1975turbo

We are trying to sort out a problem that is puzzling the very highly experienced Porsche specialist who has known my car since new. The car has the 930/50 type engine (not sent to the USA we believe), with the earlier type Bosch fuel distributor 013 and no fuel accumulator.

The problem we have is overfuelling on initial start up, resulting in having to crank the engine over for 7-8 seconds with the throttle fully open, before it clears and the engine starts. This is a new problem as previously it was an instant starter. He thinks that the fuel distributor piston doesn't appear to stay in the down (no fuel delivery) position after an extended stop. As soon as the fuel pumps are triggered, fuel is injected until the piston returns to its correct position. This only takes 1 or 2 seconds but temporarily floods the engine, giving excessive fuel "wash" and then takes 7-8 seconds to clear and start.

Bosch have overhauled the fuel distributor and warm up regulator and new injectors have been fitted. Fuel delivery system pressure is to spec, as is fuel control pressure. The sensor plate within the metering unit is correctly positioned. Fuel pressure retention is also to spec. The problem is present whether the electric starting valve on the metering unit is connected or not. It has only shown itself since fitment of the new injectors, which are now keeping the injection lines filled with fuel where the previous worn injectors were "dribbling" fuel.

Any help on this problem will be much appreciated. Would lack of a fuel accumulator have any bearing on the problem, such that fitting one would be worthwhile? Would it actually be detrimental to fit one with the type 013 fuel distributor, as they were only factory fitted with the later 016 type?

Car photo attached for interest, together with a 1975 photo of the car when new, showing (non factory approved) alternative use of the rear spoiler

mel_t_vin

Welcome to the Forum! Well-worded first post.

Thanks for including photos of your car...beautiful. Where was that photo in '75 taken...Austria, Switzerland, Germany?

As far as your technical question goes, I wasn't aware the earliest 930s were not fitted with fuel accumulators. I would have suggested replacing old, possibly leaking, injectors but since you have already done that, is it possible that something is preventing the fuel metering plate, attached to the fuel distributor, from properly closing?

There are several folks in this forum well-versed with the early '75/'76 turbos. Hopefully, a few of them will offer some additional guidance/suggestions.

By the way, love the "(non-factory approved) alternative use of the rear spoiler".

1975turbo

Hi Allen,
Many thanks for your kind response and I have passed your suggestion about the fuel metering plate on to the workshop.
The photo was taken in 1975 by my Late father not long after taking delivery. The venue was a Porsche Club meeting somewhere in the Midlands and the Lady in the picture is my Late Step Mother. I was also present, either in a 356SC or a 912, and partook of the repast. The photo appeared in Motor Sport with the caption "The most expensive picnic table in the World?".
Dad specified the car with the full blue leather interior you can see in the attached photo. I bought the car off him the in 1980's, but not being able to afford to run it, sold it on with 19k miles. I found and bought it back 20 years later, with only 21k miles and have since taken it to 32k.
Kind regards,
Chris.

MUSSBERGER

I think you're stepmum is checking for overdone meat.
Nice backstory and your Dad had terrific taste.

mel_t_vin

Chris, you were able to track down and re-adopt the car...20 years later? What a great story!

Thought about something else...the fuel pump in your car should not run with just the ignition on/engine off. As far as I know, the fuel pump should only run when the metering plate is deflected while cranking, indicating engine vacuum/cycling. Someone will correct me if I'm wrong but I believe there is a small sensor [green head?] on the back side of the fuel distributor that ensures this, and prevents the fuel pump from running on in the event of an accident. To be honest, not sure if the earliest cars had this sensor.

Maybe this sensor, or its wiring, is defective in your car and your injectors actually start spraying fuel prior to cranking the engine?

1975turbo

Thanks Allen, an interesting angle. A fault in that sensor, if we have one, would indeed cause the problem we are having. Will check into it and advise.

The story on the car is quite a bit more extensive. I'll have to get it down on paper and post it!

Chris.

mel_t_vin

Looking forward to it, Chris. And maybe a few more photos of the countryside from the fatherland...

Mistergee

Are you sure thats correct with the early Euro 930's, ?? there has been a lot of debate on that topic,
I was on the understanding that pumps would run all the time (with the 3.0)and circulate with the CIS syphoning off when needed, or mine doesnt work and i need to do a thread.
Or perhaps it comes down to whether its a ROW or EURO or 3.0 or 3.3 as theres lots of variations. a tricky area to work out at the best of times and if its a Euro ROW like mine there are no @##$# manuals or wiring diagrams either

What im saying is if that is definitive for his model is it for all 3.0?ss?
not trying to hijack but im always on the lookout for this type of info as its so scarce on these

1975turbo

This is the response I have from the workshop in answer to Allens hypothesis:

"The 'sensor' that has been spoken of I believe is what I know as the safety switch. It is on the metering unit, not the fuel distributor, and yours is working correctly. This prevents the fuel pumps running when the sensor plate is at rest, even with the ignition on. As soon as the ignition key is turned to the start position, this switch is overridden and when the engine starts, the safety switch is then out of circuit. This is just to prevent the fuel pumps running with a stopped engine in the event of a collision. These safety switches, or an electrical/electronic variation of it is part of every K-Jetronic system, for safety reasons".

In answer to mistergee's question, what was standard fitment on a 1975 m/y car is certainly not definitive for all 3.0 cars 75-77. For example, my 75 car has no fuel accumulator. They started fitting one for 76 and I think changed the size again sometime during the run. Other components also changed throughout 3.0 production so it is indeed a bit of a minefield! My problem continues, pending further tests into fuel pressure retention.