911 just about left me stranded need advice

[LCOX]

I've got a feeling this may turn into a long thread. I'll try to keep it short.

77 911 with no known running issues. Recently tuned up with no injection problems that I'm aware of. I was on interstate in 5 pm rush hour traffic. oil temp 210 degrees. The car just cut off like you turning the switch off not like running out of gas which is a different sensation. Plenty of gas in car.

The tach dropped to 0 in an instant and a second or 2 later the car backfired and started to run again. I tried my best to keep it running just to get out of traffic and it would run smooth for a mile or so and then cut off then backfire and run again a few seconds later Finally got it home. Where do I start? Any other threads covering the same problem? Thanks L

[bpu699]

Originally Posted by LCOX

I've got a feeling this may turn into a long thread. I'll try to keep it short.

77 911 with no known running issues. Recently tuned up with no injection problems that I'm aware of. I was on interstate in 5 pm rush hour traffic. oil temp 210 degrees. The car just cut off like you turning the switch off not like running out of gas which is a different sensation. Plenty of gas in car.

The tach dropped to 0 in an instant and a second or 2 later the car backfired and started to run again. I tried my best to keep it running just to get out of traffic and it would run smooth for a mile or so and then cut off then backfire and run again a few seconds later Finally got it home. Where do I start? Any other threads covering the same problem? Thanks L

Fuel vs ignition...

Sounds like fuel pump, fuel pump relay, or ignition capacitator if I had to guess...

Start by checking your car battery voltage in case regulator went dead or alternator, could be simple...

[mytoy]

First thing to check is the coil wire to see if it is seated in the coil and the distributor. I had the same issue as you and found the coil wire came dislodged from the contact in the coil. If I just looked and the wire it looked like it was seated but upon pushing on the wire I found it was loose. Took the wire off the coil and looked inside the tower and found the contact was eroded away. Car would start and run for a short time then just shut off just like yours.

Hope this helps

[spoke]

Since the tach dropped to zero with the engine still turning, definitely electrical issue. Does the '77 have inductive pickup in the distributor or points and condenser?

[manbridge 74]

77 should have points. A quick check is a small piece business card to gap points when distributor lobe is at highest point. Recently had a 79 SC with a loose CDI wire at fuse box intermittently not contacting causing car to die randomly. Many screws on top row were loose and needed tightening.

[Walt Fricke]

77 has points, but no condenser. The points connect to the CD box, and to the tach itself. So take a look at the points.

The CDs often don't last forever (40+ years isn't bad), but tend to work fine until they abruptly quit. So maybe your problem is as simple as putting in new points and setting them.

Or upgrading to a transistor based points function system, or the like, where very little current passes through the points.

[faapgar]

Just wipe a clean match book cover through the points and see if there is a film of oil.It is a low voltage system.Very common.

[T77911S]

the points only provide a ground.
you can check the gap but I would think once the gap got too small its not going to run at all.

probably the CD or the coil going bad.
they will cut out when hot, then work once cooled.

problem you cant fix it if it aint broke.

do you still have the bosch CD unit

[Paulporsche]

Over the years I've had this hhappen several times when the points rub block had worn down. As others have mentioned, check the gap and reset or change them as reqd. It's always cured it for me.

Also check the round black plugs under the dash on the bulkhead. These can loosen up.

Who did the recent tuneup? Did they change or set the points?

Do you have a Permatune CD box? There have been reports on this BB about these failing when temps go up.

[Sunroof]

Happened to me several times on my 1973.5T! It turned out that the wiring harness from the CDI unit to the distributor was getting too had and loosing conductance. Does the car restart when all is cooled down? A failing CDI also will overheat and shut down as too the coil. I installed new points, new cap, rotor, ignition wires, spark plugs and new coil and had the CDI unit rebuilt before I realized it was that damn harness from the distributor. I do not know if you have that GREEN WIRE coming from the distributor.

Good Luck
Bob

[Sunroof]

LCOX......sent you a PM

[Nditiz1]

This happened to me as well recently, but only on a long trip and only when the cars temp was up around 210. When I left for the long 2 hour trip temps were cooler and the car never saw more than 200. I can only assume the engine compartment was cooler as well. Driving the same trip back in the afternoon ambient temps had increased by about 20F degrees. It happened about 4 more times every 15 - 20 mins or so. It has not happened since and I have driven on some warm days, but never more than 30 mins. My CDI box was also recently refurbished so I know it is not that. I can only guess that it was the green coil wire loosing connectivity as the same thing happened the another user a few months ago (pelican member Rich something).

@Sunroof - Did you just buy a new green wire for your fix?

[LCOX]

This engine has the earlier ignition points in the distributor so I've started there.

Before removing the points. I checked the dwell which was 37 degrees and the points were gapped at .012

Took the points out of the distributor and they looked practically new with hardly any wear at all on the plastic rubbing block. No oil or grease on the points and the wire looked good. I cleaned them and reinstalled them and reset the gap to .012 and put them back in and the dwell was 37 degrees again. Ive got the point gap specs and dwell from an older thread here. I may be off if so let me know.

Car is running very well but I haven't gotten the oil temp up to 210 degrees where it started to cut off the other day. I have a feeling that something may be breaking down when the engine gets hot but this is just a thought.

[T77911S]

the gap is not critical.
it just needs to open enough to break the ground.
I always eyeballed my gap on my 77. never any issues with it. I experimented with wider gaps and narrow gaps.

I carry a spare coil and CD unit. I replaced my bosch with an MSD and I carry the spare bosch.
the coil went bad on the road once, the spare got me going.

[Paulporsche]

Do you have a Permatune?

Is your ignition switch OK? How many keys on the fob?

After verifying ignition and wiring, have you checked your warm control; pressure (WUR)?

[grant lyon]

Check points wire at external threaded post going into the distributor. Wire crimp at spade could be bad causing intermittent connection.