71 Pantera spark comes and goes?

I am working on a 71 Pantera,this car is new to me, and my problem is irregular spark, this is whats happening: car has been sitting for a number of years for starters, I have a new carb, installed and electronic distributor, new solenoid. used, but good, 825 cca battery. I have gotten the car to fire and run on what sounds like all 8 cyl. but it will only run 15 to 20 seconds then it dies, I installed a spark tester, where I can monitor the spark, after a 10 or 15 min. wait I can restart with strong spark, it runs 15 to 20 seconds then it dies, what I have noticed is when it dies its because it has no spark, if I try to start it immediately it has no spark, but after waiting 10 to 15 min. it will start but do the short run thing...I am lost on this.One other item of note is the carb has an electric choke that I have wired in at the power panel , but not at the coil, I used a key on 12v. supply, can I use power from the oil pressure sending unit? Any help is appreciated
Original Post
Welcome to the forums Al.

The "intermittent" ignition is probably the ignition module. Is it a Ford "Duraspark"? If so, all you need to know to replace the module is the color of the plastic "strain relief" where the wires come out of the module. Replace it with a module having the same color "strain relief".

The OEM fuses and fuse panel are notorious for bad connections ... so when in doubt, give all the fuses a spin or two to help them make contact.

The OEM power to the ignition is routed through the ignition switch, the contacts in the ignition switch are normally in quite bad shape by now. The dirty & charred contacts will create a high resistance path for the current trying to flow to the ignition. The high resistance drops the voltage so much there's hardly enough to operate the ignition. As it heats up the resistance increases, and the ignition stops functioning.So the ignition switch is another possible source for the problem. You can troubleshoot this by running a piece of 12 gage wire directly from the battery to the ignition. If the engine runs OK, suspect the ignition switch. When its time to shut the engine off, just pull the wire off the battery. The ignition switch can be disassembled and cleaned.

-G
Thanks George, the car does not have the Dura spark set up, I removed a Mallory Dual Point that was pretty fried. I did check the fuses prior to this issue, cleaned all the contacts and replaced all the fuses...funny thing...past owner had wrapped 3 fuses in foil to get thing to work, guess he didn't have fuses, replacing the with new ones appears to have done the trick. This car only has 18,000 miles and most everything I check looks new. Al
Connect the jumper to where ever you are supposed to supply power for the new ignition. There must have been a wire or terminal the instructions for the new ignition said was the power connection. In other words, supply the new ignition with power connected directly to the battery, and thereby bypass the entire wiring harness of the Pantera. If you used the power wire from the OEM coil to power the new ignition, then remove that wire and use your 12 gage jumper in its place.
So I finally got back to the 71 Pantera, started checking out the suggested issues, coil, Ballast resistor and Alternator. the alt. had grinding sounds so I took that down to NAPA and found out the alt. was not charging, so I replaced that, now I have a solid 12v during idle but still only runs for 15 to 20 seconds then stops ...no spark, I am believing / hoping the coil is good because it is new and was installed at the same time as the new distributor, I know its been suggested that the ignition switch could be a source of resistance and may need cleaning or replacement, but removing and cleaning seems just a little intimidating...so that leads me to the ballast resistor, the one in the car appears to be an Autolite original, where can I find one? or what can I use? looking at the simple less expensive items 1st before I hit the switch
quote:

Originally posted by over50:

Exactly what distributor and coil do you have in the car?



excellent question Norm.

Al, the dual ballast in the 1971 Pantera is not a Mustang part. You're not going to find it at the nearest parts house. It shouldn't be needed by a new "electronic ignition" either.

If you would perform the test I suggested, it would tell you this much:

(1) If the engine runs without shutting off in 20 seconds then the problem lies within the Pantera wiring harness.
(2) If the engine continues to shut down in 20 seconds, its the new parts that are a problem.

I believe the instructors in various fields who teach troubleshooting refer to this technique as "splitting the system". It narrows down your search for the source of the problem. A length of 12 gage stranded wire and a couple of alligator clips is cheap, and useful over and over. Its better than buying parts you didn't need to buy. It saves time too.
George, so I did try your suggestion of by passing the switch with the 12 ga. wire, and it started but.... 15 sec. or so she died again..as I said I had a ballast resistor in my parts bin, I think it was from an old Mopar I had, anyway it had 4 terminals so I hooked it up and bingo, she fired right up had it running about 15 minutes, got things good and hot and all seemed good, I shut it off so I could permanently mount the "new" resistor and fired it up and it ran for 15 sec and shut down..so I know the issue lies with that resistor..my thought is get a new one..what do you think..any ideas?
quote:

Originally posted by Al SPODEN:

... I know the issue lies with that resistor..my thought is get a new one..what do you think..any ideas ...



Al, the dual resistor is an oddball set up found on 1971 - 1972 Panteras. One of the resistors is wired between the coil positive and the battery power, the other is wired between the coil negative and the distributor (breaker points). This places the coil primary in sries with the two resistors, smack dab in the middle between them. The sum total of the two ballast resistances was 1.35Ω. The coil had 1.47Ω primary resistance, 8,200Ω secondary resistance. I've never seen this split ballast resistance set-up in a Ford (but my memory is faulty these days).

The whole thing was replaced with a standard set up in mid-1972 (Pantera L models), a 1.35Ω resistance wire was inserted in the wiring harness between the coil positive and the battery power, no resistance between the coil negative and the distributor.

I seriously doubt the new ignition needs to split the ballast resistance ... perhaps it needs a different amount or none at all. I would think the new ignition would have came with a new ballast resistor. No?

I am not familiar with the ignition you purchased. My only advice is to wire the ignition power circuit exactly as the manufacturer instructs, assuming the manufacturer provided instructions. Proper resistances, etc.

-G
So I'm back working on the ignition issues, here is where I am, I contacted the seller of the distributor, coil, wire set...nothing fancy not a name brand, but he thought I may have a bad coil and he also said do not use a ballast resistor, so here's what I did, eliminated the resistor by installing 2 inline fuses with 10a fuses( I did that so I would not fry something else) replaced the coil using a MSD Blaster 2 coil for electronic ignitions(not points style) I have no spark at all now, testing the wires going to the coil I have red wire to positive + sending 12 volts the blue wire (which used to go to the ballast) that also went to the negative side of coil showing just a very minimal current ( a 12 volt bulb barely glows) so I got nothing and I'm lost...thinking I could just ground negative coil side to battery ground to get fire...will this work? Asking first before I blow this thing up..lol
quote:

Originally posted by Al SPODEN:

...thinking I could just ground negative coil side to battery ground to get fire...will this work? ...



Nice choice of words. You will indeed get FIRE! Grounding the negative will turn the coil into an 8 amp electric heater ... or make it glow like an 8 amp night light ... until it catches fire. Eeker

Grounding the negative is not advised. Smiler

You need these connections:

(1) The red wire (actually pink I believe) from the car's wiring harness wired directly to the coil positive. This is battery power to the coil.

(2) The Blue wire with black stripe from the car's wiring harness wired directly to the coil negative. This is the wire going to the tachometer.

(3) A new wire providing battery power to the electronic ignition. Perhaps connected to the coil positive, sharing the power provided by the pink wire.

(4) A new wire from the electronic ignition to the coil negative, triggering the coil to fire.

(5) A new wire from the electronic ignition to ground. If the ignition (distributor) is grounded by its contact with the engine block, then this wire isn't necessary.

Good luck!
quote:
Originally posted by Al SPODEN:
I am working on a 71 Pantera,this car is new to me, and my problem is irregular spark, this is whats happening: car has been sitting for a number of years for starters, I have a new carb, installed and electronic distributor, new solenoid. used, but good, 825 cca battery. I have gotten the car to fire and run on what sounds like all 8 cyl. but it will only run 15 to 20 seconds then it dies, I installed a spark tester, where I can monitor the spark, after a 10 or 15 min. wait I can restart with strong spark, it runs 15 to 20 seconds then it dies, what I have noticed is when it dies its because it has no spark, if I try to start it immediately it has no spark, but after waiting 10 to 15 min. it will start but do the short run thing...I am lost on this.One other item of note is the carb has an electric choke that I have wired in at the power panel , but not at the coil, I used a key on 12v. supply, can I use power from the oil pressure sending unit? Any help is appreciated


1st i have to ask why you decided to change out the ignition system, did this same problem exist before the new dizzy, coil & wires?
4V and Proud...I removed the old system because : 1st it was not the original, the previous owner had installed a Mallory dual point and then somehow fried it, the points were burned together and the condenser was also bad, add to that the cap was cracked and the rotor burnt, so I decided to take the opportunity to upgrade to a HEI system. When the car was purchased it did not run or even crank, a new solenoid got it to turn over, I have replaced the entire cooling system, tubes, radiator, hoses,correct thermostat, new timing gears and chain,water pump, master cylinder, brake hoses, clutch cylinder and master....so then I started this issue with the ignition.
so it's safe to assume there may be a possibility of some kind of damage in the harness, whether it's heat related from leaving the ignition On forever with points or some mis-step by a previous owner attempting a repair or upgrade

your description of the 'time out' after the new ignition system shuts down sounds like a circuit breaker resetting?

i'm not familiar with the 1971 Pantera wiring plan but i'll bet George and hopefully several others here can pick your brain & guide you through figuring it out, try not to take prying questions personal there's no other way to get through it Smiler

have you tried a direct hot wire from the battery to the coil + ? an aftermarket EFI should run full charging voltage, most of them are GM style modules

yeah i noticed you're not very far from here too, is your roof skydiver rated?

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