A little background on my truck It is my project truck. It just sits and i work on it when funds and time permit. It is an 1985 F150 with a modified 300 six in it. I have done a DS II swap, and that's it for mods.

I had it working good and starting from the key. Then one day i go outside and it wont start. Nothing no lights or any thing. Come to find out i had let the battery die. Charged the battery, still wont crank from the key still no lights.
How ever if i put the key in the ignition turn it to run and go under the hood, take the starter cable off the starter side of the solenoid and put it on the battery post of the solenoid it will crank just like a charm. so I decided to do some checking with a multimeter. I disconnected the s terminal wire a and had someone in the truck put the key in a turn it to all the different positions. Results were Off 0 Volts, Run 0 Volts, Start 1.5-2 Volts. Then I did the same except i put the multimeter on the s terminal itself Off 0 Volts, Run 12 Volts, Start 12 Volts. The tests was done after a brand new ignition switch was put in (I did continuity checks and the switch is perfectly good). what on earth is going on here.
I love this truck but its turning me into a madman.

Any help or other suggestions as to what the problem is will be greatly appreciated.


Jonathan.

 

I don't quite understand what you're saying there, where the meter was connected in each scenario and what was connected to what.

That red/blue wire should feed battery voltage to the solenoid when the key is in START and 0 at all other times.

You can use a small jumper wire to jump the battery + post to the S terminal of the solenoid, then see what the solenoid does - it should connect the two fat cables together, thereby supplying + voltage to the starter. If your - battery cable from the block to the battery is good, that should complete the circuit and your starter motor should turn over.

In 1985, whether you have an automatic or manual transmission, you should have a Neutral Safety Switch or Clutch Switch that interrupts the flow of current to that red/blue wire.

 

ctubutis i apologize for any unclearness on my part.

In the first test i was putting the positive multimeter probe directly into the wire that comes off the s terminal.

In the second test i was putting the multimeter positve probe diectly on the s terminal itself.

What I did here is I took the cable that goes from the solenoid to the starter and disconnected it at the solenoid.
Then i would hold it in my hand and touch it to the solenoid post that the battery connects to, and that will start it.

I have tried to put 12 volts directly to the s terminal via jumper cables and nothing would happen. No click no nothing.

I hope this clears it up for you. If you need any other info i will do my best to provide it.

Jonathan.

 

The starter solenoid is bad.
You confirmed that you are getting 12V to the solenoid when you turn the key to "run" position.
You confirmed that the starter is working when you touched the heavy starter cable to the batter terminal on the solenoid.
Now you just need to replace the solenoid and you're back in service.

 

The small signal wire that goes to your starter relay (solenoid) should show a full 12 volts with the key in the start (cranking) position. That 12 volt signal activates the relay and energizes the starter.

Test 1 would be to see if you get 12 volts at the signal wire with the key in start (not run).

Second test would be to run a jumper wire from the + post of the battery to the signal wire post on the starter relay. I think there are probably two small posts on your starter relay and you need to make sure you're applying power to the right one. If you apply power to the wrong one the starter relay will not activate.

If applying 12 volts directly to the signal wire post of the starter relay (solenoid, whatever...) with a jumper wire does not activate the relay (causing the starter to crank) then it's likely the starter relay is bad.

 

CountryBumpkin
I am not getting 12 volts to the s terminal through the signal wire.
The signal wire is only providing 1.5-2 volts.
The 12 volts I am getting are when I disconnect the signal wire and test the bare s terminal.
It is as if the battery post on the solenoid is connected to the s terminal internally on run and start.
I have talked to a few folks where I am and they said it sounded like there is some other problem in the truck that keeps frying my solenoids. It has fried 3 in a row with no changes.

Brnfree
I am only getting 1.5-2 volts to the signal wire

. I have tried this and I have made shure I used the s terminal not I. Nothing happens.

I have just pulled the whole interior out of my truck for ease of wire checking. So if any one Has any suggestion on things to check please speak up

 

Are there wires attached to each of the small terminals on the starter relay?

One of the small terminals is for the signal wire that activates the starter relay and, on mine, the other small terminal is a bypass that energizes the electric fuel pump while cranking. However, I've seen other diagrams where the bypass terminal energizes the ignition with a full 12 volts while cranking.

The observations you're reporting have me confused, unless...you've got your wires crossed? If you've changed your relay 3 times now, it's possible. You might try disconnecting both of the small wires from the relay and try jumping 12 volts to the other small terminal to see it that activates the relay and cranks the starter.

If there are two small wires going to the relay test each of them for the start signal.

Is it an automatic? If so the neutral safety switch might be bad. Try putting it in neutral and see if you get voltage at the signal wire then.

When my original Motorcraft relay failed I too went through 3 NAPA Gold aftermarket relays in short order.

One of the failures resulted in the bypass wire remaining energized at all times, causing my fuel pump to stay running with the key off, draining the battery and finally frying the fusible link. If your relay failed similarly then you would have 12 volts at the bypass terminal at all times.

Eventually I replaced the + battery cable from the battery to the relay and switched to the lower grade NAPA "mileage plus" solenoid and so far so good (*knocks on wood*).

 

No, I only have one, and it goes to the s terminal.

Not an auto. It is a manual. I will check the clutch switch next.

 

The starter relay grounds through its mounting bolts.
Is it bolted to clean metal?
Is the body to chassis ground strap(s) good?

What do you read from the blue/red wire (disconnected) to the negative post of the battery if you have the ignition switch in start and run?

 

Yes clean and tight.

Tell me where it is and I can check.

Run 0 Volts. Start 1.5-2 Volts.

 

I hate those. If given the choice I always use insulated ground solenoids and run an actual ground wire, like the one posted here: https://www.ford-trucks.com/forums/1...l#post13475092

 

If you only have <2V at the trigger 'S' terminal it is not enough to pull the solenoid down.
Don't worry about the body ground.

Try and find where (NSS/Clutch Interlock?) the resistance is high and the voltage drops.
Use a test light.
A DVM does not draw enough current to accurately find it.