81 911 sc dies while driving

[pjaswinski]

Okay, I have a 1981 911sc that seems to be have a problem while driving down the road. I am not a mechanic (I know my way around) and I pretty much wanna know what I'll be getting into with its problem.

Anyway, the car is strictly a summer car and isn't driven too much. While driving down the highway at about 60-65, the car will all of a sudden die. RPMs drop like a rock to 0. All we do is turn the ignition on and off and it usually starts up again. Sometimes the rpms will drop then come right back up, sort of like a stutter. Also if the car doesnt start again, it usually has a tough time starting/cranking while stopped on the side of the road. This problem also happens wile idling along in 1st or neutral. The RPMs will drop and the engine will knock and sometimes sends some oil smoke.

Sometimes the car will drive fine, no problems and none of this happening. It usually wont happen above 3000, but when in the mid-high 2000s, it will die. I was thinking it was a problem with the ignition or coil, but i don't know.

Any insight or help would be greatly appreciated!

Thanks, Pierce

[Bob Kontak]

Just a thought - Take a look at your fuel pump relay. It is the red one closest to the driver on the fuse panel in the front.

My old one used to creep out of the sockets and kill the car. You can take out the relay and flare the prongs just a wee bit with a thin blade. Look close, you will see what I mean. Although, when this would kill the car it would be one or two second drop in RPM - not drop like a stone.

I would order another for insurance even if this is not the problem.

What ignition box do you have? Bosch/Permatune/MSD?

Is your oxygen sensor system working? If your coil wire shorts (sparks) to one of the primary terminals on the coil that can cause issues.

Hoping it's just a poor connection somewhere.

[pjaswinski]

I checked the fuel pump relay, was backed out maybe a few mm, def not enough for a bad connection.

The ignition is a permatune which was put in there about 15 years ago when the old one failed.

Oxygen sensor is working I believe and I am questioning the coil at this moment. (It was ghetto rigged on there by my uncle about 5-7 years ago)

Hopefully just a loose connection somewhere.

Worst case scenario?

[timmy2]

Originally Posted by pjaswinski

I checked the fuel pump relay, was backed out maybe a few mm, def not enough for a bad connection.

The ignition is a permatune which was put in there about 15 years ago when the old one failed.

Oxygen sensor is working I believe and I am questioning the coil at this moment. (It was ghetto rigged on there by my uncle about 5-7 years ago)

Hopefully just a loose connection somewhere.

Worst case scenario?

Worst case,
Replace the permadoom with an MSD 6AL and Blaster II coil, replace the fuel pump, replace all igntion parts like cap, rotor, wires, plugs. Replace O2 sensor.
Or a combination of the above as needed. (You did say worst case....)

[pjaswinski]

Hopefully wont be needing all of those. Went out to Auto Zone and bought an MSD Blaster 2, 40 bucks while the "factory" one was $215. Holy shnikies. Anyway, put that on replacing my Accel Super Stock. Started right up no problems and we shall see if the problems continue.

[timmy2]

Good job, hopefully you won't need to do anything else but drive it.

[Bob Kontak]

Originally Posted by pjaswinski

The ignition is a permatune which was put in there about 15 years ago when the old one failed.

Legacy Perma-tune. Save your pennies and buy the 6AL. Nine years now without a hint of a problem. I had two Perma-tune units prior.

Drive it as Timmy2 says but know that it's damned good insurance to get the MSD.

[Bob Kontak]

Originally Posted by marcgaugha

It is the red one closest to the driver on the fuse panel in the front.

This user reported as SPAM generator.

[T77911S]

Originally Posted by timmy2

Worst case,
Replace the permadoom with an MSD 6AL and Blaster II coil, replace the fuel pump, replace all igntion parts like cap, rotor, wires, plugs. Replace O2 sensor.
Or a combination of the above as needed. (You did say worst case....)

+1
it could be the coil or the CD unit. it could also be the wiring from the dist. but i would do the above, wait, i did that.

the O2 wont make it cut off, but if your circuit is good and working, replace it if it has more than 100k on it.
this would be a good time to go through and check for air leaks, or just have a smoke test done or replace the potential air leaks. then take it and have the fuel pressures checked and the mixture set and drive it for another 30 years.

[pjaswinski]

Put the msd blaster 2 on it, took it for a long drive and no problems. Will be driving it for a little longer later. Hopefully there are no problems, but it seems to be running normally again.

[pjaswinski]

Originally Posted by pjaswinski

Put the msd blaster 2 on it, took it for a long drive and no problems. Will be driving it for a little longer later. Hopefully there are no problems, but it seems to be running normally again.

Well, my father drove the car and it died on him a total of six times. I took it for a long drive and no problems, ran like a top. Seems to be a recurring problem with different drivers.

Anyway, we were going to take it to a garage and check/change the points and plugs.
Hopefully wont be having to get an MSD 6AL in the near future.

[emac]

No points in a 81sc

[tazzieman]

Plug wires , esp coil wire?
What's new , what's old?

[pjaswinski]

Ok I didn't really know that it doesn't have points. As you can see i'm no porsche mechanic. It's all old. Jeez, it's definitely not new and plugs etc are probably 10 years old, if not older. Rest of it except for a brand new coil and an old Permatune ignition are what's "on it."

Could failure of another system or part on the car lead to the coil failing? Or vice versa? Possibly the Permatune?

[Bob Kontak]

Regarding Permatune. How long does it take before you can start the car up again after it dies? My P-Tunes would have to sit for a few minutes to cool down and work again.

[pjaswinski]

If the car dies and glides to a stop, if I try starting right away it will usually crank over without starting. Last time it took around 5 minutes before it would start. Usually after it happens it won't start right away like normal but will crank for a little and then starts.

[Bob Kontak]

Perma-Tune unit is on it's way out. The end.

The MSD box is cheap and only a moderate job to install. I put mine under my driver's seat so it took a little longer. There is plenty of info out there on install and install trouble shooting.

Alternatively, the newer P-Tune boxes are more rugged and a used Bosch box is definitely an option. These would be simple to change out but the spend is not as attractive as MSD.

[sea911]

I had a the same problem , ended up being some corrosion on my fuel pump fuse. When I pulled the fuse a chunk of corrosion dropped out.

It was rather large....

[T77911S]

again, replace permatune withan MSD.

there is still a chance it can be the pickup inthe dist, but i would go with the MSD first.

[Paulporsche]

I'm wondering if it's your ignition switch and/or wiring.