Sport Fuel pressure problems

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Yes, it’s annoying I don’t have a guage and I’m away for nearly 2 weeks from Monday (was hoping to take the car!!)

I’ve tried to approach things with a bit more logic this morning - I wanted to confirm if the old parts were broken or not.

Fuel pressure sensor - old one reads 4.6ish volts no matter what (on ignition, whilst cranking, on idle and whilst revving!!) so that part I deduced, was knackered.


After putting the new one back on…
0.41 volts on ignition
0.85 volts on start
0.75 volts once idling (for the first few starts)
And increase with revs

So new sensor works.

Then the code comes back after 5 or 6 starts, everything is the same except it now idles at 0.83 volts and the high pressure code comes back.


Then
I thought I would change the regulator back to the old one, just to double check the new part isn’t faulty.

Suddenly the car rough idles, voltage at 1.03 from the sensor and same code… what’s baffling is that how it seems both the sensor and the regulator were dead!??? Which I find unlikely.

I also don’t see why I faulty fuel pump would damage the sensor and regulator.

It was happy as anything when idling at 0.75 volts.

Now going to put the new regulator back in and hopefully re-establish a smooth idle!

Starting to get a bit fed up and slowly coming to conclusion that after all this money and effort it may still end up in the garage!
 
Just stethoscoped my injectors again, all sound pretty similar and very nice ruthmic clicking coming from all 3.

However when listening to the run offs, one out of the 6 has a high pitched whine/squeal to it.

Thinking possibly run off problem? Unlikely but clutching at straws here
 
lj5000 said:
Just stethoscoped my injectors again, all sound pretty similar and very nice ruthmic clicking coming from all 3.

However when listening to the run offs, one out of the 6 has a high pitched whine/squeal to it.

Thinking possibly run off problem? Unlikely but clutching at straws here
Click to expand...
Need to do a leak off test.
 
lj5000 said:
Unfortunately I don’t have a pressure guage that can read this.

The loom is fine in every measurable way using my multimetre. All continuity is perfect to the ECM, no signs of a short on any of the 3 wires.

It’s weird the fault has changed, to me it says one sensor is dodgy (probably the old one that’s in now) but I’m not sure.

From the start, I was thinking it’s the high pressure fuel pump so I started replacing cheaper, easier parts mainly in hope. And it’s clearly having an effect. There’s this and also the problem originally started with a low fuel rail pressure code so now I’m not so sure.
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hi

have u had any joy with this or still the same plse

indeed need a pressure gauge for that test point so u can then at least see what pressure u have

alas u can get caught out just using a multimeter when testing for continuity, really need to put it under load with something like a test light , enclosed a picture of some of the things I’ve used

indeed with these vehicles being so complicated a decent code reader is a must where it will also provide u with live data, some of the ones I have has the facility to run a log test so that u can see what’s going on whilst driving , allows u to then look back at the data

personally would start at that test point to see what kind of LPFP pressures ur getting

also wouldn’t hurt to check the live data for ur 2 x Mafs and 1 x map sensor to ensure there correct

hope that helps


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Plus just thought , do u know when the fuel pump belt was last changed plse , as on the D4 there timed and have heard of them skipping a tooth and therefore taking it out of time

doubt it but just wished to mention it

regarding injectors on my D3 can test the fuel trim offset figures for them, wondering if ur scanner will do the same , have a gap iid and an Autel MX808

have u also checked ur inlet manifolds plse as there’s reports of them splitting

right


left


fingers crossed it will be a simple fix, just wished to at least mention it so ur aware
 
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Hello,

Sorry I have been away for a while so only just got back to this.

Did a leak-off test today (accidentally breaking a couple of the clips so need to replace them now) and there were some significant differences between the injectors, with one in particular just pouring out.

I have now pulled all 6 injectors and they certainly aren't in the best condition. See photo below, all 6 looked something like this or worse. Obviously need a good clean, from how the engine sounded and stethoscope-ing the injectors, they all appear to be mechanically working perfectly well.

A couple came out with a bit of oil on them, unsure as to how bad a news that is and if I can just ignore it!??
 

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It is unlikely to be your original fp sensor at fault. After market are known for not working and giving high pressure fuel reading faults.

Test your low pressure in tank fuel pump if all OK then suspect and replace the hpfp. It is NOT a body off job.
 
If your diagnostic does live data, look at that with the engine running. I would expect some change in value when you rev the engine ?
 
stemac33 said:
Are you sure it not just fuel and soot
Click to expand...
No, it probably is but the difference in leak off was significant so there must be something going on?
biketeacherdave said:
It is unlikely to be your original fp sensor at fault. After market are known for not working and giving high pressure fuel reading faults.

Test your low pressure in tank fuel pump if all OK then suspect and replace the hpfp. It is NOT a body off job.
Click to expand...
Original sensor was bust, however only seems to be part of the problem, it had absolutely no change in voltage output from ignition, through starting to revving, The new part is an original, brand new identical bosch part.

What pressure should I be getting at the schrader valve on top of the engine?

pwood999 said:
If your diagnostic does live data, look at that with the engine running. I would expect some change in value when you rev the engine ?
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New sensor changes in value with revs yes.
 
One injector was bad, but whilst changing the leak off pipe I decided to have a look at the engine running,

Look at the amount of diesel coming back towards the rail from the leak off pipe…. Surely that’s not right!? Fuel is supposed to be going the other way!

Bad pump? Valve?
 

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Mark Piercy said:
the mechanical side of the injector can stick or be blocked and the ecu cant sense this. this is when a possible high or low rail pressure case can happen. a leak off test on the injectors can reveal any physical issues.
the test has to be done on all the injectors at the same time to measure the fuel being returned to the fuel system. this can be done on the vehicle. any difference in the fuel return from any one or more injectors will result in a or all injectors to be replaced. the fuel return quantities should all be very similar.;)
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Ready this properly then? 🙄
 
Mark Piercy said:
Ready this properly then? 🙄
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I read it perfectly well yes, I did a leak off test on all 6 injectors thanks to your post and found one that was clearly wrong.

What I wasn’t doing at the same time was looking at what was coming out of the leak off pipes when they were not attached to the injectors.

The picture, is fuel coming from the top of the pump, down the leak off pipe towards the injectors.

A new leak off pipe with non return valve in it has solved that problem, but alas I still have the code.
 
Just for a while today, I thought I had fixed this.

Old leak off pipe had a bust one way valve, so diesel was coming back from the pump, towards the injectors along the leak off line.

New leak off line fitted, no diesel coming back down down towards the injectors. Clear code, start car at least 25 times in a row, code does not return (used to return in 3-5 starts max after clearing code)

I then let the car sit for an hour, started it and the code came back!! 🤬.

Clear code again, it’s fine as long as I want it to be if I keep restarting it but as soon as I leave it for 30 mins then go back to restart it, the high pressure code come back.

Whatever I’ve done with the leak off pipe and injectors clearly hasn’t completely fixed it but it has massively improved the situation.
 
Don't know your engine, but looking online it appears the pump return joins with the leak-off. I would assume this should be at similar low pressure to the leak-off from the injectors ?

Have you checked pressure on low side as well as high side ? . . . .and check all three pumps !

This thread has some ideas.

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