VAG 6cyl 2.4td, lack of power

A recent development.

Generally runs well, no smoke per-se, but rather noisy.

Recently at much over half throttle, the engine is holding back badly. No missfires as such, just a general lack of power, and occasionally some smoke at the rear, but not always.

Its been a while since I changed the fuel filter ( say 30-35k miles )......engine is of unknown history, although I have put about 50k of reliable motoring onto it since I bought it used for my car.

I had previously tinkered a bit, and at WOT had been seeeing EGT's close to 700degC, these are now down to a little over 500degC at full throttle, so clearly there is a fuel supply problem of some sort.

What sort of sypmtoms would a failing pump give ??

Change the fuel filter as a start. If the pump was going out you'd see other issues, like hard starting or leaking fuel, first. If the problem is fuel supply related, the filter is the first thing to check, esp if you already know it's old. There are other possibilities as well though. If it is both smoking and lacking power, then that generally means fuel supply is not the problem.

Timing is OK? If it's running noisy that could indicate injection timing being off.

Valves adjusted?

You say you've done 50k, you know that timing belt is only good for 60k, right? Probably time to change it unless you know for sure it was done within 10k of the time you bought the car. If the front belt breaks your engine is dead. Rear belt that drives the pump is not a danger to engine health, but if it's really old and slips a tooth or something it could make your engine run bad or not at all.

If it came on suddenly, could also be a bad tank of fuel. If all the above stuff checks out OK then I'd wait and see if things change after the next fill-up.

What kind of "tinkering" did you do? Boost bump?

Good to see another Volvo D24T owner on here! I have an '85 740 TD.

v8volvo said:

Change the fuel filter as a start. If the pump was going out you'd see other issues, like hard starting or leaking fuel, first. If the problem is fuel supply related, the filter is the first thing to check, esp if you already know it's old. There are other possibilities as well though. If it is both smoking and lacking power, then that generally means fuel supply is not the problem.

Timing is OK? If it's running noisy that could indicate injection timing being off.

Valves adjusted?

You say you've done 50k, you know that timing belt is only good for 60k, right? Probably time to change it unless you know for sure it was done within 10k of the time you bought the car.

If it came on suddenly, could also be a bad tank of fuel. If all the above stuff checks out OK then I'd wait and see if things change after the next fill-up.

What kind of "tinkering" did you do? Boost bump?

Good to see another Volvo D24T owner on here! I have an '85 740 TD.

Click to expand...

Sorry...to clarify. Ive owned the car for several years,, but had a whoops, with the engine due to a holed radiator. ( temp gauge didnt work very often lol, so damage was self inflicted. )
I bought a used engine, on which I renewed the belt etc when I fitted it. Engine has unknown history before that, but has served me well for some 50k.
its hydraulic tappets.

When I fitted it...engine was smokey and knocky, I adjusted timing until smoke cleared. But my old engine was damn noisy too....I just assumed they are like that ?
PITA to adjust timing though.

Generally I'd say less smoke..just no go. It isa fairly recent development...past few weeks. Not just one tank of fuel.

As for tinkering.
I fitted a turbo with a smaller turbine housing to help spool earlier. I also upped boost slightly, and adjusted the fuelling screw as much as I could, whilst retaining a sensible idle.
I also adjusted the kickdown linkage to allow me to use a decent amount of throttle, without it kicking down gears...not that there are many gears..but anyway

No leaking fuel, easy to start hot or cold.

ALthough oddly....I was damn sure I could smell diesel when driving at times...but no signs of leakage.

Will get a filter and change tomorrow...and hopefully thats it

Might want to fix that temp gauge if it's already cost you one engine. The D24 has zero tolerance for overheating, one burn and it's done.

The D24T should run really quiet for a diesel. Much quieter than a VW IDI or TDI, especially a later version like yours in a 940 with lots of insulation, hydraulic lifters etc. If it's loud then something may be off.

How did you do timing? Just "by ear" or with the proper tools and procedure?

Is your cold start device operating properly? If it jams in the cold position or somewhere in between, it can affect timing and make the car run funny. They fail all the time.

Did you give the crank pulley the proper torque of 350 or so lb-ft (>500nm)? If not, they can work loose and start to slip... could be happening and letting your timing slide out of spec? If that were the case a big disaster is right around the corner, so hope you got that torque right.

If you are smelling fuel sometimes, your injection pump shaft seal could be going out. When the car is running, they don't leak fuel out, rather, they let air get sucked in. Fit a piece of clear tubing in the fuel return line. Do you see air bubbles in the return fuel? If so this could be the problem. However, usually hard starting accompanies this because the leaky seal lets the pump lose its prime, and you said you aren't seeing that.

Try the new filter and check this other stuff and see what happens. Simple mechanical motor, not like a computerized TDI, so should be pretty easy to figure out.

Thanks for a very comprehensive answer.

Yes...after the blow up, I did fix the gauge. The Volvo insturment cluster isnt the most reliable though. Head ended up like a banana lol

Timing was adjusted by swinging as much as the slots would allow....to stop the thing smoking ( was usually blue smoke )
The slots are as far as they will go...so cant go any further that direction without a lot of work. I can live with the noise...as both engines were noisy, I didnt think it unusual.
Inside the car its fine, but outside is noisy

As it will be due a belt soon, I may look into adjusting the timing further....it would be nice to quieten it down for sure.

Anyways....removed old filter, and pleased to find lumps of brown congealed goo inside. This was blocking diesel flow, so cleaned the pipes out etc, new filter and all is well

From memory....the entire crank pulley doesnt have to come off for belt removal ?? Just the front section unbolts... 4 x M8 bolts ?? Been a while though.

Cold start thingy----the wire broke on it ages ago, but it starts and runs fine without it, so no big deal. I do have another on my old engine...but no real need to change it.

As far as properly setting the timing....is there any easy way to do this ? I recall reading about other diesel engines, and it usually involved getting DTI gauges into ipossible places on the pump to set.
Diesels arent really my thing....if it runs, Im happy lol

But to run quietly, would be excellent.

stevieturbo said:

Timing was adjusted by swinging as much as the slots would allow....to stop the thing smoking ( was usually blue smoke )
The slots are as far as they will go...so cant go any further that direction without a lot of work. I can live with the noise...as both engines were noisy, I didnt think it unusual.
Inside the car its fine, but outside is noisy

As it will be due a belt soon, I may look into adjusting the timing further....it would be nice to quieten it down for sure.

Anyways....removed old filter, and pleased to find lumps of brown congealed goo inside. This was blocking diesel flow, so cleaned the pipes out etc, new filter and all is well

Click to expand...

Shouldn't need to have the adjustment range maxed out. Timing is not that hard, just need the dial indicator and adaptor tool. On your side of the pond any mechanic ought to have a set, same tools are used on older VW, BMW, and many other diesels. Probably would be worth setting it right. Too retarded and it won't start or run well and will smoke a lot. Sounds like that's not your issue. Too advanced and it will adversely affect engine wear and lifespan. Just right and you'll get good starting, no smoke, plenty of power, and long engine life.

So the filter fixed the original problems?

Too retarded was causing the smoking issue for sure. So I advanced gradually until the smoke was gone...but that meant it was at the limits of the slots.

There arent too many garages here that would ever go the the trouble of setting the timing properly....and in fact, half wouldnt have the tools, or know how.

But yes, new filter and cleaning the housing and lines has cured the problem

stevieturbo said:

There arent too many garages here that would ever go the the trouble of setting the timing properly....and in fact, half wouldnt have the tools, or know how.

Click to expand...

That surprises me. We over here often think of the UK and the rest of Europe as a promised land where there are lots of happy diesels and everyone knows how to work on them, not wreck them like most mechanics do over here. Considering there are about 200 times as many Volvo diesels (literally) running around in the UK than we have here, and tons of VW diesels, you'd imagine people over there would be pretty familiar with them and what they need...

Either way, the tools can be had for about $50 on ebay and it's money well spent if you want your engine to last, perform right, and not be loud.

Glad you got the problem fixed.

If you're at the limit of the slots, it's too far advanced and your pistons and rings are suffering. If you're able to easily start it on a cold morning even with that cold start mechanism disconnected, that's another clue you need to knock it back a little. You'll be glad you did.

I'll give it a go and let you know how it goes. But I'm almost sure even the smallest amount will have it smoking again.

Im sure there are some diesel specialsts...perhaps more so in England, than over here in Northern Ireland.

But lets face it....most diesels run for a very very long time. And the most maintenance they require is regular servicing. Often if a pump etc fails..it can be cheaper just to source a used engine complete. So it isnt that often full timing needs to be checked, just to get a car running again.
And again..often its faster just to swing the timing a bit, and play it by ear.

When my fathers Ford 1.8td broke a belt, I refitted a pair of belts ( yes, amazingly no damage ), and the car wouldnt start.
Somehow timing was off. But it literally only took a few minutes of trial and error to get it running well again by swinging the vernier pump pulley.


Do you have any info on how to actually set the timing on the VAG 6cyl ?

If you visit volvoturbodiesel.blogspot.com and look for the pages from the official Volvo factory service manuals he has posted on there, you will find the ones that detail exactly how to set the timing properly on a D24T. Requires a little patience and about $70 worth of special tools, a good investment since they work on a lot of other diesels too (VW, Audi, Dodge, and whoever else over in your parts used the Bosch VE pump, probably Peugeot, BMW, etc too).

Note though, that the shop manual on the site I linked above refers to an American-spec D24T from 1985. Your engine clearly has some differences from the ones we got here, due to its being a more recent, updated design, so there may also be some differences in the procedure for setting the timing, and the recommended specs for what to set it to may be different as well. The tag under the hood of the car will probably list a recommended spec that's right for your engine -- look for it and go from there.