Engine ground

[bkahler]

Ok this one has me stumped. Most vehicles have a bonding strap between the engine and the frame. I haven't been able to find any reference to an engine bonding strap in my documentation.

On the B3 series trucks the positive battery terminal goes to the frame and the negative cable goes to the starter solenoid. So what is the ground path for the engine? Hopefully not the temperature gauge sending tube . I've seen that happen before and the tube starts glowing cherry red before it melts.

Thanks!

Brad

PS, I hope all of you have a happy and safe Thanksgiving.

[Reg Evans]

The positive ground strap usually bolts to a transmission bolt,not the frame.

[Merle Coggins]

I agree with Reg. That's how I have mine. But I often wonder if I'll need to add a ground to the frame or body so that the lights will work. I don't remember having to remove one when I disassembled the truck. I suppose it wouldn't be too difficult to add one, but what is correct for these trucks?

Merle

[bkahler]

The positive ground strap usually bolts to a transmission bolt,not the frame.

Reg, that makes sense as far as "current" carrying requirements for the starter. But as Merle brought up, how do the lights get their ground? I realize there are several places with metal to metal contact between the engine and the frame but none of those should be considered as "current" carrying paths.

As Merle suggests I'll probably add some kind of ground wire between the engine and the frame or from the battery to the frame. Since I'm wiring the truck myself I might be able to add something from the regulator down to the engine that blends in adequately.

Thanks!

Brad

[greg g]

I believe the rear motor mounts serve as the engine to chassis ground, and the body mounts serve body to chassis needs. But with anything this old, more grounds is good grounds. A braded strap from the firewall to the bellhousing is probably a good choice and genny mount to frame would work also.

[Merle Coggins]

I believe the rear motor mounts serve as the engine to chassis ground, and the body mounts serve body to chassis needs. But with anything this old, more grounds is good grounds. A braded strap from the firewall to the bellhousing is probably a good choice and genny mount to frame would work also.

The only problem I can see with this theory is that both the engine and cab are rubber mounted. There is no mechanical metal to metal connection. There are some incidental connections, as Brad points out. One I can think of off hand would be the park brake cable. At least on the trucks with under dash pull cable park brakes, the cable housing is bolted solid to the cab and is clamped to the frame and attached to the trans. this could provide a path for electron flow, but I'd rather give them a dedicated path to use.

Merle

[bkahler]

but I'd rather give them a dedicated path to use.

Merle

Agreed, a dedicated path would be ideal. I also agree with you that the engine to frame mounts are rubber isolated enough to make any ground path suspect.

I can't deny however that obviously the electrical systems worked for years and years as they came from the factory but I will still feel better knowing that there is a true uninterrupted path to ground from the engine to frame & body.

Great discussion and thanks for all the feed back!

Brad

[greg g]

I think, at least on the cars that while there is a rubber vibration damper o the rear mounts, there is a metal sleeve through the assembly ant with the bolt head and washer, the assembly does indeed conduct the ground circuit. Not familiar with the truck but I gotta believe they are similar. Also on my car I have the ground strap ging to the generator bracket to the battery so that is a direct connection.

[Don Coatney]

My battery ground strap connects to the lower generator (now alternator) bracket. I added an extra ground strap from the engine to the firewall. I am not looking for originality. I am looking for what works.

[Reg Evans]

Originally the trucks just came with the ground to the transmission only but I agree with everyone that more grounds on these old rigs is better.