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.

 

[bonbon]

The suspicion was correct - the starting has become a bit more erratic - especially 30-45 minutes after turning off the engine (when the sensors are hottest - cuz no cooling).
Replaced the sensors and all seems well - (48 hours). Seems this failure mode is well known (It's my daily - now at 485k km)

 

[bonbon]

Ok - mostly fine - but it occurred again with an engine which was switched off ~45 mins ago.
Seeking further - all above mechanisms are correct - but bottom line, it appears that with an aged car the starting procedure is critical.
If one does not do it correctly the fuel mix is messed (flooded) and it takes time for the gas mix to settle itself out.
Need to concentrate when starting.
1. Key ON - position 1
2. Wait until dashboard lights go out.
3. Wait 3 more seconds
4. Crank engine.
Doing it faster messes things up and it floods.

 

[bonbon]

Nevertheless my starting is angain erratic and the saga continues. 🫣

 

[ChrisD]

Sorry haven’t read your entire thread so don’t know all that you’ve tried but if you’re convinced the issue is excess fuel then replacing/cleaning the fuel injectors might be a good call.

 

[bonbon]

I now suspect an erratic fuel pump relay. Will have time to swap on Sunday. I must admit I feel like a real tosser. Instead of identifying the problem, I changed things over the 2+ years in logical order and each time I thought it was sorted because of the of erratic behavior.
Not surprising being a Spurs fan ....Spursy.

 

[FLZ_Boy]

Not sure if the euro Z3's had a fuel vapor breather located near the front side (LHD side for US Spec), but this emission item we had in the US could cause fuel vapor lock and cause hard starts.

 

[bonbon]

Ok - seem like finally after about 2 years of erratic pain found the problem. Removed the fuel pump relay and now seems ok - so far . It is located in the left footwell above the speaker. Pic attached. Also have a look at the removed relay - the legs look like crap and the relay contacts are oxidized. Looks like the culprit. Under the assumption that it's now sorted - it kills me to see that I wrote on March 8 2004 that it could be the fuel pump relay (which took 12 minutes to replace and a total of £19). I recommend to replace if it's your daily - pn 61368373700
Hoping we now move on...
One week later - appears that the fat lady finally sang. Two frigging years of futzing around ....and replacing stuff..