SQ5 2015 Cutting out

[graham 500]

Had a problem 6 months ago and car, when drawing to a stop, it would struggle to tick over as it was trying to cut out and did sometimes. Booked into Vagtech and they replaced fuel pump and filters and it seemed to do the job. However it started to do it again a couple of days ago, but does not show any faults on screen. But i have driven since and its fine as it seems to re set itself. Has anyone had same issue, if so how was it rectified.

[Dr G]

Fuel filter would have been my first guess had it not already been done; this will need careful diagnosis and may be difficult to pinpoint. Given parts already replaced a fuel system fault remains a possibility. It's relatively easy to test injectors (and problems here are not unheard of) but given that the problem may be impossible to replicate under workshop conditions there may be no smoking gun.

[catso]

graham 500 said:

Had a problem 6 months ago and car, when drawing to a stop, it would struggle to tick over as it was trying to cut out and did sometimes. Booked into Vagtech and they replaced fuel pump and filters and it seemed to do the job. However it started to do it again a couple of days ago, but does not show any faults on screen. But i have driven since and its fine as it seems to re set itself. Has anyone had same issue, if so how was it rectified.

Don't know if it might be a similar thing, my Sons' Golf would sometimes die, usually within a mile or so of starting up.

Fuel starvation, I suspected the filter so I changed it but the old one was fine (I even cut it open to check for blockages), then the high pressure pump but that was fine too so I looked at the 'lift' pump (in the tank).

As it wouldn't always do it, I disconnected the lift pump, car started up fine, ran for maybe half a mile on the fuel already in the system, then died -exact same symptoms when it was doing it randomly.

The pump itself was fine so it turned out to be the controller for the lift pump - looks like a sort of relay/plug device on top of the fuel tank/pump assembly, apparently it controls the rate of the pump based on engine demand so that it's not constantly running at full speed if not required.

Anyway intermittent failure, the good news is that they are easy to change and not expensive; around £20 - £30 IIRC.



When you first turn on the ignition but don't start the car, can you hear the fuel pump cycle for a few seconds? May need to lift the rear seat to expose the top of the pump housing to hear it - on ours the pump would generally cycle but it was noticeably faster/louder with the new controller.