Greetings fellows,

Saturday i bought my first Porsche, an `89 928 S4 autimatic. Tested it and looked through all parts before i bought, and started it approx 10 times before i paid. No problems. The engine was then warm all the time. Drove it home, 500km without any problems. Happy camper.

Sunday i started it up in the morning, no probs. Drove it to a nearby gas station(6-8 minutes) and washed it outside. When i was finished it would not start. The starter engine runs fine, but the engine will not start. Tried a lot until there was no more battery. Removed the plugs and they was as a result of my trying, wet in fuel. Replaced the plugs with new ones and tried again(with battery power from another car) but it would not start. Then i waited until dawn(6 hours) and tried again. It started and runs fine. Drove it for 1 hour to be sure there was no problems. I then assumed something got wet in the washing process, and i thought this would not happen again, so i was not that concerned.

Today, monday, it starded fine in the morning again. Drove it to the gas station and washed it inside. AGAIN, not starting afterwards. Not fun. I am now waiting for the engine to get cold so i can give it another try.

My conclusion is that it starts fine cold, and fine warm. But after a short trip and a little wait (1/2 hour) it will not start.

I can mention that fuelpump, waterpump and rotorcaps were replaced 25000km ago.

The person i bought it from says he had a little starting trouble when he first got the car, but after this he have started the car with the gas pedal half to the ground. He claims that with this he never had any problems. He told me this after i got the troble and called him so i did not know about this when i bought it(it isnt supposed to be like this right?). I have also tried this when it will not start, and it does not help.

Anyone have any idea what the problem might be?

Thanks, from a little sad first time Porsche owner

Paal.

 

First off, welcome.

Sorry to hear about your issues. Sounds like something is getting wet. Did I read correctly, that you washed the car each time this happened?

 

Hello, thank you.

yes. but not the engine. first time, exterior. second time interior. so i dont think it has something to do with that.

I must say, the car is just awesome to drive and i love the power! when it starts.....

 

Wow.. this is an EXACT same story about a year ago... but that guy bought the car, drove it to a gas station and it woudnt start. let it sit and it started back up. I just wonder if its the same car and the problem never got fixed. Good luck

 

it is not the same car i think, as this is a Euro spec.

If the engine is warm and have been running for a while, and i stop it for 15 minutes it starts fine.

It has only happened when i cold started it, drove it just a little while, waited 1/2 hour and tried to start again.

I have only had the car for 2 days, so i will post if something else happends, but this is the experience i have at this time.

I have read a lot of starting prob posts here, but i can not find anything that sounds like this. Looks like most problems is related to never starting at all.

Since it starts when cold and warm, but not in between, it is probably not a relay issue?

 

update:

Got the car running now, as expected.

What i did not mention earlier was that last time after i got it running it was vibrating and running very badly and the fuel consumption shows is uses A LOT of fuel. A battery reset(5 mins off power) solved this and the car was running smoothly again. I did not mention this because i thought it was a result of all the cranking at low battery.

but the same thing happened now. it runs badly though not as bad as last time. Same thing, removed the battery pole for 5 min and it is running like a charm again.

Also i went to fuel up. Engine warm, fueld up and it starts right up.

So i conclude that if i stop the car before it reaches work temperature, i can not start it again until it cools totally down. strange.

Any ideas?

 

The only thing i can think of is the LH is going south and something in the LH is heating up. (LH=Computer, and not an uncommen problem with age in a 928) You are going to have to heat it up, get it in a non-start state and find out why it will not start, spark? Fuel?

 

I would try the following:
- clean MAF
- clean O2 sensor
- clean injectors (try adding injector cleaning fluid to your gas first)

 

okay, thanks.

MAF is hmm...map air fuel? or something? and where located?

O2 sensor located?

I will also try injector cleaning fluid.


I spoke to a guy with a Porsche workshop not that far away, he told me he could do a diagnose while i wait if i step by, so i will do that. But maybe try these things above first.

 

MAF = Mass Air Flow sensor. It's located under the airbox /air filter. You have to be careful with this because it's very delicate. Here's a link to a page with some pictures. http://members.rennlist.com/v1uhoh/underthe.htm

O2 sensor plugs into the back of the cats.

Do a search on both items here on Rennlist and you will find a lot of information.

Then again a diagnosis at Porsche using the Hammer will be quick and you'll probably find out the cause faster..

 

Stuck ISV? try the WD40 trick into the breather hose that goes under the intake on the driver's side. Search -- there are pictures from many discussions on this. If that is it, the only permanent solution is replacing the valve.

 

Hello Paal
How many km on your 928 ?

What is the water temp (shown on LHS of dash) when the car is not wanting to start ?

 

ope3n up the fuse panel cover and with a light look up under the dash your looking for water stains that might be dripping from the bottm of the blower grill , this water dripping onto your CE panel will kill your relays, you should also remove every fuse and relay looking for corrosion and seeing if any might have filled with water, also check the hot post under the hood near the shock tower there should be a plastic cover on these and it might have gotten corroded as alwyas disconnect the battery when working on the electronics. And charge the battery with it disconnected fromt the car. DONT try to jump the car with a flat battery as you may damage the LH/EZK computer.

 

Okay, i will try the WD40 trick. Found the thread about it.

It has 274000km, but the cambelt collapsed at 250000 and the engine was refurbished at a Porche workshop for A LOT of money, so it should really be ok.

Water temp was about 70 . But, it does not start cold either, without putting the gas pedal halfway down. And if i try this once (without gas) and dont succeed, i can forget starting it in any way for some hours.

I removed the MAF sensor to clean it, but the strings looked good as new so i did not dear to do anything about it. Only cleaner i found was electric cleaner anyway. Not sure about how smart that would`ve been...

I have also put a bottle of injector cleaning into the fuel tank now. Do not know if that made a difference yet.

 

AT that mileage, the MAF could be the problem, if it is the original item. It will be badly aged.

You can't identify MAF ageing by visual appearance, or simple resistance tests.

See http://www.jdsporsche.com/main.html and then read the MAF FAQ from the link at the bottom of the screen for more information...