DDK - Die Deutschen Klassiker

Some opinions please folks.

Last summer I suffered hot starting probs with my 12. I've put this down to fuel evaporation from the original Solex carbs. The car will start perfectly from cold but would crank over for ages when hot after a 5 or 10 minute stopover at a shop.

Well, I've aquired a couple of unused SU electronic fuel pumps and am thinking of setting one up on the 12. Can anyone forsee any problems? Has anyone already tried it?

My hope would be for 4 psi of fuel pressure, delivered on turning the ignition key to the first position and without all the cranking in the car park (there's a line thrown to Cubist if there ever was one!) This would hopefully fully recharge the evaporated float chambers and hey-presto, away I go.

Any thoughts on fitment, suitable pick up points for feed, do I or don't I bye-pass the original lift pump etc. gratefully received.

Cheers
Paul

Sounds like it should work, after all that is how most carbed 911's are from the factory anyway! Just have to be careful that your pump is regulated to 3-4psi, not sure if SU pressures are higher (have a vague recollection SU carbs use 7psi, anybody?)
Not sure if you'd need a lift pump anymore, I know most electric pumps (like Facet or Bendix) can prime and lift a couple of feet ok.

You've probably already checked, but before doing all this, it might be worth checking that all the fuel hoses are well away from any hot bits of the engine to make sure you're not getting vapor lock causing your problem. Also some carbs use insulating spacers between them and the manifold to prevent evaporation, have you got these, not sure if normal on a 912.

hope that helps a bit

domo1977 wrote: some carbs use insulating spacers between them and the manifold to prevent evaporation, have you got these, not sure if normal on a 912.

... these are supposed to be on 912s. They're about 8mm thick. Mine originally didnt have them and was tricky to start when hot.

I fitted a Facet solid state pump to my 12 last year, much more reliable than the original pump, better starting hot and especially cold as you can get pressure with the ignition on and primethe carbs without cranking.

Nick do you need to fit a presure regulator? or can you regulate the presure at the pump?

Lewis

I chose a low pressure pump