940GLE 2.4TD Auto (1994), D24T Diesel Engine

While driving, the diesel engine suddenly lost power and started to make noise and began to idle very rough and then cut off, restarting the hot engine got it running again but very rough, sounded like only 2/3 cylinders were firing and noisy and started to blow blue smoke from the exhuast and the engine would stop if the foot was taken off the accelerator padel.

Now with the engine cold although it manages to fire it blows black smoke and cuts off making a loud noise and smells of unburnt fuel.

Could it be that suddenly the timimg has gone wrong? can such a thing happen?

Could it be that the pump is not feeding fuel to some of the cylinders?

Could it be the compression has failed on some cylinders, I did have a new Head, camshaft, valves, replaced just 10K miles ago (its been 18months), cost me over 2 grand!!.

I did experience this twice while driving for a few seconds and it became normal so I didn't pay any attention but now it is for good!

Are there any VW diesel mechanics who may be able to advise what has gone wrong with this engine because most Volvo dealerships don't have clue about this engine and its characteristics.

Any advice will be greatly appreciated.

Mike
NW London, UK

[sheerwater]

Not totally geared on this engine but have worked on some non common rail diesels. 1/ timing is crucial and if slightly off will sound real bad!!! 2/ It needs an expert to adjust with the right gear!!! 3/ principle basically is that fuel is injected at just the right point for it to explode / burn. If this is off then it wont inject at right time to explode thus unburnt fuel and rough running. Sorry dont know how to adjust. Cheers Nigel

[pettaw]

Yeah, pump timing is crucial. I was just wondering whether you had your head re-torqued up after replacing the gasket. It might have loosened off after bedding in and compression could have been lost.

Also, is it possible that the timing belt has jumped one tooth. Check that as well

Many thanks for the advice, I did take the Volvo to the independent Volvo garage who did the job and did also tell them about the head tightening requirements. I was there for about 30mins and they said everything was okay and I thought they would never have re-tightened the head bolts in such a short time, so I asked whether they did that, and their response was oh! on the newer models it was no longer necessary. I didn't argue further and left it at that.

I have since clocked 10K miles with never any problems, it always started first crank of the starter regardless how cold it was outside which proved the compression was spot on.

During this period I had experienced twice a loss of power from the engine intermittently for 20 secs or so each time but it got normal and so I thought it might be some dirt from the fuel tank and thought no more of it.

But this time this intermittent loss of power is now permanent and now it seems starting is a problem from cold.

I am waiting for a diesel mechanic to come and have a look at it and I will certainly mention to him about the possibility of the head bolts have become loose.

Once again thanks for your kind advice, I would be delighted to pass my knowledge of the experiences I have encountered on this rare 940 with a diesel engine.

My mechanic also told me that there is no need to re-tighten the headbolts when the head has been replaced. I had head and gasket replaced a few thousand miles ago. So far, no problems but we'll see.

George

Resident near Leuven in Belgium

'87 745 GLE Turbo Diesel Intercooler
'88 745 Turbo Intercooler

I have had to finally get the 940 towed on a truck to the garage, this time to someone I know who specialises in all makes and models. I didn't have much faith in the Volvo independent garage where I had the new head fitted.

It has turned out that due to the timing belt tensioner becoming loose the timimg belt slipped and as a result the valves of 3 cylinders got damaged and valves and head gasket have had to be replaced. Getting the parts were extreamly difficult although it is a VW LT engine the valves etc, are of different spec to the VW sourced, finding the belt tensioner was almost impossible but finally it was traced, I have yet to be told what the cost is going to be as all the parts had to be sourced from Volvo. Yet another big expense in just 12 months and 10K miles.

The state of the engine now is that it fires but the pump timing has still to be done.

I will keep you informed.