Hot restart / no start '99 996 Mk1

Got into the upper 90's yesterday, car had been sitting outside a couple days without being driven. I hopped in late in the afternoon for a 20 mile run to the store, started right up. Mostly uneventful run, except one little blip or hiccup exiting a low speed corner -almost like I was in too high a gear. Barely worth mentioning I think. I went in the store, 5 minutes. Interior had barely cooled down on the way over. Came back out and all seemed normal except no start. Turns over fine, all lights and stuff looking normal, just spins like I'm not getting fuel. I did the clutch all the way to the floor for sure thing, even removed the mat. Key switch felt fine, had oil pressure building but I wish I'd looked at the tach while cranking. Don't think it's a key switch/ batt/ alt deal. I made the call and had it flat bedded to my indie, 15 minutes away. Of course it started right up repeatedly over there. No CEL.. So, my first instinct was CPS crank position sensor? Clutch safety interlock switch? Fuel pump? It's been a great car, no issues before or recent repairs, it's stock and maintained well. What say you guys?

Hey Gulliver! I've had that happen as well when the engine gets particularly hot from hard driving or a hot day and I shut it off for a short time as you did. It cranks quickly but won't catch as it usually does. I attribute it to the fuel percolating from heat soak and find that cranking it for about 3 or 4 seconds whilst lightly pushing the gas pedal will get it to catch and start. Once its started I keep the rev's at about 1500 for a few seconds to feed the hot fuel through the injectors and then it will idle at normal RPM and be back to normal. It may be some other underlying problem that causes this condition but it works for me on those odd occasions.

Mine is sometimes slow to catch after a short break following a hot run, but not to the point of not firing at all. Check the ground straps. Check for corrosion on the + terminal. If you can find access to a Durametric, scan for any sensor issues, like the CPS as mentioned above. Check the fuel pump relay...

Next time it happens, watch the rev counter -does the needle move/bounce while cranking ? If it does not or only moves erratically ,it may be the CPS deteriorating.Heat soak just makes it worse.$100 easy fix with a generic Bosch part. # 0261210204 ?

Amazon is the best deal with free shipping http://www.amazon.com/Bosch-0261210204-Reference-Mark-Sensor/dp/B006K8ZHOU http://www.amazon.com/Bosch-0261210204-Reference-Mark-Sensor/dp/B006K8ZHOU

If the car starts when the car is cool and doesn't when the car is hot it's likely the starter.

To clarify, when you went to start it, it was making a "click click click" noise like it was trying to turn it over? If it clicks, but didn't start it could be the starter or the ground at the passenger side cam cover. That ground gets loose, which causes a symptom like this when it gets hot. If it didn't click it could be the clutch switch. -Luccia

OP indicated that the starter is engaging, but the engine isn't firing. If it was starter heat soak, I wouldn't expect the starter to be working normally.

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Yes, as stated, it spun over fine just wouldn't run until 20 min. later back at my indie. Started right up several times, no problem. I ordered the cps and will keep you all informed. Thanks for all the tips and suggestions, you guys are a great resource and a wealth of knowledge. And smarta** comments. I love it.

I have to jump in here, I am fighting the same thing. I have noticed after the engine gets to temperature and I make a stop for longer than maybe 15 minutes it happens. I also pedal it slightly while cranking and it has always started, I do however get the condescending looks from others. I have taken it step by step in replacing items one at a time to find the culprit, of course starting with the cheapest items first and I always hold on to the old part. I have owned this car for almost a year now and never had this issue during the winter months, but once we began to get the 80 - 90 degree weather it has began. I did get lucky one day though, I was checking the fuel pressure after the motor had warmed up and once I had hooked the gauge up I checked the pressure with the key-on and running. Tried to start the car and it wouldn't start, checked the pressures and everything looked okay. I will say though, the measured pressures were reversed from what the book says they should be. Cant remember the exact numbers but if the book says like 50 PSI with the key-on and 45 PSI with the engine running my readings were reversed. I also have the CPS sitting on a shelf to install, that was the next thing for me to try.

I had the same issue last year until finally I got stuck and needed a jump to make it home. Turned out my original battery was worn out, so I replaced it with a new one and haven't had a problem since. Does seem odd that it was the battery, but the problem is gone.

With these cars it seems a that weak battery brings out the electrical gremlins. I would test the battery so that you can exclude it as a cause.

Fairly certain my battery is good. I replaced it maybe 6 months ago, previous owner had the wrong size battery in it, Walmart special, I think the sticker said $45. It could be the a defective battery though, seen brand new batteries go bad in a few days.

Check the evsporative valve next to the throttle body. When they get stuck, it will let too much air in during start up and the engine won't fire. Mine was like this. Easy to check with a 9v battery and blowing through it.

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Thanks for the idea. Checked mine this morning and it was sticking a lot with the 9v battery. Cleaned it until it was clicking with every touch. Time will tell now. Thanks again.

Brilliant simple zero cost test -your lungs + a smoke alarm battery ! Thank you for suggesting this . I think the part in question is : 96420106200 ?? Item 8a in this diagram? http://www.deroure.com/diagrams.asp?...SMO=0&ST=&SC=0

There was a member, Shark Attack, that was fighting the same issue a few years ago. I haven't seen him post for quite a while, but do a search with his name. It might help you out.

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It's #30 here and the official term is regeneration valve. http://www.autoatlanta.com/porsche-p...section=107-10 Yes, his case was quite interesting. His problem was actually the coolant fans not running, which led to high engine temperature that caused the starter to seize. All the lights dim when he cranked as the seized starter basically shorted out the battery.

crank position sensor

Yes, #30 from two posts above.

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Can you explain in more detail what you are describing? I have had this problem intermittently as well.

Look at the #30 item in the parts diagram link above. Remove it, apply 9V to the two pins and listen for a click. Do it a few times to see if the response time slows down or not. Then, do the same while blowing into it. It will open and close as the 9V is applied. They usually gum up a bit.and stay open. If it does, spray some brake/carb/throttle body cleaner into it and let is soak (plug the other end with your thumb). Then, drain it and check the opration with the 9V battery again. Whe the gumming up material is gone, the valve will react quicker and be louder too. Also check and see if air stopped passing through it when it's closed.

^awesome. Thank you for the details Imo000. That makes sense. I have done a lot of wierd things for my 996, but I think "blowing into the regeneration valve" will be an all time high (or low) for me ��. .