Why is a Ford starter solenoid needed to start the car?????
04-13-2003, 01:11 AM
#1
Drifting
Thread Starter
Why is a Ford starter solenoid needed to start the car?????
I friend got a 78 this winter and I have been helping him out with a few problems. To those who have helped us recently great thanks to you all.
For the most recent problem:
His starter was cranking slow. Battery was new. Voltage was over 13 volts. Fresh tune up. So he changed the starter. The new (rebuilt) starter would not crank at all. Thats where I came in. He only has the (large) battery wire hooked up at the GM starter. (No (small) solenoid wire on the GM solenoid) This car has a Ford :rofl: (sorry) starter solenoid feeding battery voltage to the GM starter. The Ford solenoid gets energized from the (small) solenoid wire that should go to the GM starter. After the Ford solenoid energizes battery power goes down to the GM starter. We had to put a jumper wire at the GM starter to get the GM solenoid to energize. We put a small wire on the GM starter from the (large) battery terminal post to the the (small) solenoid terminal post. Now the starter will energize and crank the engine after the Ford solenoid energizes.
We tried to get rid of the Ford solenoid but could not. The small solenoid wire hooked to the Ford solenoid only gets 6 volts when the key is turned to start. 6 volts is enough to energize the Ford solenoid, but not enough to energize the GM solenoid. We tried, the GM solenoid wont energize on 6 volts. That is the only reason I can see for installing a Ford solenoid in the first place.
Where does that solenoid wire get power from? Directly from the ignition switch? Is there some type of resistor in the circuit that could be bad? I only assumed the solenoid wire should see full battery voltage when the ignition key is turned to start. What gives????
[Modified by Paul G, 12:14 AM 4/13/2003]
For the most recent problem:
His starter was cranking slow. Battery was new. Voltage was over 13 volts. Fresh tune up. So he changed the starter. The new (rebuilt) starter would not crank at all. Thats where I came in. He only has the (large) battery wire hooked up at the GM starter. (No (small) solenoid wire on the GM solenoid) This car has a Ford :rofl: (sorry) starter solenoid feeding battery voltage to the GM starter. The Ford solenoid gets energized from the (small) solenoid wire that should go to the GM starter. After the Ford solenoid energizes battery power goes down to the GM starter. We had to put a jumper wire at the GM starter to get the GM solenoid to energize. We put a small wire on the GM starter from the (large) battery terminal post to the the (small) solenoid terminal post. Now the starter will energize and crank the engine after the Ford solenoid energizes.
We tried to get rid of the Ford solenoid but could not. The small solenoid wire hooked to the Ford solenoid only gets 6 volts when the key is turned to start. 6 volts is enough to energize the Ford solenoid, but not enough to energize the GM solenoid. We tried, the GM solenoid wont energize on 6 volts. That is the only reason I can see for installing a Ford solenoid in the first place.
Where does that solenoid wire get power from? Directly from the ignition switch? Is there some type of resistor in the circuit that could be bad? I only assumed the solenoid wire should see full battery voltage when the ignition key is turned to start. What gives????
[Modified by Paul G, 12:14 AM 4/13/2003]
04-13-2003, 08:04 AM
#2
Le Mans Master
Re: Why is a Ford starter solenoid needed to start the car????? (Paul G)
ok alot guys install the ford style solenoid to help cure a heak soak problem,but you should have 12 volts going to that solenoid from your ignition switch,actually youll have 12 volts from the purple wire on the ignition switch to the nuetral safety switch then to you starter solenoid.So is the wire your testing a purple 10 guage wire?
04-13-2003, 08:56 AM
#3
Drifting
Re: Why is a Ford starter solenoid needed to start the car????? (Paul G)
Here's my take:
The GM solenoid (acutally all of them) are prone to needing much more current to energize as they get hot. The GM unit is the worst since it sits on the starter and can be exposed to excessive heat from headers.
What happens is the ignition switch and all the connections the ignition start wire goes through to get to the starter build up resistance over time. This means that when the GM solenoid needs the most current to energize when it is hot, the current might be reduced because the ignition switch and wiring can't supply it.
The Ford solenoid is acting as a relay (I use a relay in my car instead of a bulking solenoid).
You need to first find out why you only get 6 volts from the igniton start lead. Have you discounted the lead and sured the wire with no load? If it's 12 volts with no load then it's OK, it just can't supply enough current when hooked to a solenoid. If 6 volts disconnected, you will have to find the reason.
In my car I bout a generic relay from the parts store. I use the ignition start lead to energize the relay (relays take much less current than a solenoid so they are best and the Ford solenoid still requires too much and is overkill). I then used a fusible link purchased from the parts store and connected it to the big terminal on the stater. This gives me current right from the battery lead. The fusible link then connects to the input of the relay. The output from the relay then goes to the GM solenoid S terminal.
Once I installed the 6 dollar relay 15 years ago, I never had another case of heat soak on the GM solenoid.
Dave
The GM solenoid (acutally all of them) are prone to needing much more current to energize as they get hot. The GM unit is the worst since it sits on the starter and can be exposed to excessive heat from headers.
What happens is the ignition switch and all the connections the ignition start wire goes through to get to the starter build up resistance over time. This means that when the GM solenoid needs the most current to energize when it is hot, the current might be reduced because the ignition switch and wiring can't supply it.
The Ford solenoid is acting as a relay (I use a relay in my car instead of a bulking solenoid).
You need to first find out why you only get 6 volts from the igniton start lead. Have you discounted the lead and sured the wire with no load? If it's 12 volts with no load then it's OK, it just can't supply enough current when hooked to a solenoid. If 6 volts disconnected, you will have to find the reason.
In my car I bout a generic relay from the parts store. I use the ignition start lead to energize the relay (relays take much less current than a solenoid so they are best and the Ford solenoid still requires too much and is overkill). I then used a fusible link purchased from the parts store and connected it to the big terminal on the stater. This gives me current right from the battery lead. The fusible link then connects to the input of the relay. The output from the relay then goes to the GM solenoid S terminal.
Once I installed the 6 dollar relay 15 years ago, I never had another case of heat soak on the GM solenoid.
Dave
