99 A4 2.5tdi AFB difficult starting, particularyl when warm.

[aliw]

Hi all,

I have a 1999 A4 2.5tdi Quattro Avant. As in the title the car is difficult to start when warm, usually requiring 8-10sec (sometimes more) of cranking before it fires up.

I have owned the car for 3 yrs, and this was an intermittent fault (mostly in warm weather). The thermostat was stuck open , so the car always ran cold (heaters worked and as it was such a big job to do I lived with it). The injection pump was changed for a re-con unit when I bought the car.

About 2 months back the alternator died, and whilst the car was in service position I had the timing belt, water pump and thermostat changed at the same time.

Since having the car back the (it now runs at 90deg on the gauge), it is difficult to start when hot. It is ok when cold.

I set the pump timing some time before it went in to have the belts done, and have just re-checked it and it is 2deg ATDC (LATE) in field 3 of basic settings Group 4 on VCDS, with the coolant temp above 85deg C...which I believe is bang on. When running it pulls well, doesn't smoke and is good on fuel (40ish mpg on a run...it is a quattro).

If I disconnect the coolant temp sensor (blue one) the car fires up much quicker (within 2sec or so). I don't think there is any fault with this sensor as it only generated a logged fault when disconnected, and seems to feed the ecu/gauge with consistent temp readings.

I have searched for possible causes other than the above, but have not found anything that seems to make any difference.

The only other possibility I have come across is that the started motor is slowing down, but for the most part as far as I can tell it seems to be turning the engine over ok. If it was a simple job to change this I would give it a go, but as the only way of changing it is to put the car in service mode again, remove the aux belt and alternator, and then be able to remove the starter motor, I am reluctant to spend out again on it.

Has anyone else had these issues, or does anyone else have a possible cure for this problem?

[adamss24]

The pump timing is wrong, needs checking and adjusting with VCDS... Where abouts are you ?

[aliw]

Hi, Thanks for the reply. I live in Bridgend S.Wales.

As I said above though, I have checked the timing on VCDS and it is at 2 deg ATDC (Late) , which is where it is supposed to be according to the spec. Is there something else I need to be checking/adjusting. As I said the belts have only just been done, and it was the same before, although the fault did not cause so much of a problem due to running cold all the time due to the stuck open thermostat.

When I checked the pump timing prior to the belts being done it was running at 0 deg, and was the same to start when warm, but sounded very "diesely" all the time, whereas it is a lot quieter at 2deg.

Many Thanks.

[ametlib]

I have seen this problem a few times and usually a new CTS or a new cam belt is the cure , but not always I'm afraid. If nothing else works, solder in a 5k ohm resistor serially in the G62 circuit, then fit a switch to short the resistor out.
When starting from hot engine, push the switch to "open" and the ECU will be fooled to inject more fuel and makes the engine start much easier.