MK5 golf 1.9TDI bad starting when warm

[harminder]

Hi, my dads golf has started playing up when being started warm. It's fine on cold mornings (so cant be starter motor) and runs perfectly fine once started.

You turn the key and car tries to turn over but it can take 3-8 secs before it fires up! Did a quick search on the net and found the following on honestjohn:

'On TDIs a starting problem may be due to a faulty relay under the dashboard. As this relay also controls the fuel cut-off valve, it means that, even with the engine hot, the engine will not start no matter how much it is churned over. However, if the glow-plug light comes on, however briefly, the engine will start immediately. Replacing the relay solves the problem.'

This does sort of make sense! So does anyone know the exact relay at fault and where under the dashboard it is? Can this be a job done at home?

Cheers

H

[Rustynuts]

That tale relates to a Relay 109 fault which isn't what yours sounds like to be honest. 109 faults appear at random, usually when you've been driving for a while and the relay gets hot, then the car just stops. When you try to restart there's no glowplug light signifying no power to the ignition relay. Eventually the relay cools down and you can restart as normal.

As your problem is happening only when the engine is hot after you've turned it off (as opposed to cutting out) then it'll be something else. Possibly try the coolant temp sender first.

[legin]

It could still be a starter issue:-

I had a similar problem with my 04 1.9 TDi engine. ie. perfect cold start, but when hot, cranks 5-10 seconds before firing.

It turned out to be a poor electrical connection onto the starter motor (although to me, it seemed to be cranking fine, when hot or cold).

Apparently, when ECU senses the engine is hot, when starting, it does not start injecting deisel until the starter is turning engine over at 250 rpm or higher.

When hot, the engine compression is higher, so it puts a bigger demand on starter motor and battery, and hence makes it harder to reach 250 rpm threshold. (Supposedly a weak battery or weak starter can also cause same problem). Try cleaning & retightening connections onto starter motor, and battery...also try a hot start with jump leads to rule out battery.

[belly danser]

i have a 19.tdi 05 mk 5 vw golf. it seems to have a very simular problem to that of the golf talked about above. on cold morning it would seem to start easier but would still require the key to be turned on several times until the glow plugs light comes on on the dash and the pump in the tank comes on. it simply will not start until this light has come on. i'm told its a relay problem. the heater plug control relay has been mentioned but the where abouts is causing me trouble. i've tried moving like for like relays under the dash but to no avail.

can anyone shed some light on this problem.