GP Relay - correct voltage?

[I_Publius]

I am trying to figure out why my truck is not starting and I believe it is an electrical issue. This morning I "finally" learned how to use a voltmeter, thanks to YouTube.

I tested:

a. Batteries - fine
b. Alternator - (Only one; Roscommon 12v truck) - seems to be fine
c. Firewall bank where batteries and other electrical components are connected - seems to be fine
d. GP relay - questionable

- Key off position: power to upper
- Key off position: small wires - no current
- Key on position: small wires - very little current
​

My big question is, after searching all morning, is what should the two small wires be reading when the key is turned on? What else should I be checking for why the truck is not starting? I'm sure there is a TM page that shows this, so if someone could point it out, I'd appreciate that, as well.

Background:
It ran fine up until last weekend. I ran it for 60 miles, brought it back home, and now it will not start. I changed the temp sensor and the GP relay, re-spliced a couple of connections, and still it will not start. Batteries are fully charged.

OH...again, it's a 12v truck, Roscommon converted.

Thanks, in advance.

 

[MarcusOReallyus]

Is it cranking at all? What happens when you turn the key? "Not starting" covers a lot of territory, from "Nothing happens at all." to "It turns over but won't start."

Please, tell us! Inquiring minds want to know!

 

[Warthog]

Also want to add that we added a manual switch to the system.

What relay did you end up using? Part number?


The small pink wire should have 12v when the key is on and 0v with the key off.

 

[I_Publius]

Turns over extremely slowly. Does not fire. I hear the click inside the cab when I turn the key on and the wait light lights up and turns off, but after almost 20 seconds.
The starter was rebuilt a couple of months ago, twice. (Long story, but it had to be done after a "small" fire.)

 

[I_Publius]

the small pink wire is not getting 12v....maybe 2-4v when key is on. I did put a new connection on the pink wire yesterday and maybe it's possible that I did not seat the connector well? (it was raining and cold when I was trying this yesterday.)

the GP relay is an AC Delco #43-254.

 

[I_Publius]

small pink wire is getting between 10-10.5v.

small red wire beneath the pink is getting 0 when turned on.

 

[I_Publius]

TM -20 shows a list of wiring, their colors, and where they go, but I'm not seeing a red listed. I'll look for another TM that may show that. It seems as though the red wire (lead) goes through the firewall into the cab area. I'll bet it goes to the GP card.

 

[I_Publius]

TM -20 shows a list of wiring, their colors, and where they go, but I'm not seeing a red listed. I'll look for another TM that may show that. It seems as though the red wire (lead) goes through the firewall into the cab area. I'll bet it goes to the GP card.

 

[doghead]

the small pink wire is not getting 12v....maybe 2-4v when key is on. I did put a new connection on the pink wire yesterday and maybe it's possible that I did not seat the connector well? (it was raining and cold when I was trying this yesterday.)

the GP relay is an AC Delco #43-254.

That number is a fuel pump, not a relay.

 

[I_Publius]

Ugggg!!! No wonder it's not working!!!!



Sorry for the wrong part number. Let's try AC Delco number D1777, instead.

 

[I_Publius]

I think I have ordered too many parts lately.

 

[doghead]

Why did you select that relay?

 

[I_Publius]

I will find the link, but I am 97% sure that it was a thread here on the forum.

Seeing your response, I am going to bet that was probably not the correct one.

;(

 

[Warthog]

The red wire is one that I added for the manual switch. It goes to the "old" starter push button under the steering wheel. The second red wire goes to ground.

there should also be a light blue wire on the same terminal as the red wire.

 

[I_Publius]

That would explain why the blue wire was hot.

Manual starter? I forgot that was added.

 

[Warthog]

The sheriff had that manual start button. I disconnected that and used the button for the manual glowplug backup.

so when I left your starter worked off the key, the glowplug card seemed to be working and the manual button was there for backup GP operation. With in being 100 degrees in September I can't say for sure if the GP controller was functioning correctly.


To clear up the situation for everyone, I made a trip to Texas on Labor Day. Barrman and myself helped clean up the hack job of the Sheriff dept wiring. We corrected the wiring to the Rosscommon setup and also removed the resistor pack from the GP system.

The sheriff dept also bypassed the ignition switch and wired the starter directly. That was all returned to stock.

 

[I_Publius]

So, in theory, How would I utilize that? With the key turned on, I'd be able to push the button and start the truck?

 

[I_Publius]

The d1777...is that a bad relay? Should i have chosen the powerstroke relay or another?

 

[Warthog]

Turn the key to the on position. Push the button and listen for the relay to make a clunking sound. If it does, hold the button for 8-10 seconds and then try to start the truck.

Have you charged your batteries lately? The starter needs to spin preaty fast to start the engine.

 

[Warthog]

From what I have found, they D1777 should be okay to use.