1979 F150 4x4

Tried starting this past winter via jumping (battery pretty dead from sitting) etc. Solenoid started to get hot, smoking and melting. Replaced the solenoid, wiring, battery cables, and starter. Also put fuses on all the wires leading to the solenoid. Checked to make sure grounds were good. Started truck (truck did start) and starter kept running even with key off. Disconnected battery cable to stop starter. Reconnected and tried again. Starter broke off in bellhousing big time. Stopped messing with til today.

Dug parts from old starter out of bell housing. Bought new starter and used a shim this time. Also replaced ignition lock (not the switch). Truck fired up---hooray---shim seemed to work and did not hang up. Turned truck off with key. Tried starting again and no go. No dash lights. Nothing. Checked the fuse on wire leading to the solenoid from I guess the key/ignition switch. The fuse is blown.

I figure if I replace the fuse, the truck will fire up again, but more than likely blow the fuse again too. Sooo, my question, what is causing the fuse to blow? The ignition switch maybe? Bad solenoid (even though new)???

I'm no mechanic here, a good grunt, but no mechanic. So I apologize up front for any obvious ignorance. Thanks for any and all help.

 

What size fuse did you use? The coil in the starter solenoid acts as inductance, which means it draws a lower current at first, but as current pulls through it, it draws more current as the coil effectively shorts.

In the factory setup, the wiring at the solenoid is protected using fusible links. These serve as a last-ditch effort to keep the truck from setting on fire in the event of an electrical disaster, including but not limited to someone wrapping blown fuses in aluminum foil and reinstalling them (it happens - "here's your sign!").

If you had to shim the starter, something is wrong.

 

20 amp fuse.

If the solenoid has a fusable link in it already, does this mean I probably did not need to add the links myself? A chance that maybe if I increase to a 50 or 60, it may not blow? Or better yet, take out my link and just use the solenoid"s?

And thanks for the quick reply.

 

The fuse size will depend on the wire gauge you're using. Can you describe what you've ran to where? And what size wire you've used for each.

Do you have power to anything at all? If you don't have a multimeter, this would be a good time to get one. Even a cheap $10 analog meter would suffice for most purposes.

 

Thanks for the continued help. I took a photo and diagramed it, but am trying to figure out how to post it....

For now, on the front side of the solenoid there is the: wire running from the negative post of the battery to the solenoid and there are three wires coming off the solenoid that we put fusable links on...two run towards the firewall/cab and one runs toward the alternator (this is the one that blew). On the opposite side of the solenoid is the wire running from the solenoid to starter.

Thanks again.

 

That all sounds wrong. Here is what you need:

1. Battery cable running from the positive battery terminal, to the large lug on the solenoid that is closest to the battery. (Heavy gauge) This lug serves as the distribution point for your vehicle's electrical system. Your main power harness to the cab runs from here, as does the alternator. In other words, you will have a couple other ring terminals connecting here.
2. Starter cable running from the other large lug on the solenoid, down to the starter. (Heavy gauge)
3. Hot-in-start from the ignition switch to the small 'S' post of the solenoid.
4. If you have a fourth post on the solenoid, it will be a small post labelled 'I'. This goes to the positive terminal of the coil; it's a start bypass signal to short the coil ballast resistor during startup.

The solenoid grounds through its mounting bolts. The only thing the negative battery terminal should go to is the engine block. This is your electrical system's ground. The solenoid then grounds by mounting to the fenderwell, which mounts to the firewall, which is then grounded to the engine block through a braided ground strap. The truck body and frame are not automatically grounded; they must be explicitly connected to the engine block by way of ground straps. Nothing from your solenoid should run to the negative battery terminal.

My advice would be to pick up a shop manual with wiring diagrams, and a multimeter. You're attempting moderate electrical work without the proper tools.

By the way, welcome to FTE!

 

Whew. Job done. And the beast has come back to life. Learned a lot on this little set back. Bottom line: I had the solenoid on upside down and all the wiring backwards. I think the S and I on the solenoid must stand for stupid and ignorant cuz that is how I felt when I realized the problem. But, after flipping and switching, back on track with a lot of new knowledge and parts (I picked up the multimeter).

Thanks for all the help. I have no doubt I'll posting again!

 

I'm glad to hear it worked out. Sometimes doing something wrong teaches you more than if you had done it right.