Authored by Wes Vann, last revised on March 28, 1997
PLEASE NOTE: Any time that you work on the electrical system of yourcar, disconnect the battery! (I like using a SCCA approved battery disconnectswitch)
The intent of this page is to clear up the questions in regards to addinga Ford starter solenoid and to help with the dreaded "heat soak"that seems to get all of us Chevy guys (and also girls, in order to bePC) at one time or another (normally while trying to show off during thatfirst date).
This information is "general" in nature and shouldn't be consideredas exactly what you have in your garage. (it is exactly like the car inmy garage)
Other than differences in the gearing, (to accommodate different flywheelsizes) there are basically two different starter motors. A low torque anda high torque. You can tell a set-up with the high torque starter motordue to a spacer being required between the solenoid and the electricalconnection to the starter.
THIS IS THE ORIGINAL GM WIRING CONFIGURATION
The battery wire to the solenoid in the stock configuration is hot atall times.
The sequence of events that happens in the standard GM when you hitthe starter is as follows;
1. The electricity has to go from the starter switch through the loomto the neutral safety switch.
2. If you are in park (or neutral) the electricity then goes throughthe loom to the stock solenoid "s" terminal.
3. When the "s" terminal goes hot, it energizes the solenoid.This causes the plunger to throw the starter gear out to the ring gear(flywheel). It also closes an internal set of contacts that sends electricityto the starter motor and also to the "i" terminal.
4. The starter motor doesn't get power until the solenoid contacts areclosed. The wire from the "i" terminal is a ballast resistorbypass for the coil. It gives a solid 12 volts to the coil during cranking.
Here is where a problem is encountered. It takes a fair amount of currentto energize the stock solenoid when hot. Due to the amount of resistancein the wiring set-up, it may not be possible to supply the required current.This is where the Ford solenoid comes into play.
If you question this being the problem, you could add a temporary wirefrom the "s" terminal on the solenoid, to near the battery. Whenyou have a problem starting your car, touch the end of the wire to thepositive terminal on the battery. If the car cranks over, you know thatthe Ford solenoid will solve the problem. NOW TAKE NOTE!!!!! This is howthat thief down the road would hot wire your car and you just made it realeasy! ALSO NOTE!!!!!! You have bypassed the neutral safety switch withthis wire and you could start the car with it in gear and have it driveaway without you!
THIS IS THE MODIFIED WIRING WITH THE FORD SOLENOID
If you are running an HEI distributor, don't worry about wiring to "i"terminals.
1. The wire that goes to the "s" terminal on the GM solenoid(closest to the block) is removed and wired to the "s" terminalon the Ford solenoid.
2. The wire that goes to the "i" terminal on the GM solenoid(farthest from the block) is removed and wired to the "i" terminalon the Ford solenoid. The "i" terminal on the GM solenoid willnot be used. When you purchase the Ford solenoid, make sure that it hasthe "i" terminal if required for non-HEI distributors.
3. The battery cable is removed from the GM solenoid and is put on oneof the large terminals on the Ford solenoid.
4. A battery cable is run from the other large terminal on the Fordsolenoid to the large terminal on the GM solenoid.
5. Also on the large terminal on the GM solenoid, you have to add aheavy gauge (10 gauge) wire to the "s" terminal on the GM solenoid.
Now, this is what happens when you hit the start switch;
1. The electricity from the starter switch only has to energize theFord solenoid (that is mounted in a relatively cool location).
2. The "battery" cable to the GM solenoid goes hot. The Ford"i" terminal also goes hot, providing non-ballast voltage tothe coil.
3. The GM solenoid now gets a solid "high capacity" currentsupply and works the plunger and contacts. The internal contacts send voltageto the starter motor.
There are a few things that should be noted.
This set-up DOES NOT make the GM solenoid any cooler. It justgives it a better current supply. Anything that can be done to shield thestarter from the header heat would be beneficial. There are several heatshields on the market and even GM makes one.
Always be sure that any wiring doesn't come in contact with the exhaustpipes.
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