Glow plug rail power source

[Aaroneous]

Going to try to fire her up this weekend, but I'm confident it won't run without this issue being solved...

The PO disconnected the power feed wire for the glow plugs, and I'm curious if there's a standard place it should source it's power. I was looking all over for a relay, but didn't see any on the firewall or the fender well. There's a plastic connector coming out of the wire loom through the firewall that has a single female paddle connector, and I was going to look for 8.5V there with the key in the "on" position, but figured I'd ask here first before just plowing ahead. There's also a plastic connecter with perpendicular female paddle connectors that is currently going nowhere, thought that might be hot and ground if there's another wire that should be paired with this one.

The feed wire needs to be replaced (see the electrical tape wrap), but where should this sucker plug in? In my googling, I've also seen a lot of pictures with wires coming from the post in the manifold (lower left), but clearly I'm missing something there. I know it ran in this condition recently, so I'm assuming it's not critical.

Thanks for the help!

Glow plug power rail feed wire

• Aaroneous
• Nov 24, 2016

Where does it go?

 

[Mr Cimarron]

My relay on my 77 is on inside firewall on the passenger side, under glovebox. Also connects to the glow controller on left side of dash. Without being able to look at mine at the moment I can't remember how the harness snakes around.

 

[Squash]

Otherwise try searching Wilson switch.
If the power source is disconnected and you just have to start it, hook a jumper to your + batt post for lets say seven seconds.

 

[cruisedeisel]

x2 on jumping it. Might as well see if she'll live before scratching a hole in your head.

 

[cruisedeisel]

Don't hold the jumping cables on for long because the glow plugs don't normally get 12 volts. More like 7v.

 

[Aaroneous]

I will start by jumping 12V to the terminal on the bus bar and see how far we get. Good call cruisediesel.

Thinking it all the way through, if it's a 12V / 8.5V glow controller style pre-heat system, I should really just have a single relay like Mr Cimarron suggested and the bus bar should be fed directly from the controller in the dash. Is this correct? Here's a picture of what I think is the relay system Mr Cimarron alluded to. The flash made it hard to read, but it does say 12V on it.

Glow relay

• Aaroneous
• Nov 26, 2016

Does this control the Superglow 12V / 6V stepdown?

I can go searching for 8.5V in all of the open connectors in the loom at the firewall, but if anyone knows where the standard connection point is, that would be helpful. Wire color, connector style, etc? If I had to guess, I think this is the connector I should be tying into for bus bar power. Driver's side firewall next to where the loom comes through.

Glow plug bus bar power feed?

• Aaroneous
• Nov 26, 2016

Wire is black (?) with white stripe, heavier than standard gauge

Thanks again for all of the help - I'll hopefully have good news to report back today!

 

[lostmarbles]

If that wire in your last photo is black with a yellow stripe and thicker than all the others then it should indeed be your bus bar wire.

But even so, it will show your battery voltage (when your key is turned backwards for preheat) and not 8.5V.

The voltage drops (from your battery voltage to around 8.5V or lower) only when current is flowing through your glow plugs and glow controller (ie. only once everything is fully connected and operational).

(I'm assuming this vehicle is a 12V BJ40 or BJ42 because I can't see anything here to say what it is.)

 

[Mr Cimarron]

Just looked at my wiring. Big B/Y wire goes directly from bus bar into harness. No connector. From there I believe it goes straight to glow controller in dash and then snakes to relay, which you correctly located on passenger side firewall. You should be able to hear the relay click if working properly when you turn key to glow.

 

[Aaroneous]

I have a B/Y wire, but it is going to the starter. The B/W wire seems to be correct - shows 12V when the key is turned backward, so I'm going to roll with that one. I'm not sure if the plastic connector can be sourced or if I'd have to replace both sides with something non-OEM. Will have to look around. If I find something that works, I'll report back. Thanks for the input!

 

[Mr Cimarron]

I also have a B/Y going to the starter using that connector you were pointing at.