[428RA4]

Having a hell of a time with a MSD distributor jumping 10 degrees at 2500 RPM's. Seems that running the stock starter that requires a 2nd wire - STOCK wiring harnes- is creating the module to jump timing.

The car will not start if I disconnect said extra wire. Looking for suggestions on how to fix this.

thanks

mike

[steve25]

I cant for the life of me see how having starter wiring problems will make the timing jump around at 2500, or any rpm for that matter once the engine has started up!!!!

[428RA4]

Well it's happening and confirmed by the engineering group at MSD. Yes, I have gone that far in this process. The module was designed to see 12 volts and its not getting it from a traditional factory wiring set-up.

I need to figure out how to make the electrical system work with the factory starter.

[chiphead]

What you have is a very common problem when upgrading the ignition on these older cars.

The factory system used a resistor wire from the ign switch "run" terminal to the ignition coil. This dropped the voltage down to about 8 volts to keep from burning the distributor's ignition points up so fast.

In the "start" position, the resistor wire was bypassed by a wire that went from the starter solenoid terminal to the (+) side of the coil. When the starter is cranking, the solenoid (R) terminal routes a full 12V to the ignition coil, providing a hotter spark for cranking. The keyswitch itself disconnects the "RUN" wire in "START", so without the wire from the starter it will never start with the stock setup. So both the resistor wire and the starter (R) wire are needed in the stock setup.

When the engine starts, you release the ign key and the key goes to the "run" position. The keyswitch then powers the coil through the resistor wire. The resistor wire is located in the engine harness that goes from the firewall electrical bulkhead to the engine.

You need to remove or otherwise bypass that resistor wire in the harness when running HEI or other solid-state ignition system. That will provide a full 12V to the ignition when running. There are several ways to do this. I always find another switched 12V hot and wire that to the appropriate terminal on the ignition box. Then I cut or remove the resistor wire from the harness.

The cleanest way would be to buy the replacement engine harness that replaces that resistor wire with a regular wire. Those stock appearing harness are available, but not cheap. You can even get other mods to those harnesses, like electric choke, modern alternators, electric fans, HEI, tach signals, etc built in so you don't have to cobble it in yourself.

Honestly, if you're going to do a lot of upgrades to the electrical, better to plan it all out at once. Otherwise you'll be going back into the engine harnesses over and over and it'll look cobbled together.

[428RA4]

Thanks so much for giving us the poop on this.

Since I can't just remove the wire from the harness - because the car will not start, what would be the step by step solution to fix this?

Would I just run 12 volts to the coil directly? And if so, would it be ignition 12 volt hot on?

Sorry for the basic electrical questions, but I'm no whiz when it comes to this stuff.

thanks
mike

[boater bill]

Originally Posted by 428RA4

Thanks so much for giving us the poop on this.

Since I can't just remove the wire from the harness - because the car will not start, what would be the step by step solution to fix this?

Would I just run 12 volts to the coil directly? And if so, would it be ignition 12 volt hot on?

Sorry for the basic electrical questions, but I'm no whiz when it comes to this stuff.

thanks
mike

What I have done is to solder and splice a new 14 gauge copper wire to the pink resistor wire at the firewall bulkeah connector. This gives the 12 volts to the ignition and only one wire is modified. I removed the bulkhead connector at the firewall, pressed on the blade of the pink wire to remove it from the bulkhead connector to make my connections. I removed the pink wire totally from the harness and routed and taped the harness to look like nothing was ever done.
Pretty easy.

Good luck!

[60man]

Originally Posted by chiphead

What you have is a very common problem when upgrading the ignition on these older cars.

The factory system used a resistor wire from the ign switch "run" terminal to the ignition coil. This dropped the voltage down to about 8 volts to keep from burning the distributor's ignition points up so fast.

In the "start" position, the resistor wire was bypassed by a wire that went from the starter solenoid terminal to the (+) side of the coil. When the starter is cranking, the solenoid (R) terminal routes a full 12V to the ignition coil, providing a hotter spark for cranking. The keyswitch itself disconnects the "RUN" wire in "START", so without the wire from the starter it will never start with the stock setup. So both the resistor wire and the starter (R) wire are needed in the stock setup.

When the engine starts, you release the ign key and the key goes to the "run" position. The keyswitch then powers the coil through the resistor wire. The resistor wire is located in the engine harness that goes from the firewall electrical bulkhead to the engine.

You need to remove or otherwise bypass that resistor wire in the harness when running HEI or other solid-state ignition system. That will provide a full 12V to the ignition when running. There are several ways to do this. I always find another switched 12V hot and wire that to the appropriate terminal on the ignition box. Then I cut or remove the resistor wire from the harness.

The cleanest way would be to buy the replacement engine harness that replaces that resistor wire with a regular wire. Those stock appearing harness are available, but not cheap. You can even get other mods to those harnesses, like electric choke, modern alternators, electric fans, HEI, tach signals, etc built in so you don't have to cobble it in yourself.

Honestly, if you're going to do a lot of upgrades to the electrical, better to plan it all out at once. Otherwise you'll be going back into the engine harnesses over and over and it'll look cobbled together.

Bazinga !!!...nice explanation..

[HWYSTR455]

Yes, nice explination chiphead!

On the engine harness, last I checked, they are only $95 or less, and $15 for the 'HEI conversion'. That was an American Autowire harness, all the correct ends, factory looking, etc. I always do the charge wire upgrade to 10ga ($15 option). Think there was also a CS-130 conversion for $15 too.

If you're not sure about the origin, or if your harness is original, you should replace the harness, period.

.

[Bob Crueger]

This pretty much answers why it won't run, although it should run in that short period of time after it starts and the key slips backs to "run"...the timing jump though?

[GTO Dan]

Chiphead-

Does this only happen when running an MSD Distributor without the MSD Box? I have run several MSD boxes with their distributor (analog and Digital- 6 and 7) and have never experienced this problem.

428RAV - Sorry to hijack but thought the clarification would be useful.

[HWYSTR455]

The MSD box is what powers the distributor when installed, and you usually don't use the coil wire to power or switch the box.

The timing jump is from the module not getting a full 12v. HEI distributors suffer the same when not getting enough voltage.

.

[chiphead]

When modifying the electricals, the devil is the details. There are several ways to install an aftermarket ignition. In general terms, anytime you starve an electronic system for power, it's gonna do screwy things. Some designs may be more fault tolerant of voltage sags or spikes, so it all depends on the parts you use and how you connect them.

Work on these cars long enough and you get pretty good with the common ailments:
ignition upgrades
alternator upgrades
electric fans
electric fuelpumps
crazy taillight problems

you really learn how to wire a 10-SI alternator to an aftermarket ignition when you turn the key "off" and it keeps running.

I'll have to check American Autowire out. Some of the other venders want $250-400 for quality replacement engine and dash harnesses for these cars.

[HWYSTR455]

Originally Posted by chiphead

When modifying the electricals, the devil is the details. There are several ways to install an aftermarket ignition. In general terms, anytime you starve an electronic system for power, it's gonna do screwy things. Some designs may be more fault tolerant of voltage sags or spikes, so it all depends on the parts you use and how you connect them.

Work on these cars long enough and you get pretty good with the common ailments:
ignition upgrades
alternator upgrades
electric fans
electric fuelpumps
crazy taillight problems

you really learn how to wire a 10-SI alternator to an aftermarket ignition when you turn the key "off" and it keeps running.

I'll have to check American Autowire out. Some of the other venders want $250-400 for quality replacement engine and dash harnesses for these cars.

I ordered an M&H for the clone, with HEI conversion and upgraded charge wire, and it was like $210 shipped. I was shocked. I used to get the factory engine harnesses for $55-65, then options. Was always under $100 that I could remember, hence the shock. So, even though I went ahead and got the M&H one, I shopped, and found a couple much cheaper.

.