alleged diesel injection pump issue . a6 2.5 ti AKE , starts on the button though

[rustyoldbmw]

Hi all , I've been trawling through all sorts of discussions regarding the fault code(s) that were read when this initially occurred . However none hit this nail on the head .
I've had this quattro avant for 5 years now but due to this issue she's been parked up for a year now .new tyres brakes etc etc . I did cam belt etc myself 2 years prior to this issue and have only had to maintain the vehicle for the 40ish ks worth of driving I've had out of her .

It all started a year ago when changing the clutch slave cylinder . very awkward to reach without a ramp i must say . the job took far too long to do and was raining the whole time (bonnet up) .
the very next morning on the way to work as i started to go up hill the limp mode kicked in and out with large catering noises to boot . got to work (500 yards further ) checked the car at lunch and the viscous fan had unwound itself?!? . thought well that could explain the noise screwed it back on and all was fine for another week . when once warmed up properly ( very short commute at the time ) drove off up an incline and limp mode kicked in . esp abs lit up , turbo shut off , diesel knock clattering no power won't rev above 3000 and dark blue grey fuel rich smelling smoke . sounded lovely at 3000rpm lol but useless.
I left the car for a week and she started perfectly and drove perfectly until warmed up then bang limp mode again .
I had a friend code read it and clear it . once cleared she drove perfectly pulling like a train etc etc . then bang limp mode . cleared the only code that popped back up and all was briefly well again .
the codes read by the Autel MaxiSys (£3grands worth apparently) in order were ;

00550 passive/sporadic start of injection regulation- control difference

00523 active /static IAT G42 open circuit to +

00553 active /static Mass airflow G70 open circuit to ground

01318 active /static Injection pump control unit-J399 -No communication


next screen

18265 Passive sporadic Load signal , error messages from engine CM

there were three other aircon flap faults .

00550 was the only one that returned .

without checking the codes my mate said run off lines . and surely they were a little wet here and there . I replaced those within the hour . and googled the codes .
no change .
next i changed the fuel filter .
no change (these are buggers to bleed with out a vac pump !)
it was read with a snap on machine by a vw man . just the 00550 which his machine couldn't clear , but agreed couldn't be the pump as she starts on the button .
next i went on to the in tank pump but i had over half a tank of fuel . I recall all was ok there but think i may have to go back down that path .
9 months later was when i next got to it . fuel had drained from the pump intake . vac pumped it through ran even with a pipe clamp on the diesel line !
I played with the temp sensor swapping it out for one that was meant for the 2.7 bi S4 i acquired as a replacement . it did sound nicer with the new one and worse without one .
next i went to possible sensors i damaged changing the slave cylinder . one did get knocked . mistakenly i went for a crank sensor (no where near it ) no change then played with the distance sensor (loose ) car went haywire without it . new one just fitted and all was well it seemed . glow plug light now flashes and i had no temp gauge movement until test ride . boosted awesome whole car felt lovely parked up again temp was coming up to 90 car still running and bang as the needle hit middle (90) mark the dash lit up.

Please help ! this seems like an electronic issue not mechanical to me . I wish i new diesels like i know petrols .

[Paul1944]

Check the insulation on the wires from the ECU on the injection pump, they can short and fry the ECU.

[Hannu5]

Can you try and run it with the egr vac tube removed from its connection onto the valve? Plug the end of the rubber tube with something while you do this. See then
if you get the same symptoms, no change or something different. If it drives ok like this cold, let it get fully warm and see again if you get that change when temp
comes up to where it occurred before.

The above is not intended to delete the egr but to take it out of circuit to assist diagnosis.

I've got an AKE on autobox, nice cars but still learning about it.