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Old 04-02-2022, 01:37 PM
Kaptin Kaptin is offline
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Default D24TIC Making very little power

Hi all,

My D24TIC is making very little power. Timed a 0-60 and it's 19 seconds, it's a bit brutal (it's in a 940). It's making 12 PSI boost, so it doesn't appear to be a boost issue. It also loses legs very quickly - acceleration is best between 2500-3000, it slowly accelerates at higher RPMs.

Does anyone have any ideas as to what it may be? I'm doing the timing belt and injector pump belt + timing tomorrow.

Scratching my head a bit though, as it seems to run nicely, so I wouldn't have thought the timing would be too far out!

Many thanks for any ideas you may have!
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Old 04-02-2022, 05:45 PM
v8volvo v8volvo is offline
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Definitely sounds too slow. These engines are quite speedy for an old-tech diesel if everything is in proper condition and tune. Especially the higher output intercooled edition like yours. Power should start to come on strong by around 2000 rpm and stay strong up past 4000 before it starts to taper off.

When was most recent fuel filter change? And air filter?

Any signs of excess smoke when it starts to lose power? And does the power recover quickly when you get back down to low RPM after it loses steam at high RPM? Or does it seem breathless for another few seconds, want to idle extra slow until it bounces back, etc?

Is this an issue that has always been present with this car (how long have you had it?) or did it develop more recently after the car had previously been running stronger? If the latter, did it occur suddenly or gradually get worse over time?

Loss of power at higher engine speeds is textbook classic fuel starvation. It could be textbook airflow restriction too (from clogged air filter or exhaust) but normally that would be combined with big clouds of of black smoke which you didn't describe seeing. So fuel would be the first guess.

There are a few other possibilities too:
- mis-adjusted injection pump fueling rates
- fuel system restriction upstream of the fuel filter (at tank pickup for example)
- leaking or disconnected boost enrichment signal hose from intake manifold to top of inj pump
- problems with EGR system (if equipped) causing either EGR leakage under heavy load, or restricted intake manifold from EGR oil/carbon buildup
- incorrect injection or cam timing, possibly involved with a stuck cold start device or improperly connected high altitude compensation system
- some others

But these are all less likely than a simple plugged fuel filter, so pursue that first. Even if the filter is fairly recent (or believed to be), worth changing it again, as they're cheap, and even one tank of contaminated fuel can plug a filter. If confirming no fuel supply restriction doesn't get it more lively, then there are next steps to check from there.

One other recommendation though -- experience (mine and others'!) shows that, if possible, it would be good to wait on the cam belt and injection pump work until AFTER you first finish diagnosing and solving the low power issue. Introducing more variables always makes troubleshooting harder, and if you do the belt/timing work, then you will be changing multiple factors at once, and it could become hard to know what cause is leading to what effect. E.g. -- not saying this would happen, but it could -- if cam or IP timing ended up not being right on the mark after the belt work, then that might mean there are TWO independent factors causing the engine to run incorrectly, and making organized diagnostic progress in that situation could become very challenging.

Usually much more effective to change one variable at a time in pursuit of one targeted problem, then move on to the next problem once that first one is solved. The one scenario in which you might want to disregard this advice is if you are concerned that the timing belts might be so aged that they are at risk of snapping anytime -- in that case, yes, best to change them ASAP (using correct tools/procedures) and worry about the power concern later.
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Old 04-03-2022, 03:09 AM
Kaptin Kaptin is offline
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Thanks a load for that extremely detailed answer V8Volvo. I actually bought it very very recently, I found the forum posts for the previous owner from the forum, you had tried to help him with this issue too! Though not quite as I have described it, as I've done more checking.

Boost enrichment pin is what I T'd to to detect boost, so the boost is definitely getting to there (could be an issue with the boost portion of the IP I assume though!)

Fuel system stuff is a good call, I never considered that - I have a new filter to go on, so can do that too.

It is EGR'd but will be being blanked today too

IP troubles like the cold start device worry me more, as I have no idea how to check them - I've been looking into modding the IP, and it's rather complex to say the least!

Thanks for the suggestions - one thing I meant to mention was that it's extremely clean smoke wise, so I did suspect that fuel may be related. There's essentially never a puff, which I know is odd for these - my father has one, nice and smokey. You mention the injection quantity, I'll definitely be checking that out, though I don't want to just turn it up and mask a separate issue.

I'd love to wait, but from the forum posts of the previous owner it was very overdue a timing belt a year ago! Which has not been done - so it at the very least needs done, but as you mentioned not ideal as changing multiple variables. Needs must in this case unfortunately! What I may instead do is just the timing belt, then IP belt - separately, if possible. Thanks - will let you know of any progress
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Old 04-03-2022, 11:26 AM
ngoma ngoma is offline
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Quote:
Originally Posted by Kaptin View Post
There's essentially never a puff, which I know is odd for these - my father has one, nice and smokey.
In my experience, in proper tune, these are not big smoke emitters, especially for their era, especially compared to Mercedes, Pugeot, etc.

Echoing v8volvo here, change the FF first, then look at LDA settings and inner workings. Good that it is seeing good turbo pressure, but that might not be getting converted into sufficient fuel pin movement or fuel collar movement.
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Old 04-06-2022, 03:11 AM
Kaptin Kaptin is offline
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Many thanks to both of you.

Having changed plenty of pieces, it seems that it was all down to the fuel/LDA pin. It still had the collar welded on very well, with tamper paint etc - so definitely had never been touched. Instantly resolved the power issue. I am at a loss as to whether it was misconfigured for the last 275k, or perhaps had a misconfigured renovated pump, but it is sorted at least! Thanks for all of the help and suggestions.
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Old 04-06-2022, 09:44 AM
ngoma ngoma is offline
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Glad you were able to solve the problem, but you have confused me. What do you mean by "fuel/LDA pin?"
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Old 04-06-2022, 01:15 PM
v8volvo v8volvo is offline
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Yes great news! Glad you got it sorted. Concur that it is a mystery how it could have been out of adjustment, perhaps for a long time, but it makes sense based on the fact that it was down on power yet able to make full boost, plus the total absence of smoke under load.

Could be it was a rebuilt pump at some point that was calibrated to the wrong specs -- for example with max fueling set to non-turbo values?? If the anti-tamper paint had not been broken then hard to guess any other explanation.

Based on your mention of a crimped-on collar, you are referring to what is most commonly (on this continent at least ) nicknamed the "smoke screw". I think I referred to it as the fuel quantity adjustment earlier. It sets the level of the entire fuel delivery curve for the engine, and then the LDA and the governor (the latter being manipulated by your right foot) make adjustments from there. Thus, yes, adjusting this screw will cause the low idle speed to change dramatically as you mentioned in a different thread. To compensate for that, once you have the smoke screw set to where you want it, you will need to make two other adjustments: one to the position of the low idle throttle lever stop screw (see photo and info ngoma posted in other thread), and additionally you will need to adjust the position of the ball stud on the cold start advance lever that kicks the throttle lever up to a fast idle position when the cold start advance system is in "cold" position. It will need to be loosened and adjusted towards the rear of the car. This will probably take a few days of cold starts to get where you want it, aiming for about 1000 rpm idle IIRC when cold and then 750-850 when warm.

Further -- and this part is specific ONLY to Volvo cars, unlike the steps above that apply to all engines using the Bosch VE IP -- you *may* also need to adjust the length of the turnbuckle style linkage rod that runs from the bottom of the throttle cable bell crank spool back to the actual throttle lever (and/or, adjust the position of the ball stud on the throttle lever that that rod attaches to). This is because, as you turn the low idle adjustment screw outward to reduce low idle speed setting, eventually you may reach a point where the throttle mechanism is no longer resting against that screw and instead being stopped by the throttle bell crank rotating to its minimum stop position. This is not desirable - you want the low idle screw, not the bell crank, to set low idle speed and you want an air gap clearance at warm idle between the bell crank and its stop. The factory greenbook gives a clearance spec for all this. It's due to Volvo's funky two-part progressive throttle control mechanism that they adapted to VW's engine, resulting in the additional fiddly adjustments, but it all works very nicely provided you get it dialed in.

May want to finish final adjustments to the smoke screw before undertaking all this. (aiming for just at the point of a slight puff of smoke as you push pedal to full load, and then it should clear up entirely once under steady full load, don't want any continuous black smoke) Since any further tinkering with that smoke screw will cause you to have to redo your adjustments to idle speed and related parts again.

Welcome to the board! So now on to the cambelt change? Unless you are already familiar, may want to read up a little on this forum and/or in Volvo service literature regarding the particular tools and techniques needed.
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