Rough start?
 

In my 74, I have a 82 euro 3.0 that's been giving me problems. When I start it up cold it has no problems. Turn the key with no gas and it starts right up. Then I'll run it till it get hot and turn it off. If I try to restart it right away there's also no problem. But, if I let it sit for for a bit (20min to an hour or so) it's sometime is real hard to start. Sounds like it's getting no gas. Then it usually takes gas after a little while but runs super rough. Sputters and what not unil I get it driving.

Anyone have any ideas?


Thanks-
Craig Backer

I know very little about CIS



http://forums.pelicanparts.com/uploa...1232259287.jpg

It sounds like you have a fuel pressure problem.What fuel accumulator is in the car is it the 74 or did you put the later sc style in.the sc style will have 3 fittings on it the 74 will only have 2 .On the later one it can leak fuel pressure through the 3rd fitting out the bottom this could be your problem.Also on your fuel pump there is a check valve that can go bad it will stay stuck open.these are the 2 easy things it can be the best thing to do is take it to a porsche shop and let them put a fuel pressure gauge on it and check it for holding pressure.

Sounds like vapor lock? If the car sits for a while and temps in the engine bay continue to climb the fuel boils and you dont get fuel.

On the other end of the spectrum, if you are starting cold no problem but warm is difficult perhaps you are too rich at warm start which could lead you to check out your AAV (is it not closing?), cold-start injector (is it leaking/always on/shorted?)


UFO on his/her 2nd post (!!!) may have also pegged it...when you transplanted did you bring over the fuel accumulator?

fastback, most likely you are losing "rest pressure" which is causing vapor lock, most of the time it is your feul accumulator, but you can also lose rest pressure from a few other things like check valve on the fuel pump, wur, or the pressure regulator on the feul dist. (o-ring) i did the same swap on my 75 and used the 3 port accum. but if you used the original 2 port from the 74 thats ok as both will work (yu have to cap of the retun line coming from the engine of course) it would be very easy to isolate your prob. with a set of cis gauges.

Craig,

You need to do the residual pressure test to try and isolate why you are losing pressure. Then test individual components. Unfortunately, there are many suspects, and they add up to >$1000, so part swapping off internet advice may be expensive.