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Warm Start Issue

medazzling

medazzling

PCGB Member
Member
Hi
Having had a starter motor replaced some months back (as per separate recent thread) I have recently noticed that warm starts are getting more difficult - i dont think this is related to the starter motor change as the car has started well since the starter motor was replaced, it must be 50 starts since that point and until I had noticed the issue in recent weeks.

Starting from cold I think it feels ok, circa 3 seconds of cranking, i am debating in my mind if this very slightly slower to fire? Once the car has been run and heated through, if I restart after a short stop, maybe a refuel, the car starts but it takes just a little longer to fire than I recall of old. If I leave it for say 30 minutes then the restart would be difficult, strong turn over but not firing. If I push the accelerator this seems to help it fire and then it runs without issue. No issues that I can feel when running.

The car has always been superb on warm restarts, literally a very quick crank and it fires, no need to touch the accelerator.

Pretty sure this is going to be a return to garage as I have limited tools etc, but I am interested in any guide points before I go to the garage, or maybe there is something simple you think I should try before I go?

(Did cross my mind if this could be DME relay related for example? Beyond that I did read a few threads on fuel vaporisation and engine temp sensor issues but not things I could really check as far as I could see)

Thanks as always
Darren
 
Darren, I had exactly the same issue with my 1980 Porsche 911 Turbo and the problem got increasingly worse - fine cold, or fired up with a few minutes of stopping - but leave it 20 minutes and you’d have to wait 2 hours. This all occurred, frustratingly, on a European road trip. It was the fuel accumulator! Sounds to me to be the same problem you are experiencing. Regards, Martin.
 
I'm confident in saying your car uses k-jetronic injection which is exactly the same as my 924 and these are well known for warm start issues.

Usually caused by the residual fuel pressure dropping in the system too quickly after turning off the engine so the fuel lines are just full of air and cars don't like starting on just air. Usual step is to get a set of k-jet fuel pressure gauges which hook up between the metering head and the warm up regulator then monitor coldwarmsystem pressures and in this case residual pressure after you turn the car off which should hold strong for 20 minutes plus. The accumulator as mentioned by Martin is literally a spring powered unit that holds extra fuel so when you switch off it keeps the system pressurised, if this is faulty the pressure will drop with nothing to top it up with. There is also a one way valve on the fuel pump so when it turns off it stops fuel draining back into the tank.

If you have a garage who understand older tech and can do more than read a computer screen they should be able to pin it down quickly enough. I'd be surprised if its linked to the starter motor but nothings impossible!

Good luck
 
Great guide thanks guys
I spoke to Sid at Porsche Torque today, in fairness he was busy but his initial response was my model didn't have an accumulator but he was aligned with the thoughts here that pressure was probably dropping in the system. For me the accumulator made sense, he did mention the fuel pump valve as well.

He felt that these issues sometimes correct themselves so worth trying to run it a few times over the coming weeks to monitor. The issue came on after I was out on one of the crazy hot days a few weeks back, the car was with me at an event and was truly toasted that day and driving home. Feels a long shot but OK.

I will monitor and read up more on the suggestions, see where this takes me - thank again
 
To be fair mine occasionally thows a wobbly and won't start when hot so I get the gauges out, test and it's all ok and works faultlessly for months. I think it does it to just prove that I'm not actually in control ??

Nice to see a garage not instantly want to charge you money and offer sensible advice.


 
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