Resistor Problems?

Fellas-

I have a big block ford that starts up fine, but when given some gas, it starts missing and popping. I've replaced the carb, replaced the coil and it still occurs. I have a pointless distributor with an MSD 6a box. Might a bad resistor cause this problem. Should I just replace it and see what happens?

Thanks,

Ron

Good afternoon Ron,

Check the wiring diagram for the MSD ignition, I don't remember that it uses a ballast resistor. Did you just install the box, or has it been on the car for a while?

Regards, Mark

Mark-

I've had the MSD box in for about 4 months, no problems. The problem started while I was on the freeway, noticing a slight miss. The next day, I'd go down the street and it'd pop and miss real bad. I then switched coils and carbs and it still ran bad. For some reason, I replaced my regular carb and it ran fine going around the block. The next day, it started missing and popping again. I wouldn't think the box went bad, I checked all ground wires and they look okay. so I'm wondering about the ballast resistor and whether thats bad.

Ron

Ron,

I checked the MSD instructions and the ballast can be kept in place (or removed) because it is bypassed by the MSD ignition module. This implies that it shouldn't be having any effect in circuit.

Instructions can be found on this link:

http://www.msdignition.com/pdf/6%20series/6series.pdf

Aside from the ground wires, what about the supply side and trigger sense wires?

Does the pop and miss take place only when accelerating, cruising, at idle, all of the above?

Mark

I had the same thing happen to my '29 Ford with a 289 and it turned out to be a bad plug wire. It has Taylor plug wires and one of them developed a crack down at the plug socket. If you have not done it yet I would carefully examine each wire to see if one is bad.

Your plugs are shot. Maybe bad wires, but I'd bet new plugs will fix it. Missing under load after running good for some time is almost always the plugs, even fairly new ones.

Okay, I checked the fuel pump, changed the fuel filter, checked all spark plug wires, changed spark plugs and the miss is still there. Again, it idles okay, but when given a little gas, it begins missing.

So, I'll recheck all MSD wires once again and if all looks okay, I'll have to assume the MSD box went south?

Mark...thanks for the MSD instructions, they helped alot.

Ron

Hi Ron,

I've got a new MSD 6A on the shelf (somewhere) that you're welcome to for diagnostics. PM me if you're interested. UPS charges between here and Burbank should be $2 or so.

Regards, Mark

Mark-

Thanks for your offer...I found what the problem was.....a faulty battery. I noticed that it wasn't cranking out 12 volts, so I hooked up the battery charger and although I couldn't drive it, it didn't miss at all. I understand that MSD boxes
must have at least 12 volts otherwise they get real testy. So today, a new battery goes and I anticipate that should resolve the problem. If not, I'll be back on this forum for more help.

Thanks to all for their helpful suggestions.

Ron

A bad battery shouldn't cause low voltage while the car runs. That sounds more like your voltage regulator, else a bad connection. Also, check the terminals at your alternator and battery.

Recently, I had charging problems on my 78 firebird, shortly after installing a 'one-wire' 100amp chromed alternator. Thought the new alternator had prematurely kicked the bucket, but it turned out that the heavy wire to the alternator had broken most of its conductors at the ring terminal. The few strands which remained were not sufficient to supply the current required to run the engine, lights and stereo.

EG-

You are correct. I put in a new battery and it still continued to miss. It's a mystery to me when I had the battery charger on the old battery, it didn't miss.

So, now I'll check the alternator current and wiring as well.

Thanks for the info.

Ron

I just touched off my 429 with a 6AL and I'm going through the same aches and pains. It feels like its dropping off a hole or two when you slowly roll it on from idle to 2k+- then O.K? Seems to be workin way too much to run. Cam is run in for bout 1/2hr @ 2k. I changed plugs, wires, cap and rotor, checked TDC on new balancer again, checked cam degree again, swapped out carb.....The 6AL was from ebay...another ebay disasteer!!! I'm consisering shelling out for a new 6AL on sale at summit now about $20 off.....
Open to any suggestions!

This is a long shot but dont forget fuel quality. Take a fuel sample, and check for water.