# Starting issue



## Praxis (Feb 23, 2014)

Please help. 1967 GTO with highly modified engine using MSD ignition with “brains” in the distributor body, not a separate box, automatic AC car. The car ran fine for quite a while. The ship that did the engine install also beautifully replaced The engine harness resistor wire with a non-resistor wire to the coil for the HEI. An issue began to develop a few months back (the car sadly is not driven as often as it would like to be!) in that it began to start roughly, like not firing all 8 for a few moments, then smoothed out. The issue progressed to a few seconds, then on to often spitting back through the center carb (tri-power) and running on only a few cylinders for some time before hitting all 8 and smoothing out. If I run a heavy jump wire from the + battery post to the + coil terminal it starts right up as it should. I am running 12 degrees initial advance with bypassed vacuum advance, mechanical only. I get 12 v to the coil on “run” and 10 v on “start”. With the jumper lead on, the alternator light is very bright on the dash from back feed, when I turn the key to run the light dims considerably Even with the jumper still connected. What is this starting issue caused by? I am told I need a new ignition switch, and I need a new engine harness. I am prepared to do those but I don’t want to miss something simple and more common. Help!


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## Lemans guy (Oct 14, 2014)

It sounds like your ignition “Start wire” has too much resistance. It is 10 volts when should be 12 volts. The wire could be checked with an ohmmeter to see if their is too much resistance. An easy way to see would be to get a 12 volt relay from an auto parts store and hook it up to the Start wire. You will have to run a short ground and a good power 12 volts to the relay.

then when you try to start it the relay will provide 12 volts to the coil instead of 10 volts and by your own test will be easier to start.

highly modified engine with digital distributor make sure that your did not lose lose your idle timing setting somehow. But I think you have solved your own problem with the 12 volts to the coil starts fine.


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## Praxis (Feb 23, 2014)

Lemans guy said:


> It sounds like your ignition “Start wire” has too much resistance. It is 10 volts when should be 12 volts. The wire could be checked with an ohmmeter to see if their is too much resistance. An easy way to see would be to get a 12 volt relay from an auto parts store and hook it up to the Start wire. You will have to run a short ground and a good power 12 volts to the relay.
> 
> then when you try to start it the relay will provide 12 volts to the coil instead of 10 volts and by your own test will be easier to start.
> 
> highly modified engine with digital distributor make sure that your did not lose lose your idle timing setting somehow. But I think you have solved your own problem with the 12 volts to the coil starts fine.


Thanks!
Indeed that seems to be the issue, whether it is because of the start wire getting old or some as yet undetermined drain. But yes, once the motor starts, jump wire off immediately, runs great. In fact after a drive, turn off, restart immediately, most times it fires right up. On occasion it does the same as cold start. I’m thinking put the new engine harness in, because most of it is no newer than 1990’s when the car was supposedly restored the first time, but my hunch is the harness is 1967 vintage.


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## Praxis (Feb 23, 2014)

More information in case this rings a bell for someone: even before the start issue got so bad, one day a year or more ago I was driving, it was dusk, I turned on the headlights and the engine quit momentarily but immediately went back on song. Repeatable problem. So I added headlight relays. Problem solved. I know the lights are a separate harness from the engine, and I know some will start to point at the ignition switch again, but I want to hear from you all. The dash harness is brand new M&H installed about 3-4 years ago, but the ignition switch is original. No one makes a proper reproduction 67 switch, #1116676, but 66 switch can be used but the tumblers are different. I have a new repop 66 switch with tumblers and door locks keyed alike. The big difference is 66 doesn’t have the dash light for the switch. Otherwise should plug right in. It’s just that the AC ducts have to be dropped to get to the ignition switch and they are a pain to put back. Any more suggestions out there?


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## Praxis (Feb 23, 2014)

More update: testing today showed rough running on run, but start circuit seems OK. I will put the relay inline with run wire per “Addendum” published by MSD. Update to follow.


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