Ignition issues during starting
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Senior User
Joined: Apr 2014
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Ignition issues during starting
1966 F350 352.
I have replaced the 352 with a 390. While the truck was a 352 I replaced the coil with no issues, ran fine. I have now replaced the 352 with a warmed over 390 which has a MSD and coil. The issue I have is I tested all the wiring pre 390 install and found no issues. While trying to start the 390 this weekend i could not get it to run due to low volts at the coil (which i did test) Volts at the coil are 2.7 VDC. To get the 390 to start I jumper the coil during the starter operation and got it running. After the start up I checked the coil wire again during startup and got 12.7 VDC. STRANGE. No wiring changes by myself......Bad contacts? hidden ballast resistor? resistor wire?
I have replaced the 352 with a 390. While the truck was a 352 I replaced the coil with no issues, ran fine. I have now replaced the 352 with a warmed over 390 which has a MSD and coil. The issue I have is I tested all the wiring pre 390 install and found no issues. While trying to start the 390 this weekend i could not get it to run due to low volts at the coil (which i did test) Volts at the coil are 2.7 VDC. To get the 390 to start I jumper the coil during the starter operation and got it running. After the start up I checked the coil wire again during startup and got 12.7 VDC. STRANGE. No wiring changes by myself......Bad contacts? hidden ballast resistor? resistor wire?
Tuned
Joined: Feb 2010
Posts: 277
Likes: 21
From: Western Montana
Could be dirty ignition switch, starter solenoid terminals, or a grounding issue. I would start by cleaning up all of the engine and body grounds in the engine bay. Starters pull a lot of amperage and without enough clean metal-to-metal ground paths there won't be enough capacity to run everything at the same time.
Tuned
Joined: Feb 2010
Posts: 277
Likes: 21
From: Western Montana
Nice looking 390.
The resistor wire should knock the engine running voltage to 6v at the coil. Starting voltage should be full battery voltage at the coil.
Start tracing the +coil wire looking for damage, or run a new one from the coil to wherever your diagram says it should go.
The resistor wire should knock the engine running voltage to 6v at the coil. Starting voltage should be full battery voltage at the coil.
Start tracing the +coil wire looking for damage, or run a new one from the coil to wherever your diagram says it should go.
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New coil literature states NO ballast or resistor to coil...ie full voltage for 8 cly. My thinking is to run new wire from coil + to ignition switch around resistor wire. Any special trick to remove ignition switch ?
Tuned
Joined: Feb 2010
Posts: 277
Likes: 21
From: Western Montana
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 787
From: Simi Valley, CA
C0LF-12250-A .. Resistor Wire-Ignition Coil (Motorcraft DY-37) / Obsolete ~ Available NOS and from auto parts stores.
61.49" long / Colored coded pink / 1.30-1.40 ohms resistance / #20 gauge wire.
Applications: 1960/70 ALL FoMoCo vehicles.
Note: In order to remove the ignition switch bezel, the ignition cylinder has to be removed from the switch...first.
Once the cylinder is removed, the bezel can be removed, the switch is now free of the dash and once it's removed from its hole in the dash, the ignition switch spacer will fall out onto the floor.
The spacer is located between the ignition switch and the backside of the dash. See 10A885 in this parts catalog pic.
61.49" long / Colored coded pink / 1.30-1.40 ohms resistance / #20 gauge wire.
Applications: 1960/70 ALL FoMoCo vehicles.
Note: In order to remove the ignition switch bezel, the ignition cylinder has to be removed from the switch...first.
Once the cylinder is removed, the bezel can be removed, the switch is now free of the dash and once it's removed from its hole in the dash, the ignition switch spacer will fall out onto the floor.
The spacer is located between the ignition switch and the backside of the dash. See 10A885 in this parts catalog pic.
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Laughing Gas
Joined: May 2011
Posts: 855
Likes: 40
From: SoCal
Hello Candoo, please pardon my rough intro but I have been lurking here for a long time. If that distributor is an MSD "Ready to Run" model it requires a full 12 volts to work. You will need to bypass the resistor in your ignition wire. Symptoms are the engine will start when the key is in the start position and then die in the run position.
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