backitoff

Hi guys
My 964 C2 has decided not to start when hot. I recently went on an 80 mile journey and stopped for fuel and it refused to start. Cranking was fine with loads of battery power.
After about 30 mins I tried again and after considerable cranking she lumpily fired up then cleared her throat and ran fine.

I had already replaced the crank sensor, dme, and ecu due to a previous refusal to start period.

So, after further investigation I have just replaced the fuel pressure regulator. Started up from cold no problem. Took it for a 10 minute drive, switched off and hey presto it wouldn't start.
Fed up to the back teeth with it at the moment. I can live with the little ongoing repetitive issues but i cant suffer unreliability.

Anything i haven't thought of, or pointers in the right direction would be greatly appreciated.
Thanks

Turbohead

Head temp sensor ???

DME Relay ??

Elliot

backitoff

Replaced head temp sensor OPC 1 year ago. DME new from OPC.

Tmistry

Delete / best of luck tracking it down.

klokwerk

Hi there....wondering if this is a temp sensor problem.
I'm new to the 964 but not to general automotive troubleshooting.

If it starts when cold but not when hot coupled with the symptoms you've described, it sounds like a temp sensor issue where the ECU things the motor is cold when it's hot and dumping too much fuel stalling it out.

A quick search turned up a few threads on the topic of cold/hot start issues and it sounds just like what you're dealing with.

Good luck!

Feudal Serf

You should check the idle microswitch to make sure there is good contact. Recheck when there is a warm non start. Throttle cable can fail to fully release causing poor contact.

Good luck, hope the issues are resolved soon.

Cheers
FS

lushlife

Might be the fuel pump check valve.

backitoff

Is the Fuel pump check valve part of the fuel pump, or located somewhere else?
Thanks

Duck

I am pretty sure it is connected on the outlet end of the fuel pump. I am no expert, but I would think issues with the check valve would be hard starting after sitting (fuel pressure to rails drops and would need to build). Maybe if the fuel is completely draining from lines it would take some cranking to build enough pressure.

LM964

Charcoal cannister under the left rear wing. Part of the fuel evaporative system and known to cause rough idling or starting when hot. Had the same issue. I changed this and no further problems. I can provide more detail later today...

LM964

Had warm engine erratic idling/starting problems a few years back (ISV fine). Found out in the end it was the dud charcoal cannister. Changed that and all good.

From the workshop tech spec; the charcoal cannister is the main component of the 'Evaporative emission control system'. Here's the actual mention - "A faulty evaporative emission control system can cause hard starting when warm, erratic idle, poor acceleration if fuel vapours are drawn into engine at the wrong time. Restrictor prevents rapid cannister purging"

And that's it. It then goes on the mention that this usually only affects driveability when the engine is warm or ambient temps are high. Cold running issues not normally any association. I thought it prudent to replace the cannister anyway after 24 years and 100k plus miles of use...

boxsey911

Good find Marcus, never heard that one before. As you say, how many of us have the original...most I would think! Mine too can be difficult to start when hot but have always put up with it as one of those things.

Tmistry

This is really good info. I'll be changing mine over Christmas.

LM964

Cheers. The bummer is that quite likely the useless bracket that holds the cannister (bit like a can of deodorant) has evaoprated under years of heat and moisture or at best hanging off. Had to cut mine out as the fixings were competely concreted in corrosion. The bracket wasn't cheap or easy to get a new one - OPC had to order one from Germany.

backitoff

That's really great info definitely worth a try, thank you!
I have spent a lot of time under my, car but can't recall seeing anything like a charcoal cannister under the left rear wing. Would you have any part numbers or images so I can order from OPC.
Thanks again.