Quick tip for those who have bypassed their glow plug relay

[Jon Schwenke]

The light is controlled by the famous "brain" in the controller. The brain get's info on how long to glow from the voltage drop across the z-bar shunt on the controller(the shiny silver piece). If you are grounding the white wire to manually activate the glowplug relay, the current for the glowpugs is still passing through the z-bar shunt, so the brain doesn't know any different and is still trying to control the relay, and can't because it's disconnected. But it can still turn the light on in the dash.

I definitely have a separate solenoid setup. I think I'm taking the original "always hot" lead to my new relay (starter switch). I have a 12v wire going to my momentary switch. It operates the new relay and sends 12v back to the original relay on the gp (output) side. So I guess the original relay must take the 12v from the gp side, do that resistance thing you mentioned and control the wait to start. Cool. So if the original won't close and pass power, it still may be useful as a timer if that function still works. At least it appears that way in my truck. Does that make sense? Am I correct here?

 

[Jon Schwenke]

I think I did it the same way in my '96 Chevy k2500 Suburban too..

 

[franklin2]

I definitely have a separate solenoid setup. I think I'm taking the original "always hot" lead to my new relay (starter switch). I have a 12v wire going to my momentary switch. It operates the new relay and sends 12v back to the original relay on the gp (output) side. So I guess the original relay must take the 12v from the gp side, do that resistance thing you mentioned and control the wait to start. Cool. So if the original won't close and pass power, it still may be useful as a timer if that function still works. At least it appears that way in my truck. Does that make sense? Am I correct here?

Not positive what you have going there, but if you are running power through the original glowplug controller and z strip, you will have some function of the brain but you will find it will be somewhat faulty. The reason you bypassed the original controller and the brain, was because of faulty timing it was giving from bad glowplugs and bad harness connections correct? I have found on mine, the light still works but it doesn't stay on long enough. If I go by the light when I use the button, the engine usually will not start, the cycle is a little too short.

 

[Jon Schwenke]

Not positive what you have going there, but if you are running power through the original glowplug controller and z strip, you will have some function of the brain but you will find it will be somewhat faulty. The reason you bypassed the original controller and the brain, was because of faulty timing it was giving from bad glowplugs and bad harness connections correct? I have found on mine, the light still works but it doesn't stay on long enough. If I go by the light when I use the button, the engine usually will not start, the cycle is a little too short.

The reason I changed the setup was that the original relay no longer closed and passed power through it. It was cheaper for me to switch to a manual setup. Luckily, my wait to start light length works properly (I guess) and has for a few years. We'll see what the future holds. Kind of a happy accident....for now.

 

[Black dawg]

another tip for those with manual glow plug control.......Dont lend out your truck unless you have plugs that will not burn out from over use. Have seen too many idi motors junked over overglowed plugs loosing tips and crunching pistons/rings.

 

[Big Bart]

another tip for those with manual glow plug control.......Dont lend out your truck unless you have plugs that will not burn out from over use. Have seen too many idi motors junked over overglowed plugs loosing tips and crunching pistons/rings.

Adding to Black dawg‘s warning.

Never use anything other than a momentary switch of quality for a manual glow plug set up. Someone else is likely to bump it or leave it on. A cheap one can fail too.

It’s a bit of work to diagnose a 7.3l glow plug system that is not working and fix it. But when they are working, they work really well. They manage the time, they let you know when you have bad glow plugs, and prevent fires from bad wiring or leaving glow plugs on. So best to fix them when possible.

No judgment for those who go manual, but there is some risk of doing so. Many use the 7.3 controller in manual mode and this why the light acts like a timer if the glow plug system is healthy.

 

[NeverHave-I-Ether]

If you want the WTS light, just cut the blue wire, and attach it to the ground for a momentarily switch. Then it turns on whenever grounded from the switch or controller.

 

[Booyah45828]

My bus has the light illuminated off the same relay terminal that the plugs are on. If the plugs have power, the light should be on. No power, no light. I can't argue that a factory system can work good, when it's working. The controller on the bus is what originally failed. To "fix" it, all I installed was the push button and the new 60g plugs. I feel the plug cost is moot, as the old plugs were burnt out and needed replaced anyways. The push button was a lot cheaper then a new controller.

I don't think the 60g's swell, and I'm pretty certain they're self limiting. The only issue I've had is explaining to people how/why you have to hold down the button before starting.

 

[Black dawg]

I don't think the 60g's swell, and I'm pretty certain they're self limiting. The only issue I've had is explaining to people how/why you have to hold down the button before starting.

The 60g is self limiting, and I have not seen one swell.....but........I have seen more of them with missing tips (sometimes the whole thing) than all other glow plug brands combined. I know this isnt what everybody all over the internet has experienced, but that is what I have seen on a few different trucks (6.2-6.5) that werent the best starters and plugs would get abused with a button.