P38 Diesel loss of power when changing gear possible fix

Hi all,
since i've had my P38 (since last June) ive always had the problem of the MIL coming on during decelleration and a loss of power unless i lift off then re-press accelerator. the fault that comes up is fuel quantity actuator solenoid or something to that effect. untill now all the stuff i have read online about it (plenty of people with the problem) recomend to just replace the pump.

i'm not a fan of replacing thing without fixing the fault so i decided to look into it more, Rave manual shows a potentiometer on top of the fuel pump that tells the ECU the position of the throttle. i was convinced it was to do with this, as it only happens during over-run which is the only time the ecu is telling the pump to not inject any fuel, and as it is running as it should is seems the fault is actually with the potentiometer thinking its still injecting fuel. i was hoping i would find a worn track that a connector sits on and rotates but it was actually more complicated but the end result is the same.

it turns out that (certainly in the case of my pump) the stop for the throttle return is worn so it actually stops after it should. anyway long story short (its long enough already) what i did was to take the top of the pump off (i removed inlet manifold as was doing glow plugs at same time and gave better access, although its fairly accesible without removing.







i hammered a 7mm 1/4 drive socket onto the security bolt



once the other torx bolts are undone the top of pump can either be removed completely (need to remove return line from back end of it)

which will give you this:



the arm with the 10mm nut and torx screw is what rotates with the throttle to tell ECU its position. i think the Xmas cracker shaped thing infront of it is the fuel temp sensor which i gather can cause problems? although i havent looked into it. looks easy to change though.

basically what i did, was hold the arm with a 10mm spanner then crack off the torx screw on the top, then turn the 10mm nut anti clockwise (it will be tight, as it is on a taper, once it cracks off the arm will be free to move independant from the throttle arm. i then turner the arm anti clockwise till it was near enough against the black thing next to it, then re-tightened torx screw. put it all back together and hey presto its not done it to me since

*i take no responsibility if you mess it up or it doesnt work for you, just reporting my findings, it seems people are scared of taking the pumps apart and treat them as a disposible item*

hope this helps someone
Adam

The usual cause of the problem you describe is injector number 4 needle lift sensor or the crank sensor playing up, I'd want to see some live diagnostic data before even thinking about doing what you have done. Maybe you are just covering up the real problem.

Fair enough, like i said i am just reporting my findings. number 4 injector is new. throttle stop has worn so is now returning past where it would have done when originally calibrated. if crank sensor was the fault i cannot see how this would mask it. if it was not giving the correct signal re-alligning this would not magically make it start giving a signal again.

aniesigh said:

Fair enough, like i said i am just reporting my findings. number 4 injector is new. throttle stop has worn so is now returning past where it would have done when originally calibrated. if crank sensor was the fault i cannot see how this would mask it. if it was not giving the correct signal re-alligning this would not magically make it start giving a signal again.

Click to expand...

Absolutely, but the ECU needs both the number 4 and the crank sensor. When you lift off the throttle there will be no signal from the needle lift sensor so the ECU needs the crank sensor to know the engine is running, a dicky crank sensor will cause your problem. Doing what you have done may mean that the needle lift sensor is still operating as the fuel is not now shutting off. Just a thought, but as I said there is no substitute for having a good diagnosis before operating on the patient

ok makes sense, but if thats the case how could needle lift sensor ever be the cause of the problem?

aniesigh said:

ok makes sense, but if thats the case how could needle lift sensor ever be the cause of the problem?

Click to expand...

In your case it would be the crank sensor at fault as you have eliminated the needle lift sensor. I might be wrong, but as I said, personally I would never do what you have done without the evidence to prove I am doing the right thing. You may have just created a situation where the needle lift sensor is now masking a crank sensor fault because the fuel is not shutting off as it should. You could have ****ed your FIP, I hope not

i mean how could the needle lift sensor ever cause the MIL coming on on over-run when its not giving out a signal? like you say it obviously wasnt that in my case as its new but ive seen it suggested when other people have asked the same question. don't see how i can have ruined my FIP? people seem scared to open them up but at the end of the day its mechanical components connected together. put it back how it came apart and you can't go too far wrong. go careful and mark things if you're concerned. take pics whatever you want but going and spending £000's on new fuel pumps because a throttle stop is 2mm worn seems stupid.

aniesigh said:

i mean how could the needle lift sensor ever cause the MIL coming on on over-run when its not giving out a signal? like you say it obviously wasnt that in my case as its new but ive seen it suggested when other people have asked the same question. don't see how i can have ruined my FIP? people seem scared to open them up but at the end of the day its mechanical components connected together. put it back how it came apart and you can't go too far wrong. go careful and mark things if you're concerned. take pics whatever you want but going and spending £000's on new fuel pumps because a throttle stop is 2mm worn seems stupid.

Click to expand...

yes there must be a way of adjusting the fip, however i would not be happy to do this, damn things are temperamental at the best of times without any help,why can't the pump be adjusted? only option i have had is to replace the pump,why should that be,when most pumps can be adjusted why should this one be different?

Have it your own way, I think you are ****ing in the wind. How could you have known before you took it apart that the item you call the throttle stop was worn? Do you even know what a good one looks like so that you can tell that it's 2mm worn and not made that way?
Nowt more to say, I hope it works well for you but I would say to anyone else, diagnose the root cause of the problem before tweaking things on spec

roddy4 said:

yes there must be a way of adjusting the fip, however i would not be happy to do this, damn things are temperamental at the best of times without any help,why can't the pump be adjusted? only option i have had is to replace the pump,why should that be,when
most pumps can be adjusted why should this one be different?

Click to expand...

Cos the control is electronic

Datatek said:

Cos the control is electronic

Click to expand...

yes but it still has moving parts which wear, electronics which have no moving parts, but still deteriote over time,are these parts able to be changed or is it a cheaper option to replace the pump? the mechanical parts can they be replaced? are there people out there who will supply these parts,
just looking for a cheaper option,but it doesn't look like there is one,
all i get from any landrover mechanic is to simply get a recon pump or new, no other option, just thought they were just after my money,but on looking into it,that could be the best way to go.

@datatek, I don't see how you can tell me I'm ****ing in the wind when youve not seen my pump. I'm telling you there was a regularly occurring fault before and now it's gone. I'm not trying to insult your knowledge of them in fact you've helped me in the past I just like to understand things and how they work rather than follow lots of advice online and just replace parts untill the problem goes. You've recommended to me before It could be the needle lift sensor but then contradicted yourself by saying on overrun the needle lift doesn't give a signal so how could it be that?!
You're correct this is the only pump I've taken apart but if you're telling me there should be a 2mm recess in It from standard then show me a pic of a re-con pump stripped down. My p38 has done 164000 miles which means the throttle has probably sprung to the stop position millions of times thus wearing the stop. I've not seen any threads on here where people have changed crank sensor to cure the problem and I can't see it being that personally. It wouldn't make the mil illuminate as if the quantity actuator was reading 0 on overrun which it should and the crank sensor stopped giving a signal it would just think the engine had stalled. I'm willing to listen to an argument that makes sense but youre not answering with anything to change my mind? Like I say I'm not trying to argue for the sake of it it just doesnt make sense to me.
Adam