P38A Diesel engine probs

Dieselmech · Jul 2, 2019

Hi,
New to the forum and I need some help with my P38 please.
Its a 2001 DSE auto. I put a new recon injector pump on it in December last year. All has been good until about 3 weeks ago when it has developed a problem.
When at idle if the gearbox is shifted from neutral into gear whilst the aircon compressor is running it quite often stalls the engine. Sometimes it can stall if only one of these engages at idle - (either the aircon or gearbox). The revs always drop in such a way that for a split second you think it will stall even if it picks it self back up. If it does stall it starts up again straight away no problem. Also very occasionally sometimes when driving along the power will drop away and then come back after a second, as if you've taken your foot off the accelerator. It runs perfectly other than these two issues!
It has a tuning box which I have completely disconnected, have checked for air in the fuel lines and fuel leaks. All other piping I can see is well connected and in good condition. Electrical plugs are all connected and look ok.

Any help would be much appreciated to sort this.

TIA

Wazzajnr · Jul 2, 2019

@wammers is your man for this.
Normally, I think he would suggest quantity servo in the fuel pump being at fault. That said, you said you replaced it with a recon pump so I'd be talking to whoever supplied you with the pump.

RangeRoller dt · Jul 2, 2019

Nanocom 06 is the boy.
Wammers is the gent, and even betterer

Grrrrrr · Jul 2, 2019

2 good answers.

Any better with MAF disconnected?

Dieselmech · Jul 3, 2019

Grrrrrr said:
2 good answers.

Any better with MAF disconnected?

It's exactly the same. Have left it off for quite a while to see but to no avail.

Datatek · Jul 3, 2019

An electrically duff MAP sensor can cause problems.
What is the idle speed?
Is the in tank pump working?
Needs to go on diagnostics to check modulation etc.

wammers · Jul 3, 2019

Get it on diag you will have a quantity servo feedback fault.

Dieselmech · Jul 4, 2019

Datatek said:
An electrically duff MAP sensor can cause problems.
What is the idle speed?
Is the in tank pump working?
Needs to go on diagnostics to check modulation etc.

Hi Datatek,
Will a diagnostic check show if the MAP is faulty? I haven't checked that.
The idle speed is about 800 I think but will double check, the pump in the tank is working I think because fuel poured out of the supply pipe when I bled them after fitting the new pump.

wammers said:
Get it on diag you will have a quantity servo feedback fault.

Is that going to mean I need a new fip? If I recall the diesel shop I brought the reconned pump from said the electronic part of these Bosch pumps is obsolete? It was a recon from Bosch. The guy said he can test the pumps but I think he will send it back as he said it was the cheapest option when I took in the old pump.

Grrrrrr · Jul 4, 2019

Dieselmech said:
Hi Datatek,
The idle speed is about 800 I think but will double check, the pump in the tank is working I think because fuel poured out of the supply pipe when I bled them after fitting the new pump.

Is that going to mean I need a new fip? If I recall the diesel shop I brought the reconned pump from said the electronic part of these Bosch pumps is obsolete? It was a recon from Bosch. The guy said he can test the pumps but I think he will send it back as he said it was the cheapest option when I took in the old pump.

Should idle at 750 unless someone has been fiddling to stop it stalling.

Yes, if quantity servo gone then unless you're very good a refurbed FIP will be required. I got mine from Diesel Jones in Manchester.

Dieselmech · Jul 4, 2019

T

Grrrrrr said:
Should idle at 750 unless someone has been fiddling to stop it stalling.

Yes, if quantity servo gone then unless you're very good a refurbed FIP will be required. I got mine from Diesel Jones in Manchester.

Thanks Grrrrrr. I will have to check the idle speed. If I was very good is the pump repairable, im not, but just wondering if it was possible as I love messing with diesels.

wammers · Jul 4, 2019

Dieselmech said:
T

Thanks Grrrrrr. I will have to check the idle speed. If I was very good is the pump repairable, im not, but just wondering if it was possible as I love messing with diesels.

Injection pumps cannot be refurbed at home they need to be recalibrated on a very expensive machine.

Datatek · Jul 4, 2019

Grrrrrr said:
Should idle at 750 unless someone has been fiddling to stop it stalling.

Yes, if quantity servo gone then unless you're very good a refurbed FIP will be required. I got mine from Diesel Jones in Manchester.

750 +/- 50 rpm for idle. MAP sensor operation can be checked in diagnostics.

wammers · Jul 4, 2019

Datatek said:
750 +/- 50 rpm for idle. MAP sensor operation can be checked in diagnostics.

Idle should be rock steady 750 RPM. May vary + or - 50 as loads are applied and removed. But auto idle control should return it to 750. Auto idle control should react instantly to drops or rises in idle speed. Problem with stalling from idle is that if the idle RPM drops below 500 RPM or the wiper loses contact with the pot the engine will stop. This is usually caused by the quantity servo feedback wiper losing contact with the feedback pot. If the wiper loses contact with the pot at any speed and the ECU does not know the servo position, the stop solenoid drops.

Dieselmech · Jul 4, 2019

wammers said:
Idle should be rock steady 750 RPM. May vary + or - 50 as loads are applied and removed. But auto idle control should return it to 750. Auto idle control should react instantly to drops or rises in idle speed. Problem with stalling from idle is that if the idle RPM drops below 500 RPM or the wiper loses contact with the pot the engine will stop. This is usually caused by the quantity servo feedback wiper losing contact with the feedback pot. If the wiper loses contact with the pot at any speed and the ECU does not know the servo position, the stop solenoid drops.

Hi thanks,
its idling at 800 i've just checked. The needle drops about 200 revs for a split second when it doesn't stall if not a bit more, quite sharply as well. The other one we have the needle only twitches really, hardly noticeable. Looks like the pump will have to come off!

RangeRoller dt · Jul 4, 2019

Dieselmech said:
fuel poured out of the supply pipe when I bled.

Is there a hot-start fitted?

Dieselmech · Jul 4, 2019

RangeRoller dt said:
Is there a hot-start fitted?

Not sure, how would I know?

RangeRoller dt · Jul 4, 2019

It’s nothing, I’m just curious.

Dieselmech · Jul 4, 2019

RangeRoller dt said:
It’s nothing, I’m just curious.

Ok no worries, do they have hot start devices in the fuel pumps sometimes then ? I wouldn't know where to look for it.

RangeRoller dt · Jul 4, 2019

It’s sometimes added as an aftermarket modification to earlier models or to hide fuelling problems.

Started off with a thread on here years ago. Ended up £35 on eBay everywhere

RangeRoller dt · Jul 4, 2019

It’s got nothing to with your problem just ignore me

P38A Diesel engine probs

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