Hi Folks,

TDI Octy Mk1, 140k miles, just had general service, timing belt due (but garage did not have time, so advised book it in for that next).

Following the service, it occasionally does not start properly, apparently after it has sat for about 1 h from hot engine - it has not shown this behaviour from cold start (yet).

The starter motor turns, but it seems not to find the mechanical load of the engine. Battery and start motor seem fine, but occassionally I have to keep it turning for a long time (>10s) before I hear the engine being moved and then it fires up OK. It is as if the thing which stops the engine from driving the starter is engaged before the engine has fired up. I base that on a) the starter has a slightly different sound as it turns, a bit smoother and higher pitched, b) there is not vibration associated with turning the heavy lump, c) as it starts to 'engage the engine', the sound changes to the one I am familiar with (for about 1-2 s), then it fires up as normal. I'm on my own so I have not been able to see what's going on in the engine bay whilst I am trying to start the engine.

I had a search around the forums and saw some things that might be relevant, but nothing very definite.

 

Any ideas?

 

Thanks,

Keith.

38 minutes ago, TurboTurbot2 said:

Any ideas?

Yes: They're even relevant so, in ascending order of cost:-

1. solenoid or HVLT cable issue
2. weak/old starter motor, or worn starter cog
3. worn ring gear. Replacing this is a gearbox out job, so you might want to get the flywheel and clutch replaced at the same time.

Thanks, Ken.

I got a neighbour to turn the key while I listened in: the solanoid gave a good solid click and all seemed fine (it is a very intermittent problem at present). Given that it only occasionally fails to engage the engine, I suspect it is not yet the teeth on the flywheel / starter cog, more likely the solanoid or plunger don't always work properly (presumably partial meshing would result in damage). Contacts and wiring all seem fine to me, though I don't think I saw ever part. There is a long waiting time for garage services at the moment, so the car will only be used when absolutely necessary.

Pinion sprag clutch failure, if you are lucky it may behave if you flush it through with a degreaser.

Sounds good, J.R. Given the intermittency, it seems very plausible that the one-way (overrunning) pinion clutch is going. Maybe a spring guide out of kilter or broken spring in there (ref: https://www.quora.com/What-is-the-mechanism-by-which-a-starter-motor-drives-the-flywheel-through-the-pinion)

It is going to be done by a very reliable workshop (Lauthers, Belfast) on 2nd November and I have said they may as well replace the whole starter system at the same time and look at the pinion and flywheel too (just in case).

I will keep the forum updated. MOT is on the 3rd, so they know I need it to start reliably for that.

Its usually a roller ramp bearing free to rotate in one direction (when the engine fires) but the rollers lock in the other direction, it looks like a needle roller bearing only slightly thicker, if you have not heard any squawking/graunching noises then it hasn't broken up & will probably be simply gunged up.