willyexner

Hi 911 Rennlist fellow members,

I am an old bones automotive project engineer, live in Europe, I joined this community some weeks ago to ask for opinions and advice as I was contemplating the idea of buying my first ever Porsche, a fancy lady that an observer called humorously a little black-****, ***-engine slot car



a 1985 PORSCHE 911 Turbo WPO ZZZ 93 ZFS 00 35X which you may see in detail by clicking this link taking you to a pictures gallery.

As the bug bit me, she is now in the stable and, after a thorough inspection, I am convinced by many small signs that the low tachometer mileage is genuine.

Just to say, she still carries the original brake disc rotors with wear commensurate with her 54,000 Km.... she still wears tires dating from 1991 and 1993, with flats typical of a car which has been waiting long periods.

When it comes to my opinion of the 930S, I have very mixed feelings.

I speak as someone with the experience of having owned many period cars, Ferrari, Maserati, Lamborghini, Lancia, Alfa Romeo... and also raced for many years modern Formula 3 single seaters and also HRC, Lotus 22, Lotus 23...

Well, if I ever in my life met Dr Jekyll, there she is, the 930 S Slant Nose.

She is very sexually attractive to start with, sweet looks... but after she hooked you she no longer hides her true temper, that of a brute. Those of you who slept with her sisters know what I mean.


Coming to the subject of this topic, I need some expert advice

Car is 930S m/y1985 # WPO ZZZ 93 ZFS 00 035X
Engine is stamped 930/66 S
Cold engine starts at touch
PJ functions correctly throughout the rpm range,
Restarting the hot engine, two cases:
a) Anything up to say standing 15 mins, it starts with difficulty, kind of chocked
b) After standing 1/2 hour or more, no start at all although the battery makes it turn like a fan.
Returned to cold, which takes hours, after about 5 seconds of starter motor turning, wroumm, she fires!
Problem seems typical of a vapour lock.
Some non-return valve perhaps?
I ordered the Bosch Workshop manual but won’t get it for a month.

Should any of you understand the cause/s and be able to suggest the cure, thanks in advance for the help!



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PorschePhD

Do you have a set of pressure gauges? It sounds like the fuel check valve at the pump or the fuel accumulator is not working. There are two readings, one after 5 minutes the other after 20 minutes. Sounds like that is what the issue is. It is a form of vapor lock, the fuel head is what locks.

I would need to confirm for your year but it should be something like 1.9 bar at shut off and 1.6 bar after 20 minutes.

willyexner

Stephen,

Thanks for your answer.

I went first to your site to see what Imagine Auto do. My compliments, I was impressed, real top league stuff!

As for your suggestion I think you put your finger on the possible causes, though please appreciate you are talking to someone who has yet no idea of the 930S Petrol Injection system details and hasn't yet either the 930/66S engine or the PJ (is it the Bosh Motronics ML3.1?) workshop manuals, which should come in some weeks from now.

Hence I shall ask a number of questions which to a man of the art like you are may sound trifling.

More... on top of being ignorant for never having put my hands under a whale tail, I have at present the handicap of freshly fractured collarbone and two ribs, which is impairing to say the least. But I noticed that you have an R1 in the stable, I have a 996 SPS.... so you’d understand.

But the fact that I cannot use my spanners should not impede that I try to put to work what's left of my brain.

Forgive my English; is the “check valve” a non-return valve with the function of not allowing the system pressure return to the tank?

Where is the check valve located?

Is it integral with the fuel pump or installed elsewhere?

Can it be opened up and serviced?

BTW, when the engine turns I hear the pump twirling somewhere in the car front: but when I simply turn the starter key switch, engine off, I hear no pump. So the pump must take its juice through some relay activated by some signal. Which signal?

Going onto the fuel accumulator, is it a kind of a balloon tank to hold and stabilize fuel pressure? If so, where is it and what does it look like?

I presume that in my car the hold on pressure drops so the fuel boils. I presume the fuel pump turns when I turn the starter motor on to fire the engine, but I cannot hear it. Though even if I keep the starter motor turning long enough to make me feel uncomfortable, the pressure build is not enough to get rid of the fuel vapours and squirt through the injector nozzles.

Nothing scientific in my theory, just guess work.

My perplexity is, since the system does not leak to the outside, where the internal leak/s may be? One I understand could be fuel returning to the tank through the pump check valve. What about the other/s?

I realize my questions are many; please to not feel obliged to answer...



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WERK-I

*****,
There are two fuel pumps for the 930/930S. One is located in the underside the front suspension pan, back from the fuel tank near the aluminum front crossmember. The other is located is an area in front of the left rear wheelwell forward of the torsion bar tube.
You should hear both fuel pumps whine when the engine is running. They are activated only when the ignition is 'on' AND the fuel metering plate is pulled when a vacuum state from the engine turning over. The engine will run with one pump, just not very well under loaded conditions. These pumps are controlled by two relays under the front bonnet on the electrical distribution/fuse/relay panel. They are easy to find since they are both marked by their red covers.
Hope this helps. Have a good weekend.

willyexner

Hello Stephen and Dave,

have a look please at these tables
:


Now I'd need a good samaritan to place my finger over the correct figure/number for accumulator and check valve
these are tables i found in the site
http://www.sportwagen-club.de/TechSt.../911_84-86.htm
There are a lot more, practically covering the whole 930 S 1984/86 and many more other porsche model.
Did you guys know the address already?
In the negative you owe me a pint of bitter.

WERK-I

Stephan, correct me if I'm wrong, but I thought the check valve is located within the fuel accumulator. The fuel accumulator is item 14 in drawing 2/01/10.
*****, I don't know how much the car was driven prior to your purchase, but sometimes....sometimes the system will varnish up with stale gas. A bottle of Techron with your next fill up will remove tarnish in the fuel system and may solve the problem.
As far as the bitter, we can work that out!

willyexner

Dave,
as for the bitter, you can count on me...
Waiting for Stephan's opinion as for the exact whereabouts of the gizmos, I can tell I have already treasured your previous advice, so I have been through the clog cleaning exercise on the 700 Kms representing the return trip of the little black brute to her new stable.
Techron not being readily available at my latidude (the almighty knows how much I searched) I used a Bardhal product they swore was equivalent.

Cheers,

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WERK-I

I stand corrected. The check valve is item 39 on drawing 2/01/00. Front fuel pump area.

WERK-I

Also, if the rear fuel pump is not functioning, this may manifest itself with the symptoms you suggested since the fuel system is not being fully pressurized. This may be caused by two common possibilities, the fuel pump relay has failed or the fuel pump has failed. You can temporarily swap one of the black relays for the rear fuel pump relay. The only difference between the blacks and the reds is a diode on the red relays suppresses EMF kick when the fuel pumps are turned off. But you should definitely hear the rear fuel pump whine when the engine is running. The problem hearing it becomes apparent because it is relatively close to the engine(noise).

willyexner

Roger for #39, I wonder if it is serviceable.
Any idea where the accumulator is or looks like?
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WERK-I

The fuel accumulator is located in the engine compartment, left side, mounted to body work towards to driver. It is right next to the fuel filter. I don't think the check valve is a serviceable item, only replaceable. It is a common part, since all 911's use them.

I know a fellow 930 owner that had a similiar problem, but it always started hard, hot or cold after sitting. His problem was the fuel line from the filter to the fuel metering head. His line was weeping, not dripping, thank god, but a slow enough bleed off pressure that the engine cranked a long time before it fired up. Can't remember if it was the feed line or return line.

willyexner

Dave,
the second pump I had no idea it was there. It seems an interesting trail to follow. Thanks,
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WERK-I

*****,
I was reading your earlier posts on the other thread. Is your exhaust still sooty? If so, your car won't start after warmed up is due to faulty fuel pressures(way over-rich condition) or the AAR which controls the amount of air allowed into the engine at startup(closed throttle). The fuel control pressure is controlled by the Warm Up Regulator....a misnomer, since it controls fuel pressure over the entire operating range.

PorschePhD

Sorry I am just now seeing the rest of this. The accumulator is #14 on the first pic. Your theory is spot on. When you then turn the system over the air locks the chambers and pressure has to force its way to the head. If you hear the car sort of miss and then pick up one cylinder at a time this is also an indicator the accumulator is shot. It is a little canister with a membrane and spring to maintain pressure for a giving amount of time.

The check valve is 39 on the front pump and is not serviceable. you simply replace it.

willyexner

Dave,

thanks for your brotherly attention.

The rich mixture was adjusted before I took delivery of the car, by the previous owner taking the 930S to his Porsche service workshop, a place having the reputation for earnest competence.

I can tell they took away the sooty puffs and I also detected the mixture change from too rich to marginally lean for having also a series of exhaust light pops for going downhill, cold engine, closed throttle.

The seller told me that the shop people were sorry not able to fix the hot start problem prior to delivery for lack of spares, the problem in their opinion being caused (he could tell no better) by some non serviceable membrane gizmo which was porous or leaking.

If at the time the explanation made little sense to my ears, I see now that the story fits beautifully with the pressure accumulator hypothesis that Stephan could make, based on better evidence.

I am bewildered by the results of such community team work!



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