Switched the starter, still not starting

[1985 supra MK2]

yes i agree that would work but why just use a temp fix when all you need to do is get a new positive cable that runs from the battery to the starter (selenoid) and then that would take care of the problem.? also you might want to have an electrical systems test done on the alternator just to be sure it is functioning the way it is supposed to be.

[CyFi6]

Originally Posted by 1985 supra MK2

yes i agree that would work but why just use a temp fix when all you need to do is get a new positive cable that runs from the battery to the starter (selenoid) and then that would take care of the problem.? also you might want to have an electrical systems test done on the alternator just to be sure it is functioning the way it is supposed to be.

Because that is not the problem. There are two wires that go to the starter; the positive battery cable, which is heavy gauge, and the small, blue trigger wire, that only receives current when the key is turned to start. The problem is the trigger wire, not the big positive cable bolted to it. When you turn the key to start, current goes through this blue wire, energizes a coil of wire making magnetism, and pulls a plunger, when this plunger is fully pulled, it connects two more contacts, the positive batter cable and the bigger coil of wires that turns the starter. The problem is over time that little blue wire gains resistance internally and doesnt provide enough current to pull the plunger all the way to the point where the other contacts touch, therefore you can hear the plunger moving, but its not going enough to make the starter contacts touch. This is why people usually experience this problem more when the car is hot ( heat=more resistance). So by using this relay, you can take the small amount of current supplied by the old blue wire, and use that to switch the relay which in turn will give full battery voltage.

This is not a temp. fix at all. It is permanent. You can take out your entire wiring harness from your car, trace the blue wire back through all its connections and all the other wires its involved with, and replace them all, or you can do a simple relay mod like many many others have done.

[1985 supra MK2]

well i am not trying to argue a point, i had the same problem with my 85 and i replaced the positive cable and it took care of the problem, so like i said i was not trying to argue a point i was just offering advice.

[Bill UK]

Copied from previous post HERE
One of the problems is the gauge of the wire, although probably ok when new, it is too thin and over the years the copper wire deteriorates, resistance increases due to age and the constant heat changes. This becomes more apparent when the engine bay heats up, the thin wire will also heat up, causing high resistance. A permanent fix is to fit a 30 or 40amp 12v relay in the engine compartment. Instructions below.

The thin wire from the ignition activates the coil in the relay which doesn’t need a lot of current. The switching part of the relay takes care of the amps required for the starter solenoid, The large wire going to the starter motor from the battery is the main power to turn over the starter motor once the solenoid is activated, this wire doesn’t need to be upgraded. Insructions;
1. Disconnect the battery
2. Fix the relay to the bulkhead or somewhere covenant.
3. Remove the thin wire going to the starter motor and connect it to terminal # 86 on the new relay
4.Connect terminal # 85 to earth (negative) using a 20 amp wireAt this stage you can check the relay is working by connecting the batteryand switching on the ignition as you would normally do to start the car. You should hear a click from the new relay but the starter will not turn over until you have competed the next steps.
5. Remember to disconnect the battery again
6. Connect a 20 amp wire to the spade terminal on the starter motor. (This is where the thin wire was once connected.) Connect the other end to # 87 on the relay.
7. Connect 20 amp wire straight to the battery and to # 30. connector on the relay. Job Done.

[RedAstig]

Originally Posted by Bill UK

Copied from previous post HERE
One of the problems is the gauge of the wire, although probably ok when new, it is too thin and over the years the copper wire deteriorates, resistance increases due to age and the constant heat changes. This becomes more apparent when the engine bay heats up, the thin wire will also heat up, causing high resistance. A permanent fix is to fit a 30 or 40amp 12v relay in the engine compartment. Instructions below.

The thin wire from the ignition activates the coil in the relay which doesn’t need a lot of current. The switching part of the relay takes care of the amps required for the starter solenoid, The large wire going to the starter motor from the battery is the main power to turn over the starter motor once the solenoid is activated, this wire doesn’t need to be upgraded. Insructions;
1. Disconnect the battery
2. Fix the relay to the bulkhead or somewhere covenant.
3. Remove the thin wire going to the starter motor and connect it to terminal # 86 on the new relay
4.Connect terminal # 85 to earth (negative) using a 20 amp wireAt this stage you can check the relay is working by connecting the batteryand switching on the ignition as you would normally do to start the car. You should hear a click from the new relay but the starter will not turn over until you have competed the next steps.
5. Remember to disconnect the battery again
6. Connect a 20 amp wire to the spade terminal on the starter motor. (This is where the thin wire was once connected.) Connect the other end to # 87 on the relay.
7. Connect 20 amp wire straight to the battery and to # 30. connector on the relay. Job Done.

Where can I find this in my car Toyota Supra 1988 7mgte? and where can I buy it? NAPA said its not listed on them. Please help thanks.

[cre]

That is not a Toyota part. It's a standard Bosch 30/87 SPST automotive relay. This is a hack to work around an age related issue which many experience with this car. This is a circuit you ADD to your vehicle. You can find these relays in the lighting section of most auto parts stores for $1 to $5 (depending on the shop and the area).

[RedAstig]

Thanks man...just got confuse of this starting headache when my engine gets hot, wont start...i will try this. Thanks bro.