Z3 Cranks but sometimes does not start (more than 1 problem solved)

[bonbon]

Ok - finally changed out the fuel pump. Surprised to find that the pump’s one way valve is fine. So I assume the fault was a weak pump. Perhaps there was not enough pressure to start reliably - but was fine to drive.
All ok now - you learn every day.

 

[the Nefyn cat]

A happy christmas, then.

 

[bonbon]

Next morn - not ok.
What I did learn is that it ain’t over until the fat lady sings. Problem still persisting. Nothing to do with the pump or its return valve. Will continue the search. Cranks - but need to play games for it to start (ps - it’s not the starter either - it was just sorted recently).
Any news bright ideas?!

 

[bonbon]

Ok - this is embarrassing so please nobody take the P.
I did a bit more research (which I seemed to have missed in my search 9+ months ago) and found that vac leaks can cause cold start problems.
Had a closer look at my M44 inlet piping and found a cut on the underside of the smaller pipe that exits the MAF boot. Pics attached.
I’ll know next cold start as I’ll tape it up until I get a replacement pipe. It’s driving me crazy.

 

[bonbon]

The fat lady sang. All sorted. It was the non visible tear in the pipe. ( pic above).
End of a 10 month saga
To be fair - I also removed and cleaned the idle control valve to feel useful. Not sure if or how much it contributed.
May us all have a good year!

 

[the Nefyn cat]

All sorted

Yeah, right.

But there's nothing fundamentally wrong with optimism.

 

[frankmasterjam]

where is the starter relay and what does LHD mean?

Ok - first 24 hours was erratic - but seems to have settled down.
Next steps:
1. Continue to monitor before deciding to remove the one way valve (as the way I put it in there is a 180degree bend in pipe and I fear at some point it will bend and limit flow).
2. Try replacing the starter relay - next to my left knee (LHD)
3. One other failure mechanism reported has been the ignition switch. I’ll see how things get on.
4. For completion: the camshaft sensor has solved this issue for some (even though no codes were thrown)
5. If/when I remove the one-way valve, I guess I’lll need to replace the fuel pump as the one way valve is failing.
I’ll update.

 

[KASPar]

where is the starter relay and what does LHD mean?

Left Hand Drive

 

[bonbon]

Ok - not as bad - but the problem has now appeared again, although not as bad as with the torn pipe. If I don't crank exactly one second after the lights on the dash go out, the car won't start. I need to wait a bit and try again a few times, with the hope the engine does not flood.
I now suspect cam and crank sensors - and will update as soon as the problem is solved.