DDK - Die Deutschen Klassiker

Hi Everyone,

Looking for some help in diagnosing a fault on my 1971 2.2E (MFI, CDS). While driving at a steady speed say 2500-3500 RPM the car would start to falter and then often die and come to a halt. It would then restart, run for a few minutes and repeat. Felt like ignition issue, I have replaced ignition wiring harness as wiring had been repaired 30+ years ago, and tried alternative coil and coil/distributor HT lead. Thought nailed but problem has returned. Dizzy cap and rotor all in good condition. On last run it was going fine, then died to almost stalling. Put foot to floor and after a few seconds roared back into life. In between faltering car runs strong. I hate intermittent faults!

Struggling to think what else to try to identify or narrow down the issue, whether electrical or fuel - could it be CDS system and should I leave that to an expert?

The car hasn't been used for a while and fuel is quite old, not sure if that could be issue but it starts on the button and not sure would explain problems I have?

Any advice greatly appreciated!
Thanks in advance
John

I'm feeling CDi as I remember similar symptoms when mine gave up the ghost.

Old fuel is worth ruling out though.

Can you borrow a CDI from someone?

Thanks Bootsy

Agree CDI swap very sensible check - I don't know of one I can borrow, there is a shop that does early 911s near me they may well have one they could swap out

J

Where about are you?

Fuel blockage/collapsing pipe? Maybe a pipe closes up when warm and running then gradually relaxes again when off so it starts again?

Winchester, Hampshire

Fuel pipe an interesting one - funnily enough I had that issue when I bought the car 20 odd years ago. A very well respected specialist did a load of work including sending the MFI away for checking before finding there was a simple line blockage. Have to say the shop was brilliant and refused to charge me

Having said that, this issue does seem pretty random and more or less just happens when you think it's fixed ...

Thanks for you help
John

Sounds more like fuel shortage. If it has been laid up for a while it is worth draining down the tank, checking the mesh filter in the tank outlet and changing the MFI fuel filter.

JW

Totally agree. Open the fuel lines, do as above and if possible give the pipes a blow through in both directions.
Nice fresh 99 octane and charge the batteries.

Many years ago I had similar issue, not on a Porsche, but 'fuel starvation' seemed to describe it at the time.

Turned out to be flux in the 8mm fuel tube where I had brazed a fitting to the fuel supply from the tank restricting the flow to very little.

wether its fuel line or not, it is still worth changing them if they have not been done for a while anyway... see my post the other day with one of my lines that had cracked ( line dated 2015 )

Also check the fuel tank breather is clear

Thanks everyone for the ideas and advice - will report back when fixed!