Need some help here with Doghead relay problem

[Smittyjs]

Having a starting problem and could use some advise.
I have a 1985 1028 have had it about six months with out any starting issues this weekend had nothing but clicking under the dash when trying to start.
So did some reading and it looks like someone before me did the dog head relay mode on it. Didn't know what that was but do now.
I jumped the relay and it starts up on the first crank and runs like a champ.
Figured the relay was bad got a new one installed it same problem..
Took voltage readings on terminal with large red wire 25.6 with ignition on 29.4 while engine running
no voltage to terminal with large purple wire running or not running.
the 2 smaller terminals have 8.5 with ignition on and while running..
also who ever put this together wired a small resistor between the large purple wire and the small black wire terminal.
Any help would be appreciated thanks

 

[doghead]

There should be no voltage on the small purple wire when running, only when the key is turned to crank position.

The small black wire is a ground for the relay coil.

Your ignition switch must have full travel and your ignition switch sends 12v to the small purple wire.

Our site rules request a state in your location.

 

[Smittyjs]

Once the truck is running there is no voltage on the small terminals but while trying to start I get 8.5 volts which is the problem?
Should be 12 ...8.5 is not enough to charge the relay. Any idea why I would have only 8.5 ? where should I start to look?
I mis spoke in the original post about having voltage on the small terminals while running

 

[MarcusOReallyus]

Okay, let's slow down and make sure of what you are seeing.

Once the truck is running there is no voltage on the small terminals but while trying to start I get 8.5 volts

1. Are you seeing 8.5v on BOTH of the small terminals? Or just one of them?
2. Where are you putting your ground lead for your meter? Are you sure it's a good ground?
3. Try disconnecting the purple/White stripe (small terminal) from the relay, and jumping 12v from the front battery to that terminal. The starter should engage.

 

[Smittyjs]

Our site rules request a state in your location.

Ok changed it

 

[Smittyjs]

Okay, let's slow down and make sure of what you are seeing.

1. Are you seeing 8.5v on BOTH of the small terminals? Or just one of them?
2. Where are you putting your ground lead for your meter? Are you sure it's a good ground?
3. Try disconnecting the purple/White stripe (small terminal) from the relay, and jumping 12v from the front battery to that terminal. The starter should engage.

Yes I was seeing 8.5 on both terminals red lead of meter to terminal black to ground.
I will check the grounds and if that checks out putting 12 volts to the terminal from the battery is a great idea thank you
I was looking at a colored schematic trying to trace where that purple white wire goes to pick up the 12 volts..

 

[Jack Lope]

Not sure how helpful this may be for your needs, but I have a video of the Doghead relay mod in some detail.
https://m.youtube.com/watch?v=ShsKBSamwAQ

 

[doghead]

If you did not disconnect (the only way you'll see voltage on the black wire) the small wires when checking voltage, you can read a low voltage because the load of the relay.

 

[doghead]

I fixed your location to conform to the site rules.

Thanks for your cooperation.

 

[Smittyjs]

I fixed your location to conform to the site rules.

Thanks for your cooperation.

Sorry not really enjoying my location much these days Ill try to behave.

 

[Smittyjs]

just jumped the ground on the relay to a good ground and it fired right up tried it a couple times that was it don't know why I didn't just think it through myself instead of bugging you all about it. Really appreciate the help though.
Anyone have an Idea where that black ground goes to ground?
Jack Lope thanks man I enjoy your you tube videos.

 

[Barrman]

Look above your parking brake pedal housing. You have to mash your head against the brake pedal to really see it. On the top of the housing is a single screw holding a 6 pin ground terminal. All of the under dash ground wires end up there. Take the single screw out, clean it with sand paper and everything around there. Put it back together and it should be good.

Having written how it is supposed to be. The starter relay bolts to a bent plate that bolts to the dash metal with two screws. There should also be a support rod bolted into the very bottom of the dash stamping in that area. I use that support rod bolt as a ground for my starter relay. After cleaning both ends of course.

 

[Smittyjs]

Thank you I found that six pin ground terminal and there were no wires going to it I did find one black wire that had come off it I reattached it..Thanks again Barrman