Hey all,

So I'm having some issues with my 86 F150 300 inline 6 with the computer taken out. When I have the truck running and the radio is on, everything is fine. However when I turn on the headlights my radio cuts off. I'm assuming it's a voltage issue or a ground issue?

Either way, I started doing some research and have been watching videos on proper ground and my stuff is a bit out of whack.
The previous owners did who knows what to this truck so please bear with me.
The positive terminal has wires running to the starter solenoid and from the solenoid to the starter. The wire running from the solenoid to the starter has a bracket that secures it to the frame. I also have a wire running from the negative terminal to where the alternator is mounted to the engine/frame as a ground I guess? I do not have a ground running from the battery to the starter or the frame itself.

Long story short, what is the proper way to wire this? Pictures attached.

I removed the wire running from the solenoid to the starter temporarily.

This wire runs from the negative battery terminal

The red circle is where the wire connects to the solenoid. The black is where I am under the impression a wire is supposed to run from the negative terminal.

 

In the middle is the 300 six.

 

@Franklin2 thanks for the pic.

Are the brackets I have circles only for securing the wire or do they "splice" into the wire for additional grounding? Also, is the single ground to the starter the only wire that comes off the negative terminal? I've seen videos or people with multiple grounds.

 

In the above picture, I see no ground connected to the starter. The single wire connected to the starter is the hot wire from the solenoid. In the picture above, the ground from the battery is connected to a threaded hole in the block above the oil pan.

More than likely the original ground wire was stripped of it's insulation at one of those clamps, and that provided a ground for the frame. Unless you find an original style ground wire (very difficult I would think) then you will have to strip the insulation back yourself, or just get another short fat wire and put it with the main ground wire on the block, and then run it over and put it on one of the clamp bolts to the frame. If you do strip the insulation on the ground wire at the strap, make sure you use some sort of grease or oil and cover it well to try and stop corrosion in the copper strands.

I don't think we ever addressed your original problem yet, but make sure you have another ground wire or strap from one of the bellhousing bolts to the firewall. That provides a ground for the cab. The cab is mounted in rubber frame mounts, so it does need it's own ground wire from the block which is grounded by your heavy wire from the battery.

 

Ok on my 81 F100 with a 300 six I asked about this and I had a prats truck that was also a 81 with a 300 six that was not messed with.

Factory NEG cable ran from the battery and as Davef said had a lug about half way down that went to the frame (frame ground) then on to the top bolt of the starter (motor ground).
I did not try to find a factory cable but made one. I took the lug off the old cable to use on the new cable.
New top & old cable bottom

This lug bolts to the frame with the same bolt that holds the loop for the POS. cable from hitting the hot EXH.
Loop at top and the lug bottom grounding the frame.

Top bolt on starter for ground for motor. You can also see a 2nd clip on the cable to hold it out of harms way.

There is also a wire from the left side (when sitting in the truck) of the motor to the firewall.
I used a 10 gauge wire, this grounds the body thru the motor. Sorry no good picture of this. Think the red wire in the lower right is the 10 ga wire.

The factory also used a braided cable from the firewall to the hood. I think it is at the top screwed to the firewall but not the hood yet as it was not installed.
As long as the starter solenoid and the voltage regulator and grounded good to the inner fender they should work as they should.

I think I saw in 1 of your pictures a bolt on battery cable end?
If so throw the cable away and buy the right cable. Them ends can cause issues and and not worth it.
When buying cables you have to look them over good as you want ones with large dia. copper.
If you look at the outside it may look large but it is the outside covering that is thick not the copper.

My truck has been on the road over 2 years now and only issue I had was the old solenoid.
I replaced it with top of the line NAPA one, you have to ask any parts story for top of the line parts.
Other than that it starts every time to key is turned.
Dave ----

 

Oh if you dont want to mess with the lug and 1 long cable from battery to top starter bolt you can use 2 cables.
1 goes from the battery and has a eye let at the other end that you would bolt to the frame.
The other cable will have 2 eye lets and goes from the frame where the other cable ends and run it to the top starter bolt.

I just wanted mine to look factory and why I did it my way.
Dave ----

 

@FuzzFace2
thanks for the pics and info! I'm gonna replace my battery terminals and do the two wire from the negative to the frame and then frame to solenoid. I need to look into the cab being grounded and see about that wire. Where would it connect in the cab?
Also if the grounding in the cab is not correct, would that cause my radio to cut out when the lights are turned on? I recently upgraded to LEDs so idk if that has something to do with it as well.

Pete

 

A bad body ground can cause crazy things to happen so that could be why.
When I get home from work I will see if I can remember to get a picture of that motor to firewall ground wire.
IIRC it just goes to a screw on the firewall.
Dave ----

 

I hope that is a typo. There is no large ground to the solenoid on the inner fender.

 

@Franklin2 yep! Meant starter.

 

Braided cable from firewall to hood on the right side.

Body ground cable (10 ga red wire) from motor to firewall.



Please over look the dirty engine bay I have not cleaned it in a few months.
Dave ----

 

@FuzzFace2
thanks!
​​​​

 

NP if done right you should not have any motor cranking problems or strange things going on.
Dave ----

 

Hey all,

Thanks again for the help. Got the new wires set up w/ new battery terminal connectors. The wire from the engine to the firewall was already in place and still looks good. Got a wire running from negative to the frame and then one from the frame to the bolt that holds the engine to the starter. Started up the truck, radio on and lights working as well! Radio doesn't cut off. Thanks again!

Pete

 

Good to hear it worked out.
See what bad or no grounds can do.
You would never think lights and radio would inter act like that would you?
Dave ----