MK3 1.6 AFT engine 100bhp (non gti ~ sorry ;) Strange starting issue ...

[mattymatt]

I've owned my golf for ~8 years (160k+) and sorted all problems so far but this one has me stumped !

The car will start 1st time every time in the morning (8am), but leave it for ~10 hours (6pm) and it doesn't *want* to start - but will eventually (after a few seconds) !

I've replaced the sparks, dizzy cap, rotor arm, ht leads, coil and starter motor (it was on it's way out before this), but it's still playing up.

All the parts were from GSF all were BQ if available.

I've checked the battery (12.7 to 12.8v after a run) and the voltage with the engine running between the engine block and the neg terminal 0.02v ~ so earths seem ok.

Relay 30 gets nice and warm too - the car runs sweet and if I switch it off after having trouble starting it, it will start up straight away without any hesitation.

It's bugging me that it starts quickly first thing in the morning (after standing outside all night stone cold), yet when the air is warm in the afternoon / evening it doesn't want to.

It catches after a couple of seconds - but I can tell that it's struggling to turn over. The starter is firing a ok (I can hear it), relay clicks etc and I've tried a different key (incase the immobiliser was interfering with starting).

I'm really just wondering if there's anything I have missed ? or am I doomed with a car that sleeps in the afternoon ? 

cheers

[mattymatt]

Just been out to the car again - it started instantly ie within 0.25 of a second - no waiting for a while to catch etc or missfiring ~ bloody instant ! (as expected).

It's currently pouring with rain and has been standing in the rain all night cold and wet, yet instant start.

I can guarantee by this evening it won't want to start and be back to sounding like a machine gun (until it catches).

I wonder if it's anything to do with air temperature ? as it's cold this morning, yet in the afternoon it's warmer, drier or possibly more humid ...

Is air humidity the answer I wonder ?

[lemski]

Temp sensor? I know that the renaults suffer with it and its the temp sensor. Just a thought

[mattymatt]

I had previously replaced the coolant temp sensor (the one on the engine block ~ yellow collar) when I replaced the radiator this year   It was previously reading low on temp even after a good drive, so I did it at the same time   I didn't replace the one on the radiator ~ wish I had now

[lemski]

Not a faulty battery is it. Low on amps when its been sat sometimes. My old battery was like that. But a lot worse, would start the car and 5mins later wouldn't start it