Pertronix ignition ... breaking down when hot?

In past posts I have described this problem: when I start the car ('64 roadster) cold, everything is fine for a while. Then I notice a couple of skips which increase in duration, soon accompanied by a lot of pinging when I attempt to accelerate (as if the timing is badly out). Finally, the car stops altogether. The car is equipped with a Pertronox coil and electronic ignition (installed where the points would mount). The car came to me with this setup and everything was fine from the time I purchased the car last November.
I replaced the coil, hopeful that it was the cause. No luck. Could it be the electronic ignition unit? Anyone have any experience with this? Could the vacuum advance be seizing up somehow when the engine heats up?

I doubt it's the Petronix. Rare earth magntic trigger device. I doubt the heat effects it much.

What's the cliche', most ignition problems are fuel problems. I would guess for some reason as your car heats up it slowly fuel starves itself. First showing up in lean with the pinging.

You can try cheap electricals like new rotor and distributor cap, maybe borrow some known good plug wires.

Disconnect the vacuum advance if you think that is an issue. Car will run fine with it disconnected, just lose a bit of power in the lower RPMs.

Usually an Electronic Ignition unit will fail suddenly and without warning. It's rare to have a poor running condition, but anything is possible. Check your coil or swap it with a spare and see what happens. Also change the rotor cap and distributor cap just because it's cheap and easy and will eliminate them as suspects. If you save your old set of distributor parts as spares (as everyone should!) then use those, since you know they worked when last in the car.

As Alonzo noted, check the fuel system as well. Make sure you're getting the proper fuel flow and the mixture is set properly.

When this started, had you just recently up with fuel? You may have bad fuel in the car. If the tank is only partially full, go to a different gas station and fill it the rest of the way with high octane gasoline. See if that helps the situation. Good luck!

Bad plug wires will break down with heat. I'd follow Steve's suggestion and swap the cap, rotor and plug wires first - fairly cheap and certainly can't hurt. If that doesn't do it, check the coil. Move on to fuel (clogged filter/line). the pertronix will probably outlast the car, and when they go, it is usually a total failure.

Nope, it's the module (control unit), which I would say is the hole pertronix device.

I don't think it's heat in the engine so much as a bad module (control unit) in your ignition.

When a condenser goes bad, it's generally on acceleration that you notice it the most, when the module (or control unit) they tend to do this too.

Sometimes they work, and sometimes they don't. Sometimes they totally quit and sometimes they don't work while under acceleration.

I bet it doesn't work perfect EVERYTIME it starts up cold, right? or maybe you've just been lucky.

A good way to test this is to put in a dizzy that you know works. If you have one lying around, try it.

You have a 64 B, right? So you originally had points/condenser. When a pertornix is installed, does the condenser stay or go? I haven't put one in an older MGB before. I think it disappears and the control unit does everything, but I'm not sure.

It's one or the other, condenser or the control unit/module for the pertronix.

The reason that I don;t think it's a fuel related problem is because they generally DON'T FIX THEMSELVES, they don't work at times and then not others, and they usually don't cause pinging problems.

Brian

In general when the problem develops rather suddenly you likely have an ignition issue. Carb problems never change much and tend to develop rather slowly. What Brian said.

I took my 63 to the local MG guy when it was running off. It was the linkeage from the vacuum advance to the distributor. I think that is not your issue. Anyway my MG guy installed the Petronix backwards and fried it. He put the points back in as he did not have a Petronix laying around. Does not believe in them.

The point though was the car ran just as well with the points. Two sets are less than the cost of the Petronix. I always have a spare.

Larry

Larry,
Not hard to see why your local MG guy "doesn't believe in them", they will never work if you wire them backwards!

I have Pertronix ignition on my wife's 77 that did the same thing.. There was a very small cut into one of the wires.. It was grounding to the mounting plate in the dizy ,, but only after it got hot.. Heat shrink fix it up...

Thanks for the suggestions, it gives me a few things to try. I don't have the old points as the Pertronix was installed by the PO. (there is no condenser with this unit).
This problem was first noticed on a very hot day. I drove about 15 miles and everything was fine. Upon restart, I had the skipping which got worse but I was able to get home. That happened again on the next 2 hot days, so I was getting about a 15 mile drive and upon restart, problems. Now, I drive about 15 minutes and the skipping/pinging starts, then the car quits. I did add a can of SeaFoam a while ago to try to stop the running-on problem. Maybe that dissolved some gummy stuff --- I will check the fuel filter.

dont the fuel pumps get grumpy when they get hot?
It may very well be the problem. I heard of people pouring cold water on the pump to keep it cool.
just my $0.02

Does your coil get hot when the problem happens? Even though you changed it, if it was the wrong Pertronix coil for that application, the coil will get very hot and the car will run poorly. You should have 3 ohms of primary resistance in the coil. Just something to double check.

The coil feels warm, not hot. I ordered the non-ballasted coil which was called for in the catalogue. It was the exact replacement for the unit that was on the car.

."""""" I ordered the non-ballasted coil """""""

this might be your problem...........IF you are not using an external BALLAST RESISTOR OR a resistor wire from Ign sw to coil.

If you dont have resistance in line go to a parts store and buy a creamic ballast resistor RU-10 or RU-4 in Standard igntion or equvalent.

You want to see NO MORE THAN 8 volts on the coil primary.

You may or may not have damaged the Pertronix unit.

Why oh why doesnt Pert use words of one syllable in their catalog about ballasting and the use of their products.

Sounds like what happened to me a couple months ago with my 79, ran fine for 15 minutes, start missing, stalled once, restarted, got a couple blocks, backfired through exhaust because of the unburned gas, I shut her down. Did as most of the posts above, replaced coil, plugs, points, wires, cap, rotor, had already been through fuel system. Finally replaced the pertronix unit that had probably been in there since original owner that put the weber and header on, new in 79. Problem solved for me, good luck with yours.

I have replaced ignition modules on many cars (mostly American).

In that 3 have been because the module operated inconsistently. Sometime operated well sometimes not. Almost set one car on fire.

On the other 3 they would die dead when hot and come back to life when cold and operate well. One died dead for good.

As there is no good instructions on how to test them. The only option is to replace them and hope that is the right item.

That is my MG guy is not thrilled about them. It makes trouble shooting tougher.

This may or may not solve your problem.

Larry

Larry, you are exactly right about the modules. And that is exactly what a pertronix is, just like the part they call a module in a Chevy Truck. Exactly!

Aren't the frustrating? There is NO earthly way of testing them with out equipment.

You change and pray.

BUT, you can narrow the field. You can check a coil, you can check everything else EXCEPT, the module. So, by a process of elimination, you can indeed find the module to be the culprit.

Brian.

I think that's what's happening here with Jim's car. I hate seeing people change all of these parts like, coils, plugs, wires, fuel pumps etc., etc., just hoping and praying, it gets rather frustrating.

PS. It reminds me of a story of a friend of ours, they also have a 90 Suburban. They got stranded coming back from the Colorado River with us. Out in the desert their MODULE went south. They got towed all the way back home. I kept telling them that their module burned up and the tow guy told them it was their Fuel Pump. He ALSO thought it was the fuel pump. NOT ME! Been there done that! So he has it towed to his mechanic, tells him FP is bad. So they charge him over $900, because on the Sub, 4x4 there's skid plates and the Fp is in the gas tank (40 gal) then they also charged him $55 for a module, and fuel pump relay $25.

When he showed me the receipt, I said SEE, you ding-a-ling, they KNEW it was the module too, and charged you for a fuel pump also. Makes me wonder if they EVEN REPLACED THE FUEL PUMP. There's NO WAY to see. But most customers ASSUME, that the module listed is just a part of the fuel pump system like the relay, but it's NOT! I don't know why we all assume the fuel system is always the culprit. After my first moduel mishap, I did the same thing, but the fuel pump kept making noise, so I kept looking and got lucky I guess!

brian

This is why some of us elder shadetree persons are not high on the electronic modules. If it made the car run better I would have one. On this car it makes little difference.

Larry

Thanks again everyone. I am proceding with troubleshooting starting with the cheap and simple things. Today I cleaned the gas line filter (it had some crap in it) and I removed the Pertronix module and inspected its condition (wires, etc), reinstalled but then the car wouldn't turn over, so now I'm charging the battery. The distributor cap looked good, plug wires looked good, but who knows??