Suddenly won't start after recent tandem pump change

johnyfartbox

johnyfartbox

A2OC Donor
United-Kingdom
Here goes.
Last week I replaced the tandem pump with the Bosch equivalent using the excellent spacer provided by Paul.
A very healthy battery and the engine kicked in on the 5th try proving that the pump is nice and strong.
Left it ticking over for a good 30mins then turned it off.

Left it overnight then fired it up, no problem.

On Monday just gone I decided to take it for a spin on my local estate, drove around for 15 / 20 mins and pulled into the drive.

Turned it off and went and made a brew.
Came out to move it further up the drive and it would not start.
Engine spun over with plenty of power from the starter motor, nothing.

I ended up having to use the starter motor to move the car In first gear.

I've spoken to Graham and I've done what hes suggested checking has many electrical connectors that I can get to.

I've done loads of VCDS tests and the only fault that I'm finding is the left rear door won't unsafe but I knew about because I can hear it clicking now and again and when I turnthe ignition I can hear the locks click.

When I turn the engine I can see the rev counter move so that should rule out the crank sensor.
I've just received a new OEM cam sensor just incase it's that at fault.
I just don't know where to look next guys.


HELP!!!!!!
 
johnyfartbox said:
Here goes.
Last week I replaced the tandem pump with the Bosch equivalent using the excellent spacer provided by Paul.
A very healthy battery and the engine kicked in on the 5th try proving that the pump is nice and strong.
Left it ticking over for a good 30mins then turned it off.

Left it overnight then fired it up, no problem.

On Monday just gone I decided to take it for a spin on my local estate, drove around for 15 / 20 mins and pulled into the drive.

Turned it off and went and made a brew.
Came out to move it further up the drive and it would not start.
Engine spun over with plenty of power from the starter motor, nothing.

I ended up having to use the starter motor to move the car In first gear.

I've spoken to Graham and I've done what hes suggested checking has many electrical connectors that I can get to.

I've done loads of VCDS tests and the only fault that I'm finding is the left rear door won't unsafe but I knew about because I can hear it clicking now and again and when I turnthe ignition I can hear the locks click.

When I turn the engine I can see the rev counter move so that should rule out the crank sensor.
I've just received a new OEM cam sensor just incase it's that at fault.
I just don't know where to look next guys.


HELP!!!!!!
Click to expand...
Daft question - but is there fuel at the pump or could it have drained back again?
 
dj_efk said:
I would suggest @Proghound therefore removes this post from this thread as it won't help you get an answer - it needs it's own thread.
Click to expand...
Agreed, I've moved the above posts to their own new thread.

Indeed it shouldn't be the camshaft sensor. If that were dead, the ECU would use the crank sensor to work out the engine position and still start, it would just take longer.
 
Why? As the new tandem is more efficient there is a chance anything sitting in the fuel pick up in the tank has been sucked into the fuel filter and is now restricting the flow. Change the fuel filter.
 
or at least take off the drain back pipe and replace with some clear tubing.
daft question here . could it be an immobilizer problem?
 
johnyfartbox said:
or at least take off the drain back pipe and replace with some clear tubing.
daft question here . could it be an immobilizer problem?
Click to expand...
If it's the immo, shouldn't it fire and then immediately stop while flashing a key warning light up on the dash?

Reason I'm asking about the fuelling is because of what happened when my webasto in line pump got knocked off the underside of the car last month - the starter motor would spin the engine fine but it didn't catch at all as the fuel was peeing onto the ground instead.
 
Yes, when immo blocking activates engine would run for a second and the yellow key warning light on the cluster would blink.
 
audifan said:
Why? As the new tandem is more efficient there is a chance anything sitting in the fuel pick up in the tank has been sucked into the fuel filter and is now restricting the flow. Change the fuel filter.
Click to expand...
I changed it about a month ago
20230216_145915.jpg


I have a new one here so will do it again.

Thats the old one
 
Also, on the new pump I can get a 0.10 feeler guage between the side of the pump and the block but cannot on the old good pump on my other A2 tdi.
https://youtube.com/shorts/fQCkO-rZpH

now this could be down to the way the gasket is made.....maybe.

PXL_20230219_112541634.jpg


Has you can see, the gasket is smooth where the gauge can slip behind it but on further testing, I cant push the same gauge through where the raised bits are on the gasket.
 
Never seen diesel in a clear pipe before, I too think that air shouldn't be there. Is that a new pump? Cloud the seal between the vac pump and fuel pump have failed?
 
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