6.2l k30 misc electrical

[obijuank5]

I've got an 85 k30 that I'm tracking down electrical crap. And to throw a wrench in things, I added a big truck gauge cluster with tach. Switched the oil pressure and clock from original gauges. After a new headlight switch, fixing some frayed wires, and misc problems things start working. They all seem to function except for the tach. I don't know where to find tach signal first off but the fuel gauge is good so far

THEN... I leave the headlight switch on and turn the truck off. Pull the key out of the ignition and the truck doesn't turn off. It remains running with the lights on. I turn the lights off and it kills the truck. I am not sure how these things are related and it's late. I packed it up and came inside.

What the hell is happening and where can I find a wiring diagram? Brochures.slosh.com does not feature the diesel wiring and this is a civilian truck so not sure if the cucv stuff is applicable either.

TL;DR

Stoked about the tach, not sure where to get signal.
Head light switch turns ignition off.

 

[diesel4me]

The only thing on a 6.2 that shuts it off ,is the fuel stop solenoid on the injector pump.(usually a thick pink or red wire)....evidently it is somehow getting power from the headlamp switch or a glitch in the headlamp wiring..

Other than that solenoid,and the glow plug wiring harness,the gas powered trucks use pretty much the same harness for the other things like lights,alternator,etc...

 

[SpeedlabDan]

I've got an 85 k30 that I'm tracking down electrical crap. And to throw a wrench in things, I added a big truck gauge cluster with tach. Switched the oil pressure and clock from original gauges. After a new headlight switch, fixing some frayed wires, and misc problems things start working. They all seem to function except for the tach. I don't know where to find tach signal first off but the fuel gauge is good so far

THEN... I leave the headlight switch on and turn the truck off. Pull the key out of the ignition and the truck doesn't turn off. It remains running with the lights on. I turn the lights off and it kills the truck. I am not sure how these things are related and it's late. I packed it up and came inside.

What the hell is happening and where can I find a wiring diagram? Brochures.slosh.com does not feature the diesel wiring and this is a civilian truck so not sure if the cucv stuff is applicable either.

TL;DR

Stoked about the tach, not sure where to get signal.
Head light switch turns ignition off.

View attachment 244621

My 1982 topkick that had a cat diesel had a fuse block plugged into the headlight switch I would pull that apart and look for corrosion possibly. The fuel cut off may be grabbing power around there

 

[campfire]

Like @diesel4me said, follow that pink wire from the injection pump back underneath the dash. I'll bet your problem is between the bulkhead connector and the headlight switch (perhaps at the bulkhead itself?). There's not much on the engine side of the firewall.

 

[obijuank5]

So now it starts and dies with the ignition switch. Not entirely sure how I fixed that lol but I was all over that ignition wire fixing stuff. Thanks for the tips guys.

When the headlights are turned on, the blinkers are lit up. I remember them being the other way around. With the headlights on or off the blinkers would only illuminate when the lever is depressed. I have the gm manual and it doesn't have blinker diagnosis so it must he super simple.

 

[skunked]

I had a really weird problem with my truck and I only mention this because it's a diesel cab/wiring but it has a BBC with EFI. After I swapped in EFI and wired it, if I turned on the headlights with the ignition off the EFI would turn on which would kick on the fuel pump. I was doing some cleanup and noticed two grounds that usually connect to the bulkhead on the e-brake pedal were broken off. I reconnected those and the problem went away.

 

[obijuank5]

Thanks for the tips. I'll take a harder look at it.

 

[campfire]

So now it starts and dies with the ignition switch. Not entirely sure how I fixed that lol but I was all over that ignition wire fixing stuff. Thanks for the tips guys.

When the headlights are turned on, the blinkers are lit up. I remember them being the other way around. With the headlights on or off the blinkers would only illuminate when the lever is depressed. I have the gm manual and it doesn't have blinker diagnosis so it must he super simple.

You have a bad ground in one or more of the lights. The current is flowing back through the blinker circuit looking for any available ground.

This is the very first rule of automotive wiring.

 

[obijuank5]

Hey hey hey. Easy now. Lol

I own the gm manual for this truck. I'm learning. I'm learning. I got the rest of the truck down.

 

[campfire]

Hey hey hey. Easy now. Lol

I own the gm manual for this truck. I'm learning. I'm learning. I got the rest of the truck down.

Sorry, that was a happy, winky, laughy kind of playful jest.

P.S. - I'm jealous of anyone who has a factory service manual for the civilian diesel truck, and I'm also interested in your tach installation. There are at least 4 common ways to get signal off of a 6.2, but none of them are connecting up to the ignition timing like most tachs are used to.

 

[obijuank5]

I have figured out it needs 4 pulses per revolution or at least I think so. Other than that it is dead in the water. But it has power to the fuel gauge with just a cluster swap so the big truck cluster seems to work ok aside from my grounding issues.

 

[Carcinogen]

You have a bad ground in one or more of the lights. The current is flowing back through the blinker circuit looking for any available ground.

This is the very first rule of automotive wiring.

Not saying you're wrong, in fact probably the opposite... but to play devils advocate I seem to recall a similar thing happening to one of my trucks when I first bought it and it was the wrong bulb in the tail light(single filament vs double). One more thing to check if all else fails.

 

[campfire]

Not saying you're wrong, in fact probably the opposite... but to play devils advocate I seem to recall a similar thing happening to one of my trucks when I first bought it and it was the wrong bulb in the tail light(single filament vs double). One more thing to check if all else fails.

Yessir, that would also do it.

 

[obijuank5]

Well I fixed it with many more frayed wires and a couple repaired grounds. Not sure which did it in but it is pretty cool to have a truck with most of its electrical working.