P38 Diesel power issues

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Bladerunner919

Active Member
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228
So, I have been doing my own mechanics for 25+ years, including my RRC, but the P38 is my very first foray into the world of diesel and I need a little advice.

The problem is that the car has pretty much zero power/torque when off turbo. I actually struggled to get it up a kerb to park on the pavement yesterday. Obviously I'm not actually driving it like this at the moment!

I've cleared a blockage in the MAP sensor, and removed the Rimmer Bros plug-in box to make sure that's not an issue.

I suspect that the engine temp sensor is faulty - Nanocom reports an error on it. However Nanocom does report the engine temp with what look like sensible numbers in the 'instruments' section - I'm assuming that is taken from the temp gauge sensor rather than the ECU engine temp sensor?

Also, when hot, the fuel timing mod figure is about 10-15, whereas I gather it should be 45-55 or thereabouts.

Now, could that be as a result of a problematic temp sensor, or is that a different problem entirely?

Thanks in advance four your help.
 
With modulation at 10-15% engine warm 750 RPM the static timing is to far advanced that has nothing to do with the ECU temp sensor. Gauge sensor is either brown or blue depending on year, ECU temp sensor is green. If it is faulty that could impact on your low RPM power as will the advanced injection.
 
So, a combination of the two, but predominantly the fip adjustment is the issue?

Now, I know that there is a procedure for timing the fip, and I know that people also 'tweak' it without using a dial gauge and locking pin, etc. As I don't have the timing kit, is it the case that adjusting the fip until the modulation hits 45-55% will get it into roughly the right place (or certainly better than I currently have)?
 
Bladerunner919 said:
So, a combination of the two, but predominantly the fip adjustment is the issue?

Now, I know that there is a procedure for timing the fip, and I know that people also 'tweak' it without using a dial gauge and locking pin, etc. As I don't have the timing kit, is it the case that adjusting the fip until the modulation hits 45-55% will get it into roughly the right place (or certainly better than I currently have)?
Click to expand...

Yes you can do that. Scribe a reference line on the pump flange and front case so you know where you are. Slightly undo the pump flange nuts, and i mean slightly so pump can be tapped around but NOT moved by hand. Back off a little the nut on the bracket at the rear of the pump. With a hammer and piece of wood tap pump away from engine a couple of mm then nip flange nuts up and try it. May take a while to get it right. DON'T start engine with loose flange nuts. When sorted re tighten all nuts. You can't tweak an injection pump without some sort of reference. Timing is done to thousandths of an inch the agricultural it'll do approach is not good enough. Maybe someone has advanced it to try and cure hot starting problems maybe caused by the sensor. Change the sensor first of all and see what you get.

PS. You will need to remove the manifold to do the pump. As long as you ensure nothing can fall into or get sucked into the ports the engine will run quite happily with it off.
 
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Thanks for that. I appreciate the advice and I'll let you know how it pans out.

Can I just clarify one thing - does the pump move from side to side or left and right? From your instructions on moving the pump away from the engine, I'm assuming left and right, but info I've seen on timing up the M51 engine seems to suggest back and forth? As this is my first diesel, this is all a bit of a learning experience!
 
Last edited:
Bladerunner919 said:
Thanks for that. I appreciate the advice and I'll let you know how it pans out.

Can I just clarify one thing - does the pump move from side to side or left and right? From your instructions on moving the pump away from the engine, I'm assuming left and right, but info I've seen on timing up the M51 engine seems to suggest back and forth? As this is my first diesel, this is all a bit of a learning experience!
Click to expand...
It rotates I think towards or away from the engine block.:)
 
Bladerunner919 said:
Thanks for that. I appreciate the advice and I'll let you know how it pans out.

Can I just clarify one thing - does the pump move from side to side or left and right? From your instructions on moving the pump away from the engine, I'm assuming left and right, but info I've seen on timing up the M51 engine seems to suggest back and forth? As this is my first diesel, this is all a bit of a learning experience!
Click to expand...

The pump rotates on slots that the securing studs fit through. That is why you slightly undo the nuts to allow it to move.
 
So, to return to this with some feedback, I have finally got around to have a look at the car. The problems all stem from bodged attempts to cure the hot starting problem. I managed to tweak the pump until I got withing the 45-55% modulation range, and that has made the car much more driveable.

The problem with the ECU temperature sensor was a very strange attempt at the hot-start fix, with the temp sender wire running through a relay. However, the relay isn't set up to do the usual trick of adding resistance for a short period to give the impression of a cold engine. It's set up so that the relay completely disconnects the sender from the ECU. Even stranger is what is supposed to trigger the relay (but doesn't). The feed for the relay is attached to the Engine Management light output from the BECM! I assume the idea was that when the light was on, the relay would cut the temp sender signal and force the ECU into it's cold start settings.

It was a completely ridiculous installation! Anyway, I've removed all that pointless wiring, and need to just pop in a proper hot-start fix. I've seen a few on ebay - are there any particular sellers that anyone has good experience of?
 
Bladerunner919 said:
So, to return to this with some feedback, I have finally got around to have a look at the car. The problems all stem from bodged attempts to cure the hot starting problem. I managed to tweak the pump until I got withing the 45-55% modulation range, and that has made the car much more driveable.

The problem with the ECU temperature sensor was a very strange attempt at the hot-start fix, with the temp sender wire running through a relay. However, the relay isn't set up to do the usual trick of adding resistance for a short period to give the impression of a cold engine. It's set up so that the relay completely disconnects the sender from the ECU. Even stranger is what is supposed to trigger the relay (but doesn't). The feed for the relay is attached to the Engine Management light output from the BECM! I assume the idea was that when the light was on, the relay would cut the temp sender signal and force the ECU into it's cold start settings.

It was a completely ridiculous installation! Anyway, I've removed all that pointless wiring, and need to just pop in a proper hot-start fix. I've seen a few on ebay - are there any particular sellers that anyone has good experience of?
Click to expand...
If the modulation is correct, I'm not sure you should need the hot start fix, mine certainly doesn't. If you do need one, just get one that is timed.
 
Bladerunner919 said:
So, to return to this with some feedback, I have finally got around to have a look at the car. The problems all stem from bodged attempts to cure the hot starting problem. I managed to tweak the pump until I got withing the 45-55% modulation range, and that has made the car much more driveable.

The problem with the ECU temperature sensor was a very strange attempt at the hot-start fix, with the temp sender wire running through a relay. However, the relay isn't set up to do the usual trick of adding resistance for a short period to give the impression of a cold engine. It's set up so that the relay completely disconnects the sender from the ECU. Even stranger is what is supposed to trigger the relay (but doesn't). The feed for the relay is attached to the Engine Management light output from the BECM! I assume the idea was that when the light was on, the relay would cut the temp sender signal and force the ECU into it's cold start settings.

It was a completely ridiculous installation! Anyway, I've removed all that pointless wiring, and need to just pop in a proper hot-start fix. I've seen a few on ebay - are there any particular sellers that anyone has good experience of?
Click to expand...

All you would get by doing that is the ECU using 50 degrees as a preset hot or cold. Just as it does if the temp sensor fails.
 
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