

Ok then. All fingers of suspicion point at the turbo oil seal.

I think (hope) it's more likely to be a failed seal than the turbo bearings being toast. Couple of reasons for thinking this: The turbo has a nice high pitched single whistle (no choir as you describe it, Dave, no clatter) and it only has a little over 7,000 miles on it.

The truck is 20 years old but I have no idea of how the miles it has got on it. Was it 6 miles a week or a couple of hundred miles twice a year? Either way it will have spent quite some time doing nothing at all. Could well be that the seal deteriorated whilst sitting idle all those years.

Of course, the turbo could be toast, so I may be coming back for advice on a rebuild. Right now, just as soon as this job bubbles to the top of the stack (getting my shop finished is top priority just now plus the 90 still won't go, but all jobs become easier when you can work out of the rain) I'll work out how to pull the seal and replace it.

Many thanks for the advice guys, especially Alan.

[red90]

Or stuck throttle....

[dchsw]

Don and I gave the throttle cable a good going over yesterday and it checked out ok. Also, when the problem occurs the throttle is only open ever so slightly, so even if it did get stuck, it would stick with a small amount of fuel getting in, not the huge amount observed. I still like Alan's turbo seal theory, but I'll certainly keep an open mind. Cheers, David.

[lastV8]

There is nothing wrong with the turbo other than general wear and old age. The engine is running on its oil. If you disconnect the rocker breather to the air filter housing it will no longer rev uncontrolably but you will have the smell and oil vapours to content with. Unfortunately once this unit runs on its own oil the hot spot in the head can become damaged along with the end of an injector. The only correct soultuion is to stop the piston blowby, which as you probably know is expensive and time consuming. Steven.

[dchsw]

Steven, ok, thanks of the strong opinion in favor of blow-by. I know you have extensive diesel experience, so let's assume my rings (or worse) are shot. What's the recommended course of action on this truck that I don't use everyday, but when I do I really need it. Pull the injectors and look for damage? Take the head off and inspect it? Or maybe try using some oil additive to seal things up a bit whilst I make time for a proper job? If the later, what would you recommend? Cheers, David.

[lastV8]

Hello David, If you pull the pipe from the rocker cover to the air filter your engine could continue to run for years to come. You obviously have enough compression to start the engine. I would remove each injector in turn and check the ends for damage. Shine a flashlight into the head where the injector used to sit. You will see the hotspot. Each orofice must have the same view. If you can see damage or a piece missing (wider opening) you will have to remove the head. The hotspot, once damaged has a tendancy to break up and drop in the cylinder.
If you go to the trouble of removing the head, you might as well go a bit further and fix the thing properly. Honing and new rings or rebore and pistons if bores show excessive wear. Hope this helps, Steven.

[dchsw]

Steven, thanks for the advice, I'll certainly follow up on inspecting the hotspots via the injector ports and take it from there. If I find anything interesting I'll post a follow up. Thanks again, David.

[Roverworks]

Yes, Steven could be correct….I had made the assumption you would not have bothered to import an engine with bad rings…assumptions have a 50% chance of being incorrect.

Alan
Rover Works B.C. Ltd

[dchsw]

Alan, when running normally, the truck blows no smoke and until Monday had not consumed any oil since it got here - it's been working pretty hard moving gravel around on my property for several weeks now. Consequently I had/have no real reason to suspect the rings. I drove it for several hundred miles in the UK before purchasing too and it ran smooth as a very smooth thing. But it could still turn out to be a lemon. The only way to know for sure is to have a look. I'm still a few weeks away from finishing the shop, so this will probably become a Christmas project. Thanks again, David.