Hot starting problem.

[rob_bot]

Hi,

I have a '52 Passat 130 TDi and have been running it on 100% bio for about 13k miles with no problems.

About 2k miles ago I started having hot starting problems...(different supplier, but unrelated I think)

It would start fine when it was cold, but after stopping when it was hot it took a good few seconds to start. Almost like there was no fuel in it (when you change the filter but don't fill the new one with fuel).

Depending on how long it is left determines how long it will take to start.

i.e. short drive/long drive doesn't seem to matter as long as it it hot.

If I turn it off for say 5 seconds it starts OK, then 30 seconds it takes a few more turns. Any longer - like nipping in to the shops for a drink etc, then won't start. It sometimes takes so long that the 'STOP' appears on the display with oil pressure low.

A friends car does the same and when I/we put dinodiesel in it it is fine.

Any ideas or anyone else has the same

[kenney]

Have you had a fault code read?

[rob_bot]

Yes, everything is OK apart from a position flap intermittent fault. This is the one under the dash for the heater I believe.

[vwtdi130pd]

look around the tandem pump for signs of diesel thats what my problem is
i changed the filter , the tee , the o rings a lenght of fule line and i even fitted a non return valve but its the tandem pump........costly

[STEWY L]

tdis have an air flap in the inlet manifold i believe.
are you sure this isn't the one the fault refers to?
it could be cutting the inlet air supply off,
regards,
stewy.

[smokey0123]

sounds like there isa leak in 1 of the pipes and the fuel is running back and air getting it the system. check for cracks/ leak in the feed pipes

[rob_bot]

I will have a look at the code again and post up what it is. But it runs fine once it is started.

I don't have any diesel on the ground when idling so could I rule out the fuel line leaks? Mind you it does sound like the fuel is running back into the tank...

The o-rings, t-piece and pipe were next to look at as well as the fuel temp sensor. I was thinking that that was faulty and the fuel was being sent back to the tank to cool. I disconnected it and it seemed better (but the ESP light came on randomly!) but wasn't

The tandem pump sounds likely too but, I can't figure how, if the fuel is sent back to the tank, it starts when it is cold first crank (after heating). How does the fuel get sucked back to the filter? I had a theory that the non return valve gets stuck open, but again can't explain how it starts cold.

I am going to put a clear plastic filter in line to see if it is a fuel starvation problem...

What does the tandem pump do and where is it?

Thanks.

[vwtdi130pd]

if looking at car from front take the cover off the engine and follow the line frm the filter its at the left to the rear of the head and you only need a small amount of diesel hear even a smell of it i looked a few times and said it was fine but on a closer look i found diesel at the lower end of the pump some times you can just torq the bolt and get away with that its worth a try