73.5 warm start problem...?

cnielsen · 12-28-2004, 11:47 AM

I was hoping someone here might be able to help out a little...

I have a 73.5 911T that is turning out to be an exceptional 911! One problem though, she starts easily when cold but starting when hot is a different deal. It is the short interval gas station stops or store stops that get me. It seems to only start with the hand throttle on and when it finally comes to life, it is only running on 3 cylinders...then 4, then 5, then finally 6...and then it is fine.

I would assume that there is some loss in fuel pressure to some of the cylinders. Does this make sense? Is there some easy diagnostic test I can run?

Any help would be much appreciated! Thanks, Chris

Sunroof · 12-28-2004, 02:17 PM

I went through the same issues and wound up replacing several components (needed to anyways) to get the whole issue settled. The first and best thing is check the fuel pressures. Your fuel pump has a built in check valve that often leaks and does not keep the system pressurized. The check valve cannot be replaced like the newer pump models, but a check valve can be retrofitted (its a Volvo unit I believe). The injectors can be leaking as well. Are they new? Have they been cleaned and checked? Aside from these two items, the mixture may not be set properly. I put in new injectors (pretty inexpensive), a rebuilt fuel pump and new fuel accumulator and the system felt totally refreshed and worked great. If you not into doing this stuff it would be worth your while to have a shop check it out for you to pinpoint the cause. Wayne'sook is very useful in several component repairs.

Regards
Bob
73.5T

Zuff911 · Zuff911's Garage

To really pinpoint the problem one needs to have the fuel system pressures tested (cold and warmed up) using a CIS pressure testing rig; to do otherwise is to act blindly. A rig and a trouble shooting manual can be had for a total of $100 to $200 depending upon where you purchase them. Do not attempt to fix this problem by "throwing parts at it"; one can waste a $1000 in a hurry. That being said, as mentioned it could be a bad check valve in the fuel pump or a failed accumulator causing the problem. Cheers, Jim Sims

cnielsen · 12-28-2004, 03:14 PM

Thanks guys,

I called my mechanic and he basically said the same thing. He told me to drop by later this week and he will loan me his pressure guage so I can drive around with it and try to pinpoint the problem. I hope it is an easy fix... sounds like it won't be too bad as long as the pressure test isolates the problem.

BTW, the car only has 54,000 original miles and I would assume that the injectors have never been replaced. I have all the receipts so I will go home and check.