Car just dies after long runs!

Sunroof · 06-15-2011, 04:53 PM

1973.5T CIS

I have been here before with this issue, which I thought was resolved with the replacement of a fuel filter. But it happened again recently.

Excellent cold start up (thanks hand throttle), strong run (10-20 miles) in both throttle down and stop and go traffic, no stumbling, excellent throttle response, etc. I pull into a parking lot and BANG it dies. Starter strong, engine turns, NOTHING!

My buddy sits in the drivers seat while I can feel the fuel pump working (its in the lefty rear wheel well and easily reached), the CDI is humming yet she does not start........

I did not do the ususal spark test nor loosen a fuel line to see if fuel is indeed pumping. I was about to do that. After 15-20 minutes it started up and idled fine. I turned it off and started it again and it was fine................drove home flawlessly.

OKAY......so what gives? Bad relay, electrical short, failing fuel accumulator, fuel distributor, heat issue, etc, etc,......?????Their can be a hundred things to look at, but I thought if anyone had the same problem, maybe I can save myself a big headache and try to isolate the probable cause(s).

Anyone?

Thanks

Bob
73.5T/CIS

Bob Kontak · Bob Kontak's Garage

Not a hundred things but the symptom is similar to my Permatune CD box when it failed intermittently.

mack6820 · 06-15-2011, 05:41 PM

I had that problem with my 3.0 when i first bought it. It would sit and idle for a whole day but once i drove it for about 10 miles, it would just die. Then after about 10 minutes, it would start up and go again. Turned out it was the distributer locking up. Had it rebuilt and it was fine ever since.

Bob Kontak · Bob Kontak's Garage

Interesting on the distributor. Was it a mechanical issue or electrical?

The Permatune failing did not follow a pattern except for the 20 minute wait.

mack6820 · 06-15-2011, 06:44 PM

I honestly dont remember, it was 6 years ago and my very first Porsche experience. It sat at a porsche dealership for 2 weeks and they didnt have a clue what to do (dealerships are clueless without a check engine light). So I trailered it home and had a air cooled porsche mechanic look at it. He knew right away what the issue was.

T77911S · 06-16-2011, 03:36 AM

CD unit, coil, wiring from dist to CD unit, it gets brittle.

even though the CD can make noise, it may still be bad. mine started with short little "bumps" while driving until it would just shut off and not start for a while.

i put in an MSD and blaster coild and heve been happy ever since.

Bob Kontak · Bob Kontak's Garage

Quote:

Originally Posted by T77911S

CD unit, coil, wiring from dist to CD unit, it gets brittle.

even though the CD can make noise, it may still be bad. mine started with short little "bumps" while driving until it would just shut off and not start for a while.

i put in an MSD and blaster coild and heve been happy ever since.

Ditto on the MSD. Not one issue related to ignition since 2003.

Did not know they could make noise AND be failing. Good info.

T77911S · 06-16-2011, 06:14 AM

yes, the big capacitor can go bad and the the rest still work.

Sunroof · 06-16-2011, 07:39 AM

Thanks fellas.....

It seems we have some concensus on the electrical end being the culprit, but what would you do? You would have to let it die again and then start testing components. I have the original CDI unit not a permatune, but I was always under the impression that they just die and thats it! Dead! How can I tell distributor or the infamous "green wire"?

This may be a clue......

Aftewr it died and I was checking the fuel pump, I opened the distributor cap took off the rotor (checkijng for cracks on both) and put it back on. THats when it started right up again. No resetting of points or jiggling the green wire, nothing else.

Any more clues here?

Can the CDI unit be bench tested?

Is there a source for the "green wire"?

Is their a simple test to isolate the distributor?

Thanks

Bob

T77911S · 06-17-2011, 03:54 AM

the CD can be bench tested, but as you said, if it aint broke, you wont find anything wrong.
at this point you can either drive it or shotgun troubleshoot it($$).

the bosch units can be rebuilt, but it really needs to be not working.
you could try the coil first(my first guess), its the cheapest, and if it does not fix it, you have a spare to carry with you. or, you could replace everthing, either bosch or MSD, MSD is less expensive.

removing the cap and rotor may have moved the wireing harness to and from the coil/dist/CD unit and made it run again. those wires get brittle.