73.5T CIS Dead On Road!

[Sunroof]

Well, you just never know with a 38 year old Porsche these days. You'd think after 13 years of ownership I would be able to figure it all out.

I was taking a drive around North Atlanta when after so many miles and hours of pleasant driving the old gal decides to just stop dead. I restarted and she came to life immediately and away I went again, this time taking the interstate home. Well no more then 10 minutes later it died suddenly again (for my Atlanta friends it was on the ramp to 400 north from I-285 (headin east). It would not restart and I did not smell fuel!! Great cranking power but no start. I replaced the "red" fuel pump relay with a spare and still nothing. My fuel pump is one year old and not a rebuilt unit.

I had the car towed home. Whats crazy is that when I assisted the flatbed operator with getting in the car to drive off the bed, it started right up!!

Okay, so in a few minutes I am heading to the garage to change out the fuel filter. My assumption is that before this ride the car sat in the garage for weeks (most of the winter as well) and I might have picked up trash from the tank to the pump or filter and the problem is simply a sudden fuel starvation. How likely is that though?!

I experienced fuel pump failure last summer and I am thinking this cannot be with a new pump!

Any ideas? suggestions?

thanks

Bob 73.5T

[Zendalar]

If it is the fuel starvation problem, you might have a crack in the fuel hose somewhere. My fuel intake hose had a crack in it and it did not raise the fuel pressure.

Took me quite a while to find, no fuel smell also..

Found out that there was no fuel pressure when I installed a pressure gauge in the engine room.

Other than fuel problem...faulty CDI box kills car the same way too...

[zotman72]

Was the CD whining? Can you hear the pump pumping? How good are the electrical connections at the pump? Not smelling gas, does tend to point to a pump issue of sorts. YMMV

[ossiblue]

I'd first suspect electrical problem with the fuel pump due to the abrupt dying of the engine. Clogged filters tend to show up as sputtering before failure whereas a failed pump will be abrupt. The fact that you smelled no fuel also points in that direction as well. You or the PO obviously re-wired your 73.5 as you mentioned the red relay--the 73.5 had no factory relay system and the pump worked directly off the ignition switch. You may wish to check all the wiring associated with the pump. New pumps can fail and this is certainly an intermittent problem that can be a PITA to find. However, the abruptness of the failure and the lack of fuel smell points to the pump, IMO.

[Sunroof]

Thanks.

I just changed the fuel filter and allowed the fuel in the filter to drain into a glass jar. I always detach the filter at the accumulator first (gravity is a good thing). I had very cloudy fuel with dose of fine particulate that could have raised havoc on the pump or distibutor. My assumption then its dirty fuel for now. She is a garage queen fellas. In the garage the pump sounded steady. If it were electrical I would have known right away.

Thanks Ossi on the relay info. I always thought the pump had a relay.

I will assume that the pump is capable of passing (grinding) some particulate, so if it happens again I will need to look at the wiring to the pump.

I am off again on a nice satuday drive to check it out. Atlanta's beautifu today. Thank heavens I have reimburseable towing insurance (State Farm)!!!!

I will let you guys know................CIS does need clean fuel!

Bob

[Sunroof]

Long afternoon drive.......interstate, two lane, four lane, stop and go, etc.......................Car ran like a top!

NEW FUEL FILTER.....................................solved it.

shame on me!

Bob 73.5T

[Zendalar]

Good thing that it was only that

[Joe Bob]

That'll do it....