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About a thousand miles in I'm still chasing a bit of a first start issue. If I start the car after its been sitting overnite or many hours - not necessarily fully cold - it will start - nice and quickly - then die. If I immediately give it gas it will stumble for a second then rev normally and settle into a decent idle. Idle becomes perfect not long thereafter which means this is not a question of heating up the engine or o2 sensor as the change takes place based on revving not heat, this happens inside a minute or 30 seconds when no appreciable amount of heat is being added. Today I tried not giving it any gas. It will start, die, start, die, start die... with the run times before dying growing slightly as I go.
I'm inclined to think about fuel pressure since the pump has no priming function with the stock DME relay. Bill pointed out to me that the Solid State Relay does have a prime function. I'm now wondering is this just a nice-to-have they threw in with the relay, or if the symptom I'm describing common, hence the reason for the prime function?
No I don't think I did. Because it idles perfectly once the first start issue is cleared I didn't focus on it. I suppose it may be sticky ?
Yes, that was my thought. They are easy to clean with carb cleaner. Spray in both ends to rinse out years of dirt. Keep cleaning until it rattles when you shake it.
...I'm inclined to think about fuel pressure since the pump has no priming function with the stock DME relay. Bill pointed out to me that the Solid State Relay does have a prime function. I'm now wondering is this just a nice-to-have they threw in with the relay, or if the symptom I'm describing common, hence the reason for the prime function?
Fuel pressure regulator? It maintains fuel pressure for a while when engine is not running and can be the reason for warm start issues. I replaced mine a while ago and it solved all warm start issues I had.
things seem to be improving with just one symptom remaining. On first start i can not reach idle without at least a blip of the gas. Once i give it some revs it finds itself.
have not read in depth about the regulator on this car but in principle I believe it is very similar to my BMW which I had a permanent Fuel pressure gauge hooked up to. I confirmed with the bmw factory manual that the regulator is not intended to hold pressure over long periods of time such as overnight.
this brings me back to the priming function of the solid state dme relay. Is that intended to cure exactly this symptom? Is this a ‘known quirk’ or a real issue.
I have a new solid state DME with prime for my 964 which was supposed to have gone into my 964 until the motor drop/refurb. You are more than welcome to try it.
Battery is by PO but looks fresh and performs well, my smart charger is able to bring it up to 100% so I don't believe its the culprit. I can look for a date code.
Thanks for the offer. I did a wiper relay swap with Bill in his driveway to confirm it as the source of my intermittent wiper issues but this issue presents differently over time (warm/cold) so I would need to borrow it for a few days... would you be open to that? Remind me what part of the state you are in? Happy to continue by pm.
Re SSR - I wrote to the company but haven't heard back yet. Confused that even the relay on the left lists "Primes fuel pressure for fast & smooth startups" under its features. Whereas the one on the right says "Pump-Prime" The Pump-Prime feature automatically runs the fuel pump for up to 3 seconds when the ignition is switched to the "On" position. This builds optimum fuel pressure before cranking the engine, insuring your Porsche starts as fast and as smooth as it possibly can."
Thanks to Chao I have a 3 second pump prime solid state relay on loan. Installed it and did not see a difference. Rob encouraged me to look closer at the battery which I did today - finding 12.3v. I hooked it up to my smart charger and brought it to 100%, 12.7v. I then disconnected the brake booster pump and turned the key to on three times to get the pump to prime for a total of 9seconds. Twisted the key and it lit up perfectly and settled to idle a-okay.
Next I need to check charging volts at idle/revs and drive around with my cigg lighter volt meter hooked up, if I can find it.
Once I'm satisfied I understand the battery situation I will definitely be swapping back and forth to my known good 'regular' DME relay to see if the pump priming contributes to cold starting at all.
I had the same problem today - car fired up immediately but died unless I kept giving it gas.
I hooked up the hammer and saw that I had a code for the idle switch, so I sprayed that whole area with throttle body cleaner and worked the switch a bunch.
It was then easy to confirm with the hammer that the idle switch was opening and closing as I worked the gas pedal.
04-24-2020, 11:08 AM
