172 won't start

[rpsxr]

hi

i have had my 172 cup of the road for quite a while because i was converting it into a track car over the winter.
now today was the big day: seat in, harness and reconnect the battery. started on first turn of the key.
drove around for a bit, filled up the tank (about 35 liters) and drove a little more.

got home, switched off and after about ten mins, i wanted to drive it back into the garage.
unfortunately nothing happened.
i turn the key and everything lights up normal. turn further and nothing happens at all, as if the immobiliser is kicking in.
however, i tried to lock and unlock numerous times, but that doesnt seem to be it. although, the first two times of licking and unlocking, the alarm was actually beeping in sync with the indicators. never done that before....

at the third try, it didnt do that anymore.

however, i noticed that when i switch on the ignition, there's a buzzing sound coming from the black oval shaped part on the manifold. and when i switch off the ignition, it makes a sound like (pardon my technical description ahum) the sound of a multi-cd-changer when it is changing a disc.

anybody knows what this could be or could help in any way??

rgds robert

 

[Jay Payne]

Noise in the engine bay is normal. Its the DBW throttle body.

Does the led flash in the instrument cluster? That would be immobiliser fault. Have you checked batter voltage? Engine earth etc?

 

[rpsxr]

right, it starts when cold, but not when hot,
however, as i was over at a friends, we push-started it which worked. was told it then might be an earth prob?
suggestions?

rgds robert

 

[~nomad~]

weirdly when mine did the same thing a replacement key battery fixed it, then it happened again a few weeks later and a replacement car battery solved it. Car has been fine since. Is the trip computer remembering the miles? If not then the main battery is on the way out. Long shot but thought I would suggest it.

 

[rpsxr]

thanks.
i had the battery off for a good few months. then re-connected and that's when the trouble started. fully recharged the car battery then, because i had similar thoughts...
i have used the spare key aswell to rule the key battery out....

it will be in the garage tomorrow anyway for a lot of stuff so i will tell them anyway to look at the earthing points.

think its strange tho that it is only when warm....

rgds robert

 

[Stu-]

I had this problem with mine. It would sometimes turn over but not start. Check the Relays and the fuse box for corrosion. That was the main cause of mine. Replaced that and it's been fine ever since.

 

[rpsxr]

further update:

i've looked at and cleaned the immobiliser fuses and the starter motor plug.
i'm tempted to think still it has something to do with the black thing (airflow sensor) on hte inlet where the (filtered) iar goes into the engine. it has just been making weird sounds. just made a clip and hope that somebody can tell me is this is normal or not.
buzzing sound (with initial clicking) is ignition on, and all the clicking and quiet after is ignition off. so no turn over whatsoever but does start with push....

 

[rpsxr]

let me know if the link doesn't work

 

[Stu-]

Mine done that. The starter motor relays were all corroded and there was a 30amp fuse on the fuse box popped. I'll try and dig out the pictures i took of it.

 

[rpsxr]

thanks stu. was it also only when hot?
i just started it no problem at all this morning.... but then, when it it hot it will start playing up....
it is in the garage, so hopefully they'll find it. but would be nice if i could send them in the right direction to save a bit on their research...

rgds robert

 

[Stu-]

Mine done it constantly. It wouldn't start what so ever. The first few times it done it, I could bump start it. Then after that it wouldn't start what ever way I tried. I've had a look for the pictures but can't find them. The main cause was the relay box. All the terminals were corroded pretty bad. Replaced both the fuse box and the relay box and it started first time.

 

[rpsxr]

right, just to finish off the story for everybody who helped me here:

garage found the 'trigger terminal on starter motor' corroded. doesn't really mean anything to me but hey. they've cleaned it and seems to be working fine now. i have been advised to probably replace in the future....

thanks for all your input,

rgds robert