cuda running bad

[cudanut jim]

My 1970 Cuda has a 360 with a Holley 4150 750 cfm carb. and expensive Holley fuel pump. I filled the fuel tank with 93 octane Marathon gas. Started to drive at a steady speed down the road to a destination about 3 miles away. The farther I drove, the rougher the engine ran. Started sputtering until it finally had enough. Checked the plug wires and found some full of corrosion at the distributor. (I have electronic ignition) # 5 was to the point of broken tabs on end of wire in distributor. Wires were new last October. Bought new cap, rotor, wires and spark plugs. Installed correctly and in proper firing order. Very hard to start and back-firing out of exhaust. After troubleshooting found a good spark from coil and no spark to plugs. Bought new distributor and still can't keep running long enough to check timing I'm almost 100% sure it's not 180 degrees off because I put new distributor in exactly as old one was taken out. Thinking maybe bad gas but not very likely. It has been cutting out when sitting at red lights but starts right up and ran fine. Any ideas would be helpful. thanks

[JVMopar]

You say good spark at the coil. So your saying it will throw a spark when you hold the wire about an inch from the engine?

[cudanut jim]

yes. That's exactly what I did. With new distributor I'm now getting a spark at the plugs but runs terrible.

[John Kunkel]

If you're unsure of the timing just keep turning the distributor one way or another until it smooths out or dies.

I'm curious, what made you think the original problem wasn't fuel rather than spark? Did it run OK before you filled the tank with Marathon gas? Changing parts at random is a pretty expensive way to troubleshoot a problem.

[JVMopar]

I'm with John on this one. I think it may be a fuel issue. Rather than ignition, although there must have been a reason behind why you didn't have spark at the plugs.

[cudanut jim]

The distributor had spark at first because the engine did turn over but it ran very rough. Then it lost spark. The distributor was one I bought at a chain auto parts store for about $30, which is why I suspected that. I put the clamp from the timing light over the wires and cranked it over,
no spark. It ran pretty good before I put the fuel in it, then it continuously got worse.All along I thought it was a fuel issue. I've gotten fuel at this particular station quite a lot. Never a problem.

[cudanut jim]

Last night I tried starting again. Very weak spark from Accel coil. Put old one on I had laying around. Much better spark and engine started right up. Gave acceleration and backfiring from exhaust no matter where I turned distributor. Also noticed .puddles of oil sitting on intake at bolt mount areas. Very strange. Bolts are torqued to spec.

[cudanut jim]

New problem. Cannot start car from key switch. Getting 12 volts at yellow wire on starter switch when key in start position. Both blue wire & brown wire on each side of ballast resistor get 12 volts when key in proper position. Black wire from key switch works accessories(lights, etc). Only way to start is jump relay with screwdriver or remote starter switch with key in run position. Wtf?

[John Kunkel]

Automatic? If so, the brown wire on the starter relay marked "G" is connected to the Neutral Safety Switch (NSS). If the switch is bad/disconnected or if the shift linkage is out of adjustment the switch won't provide a ground for the relay.

Quick test, disconnect the brown wire and hook a ground wire to the "G" terminal on the relay, if it turns over the problem is somewhere from the relay down to the trans.

[cudanut jim]

automatic yes. Thanks John. I'll try that with the brown wire. I looked at my wiring diagram to be sure I understand what you said. Looks easy enough. Its a pretty new switch but it's prob. made in China

[cudanut jim]

Ignition problem figured out. Either the neutral switch bad or it came unplugged from the trans. Ill' check that later. As usual , John was right.

[cudanut jim]

Okay back to the original,big problem . Starts right up cold. I took about a 1 hour ride and the temp went up to 190 deg. Ran perfect. Timing set at about 15 deg. adv. at idle. voltages running at idle- coil + 7.9v, ballast res. run side 12.04v, bal. res. start side 8.25v, alternator 14.4v, battery 14.4 v. Now when not starting coil + 9.5v, bal.res. start side 9.5v, battery 12.5v. not getting spark either. Hmmmmmmm. any ideas would be appreciated.

[John Kunkel]

Assuming you have Mopar electronic ignition, try this next time it won't start.

Disconnect the engine harness connector at the distributor, turn on the ignition switch and touch the male prong on the engine harness to ground. Each time the prong is grounded and pulled away you should get a spark from the coil. If it sparks, the distributor pickup is the problem, if not it's the primary wiring, ECU or coil.

[JVMopar]

One issue I've had was the air gap between the reluctor magnetic pick up. Drove my truck to the gas station and it wouldn't restart. So I pulled the cap and noticed the air gap looked quite large. So I closed it up a bit and the truck fired right up. Spec. is 0.008-0.010"

[cudanut jim]

I set the gap at 0.008 before I put it in. I guess I could check it again. It seems to me that after it warms up something gets too hot and doesn't work correctly. I know you men preach not to keep buying parts and to troubleshoot the problem, but if I purchased an MSD or a mallory ignition box it would eliminate the junk ECU that's junk these days, the ballast resistor that's always been junk, and the coil. It might be a feasible 1 time peace of mind purchase, which aren't Chinese-made junk like everything else. I'm up in arms on this one. Inconsistency is the big problem here. I've had two other mopar guys here looking at it who've had mopars for years and they can't figure it out.

[DanL]

Have you checked your firewall connections?

From your numbers, I see a 2V drop between the battery and the high side of the ballast resistor when it's running. You didn't specify the voltage at that spot when it doesn't start.

My $$ is on electrical gremlins.