Sharan TDI Warm Start Problem

[keithm]

My 98 TDI AFN has been suffering a warm start problem for about 18 months and although looking at various web forums and remedies I am no further forward!. I was going to replace the car earlier this year but a new car for my wife means I need to keep this running for a few years.

The car starts fine when cold but when the engine temp is more than about 54 it takes about 5 seconds of cranking to start.

So far I have:

1. Replaced the battery due to failure of the original supplied battery
2. Replaced the ECT sensor twice although all sensors show they work OK on testing.
3. Removed and sent the ECU for testing - no fault found
4. Checked the ECT to ECU wiring - no short or open circuit found
5. Replaced the MAF due to failure although this made no difference to the starting problem
6. Checked and replaced various vacuum hoses
7. Removed and cleaned the started motor
8. Found no faults with VAG software

However, when I disconnect the ECT sensor by pulling the plug at the sensor starting is fine either hot or cold!

Any ideas on this welcomed.

[boomboomer]

Try

https://www.vwaudiforum.co.uk/forum/s...light=starting

or search 'starting' in this forum.

[ini]

There is also some good hot & cold no-start info over on TDIclub.

It does sound like a glowplug or sensor/software problem?

http://forums.tdiclub.com/showthread...68#post1972368

http://forums.tdiclub.com/showthread.php?t=134622

http://forums.tdiclub.com/showthread.php?t=116576

http://forums.tdiclub.com/showthread...ight=hot+start

If you can not get to the bottom of it, you can increase main glow phase and startup fueling with Vagcom, this generally works, but is effectively masking an underlying problem.

[shabazmo]

I know this doesn't sound right but I had the same problem after running out of fuel and after spending some time cranking the engine to get the car started. After that day, I had instant cold starts and very very slow warm starts. 6 months later the starter failled and when a new starter was installed, the car was perfect. Now before you all reply and say thats ridiculous. I will say that I agree with you but, that what happened. Try changing the starter motor. Alternatively the temp sensor (4 wire one).
Regards

[shabazmo]

I should add that my can was a 98 AFN engine Galaxy.

[ini]

A 'hot starter' problem is possible.

It sounds a bit daft, but if you dont have diagnostic equipment, you can record and compare the sound of the starter when hot, and when cold on your phone etc.

If it is a binding/bearing/resistance issue it will be noticeably slower.

[keithm]

Thanks for the responses.

From the various "starting" posts on the forum and the TDI club I think that I'll have another look at the starter motor.
When starting it does seem from the RPM that its only cranking at just above 200rpm and I wonder whether it does need to be above 250rpm for fuel delivery to commence which is an issue mentioned several times elsewhere.

It would be nice to determine whether there is a spec for starting, or starter motor performance, does anyone know whether this information is available?

If review of the starter motor doesn't help, possibly an exchange one, then I think its time for a new timing belt with diesel timing checking.
If that fails to improve starting then I'll revert to my earlier thoughts of connecting a relay to the starting system which will disconnect the etc sensor from the ecu while the engine is being cranked.

[keithm]

Hot start fixed - Maybe.

Started motor removed.
Armature cleaned to remove what looked like burning or scorching of the copper contacts.
Carbon brushes cleaned.
Cleaned high current cables from battery to starter motor and also engine earthing cables, although the connections all looked OK to start with and I only cleaned them as I had them apart to inspect.

Car now starts well when hot or cold, the fix isn't perfect as it still takes slightly longer to start when hot and I suspect that I will need a new starter if the problem recurrs.