Ignition power source
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 2,545
Likes: 77
From: Toronto ohio
Ignition power source
70 Corvette slightly modified. Installed a Pertronixs 1186LS and need a 12 volt power source that is switched to put on the coil. Having ignition issues. Someone installed a street fire MSD. It has power but wasn't flashing so I assumed it was not getting a pickup signal. With the 1186 the box now flashes but just a weak spark at the plugs. Want to bypass the MSD for now. I do have a new Street fire from another project but want to make sure the MSD is the problem. wasn't aware the Street fire series is not made in USA. just can not seem to find a 12 volt ignition wire under the hood other than the wire I am using for the Pertronix unit.
Last edited by 70vetteinpieces; Jun 23, 2020 at 02:25 PM.
Melting Slicks
Joined: Jun 2014
Posts: 2,236
Likes: 498
From: NJ
Trace the ignition wire back to the bulkhead connector at the firewall. The fuse panel is on the other side of the firewall. This is a resistor wire, usually a white woven wire with a black tracer, and will not sufficiently power your ignition system. This wire needs to be replaced with a 10 or 12 gauge wire stranded wire. You need to remove the bulkhead connector and pull out the spade type terminal that feeds the Ignition wire. Then replace terminal and wire and connect bulkhead connector. ( 5/16 bolt in center of connector)
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
This has been asked/answered at least 10 times in the last year. SEARCH for 'Pertronix ignition' and lots of past info should be available.
Follow the 'stock' coil power wire down to the firewall bulkhead connector and label that wire to know where you should be working. There is 12vdc coming out of that connector and INTO that wire...which is a resistance wire, used to limit the maximum current going into the ignition coil. You and cut the wire, leaving a stub on it to splice a length of regular wire to it (16 awg would be good) to run to the coil. You need to then leave both + coil wires attached to the coil: one from the starter solenoid to get power when starting, and one from the ignition switch from the 'run' terminal. Without both of them, engine won't fire or won't continue running.
If you install a Pertronix module, you NEED to change the coil to one matched to the spark power of that module. And, you need to re-gap your spark plugs to .040-.045"..... or you didn't really need to change to a Pertronix module.
Follow the 'stock' coil power wire down to the firewall bulkhead connector and label that wire to know where you should be working. There is 12vdc coming out of that connector and INTO that wire...which is a resistance wire, used to limit the maximum current going into the ignition coil. You and cut the wire, leaving a stub on it to splice a length of regular wire to it (16 awg would be good) to run to the coil. You need to then leave both + coil wires attached to the coil: one from the starter solenoid to get power when starting, and one from the ignition switch from the 'run' terminal. Without both of them, engine won't fire or won't continue running.
If you install a Pertronix module, you NEED to change the coil to one matched to the spark power of that module. And, you need to re-gap your spark plugs to .040-.045"..... or you didn't really need to change to a Pertronix module.
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 2,545
Likes: 77
From: Toronto ohio
Not sure who put in the MSD box and replaced the points with a Accel type pointless ignition system. Could have been done by a Speed Shop, Garage, DIY or the kid next door. The car ran fine for years so I never looked into it. I followed the MSD instructions for testing and it wasn't receiving a pickup signal. quick short of the pickup the MSD box would flash. According to MSD that meant a bad pickup signal. So I replaced the Accel with the Pertronix unit. Now get a good signal but not running. Still suspect the MSD box so want to bypass it. The owner ( brother) wants another MSD box but have it set up so it can easily be bypassed in the event of failure. I just want to do the bypass first to get the car running I hope then replace the MSD if defective.
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
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Alot of info suggests the yellow wire from the wiper motor, I ran a wire from a seperate fuse panel I added next to the original one for my MSD, but the buss bar is a good place and you can add an inline fuse from there