am

I have exactly the same problem than the one a guy posted for lately but my car is a 1979 instead of his a 1988. I read it and have an idea of what can cause this problem but parts are not alike and I'm a bit confused.

The problem is that my 928 starts perfectly well when cold and the same when restart. If I try to start after 20 minutes when hot. It does'nt start. I succeed with the gas pedal to the floor but it takes quite a long time of starting.
I read somewhere that the temps 2 sensor could cause that problem.
Could it be the cause of my problem on a 1979?

See my photo: http://img545.imageshack.us/img545/3...tempsensor.jpg

Am I checking the right sensor? From the ground to the big terminal I read 1 kilo ohm and from the ground to the small terminal I read open.

Am i on the right path troubleshoothing this problem??

am

I forgot to mention that since I have this warm starting problem I noticed that when I start it cold the engine takes around 2 minutes to turn well. It's not too bad but I used to my car and I know it did'nt do that before.

tailpipe

Nope on a 79 there are no temp II sensor I would go for fuel accumulator and the fuel pump check valve. Not really a cheap fix the accumulator is just over two bills but it fixed my 78 with exactly the same symptoms.....

Rich9928p

The CIS (Continuous Injection System) is all about fuel pressure and clean/unclogged fuel passages.

My '79 has an in-tank fuel pump and an external pump. A failed in-tank pump will cause delivery problems. Check the pumps.

Next you must have the CIS pressure gauges and check out pressures.

After an 11 year slumber with the original fuel in the tank the whole time, my '79 required new fuel pumps, new accumulator, rebuilt CIS fuel distributor, rebuilt WUR, and cleaned out injectors (2 replaced). It runs great now ....

Rich

curt_928

That sensor is actually the temperature sensor that goes to the temperature gauge.

As posters above have stated, there is a valve in the fuel pumps that can get stuck "open" and this lets the fuel run back into the tank, thus lowering pressure. The fuel accumulator has a spring loaded bladder in it that "holds" the pressure from the tank when you turn the car off. When this spring or bladder goes then the pressure drops, and the car can take quite a few cranks to get it going. Also, if your warmup regulator is clogged, it can make starting a challenge. I'd personally look into these 3 things first. As stated above.

am

Thank's to all for the help. After posting yesterday I searched and searched and found that what I beleived that was a sensor would be the thermotime switch. The first thing I'll do in a few minutes is to start the engine and let it warm up then stop it to try restarting after 20 minutes but with the thermo time switch disconnected. If it starts well the thermo time is my problem (I hope)
I understood well your explanations about the fuel accumulator. I'm glad to know what's the utility of that part. Thank's

Altough when my car idles after cold starts, it has really a too rich mixture. It kind of black smoke a bit the time it idles well.

I'll try that and let know the results later for more support if I may and if it could help others with same problem.
I would be glad not to spend money for nothing on my 928 since I invested a lot lately on it and on my other ''babies''.

Thank's again

am

Curt_928 you were right it is the temp gauge sensor. I just unplugged the leads and I lost the engine temp gauge. I think I found the thermo time switch on the coolant bridge. I warmed up the engine and waiting to try restarting it in a few minutes with disconnected thermo time switch.
By the way when after started it cold it is really too rich. The idle is too slow and it takes about 2 or 3 minutes to get correct and back to right cold idle speed.

LT Texan

Do the cheap and easy thing, replace the fuel check valve at the fuel pump in your passenger side rear wheel well.

Your Old Bugger is most probably not holding fuel pressure in the system, allowing vapor lock when heat soaked.

If that doesn't work (and it will), you need to trouble shoot the fuel injection with CIS fuel injector pressure gauge - easy to do. Because if it isn't the fuel check valve (and it is!), it gets more expensive.

LT Texan

AM, 310 posts since 2002? Wow, that's on trouble free automobile!!!!!

tailpipe

Thermo time switches very rarely goes bad I have yet to see a bad one, it is more likely a bad ground or open circuit. But the thermo time switch has very little to do with a hot start anyway, it is only there for cold start fuel enrichment and it only works for a max of 8 seconds. On a hot engine the thermo time switch is basically turned off so you don't get any fuel enrichment at all. I went through all this on mine and it turned out to be the fuel accumulator.

am

So result: was'nt the thermo time switch. Still same problem when hot starting with thermotime switch disconnected.
Tomorrow I'll go check the gas accumulator.

I only have one fuel pump under the tank and it is the type with the integrated chek valve and every time I turn the key to ON it pumps for about 2 seconds. I did'nt find anything on forums about that. So question, is it the same for every 928 of that generation or the fuel pump on others is only turning when the engine is turning?

LT Texan are you sarcastic about the 310 posts or did I miss something?

Richard S

My 79 had the same problem. Turned out in my case that I needed to replace the fuel distributor.

Rich

checkmate1996

imho, progressive cold start issues are thermotine swtich ( mine actually did go bad) related and hot start issues are due to losing fuel pressure and a common culprit is the fuel accumulator. It's easy to check the accumulator. Pull off the right rear wheel cover and look for visible fuel leaks and or gas smell. If you have either...it's the smoking gun...

hb253

I vote for LT Texan's answer. Hard starting when warm is most likely loss of line pressure dur to a bad accumulator or leaking check valve. The Pelican 911 forum (or Rennlist too I suppose) should be a goldmine of info on CIS if you feel like searching there.

Hugo

James Bailey

To do any real trouble shooting beyond randomly swapping parts on CIS you MUST have two fuel pressure gauges and be checking system pressure and control pressure. The warmup/control pressure regulator is what sets your mixture cold, hot, under acceleration, at altitude but unless you can measure control pressure ?????
It starts cold BECAUSE the 9 th injector , the cold start shoots fuel into the intake for a few seconds probably would start hot as well if you tricked the cold start into adding fuel. But the fact that it does not run right for a couple minutes means the mixture is not right....So you have more than just a hot restart problem.