hard starting CIS

[Platiporsch]

1980 weissach 911 sc, car starts but wont fast idle when cold,pops back through pop off valve, if i try to rev her a bit it backfires worse however if i just let it idle for about 5 min. i can rev her up. when warm every thing is fine. i started to do a fuel system pressure check,when i went to bleed off the pressure line there wasnt any, just a trickle. my first thought was to replace the check valve. Ive discovered someone had installed a fuel pump for a 77-79 911, does this pump have a intergrated check valve because if it doesnt my car is living without one again my car is a 80 with a 77-79 fuel pump according to the part # on it, it has a long snout unlike my 83 sc which has a shorter snout and the removable check valve. thanks for any insight.

[john walker's workshop]

pressure bleed-down would be a hot start problem, not cold. you don't have a "start" problem, because it starts. you have a "too lean, cold running" problem. the warmup regulator can be adjusted to run richer, do a search for adjustable warmup regulator, for the procedure, but first make sure the hot CO is adjusted to around 3-3.5%, and leave the oxy sensor plug disconnected. sometimes it's just a tuning issue.

[Platiporsch]

Thanks john, i didnt say that after its warm [ operating temp] shut it down, let it cool a bit because i dont want to light my car on fire, then dissconect the pressure line there is no pressure in that thing, where is it going the fuel must bleed back to the tank either on the return side or back through the check valve, which im not sure is even there is it possible for the engine to run without one provided the fuel pump can keep up with demand?