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85 mustang start sol prob

jong's Avatar
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02-11-03, 06:10 AM   #1  
85 mustang start sol prob

I have an 85 mustang that I just purchased. I am sure it was orig a 4 cyl but it now has a 302 in it. My problem is that the small wire that goes to the start sol that is suppose to have 12v. when the key is turned all the way foward gets 12v. as soon as you switch the ign on. I have taken the plug off that is next to the key switch and checked all the plugs and there are no shorts there. Part of my problem is that I do not completly understand the way the whole ign sys is suppose to work in the 1st place. Any help would be greatly appreciated.

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fordtech's Avatar

Join Date: Jun 2001
Posts: 247

02-11-03, 08:33 AM   #2  
The ignition switch(electrical switch under the dash) may be out of adjustment or worn.I'd also suggest you get a repair manual if you plan on keeping this unit.Good luck.

Joe_F's Avatar
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02-11-03, 09:53 AM   #3  
I agree. Many headaches to be found by such conversions...the integrity of the conversion is not really known .

jthompson's Avatar

Join Date: Jul 2002
Posts: 471

02-11-03, 05:47 PM   #4  
The ignit switch in the steering column in my mustang just went out, a $10 part, but it would cause starting problems, may want to look there as well.

Stevo2's Avatar

Join Date: Sep 2002
Posts: 431

02-12-03, 01:39 AM   #5  
You should only have 12volts on the solenoid wire when the ignition switch is in the "start" position. This will pick/engage the solenoid and in turn run the starter, when the igniton switch is released to the "on" position voltage should be dropped on that line and then the relay and starter will disengage. Some more theory below.

This type starting motor, is a four pole, series parallel unit with a positive engagement drive built into the starter. The drive mechanism is engaged with the flywheel by lever action before the motor is energized.

When the ignition switch is turned on to the start position, the starter relay is energized and supplies current to the motor. The current flows through one field coil and a set of contact points to ground. The magnetic field given off by the field coil pulls the movable pole, which is part of the lever, downward to its seat. When the pole is pulled down, the lever moves the drive assembly into the engine flywheel.
When the movable pole is seated, it functions as a normal field pole and opens the contact points. With the points open, current flows through the starter field coils, energizing the starter. At the same time, current also flows through a holding coil to hold the movable pole in its seated position.

When the ignition switch is released from the start position, the starter relay opens the circuit to the starting motor. This allows the return spring to force the lever back, disengaging the drive from the flywheel and returning the movable pole to its normal position.

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