My CIS projects

[jk911]

O.K
I purchased my dream 1975 911. 2 months ago.! Problem ??
I have still not driven it. It has the following problems.

1) It starts when cold but not if it has been sitting for 15 minutes after it has been running.

and

2) The idle drop's below 700 rpm's when I put it into gear (sportomatic) BUT when I take it out of gear and put it in neutral the rev's jump up to 3000 rpm's or more sometimes.


I have done to following to correct this problem, but nothing has changed ???????????????

1) new fuel distributor and o-ring
2) cleaned throttle body and replaced o-ring
3) replaced injector 0-rings
4) replaced leads
5) replaced spark plugs
6) replaced alternator
7) replaced battery
8) replaced ignition coil
9) replaced fuel accumulator
10) replaced fuel filter
11) replaced sensor plate housing gasket
12) Replaced oil filter


As there has been no improvement I now plan to put a check valve in and replace the decel valve .

Here are some photos.

Any suggestions

[Adam]

JK,

Good to see another Australian on the board. Hope we can help.

I don't know about the hot-start problem, other than to suggest the starter motor solenoid or perhaps your fuel pump or fuel pump relay. When it won't restart and is warm, open the fuel tank. If it has high pressure (Pshhht) then your fuel pump may be the culprit.

On the idle problems, it could be your vaccuum advance, or a sticking cold start valve/auto choke.

I could be WAY off, but give them a look at etc. There are some regulars on the board that will probably be able to diagnose in 2 seconds. Wait until they wake up, it's night-time in the US.

Good Luck!

[epbrown]

Adam's right - some experts will be along - make sure you bump this to keep it on the first page so they see it. I'm no expert, but I'd say it's the fuel pressure accumulator and the warm-up regulator from your description.

However, when I had the hot start problem, I replaced the accumulator only to discover that it was a ground problem. I cleaned around and re-attached my grounds straps, and the problem's never happened again.

Also, some Mercedes-Benz owners I've met say that Porsche owners are too quick to replace the warm-up regulator - they simply remove it and clean it, and make sure they've got a clean fuel filter in place.

Just a couple of things to consider.

Emanuel

[jk911]

Just to clarify thing's as i was a bit vague before.

When the engine is warm and it has been sitting it turns over and over and over but the stupid thing doesn't start for a long time.
However when the engine is cold or i restart it it in less than 10 minutes it starts up perfect even when hot . It sounds like the typical vapour lock. I have changed the fuel pressure accumulator which made little if no difference. I think it must be either the fuel pump or leaking injectors, what else could it be ?

I changed the fuel distributor because the old one was leaking fuel. Hoever no change to the symptoms. I still have to take the car to porsche to adjust the fuel/air mixture.

As for the high and low random reving i don't think there is an air leak. But I know the decel valve is faulty because sometimes when I accelerate the revs get stuck ie at 3500 rpms and wont go down. However when I disconect the top vacum tube from from the valve and block it , this problem is corrected.

Has anyone had such a problem with the decel valve, or am I just hoping replacing this will solve my problem.

[Wayne 962]

Hmm, Sporto models are tough. I believe that they work off of some sort of engine vacuum system as well, so the transmission may be affecting your engine speed. Actually, it may be your problem. Check for vacuum leaks, especially at the big vacuum canister that is on the Sporto transmission.

Also, check the fuel pressure, also when the car is off. I believe that your car has a check valve in the fuel pump that works with the accumulator to maintain fuel pressure after the system is shut off (this helps prevent vapor lock, which could be the warm start problem that you are experiencing)...

-Wayne

[dean]

I had a bad decel valve. I plugged the ports and ran without one for years. Save your money and run without a decel valve

[jk911]

Won't that cause sudden idle drop problems ?

[dean]

It doesn't on my car. My idle drops down to 950 rpm, which is what it is set at. Try it out and see how it works on your car.

[jk911]

what does the microswitch attched to the throttle body do ?

could this be the culprit

[fred cook]

The next time you are ready to re-start your pcar, try this: turn the ignition switch to the on or run position, but don't crank the engine. Listen to the fuel pump whine. If it starts with one sound or pitch, and after a few seconds changes to a different sound (pressure has built up in the fuel system), then your fuel pump is probably ok. However, if the pump continues to make the same pitch sound, then the pump pressure may be too low.

Good luck!

Fred Cook
80 911SC Coupe

[jk911]

fred,

Now that I have changed the fuel accumulator, the fuel pump makes a noise for a short while then stops ie it appears to be working properly, but that doesn't mean the check valve is working does it ? infact i suspect my car doesn't even have a check valve .. take a look at the setup

[jk911]

is there a check valve on this