hot66

Just got back from LeMans and had 2 little issues arise


1. early 4am, weather cold & damp, get up start the car and drive it off my mates driveway onto the road where I wait for him ... car then promptly cuts out. All electrics etc on. Car won't restart , all electrics on & starter motor turns etc but engine wont catch. open up fuse box wiggle the relays in hope , shut fuse box & car starts 1st time .... off to LeMans we go Over next 1000 miles problem never happens again

This problem has happened once before a few months ago , again early morning cold & damp , start car drive off , 2 mins later car cuts out. Wont restart , engine wont catch ... 4th attempt car restarts & is fine every time since.



2. On way back from LeMans, good 6 hours of hard driving so engine nice & warm , get to the tunnel crossing. Park up & leave car for 40 mins. Restart car no problem, drive 2 mins around to the loading que, switch off car. 5 mins later go to start the car & it struggles to catch , 2nd attempt struggles to catch & then does ( feels like 2.4S does when its got too much fuel on start up )

Same thing happen again, 4 hours of driving later, stopped to fill with fuel, car started again fine, went round the corner to McDonalds ( I know, but i was starving ) , turned engine off , ate crap food, went to restart and again didnt fire up on the button. 2nd attempt with a slight touch of the throttle & it did

Next restart another couple of hours later was fine


Any ideas ? DME relay? temp sensor ?

iangray100

Try the ignition switch as they play up over time

fasterlaster

I have the same behavior sometimes. Nothing consistent enough to diagnose, but I do keep a DME relay with me. I should swap it out and see if it completely goes away, but apparently I'm lazy.

LM964

Interesting issue. Kinda have had the same last year to LM. Long trip fine, park up for 5 mins then the car won't start al all until about another 10 mins of cooling down. Have a suspicion it's tied in with my immobiliser sensitivity to prolonged journeys and heat.

However, have you swapped the DME out completely and tried to replicate issue? Also, what if you disconnect battery for 10 mins or so in clearing down any DME control unit volatile memory. If it's persistent and partly predictable a trip to your indie and the Bosh diags plugged in for any fault codes reading? Post up any findings...

boxsey911

Hot starting is a common feature. It goes into a sort of no man's land mode after leaving for a few minutes and needs a bit of throttle to start it. If you re-start it immediately after switching off or leave for about 30 minutes, it'll start up as normal.

I'd say the cold/damp start issue is likely to be the DME relay acting up.

hot66

thanks

That reassures me a bit. Interesting to hear the hot start thing isn't that uncommon .

I'll swap out the DME relay for my new one and see if the cutting out problem occurs again

seperate to those issues, had a great run down to LeMans, mostly cross country, along with my mate in his 1971 2.2E .

Porsche winning overall topped off a great road trip

justin-in-athens

Replace your fuel pump check valve located on the line to the motor at the fuel pump. This check valve keeps fuel primed in the line between the pump and the motor for a period of time when the car is off.

The motor is looking for a leaner mixture on hot starts because the CHT sensor is telling the ECU the car is already hot and therefore does not need the full rich mixture it would require from a cold start.
This is a common problem and an easy fix.