My 1979 F250 will not start. I had the starter tested with the wire to the solenoid attached and it works great. I have power to the solenoid but not out to the starter when all is hooked up. I tried jumping across the post to fire the starter and still got nothing. Not sure what the problem is?


Starter solenoid hooked up but no power to black cable (starter wire)

 

Welcome to FTE. Ck your wiring, is that big copper to the + on the battery?

The GREEN with RED stripe wire coming from the cab connects to the 'I' input of the regulator.*Note*that if this truck was originally wired for gauges, the GREEN with RED stripe wire is sourced differently. If that's the case, you should make that clear.

The STA stud on the back of the alternator connects to the 'S' input of the regulator. If you have a factory electric-assist choke, the STA stud also branches to that.

The 'F' output of the regulator connects directly to the FLD stud on the back of the alternator.

The large output terminal of the alternator (sometimes labeled BATT or B+) connects to the battery side of the starter solenoid through a fusible link as well as the 'A' input of the regulator.

Post #140 and #141 great trouble shooting tips from fellow FTE members. Cruise this complete thread for other bits of info that might helpful.

https://www.ford-trucks.com/forums/1...l#post16069709

 

Scary.

If that is to battery positive, very dangerous situation.

If to the negative, well ..... no wonder it won't start.

 

Meaning PrusJuice that that looks like speaker/amp wire (due to its strand size) and NOT the correct type of wiring you should have on there.

 

That wire is straight from auto store for battery a battery cable. They didn't have red in that size so the only option was clear coating. I know have power to everything except the starter I changed out solenoid and if I leave it off the firewall the starter gets power but won't start?(Ignition?) but as soon as I screw the solenoid to the wall it's grounded and doesn't pass power over to starter cable even when key is turned..

 

Ok it just LOOKS like it has real small strands, smaller than normal. Maybe this will help?

You can easily test the starter solenoid and the switch. First, the switch. You'll need a partner and a multimeter. There is a 'hot' (12V +ve) wire that is off (0V) when the key is off and on (12V) when you have the key in the start position. You just need to check if you are indeed consistently getting 12V when the key is in start. So, multimeter with one lead on ground and one lead on the wire from the key. This should be a thin (16GA?) wire coming into the 3rd post on the solenoid. Side note: Essentially a solenoid is simply a relay that uses a low current 'switch' voltage to create an electromagnet that closes a switch inside and completes the high current circuit, making the starter spin. Once you confirm that there is indeed 12V coming from the key when it's in the 'start' position, we've ruled out that the key switch is bad.

Next, the solenoid. Like I said, the solenoid is just a switch that uses low current to complete a high-current circuit (the starter). It can go bad without warning, and it's entirely possible and likely that it's bad. So, to test the solenoid (after you've confirmed you're getting power from the switch to the 3rd terminal on the solenoid) you simply take a jumper cable and clamp one end onto one side of the solenoid (12V in from battery) and touch the other end of the cable to the other post of the solenoid (12V out to starter). The engine should immediately turn over (expect a few sparks, no big deal). MAKE SURE IT IS IN NUTRAL IF IT IS A STANDARD TRANSMISSION.

If the key checks out good, and the solenoid test makes the engine spin over, then the solenoid is bad.

If the key checks out bad, you can verify solenoid operation by taking a small bit of wire and going from the +ve terminal of the battery and touching it to the 3rd terminal on the solenoid (where the key goes in) and it should energize the solenoid and turn over the engine.

 

Is the solenoid upside down (meaning its wired backwards) in the picture?

 

Good catch, that might be the problem. There is a S and a I, that have to be connected correctly, you could have it 180 out or upside down.

 

Here's what mine looks like ('78 F150 w/400)

Left side: Big Blue wire is from the Alternator (fusible link is on this), Black one next to it is from + on battery
Right side: Black one goes to the Starter. Wires on the front match what 77&79F250 shows in the diagrams.

 

Maybe I missed it, but the mounting strap on the relay has to be connected to the metal apron, that's how it gets its ground for the relay coil and pulls in the contacts.