Strange problem......
 

Hello! I'm pretty confident someone here can help me out. Thanksgiving day, I took the 930 out and ran pretty well. Then on the way back, I was in 2nd gear and it started sputtering. I shifted into 3rd and it was totally fine! The light ahead turned yellow, so I down shifted to 2nd and it started sputtering again. When I came to a stop, it just died on me. I'm able to start it, but it won't hold an idle....even when I tried holding the gas down, it would just die. I had to get it towed home......

I told my daughter, "There's nothin' like driving a Porsche....and there's nothing more embarrassing than being stranded in a Porsche, too"! hahahaha

Anyone know what it could be?

Thanks in advance,
Jason

Best initial guess: You've got a vacuum leak. Check all hoses, as well as the intercooler O'rings.

Thanks Mark! I'll give that a try.....

If you pass the vacuum tests, check your rear fuel pump. Both have to be working properly for your 930 to run in top shape.

In my case the problem was the Front fuel pump was working intermittently . But I replaced both Fuel pumps to be sure . Also check the fuel pump fuse and the 2 fuel pump relays , make sure their working prior to replacing the FP’s . Relays are easy to check ( plug the suspected relay in the horn relay socket )

Just to update.....

I finally got around to checking some stuff. I checked the vacuum lines and hoses and everything seemed to be okay! I went in the trunk and checked the fuse box......#6 fuse was missing! You guessed it.....the fuel pump fuse! I can't even find it anywhere in there! LOL I replaced it with a 25 amp fuse and all was good! I haven't taken it out yet, but it idles and revs fine so far! Thanks for the help fellas!

Jason

I had something similar happen (not exact) a while back. I was driving in 3rd down the highway and the whole car shut off. Sounded like it wanted to turn over but it wouldn't. Turned out it was 2 bad fuel pumps, believe it or not.

Jason, call me dense....or call me old....for which both apply to me. Your car would start, run kind-of, then die. Then you finally discover that the fuel pump(s) fuse was missing. If missing, your car would not start at all. One fuse services both fuel pumps. Maybe it was just barely hanging on to the mounts, and finally fell out and is now rattling around somewhere around the spare tire.

Sorry, i realize this is an old post but the problem persists. I have a new (to me) ‘79 that has just had a engine rebuild even though it only has 35K miles. My #6 fuel pump fuse keeps blowing. I can’t hear the fuel pumps running with the switch on (not running) but the car starts, but roughly and coughs for a couple of secs before reaching idle. The car seems to run fine although not great. My first 930 so I have no comparison but the car seems to lack the “punch” everyone talks about. There also seems to be a high pitched “whirring “ that increases with rpm. At some point the fuse will blow again. They are original fuel pumps and the car sat for a few years before I got it. The engine rebuild was due to corrosion in engine.
Is installing new pumps the first action? Any ideas?

Thanks

According to the circuit diagram, both fuel pumps are connected to fuse 16. If the fuse blows, both pumps do not run and the engine immediatly stalls.
It is due to safety reasons that the pumps do not run when only the ignition is turned on. The pumps only run when the engine is turning and the air sensor plate is deflected.

If the car lacks performance, you should start checking the CIS systematically, especially after a long period of sitting and partial revision.

Fritz

Thanks, you’re right about #16 fuse. I was counting from the other end. And I was confused about when the pumps run. How are people hearing the pumps with engine start?