Electronic fuel pump behaviour

[Lth0ms0n]

Is the fuel uplift pump on the GTD supposed to (audibly) prime itself when the driver’s door opens, as an X-reg 2.0l Beetle my Mum once had used to do, or is that a behaviour specific to petrol VW models?

I’m investigating a low fuel pressure issue I’m having with my ‘63 plate GTD at the moment. Came back after a week away to find it refusing to start and when it does start, it shuts itself off after a few minutes.

I’ve been working through it with my mechanic - OBD has said a combination of fuel rail/system pressure low, “Fuel Pump A” Low/Flow Performance and now a mechanical issue with the high-pressure pump.

There’s a buzzing coming from it which we’ve isolated to the regulator valve on the high-pressure pump which we’re sourcing a replacement for, now.

The uplift pump was replaced on NYE - I don’t believe the original was faulty but a new one can’t hurt.. However, now I’m paying such close attention to the fuel system, I can’t remember if the car would prime itself when the door was opened (after unlocking) or if it’s something I’m only familiar with from cars I’ve driven previously…

Can anyone with a newer, less likely to be faulty GTD than mine confirm either way for me? Just so I can rule any other potential issues or faults out…

Cheers.

 

[golfbest]

I'm sorry I haven't owned a diesel VW, but I'm pretty sure almost all gasoline VWs will run the low-pressure fuel pump for a few seconds as a pre-start when the main driver's door is unlocked and opened.I once had a MK4 that had a low pressure fuel pump failure. It would have a delay in starting if it was parked for more than two days, and the starter would work longer before it would start.

 

[Lth0ms0n]

I'm sorry I haven't owned a diesel VW, but I'm pretty sure almost all gasoline VWs will run the low-pressure fuel pump for a few seconds as a pre-start when the main driver's door is unlocked and opened.I once had a MK4 that had a low pressure fuel pump failure. It would have a delay in starting if it was parked for more than two days, and the starter would work longer before it would start.

So, that's what mine has been doing - for a while now. However, the issues which have led to my asking this question now are unrelated and have come out of nowhere (so to speak).

There's a thread somewhere else on this forum with a fix for that issue which I'd tried which involves replacing the vacuum pump and the injector/bolt inside it, due to a TSB relating to the oil pressure system. I did that to my car the last time it was serviced but it made no difference.

The trouble all started when I got home after being away for a week to find the car with a flat battery. After I got it jump started, all the other issues rose to the surface - starting with a clicking noise which was coming from the fuel tank.

I've replaced the uplift pump and the clicking has gone away, only to be replaced with a weird thumping noise which, while quieter than the clicking noise, is still not going to be tolerable for long. The car still has the glow plug & engine lights lit and doesn't idle indefinitely. If/when you drive it, there's no power and it will always (eventually) stall and there's no guarantee that it will start again.

Weirdly, when stationary, the car will rev - if it's revving, it will continue to run without issue, it's only when it idles that the engine will stall again...

OBDII says there's low fuel pressure and a mechanical malfunction with the high-pressure fuel pump. The live data from the engine also shows the fuel pressure varying - I cant't remember what pressure it's hovering around exactly.

We've checked the fuel lines - all clear. Twice, however, when the engine has stalled, there's been a buzzing noise coming from the engine compartment and we've isolated it (for now, at least) to the high-pressure fuel regulator valve. I have a new one ordered and this is going to be fitted to the car this afternoon...

I'm hoping that this is the end of it - aside from the standard 2013 model issues with the interior radiator, I've had no issues with the car, ever, and I don't want that changing, for any reason! I am concerned that it's the fuel pump controller which is faulty and the reason the new pump is making a noise is because it's running in overdrive (as I've read elsewhere that the pump will fail 'high' so as to avoid letting the HPFP run completely dry...

The new regulator will be fitted to it, I hope, in a couple of hours - will update this with the outcome of that then.

 

[misor1994]

I have not noticed the fuel pump to be active when opening the door of my last 3 or 4 commonrail diesel engine VW group cars. I know this was typical for older models, not commonrail diesels. I think it is activated rather by turning on the ignition.

 

[Lth0ms0n]

So I got to the bottom of this - it turned out to be a very expensive repair for what was ultimately a pretty minor problem.

As always, when it's a VW issue, it's always electronic and never (if not very rarely) mechanical...

After replacing the fuel sender unit, checking the fuel filter for metal residue and then replacing the mechanical fuel pump (which the car was telling us had a mechanical malfunction, with low pressure on the fuel rail) the issue turned out to be with the PCM for the fuel sender. The mechanical pump malfunction error remained on the engine after the new pump was fitted and the (new) sender unit was thumping around in the tank.

After taking a multimeter to various points on it, my mechanic discovered the current flowing erratically on the sender unit - causing it to pump fuel in different directions, constantly. We replaced that and the car is now totally back to normal.

We're clueless as to how this happened because, prior to the issues starting, the car was running perfectly. All we can attribute it to is the battery running flat while I was away for a week and the PCM shorting out when I got in and (unknowingly) tried to start it for the first time before discovering it was dead...

In total:

- New fuel sender unit
- New HP fuel pump
- New PCM
- Rail also checked for blockages (and confirmed clear).

Not ideal but fortunately, the car did all this when the cam belt was due so I've had most of this replaced under one labour bill but the next time it starts doing something this strange, I'm going straight to whatever chips are involved first (and the mechanical stuff later).