View Full Version : Weird Problem - Is it fuel or electric?

05-24-2015, 10:31 PM
OK so here is the situation: 289HiPo w/Pertronix II Ignition also has alternator instead of generator, no voltage regulator that I have seen.

The problem reared it's head 2 weeks ago. I was out driving and having a nice time for about an hour or so. On my way home the car just dies. I do some looking/testing of various things and I think maybe it is the mechanical fuel pump since the new clear filter is not showing full. Put a cup of gas directly in the carb and try to start, no joy. Weird unless spark related, right?

Get towed home, unload it from truck and the car starts right up and I drive it in the garage! So then I think maybe it was something in the fuel tank that restricted the flow and got jostled loose on the 5 minute ride to my house. Still wary I ran the car this weekend and while warming it up for 15 minutes are so, it died twice while idling, But started right up after each. I foolishly took it for a drive and made it about a 1/4 mile and it died for good. Being stubborn, I pushed it home and up a little hill with some friends. I decide to try the FlameThrower II off my Sprint to see of it had gone bad. No difference, no start. Tried it about an 2 hours later and it fired right up with the original coil.

So today, I decided to do more testing, I let it idle in my drive way and at about the 25 minute mark it died, started once after that but died again, then nada. Car is at normal temp, clear plastic fuel filter is full to and clear.

About 1 1/2 -2 hours later it fires right up like nothing is wrong.

BTW, I did have a bad Flame Thrower coil last year (June) which I replaced with the Flame Thrower II and a new set of Pertronix wires, Cap, Rotor, and a new module.

The only other thing changed out was the fuel filter. From a solid metal to a clear plastic one.

So, what's the problem?

1) Pertronix II module?

2) Vapor Lock? BTW the carb does not even get that hot to the touch, so I doubt the front bowl is boiling and there are no metal fuel lines on the engine to the carb

3) Fuel pump? Overheating, vacuum, leaky diaphragm, low psi, etc?

4) Ignition switch? Checked for heat and it is not to the touch at or around the key.

Right now I am just frustrated and gun shy to take the car anywhere until I find this gremlin.

I was going to go ahead an purchase another Pertronix II and see it that nixes the problem, then on the the fuel pump, then the carburetor.

Thanks in advance for your counsel. [BOW]

05-25-2015, 02:27 AM
An intermittent electrical problem means that it is probably a loose connection. My guess is a loose connection between the primary wire from the coil to the top of the distributor cap. You said that you had changed the coil. Check the connection where the wire plugs into the top of the distributor cap. Maybe the wire did not get plugged in all the way and it has vibrated loose.

Jeff W
05-25-2015, 10:27 AM
I would:
1) warm up to get into the "no start" situation.
2) pull a plug wire off of the spark plug side and insert a spare spark plug on the end of the wire.
3) ground the metal base of this loose spark plug against a bare piece of metal such as an unpainted valve cover bolt or bracket.
4) have a helper crank the engine (trying to start it) while you are watching for the nice strong spark from that plug.

There are other ways to check for spark but this is a nice safe process that keeps your hand out of the fan.

Should help narrow your problem and show you which fork (gas or ignition) you need to go down.

05-25-2015, 07:53 PM
Pertronix module over heating?
Kinda like an electronic vapor lock?

Check for spark after it dies would be the first place to look..
If no spark, check to see if you are getting power to the coil from the ignition switch..

05-25-2015, 08:47 PM
Update: I spoke with Pertronix today and the said it sounds like a low voltage issue since the module needs at least 8v to operate correctly. Also, I found out that the factory wiring has a ballastor resitance wire from the ignition switch. Maybe the P1 could handle the lower voltage via resistance wire without incident but the P2 can't and to Nathan's point it basically causes and electronic vapor lock (shutdown) due to overheating and drawing of more voltage, etc. Then once it is cooled down it starts back up like normal, until it gets hot again.

The easy fix supposedly is to disconnect the postive power wire from the module to the coil and wire it to a 12v switched source via the fuse block, like the radio.

I guess I will try that and move forward.


05-26-2015, 05:45 PM
Center post back of ignition Switch is a keyed source.
Might want to consider an inline fuse.. check with pertronix on what amp.. I'm guessing 15 amp should be ok..

05-26-2015, 11:24 PM
I had that same issue when I switched to a DII with an MSD. I had a few issues like poor acceleration under load, the engine would intermittently die and not start when it got warm.

As I was troubleshooting I noticed the wire harness was warm. I found the coil wire insulator melted and was intermittently grounding out. Since this is a resistance wire it was taking the all of the 12v load. I replaced the wire with regular primary wire and put in an inline fuse, I have not had a problem since.

It sounds like you may have a sum of errors and you just have to pick them off one at a time through careful diagnostics. In the end you'll probably shake your head at how simple the issue was. :bicker:

05-27-2015, 07:50 AM
I found Pertronix wiring schematics to be their main cause of problems. They are a bit vague. The main issue is that their unit needs full voltage all the time, but most early stock coils are not designed to see full voltage all the time. So you need to maintain the resistance wire or ballast resistor to feed the coil (maintains about 9 volts to the coil), but then run a main wire to switched 12 volts for the Pertronix red wire. If you get a Pertronix coil too, or one of the air-core style coils, and abandon the stock-like oil-filled coils, you can eliminate the resistor wire or ballast resistor completely and run 12 volts to everything.

05-28-2015, 12:41 PM
I agree that their documentation is "vague" and I believe it is their intent to show it as a easy drop in solution rather than any wiring modifications needing to happen. Which is the case with the original Pertronix which did not care about 12v and you could actually switch back to points/condenser as a failsafe on the road even with the resistor wire/ballast.

Anyway, I verified last night that I am only getting about 8v to the coil from the ignition switch, which looks to be the factory harness "pink wire" which would be the resistor wire. Whether I was getting less voltage or intermittent drops due to heat previous to swapping modules, cleaning the distibutor plates, and redoing connections is unknown. But both cars now are reporting 8v to the coil/pertronix in the key on position.

In looking at previous documentation on the Pertronix modules it appears that P1 only needs 6v and that P2 and P3 require a minimum of 8v, although now they state a full 12v. Luckily (and randomly) the previous owner has an additional 2 wires hooked to the ignition switch post, albeit they just go into the engine bay, are live but attach to nothing. I will verify 12v on them and use one to the coil and retest.

If this all works out, I will do the same to the Falcon and bring a true 12v to the coil, whilst retaining the original resistor wire for the emergency points fail safe or just carry the P1 Pertronix that I replaced in the Fairlane. :WHATTHE:

Thanks to all who replied on the thread. I hate electrical stuff, but I hate getting stranded even more.

05-28-2015, 02:50 PM
I hate electrical stuff, but I hate getting stranded even more.

Now that you have your Petronix module figured out, think about this: The new Ford GT has 28 microprocessors that use 10 million lines of computer code.


See: http://www.motorauthority.com/news/1098308_the-ford-gt-has-more-lines-of-code-than-a-boeing-passenger-jet

05-31-2015, 07:03 AM
Summary: I reconfigured the wiring so that the PerTronix Ignitor unit receives 12 volts when the key is in the “on” position.

My car had a PerTronix Ignitor in it when I got it. The car seemed to run alright, so I never paid too much attention to it, but all this discussion about resistor wires and low voltages made me wonder what was going on with mine.

You guys mentioned that "that the original resistor wire is acceptable because it delivers 8 volts and the Ignitor only requires 6 volts."

I looked at this site http://falconfaq.dyndns.org/Pertronix_1266/Pertronix_1266.html and they referenced the following e-mail from PerTronix:
“Date: Wed, 16 Aug 2000, “It has been my experience that most automotive enthusiasts do not even know if there is a resistance wire in their system or not. We plan on updating the current instruction manual to include "wiring diagrams for ballast resistor and resistance wire systems." As long as the voltage to our power wire is above 8 volts, then there should not be any problem with hooking up directly to the coil. The problems occur when the resistance wire condition has deteriorated and the voltage supplied to the coil is only 5 volts or even less. At that point the power wire to our unit should be relocated to the Ignition switch side of the resistance wire. Thanks for your interest, Garrett Weaver, PerTronix Technical Dept.”

I followed these directions for “Determining whether your vehicle has a ballast resistor”:
1. With the key off, connect a wire from the negative terminal of the ignition coil to the negative battery terminal.
2. Connect the black lead of the volt meter to ground and the red lead to the positive coil terminal.
3. Turn the ignition key to the “on” position. Do not leave it on for an extended period without the engine running.
4. If the voltmeter reads battery voltage (approximately 12 volts) there is not ballast resistor in the circuit. If there is less than battery voltage there is a resistor in the circuit.

My battery voltage was 12.6 volts and the voltmeter indicated a borderline 7 volts at the coil. I looked behind the ignition switch and saw a pink wire with male/female connector that I assumed was the resistor wire. The female connector coming from the ignition switch provides 12 volts when the key is “on”, and zero volts in the “off” and “accessory” positions. I unplugged the connector, inserted the end on a new red wire into the female end and sandwiched it in place by reinserting the male end of the resistor wire. I ran the new red wire to the positive terminal on the coil, leaving the original resistor wire in place. The contact at the coil then registered 12 volts (up from 7) when the ignition switch was on and zero when it was off. I'm running at full voltage! Wow! I went from marginal to optimal!


I also re-positioned the latch for the glove box cover all the way back in (towards the hood) so that lid closes a little more tightly.

05-31-2015, 08:30 AM

The pertronix can handle/wants the 12 volts - and I've never had good luck with them on anything less no matter what they say it 'can' run on, but a stock coil should not be running on 12 volts (actually 14-ish while running). You'll quickly overheat it unless it is a pertronix coil designed for 12 volts. The yellow cap Ford unit isn't.

Disconnect the 12 volt lead you ran from the coil and the pertronix red lead from the coil and connect them together only. Leave the pink wire connection on the + coil side so the coil continues to run on resistance wire. The red pertronix wire doesn't need to be connected to the coil terminal - only the black wire does to negative side.

Basically key on you should have 12 volts to pertronix red wire and your 7 volts to the coil + terminal. Both of these will bump up a volt or two with the engine running at speed (I assume you still run a generator so freeway speed will be highest voltage).

Hope this helps save your coil.

05-31-2015, 09:26 AM
Hello, Roger.

I should have stated that I also have the PerTronix "Flamethrower" coil, so 12 V to the coil should good. (I prefer to keep things stock, but am not fanatical about it. :) )

Question: The Flamethrower coil makes 40,000 V when it is operated at 12 V. When it is operated at 7 V does it make (7/12) x 40,000 = 23,333 V?

I could remove the now-redundant parallel resistor wire that goes to the coil. It isn't doing anything because now the voltage will preferentially flow in the new resistor-free wire. But leaving the old resistor wire hooked to the coil keeps it out of the way and prevents the loose end from accidentally grounding against something.

My wife and I just took the car on a 26 mile test drive and I think that the revised ignition voltage solved a "rough idle while hot" problem that it had. The traffic can be stop and go on my way home from work. The engine temperature would build and it would start idling rough and the rpm would drop when the temperature gauge rose to 3/4.

After getting home (and this is after re-wiring the PerTronix for 12 V) I put the car in Drive with the emergency brake on and let it idle to simulate sitting in traffic at a red light. I waited as the engine temperature rose to 3/4 and ..... and ..... it continued to idle smoothly!!!

I had thought that the rough idle when hot had been something to do with the carburetor. Now, I think that it was low voltage to the ignition module. The system had been operating on only 7 volts to begin with. My generator doesn't put out much voltage at idle, and the battery drops from 12.6 to 11.9 volts while sitting in traffic, while at the same time the electrical resistance in the wiring goes up as the temperature rises. The PerTronix unit was probably "flickering" from having barely enough voltage to function correctly.

05-31-2015, 09:35 AM
That's good. Maybe it will help someone else. Good to hear your drivability issues are resolved.


05-31-2015, 12:02 PM

Just a quickie that is probably negligible, but maybe significant being as how you're still using the generator.

With the resistor wire connected in parallel to the coil, it is still drawing a certain amount of current (load). Even though it is a small amount of current, you might want to consider leaving the resistor wire "hanging in the wind" to keep the load on the generator minimized.

Gene :)

06-02-2015, 07:21 PM
With the resistor wire connected in parallel to the coil, it is still drawing a certain amount of current (load). Even though it is a small amount of current, you might want to consider leaving the resistor wire "hanging in the wind" to keep the load on the generator minimized. Gene :)

Hello, Gene.

The separate resistor wire has been removed from the circuit.

I had initially hooked this up to 12 volts using some thin wire that I had. Then I downloaded and read the instructions for a "PerTronix Ignitor 1281" (See: http://www.pertronix.com/docs/instruction-sheets/1281.pdf ) and they said to "Bypass the resistance wire with a 12-gauge copper stranded wire." That was a lot heavier than what I was using so I bought and installed the correct heavier gauge wire tonight.

I looked in several auto-parts stores and couldn't find any 12-gauge male bullet connectors so I soldered the new heavier wire to the original resistor wire connector. I ordered some 12-gauge connectors off e-bay and if they fit the female coupling then I will discard the smaller gauge wire extension and plug the 12-gauge directly to the ignition switch.


The PerTronix leads coming out of the distributor cap were too long and I trimmed them to more appropriate lengths. I ran the 12-gauge wire ( the thicker red one) to the positive terminal on my 12 volt PerTronix Flame-Thrower coil (40,000 volt output). I re-checked the voltage and I am getting the correct full 12 volts at that terminal (up from 7 volts off the resistor wire). That is also where the red lead for the Ignitor unit connects so it is also now getting a correct full 12 volts. The small green wire coming off the negative coil terminal goes to my tachometer.


It has been raining for the past couple of days and I have not driven the car. Tomorrow and the day after, though, are going to be clear (20% chance of rain). This is the first time since I have had my car that the electronic ignition and high-voltage coil will be functioning as they are supposed to. When I drive the car to work tomorrow I will pay attention to how it starts, idles, and accelerates, and watch and see if the gas mileage improves.

I now have 40,000 volts arcing through my eight spark plugs! Wow! My Falcon will go airborne!