911 hard to start when hot after leaving for 30 minutes

[shawn911]

Hi, I had the engine and box in and out of my 911 3.0 sc more times than i can remeber, ive made my own special cradle and high stands that makes this job a an easy one man thing, thing is ive always had this problem, my car starts from cold fisrt time every time, if i stop it when hot then restart straight away or say up to 5 minutes it will go staright away perfect, but if i leave the car for more than half an hour when hot it just will not have it, then eventually its stars on 1, then 2 cylinders, then the rest kick in, ive checked and changed everthing i can think of, but this problem still haunts, plus i look a total dickhead when my porsche wont start outside a public place.
Does anyone have ideas on this????????????

cheers

[S ECU Repair]

Hi,you should replace the fuel accumulator .i'm sure that will fix your problem.
Good luck.

[dweymer]

haha that *********s porcha won't start; been there, done that!


You need to check the fuel pressures, get the gauge and check the cold, warm and system pressures, there is also a pressure down spec. You could have a leaky injector or a multitude of other probs. Start with the pressure testing.

[shawn911]

cheers guys, the acumulator could be a good lead as its one of a few things i havnt renewed , i have checked all the components of the k jetronic system,plus changed the warmup regulator plus many other bits including new injectors new starter injector but to no avail, when she´s running shes so sweet, doesnt miss a beat, thats why this is driving me crazy, i also changed all the rubbers on the inlet plastic box unit, the ones that connect the 6 ally inlet tubes, still the same, new high pressure fuel pump fitted too, still the same, ive been told that it may be because i live in spain, a hot climate, and that i´m getting fuel vaporisation!??

Cheers again

[targa80]

Originally Posted by dweymer

haha that *********s porcha won't start; been there, done that!


You need to check the fuel pressures, get the gauge and check the cold, warm and system pressures, there is also a pressure down spec. You could have a leaky injector or a multitude of other probs. Start with the pressure testing.

I Agree, don't jump to conclusions your problem requires that you test the fuel system with the pressure guage setup. Hot start problems can be caused by many different things including the check valve on the fuel pump, fuel accumulator leaking fuel injectors, etc.

[shawn911]

i´ll check all the fuel system tommorow, that could explain why when it eventually starts from hot it fires on 1 then after that the rest kick in untill its sweet again.
Thanks for the replies

Shawn, 1979 911 3.0 sc coupe
1 976 911 2.7 targa

[bluesky]

i had this same thing happen.

mine was the fuel injectors bleeding down because of the the heat soak from the hot engine caused the injector(s) to slightly crack open.....the injector spring(s) had weakened over time and couldn't maintain the fuel pressure under the heat.

in my case, if the car sat all nite and i briefly started it to move it and then shut it down without the engine heating up, then there was no bleeding down of the fuel system and the car would start immediately the next time i turned the key....even hours later. but, if i ran the car to operating temps and then shut it down, the heat soak would cause the injector(s) to crack open and the fuel system would lose pressure. i would then have a long start condition as the fuel pump reprimed the system.

[shawn911]

Hi, Great, someone has exactly the same problem as me, i can start my car all day long first time everytime from cold, but as soon as i get it to normal hot use and leave it for a while, she refuses to go, i have to keep cranking over in bursts of say 2 seconds then leave it 3 seconds then 2 again until eventually she will fire on 1 cylinder then the rest come in after, i must say that she behaves better at nightime than on hot days.
cheers, guys, i think i´m getting somewhere.

[kepperly]

If you don't want to worry about WASHING DOWN a a hole with a leaky injector, I would send all six of them to WitchHunter and have them rebuilt,
cleaned and pressure tested. I couldn't believe how smooth the car ran.when I put mine back in.

Keith Epperly
87 slant nose turbo look carrrera cabriolet

[Hoffmanmotors]

Usually its the fuel pump check valve, might as well buy one and change it. A very inexpensive fix. Fuel pressures should be checked first instead of dumping money on expensive CIS parts.

[bluesky]

shawn,

i went back and re-read your posts and noticed that you had mentioned putting new injectors in already. if that's the case, then re-building new injectors probably won't fix the problem. something else is occuring if those injectors are indeed new.....

[john walker's workshop]

i the mean time, you can help it start by pulling off the air filter and with the key on. raise the sensor plate arm to establish fuel pressure. you can feel it build up as the arm is lifted. not too long though, or it can flood. just a couple of seconds until you feel pressure.

[shawn911]

ive tried 2 brand new fuel pumps by the way, same problem!
cheers to everyone for the help

[porsche930dude]

Its sounds to me like your accumulator same thing was wrong with mine when i bought the car. I changed the fuel pump check valve first like people suggested but to no avail. Plus that was a nasty job. You need to clamp the fuel line to keep the tank from draining on you and if your line is old and dried out of corse it will leak after you do that. Then theres no way to stop the gas but to plug it with your thumb while you switch the lines. But in the end you end up with new parts under there as well as a gallon or more of gas on the ground. But hey it dries up quickly and i didnt need those extra brain cells anyway

[81SC]

My vote is for the accumulator as well. The symtoms you describe were exactly the same as mine, would sound like it was running on 1 cylinder, then 2 cylinders & so on until it fired on all cylinders after a hot start up. It always sounded like the motor was flooded, but after removing the spark plugs to check after a hot shut down, the plugs never looked like they were fouled.
To check the accumulator, just remove the return line on the bottom of the accumulator & if fuel comes out, the diaphram inside is the problem.

[jwetering]

Originally Posted by john walker's workshop

i the mean time, you can help it start by pulling off the air filter and with the key on. raise the sensor plate arm to establish fuel pressure. you can feel it build up as the arm is lifted. not too long though, or it can flood. just a couple of seconds until you feel pressure.

Yes - this is what you do until the new part (fuel pump with integrated check valve) arrives.

Of course JW has the answer - funny though it was quite a few posts before the it came up. I think a few years ago this would have come up sooner. It seems the problem disappeared long enough for most people to forget. Perhaps a sign that these 911's are starting on their *second* round of fuel pump replacements.

[shawn911]

Hey guess what ! problem solved, i fitted a new accumulator, problem gone, she starts now from hot instantly

Thanks for the advice guys.

[na2ub]

Originally Posted by porsche930dude

Then theres no way to stop the gas but to plug it with your thumb while you switch the lines.

Heh, heh, heh. I've never done that.

[Joe Bob]

Mine was the check valve as mentioned a few posts up.....

[mikedsilva]

reviving an old thread... which line from the accumulator, goes to the fuel filter... the one from the centre, or the one from nearer the edge?

What symptoms would present if they were hooked up the wrong way?
The reason I ask, is that I have the same problems as the initial poster here... but I have a brand new accumulator fitted.. and still no better.