The research center where I am working while I go to school has a '94 F350 4X4 with a 7.3 IDI. They don't use it anymore because a couple years ago another student "mechanic" changed the glowplugs but twisted the top off one of the old glowplugs in the process. They don't want to put any money into it (won't let me pull the head and fix it right) but would like it to be runnable and usable. Since I always seem to quickly gain the reputation of being a well versed MacGyver, getting the truck running without spending any money has been my latest project.

Anyways, we all know that the glowplug controller won't work right unless the current draw is equal to that of all eight glowplugs. So the geniass in me decided that If I wired the right resistor in place of the one glowplug, everything should work as it should. It should start alright with 7 of the 8 glowplugs.

So the question is, what do I need to get for a resistor?

 

An 8th glowplug?

No, seriously. Find another glow plug and attach it somewhere on or near the engine. Itll be the perfect resistor, cheaply.

(remember, any other resistor you get will have to get extremely hot, due to the amount of current passing through it).

 

Been my experience that one bad glow plug is hardly enough to be noticable, let alone make a difference in the others. Short of that, you can do like mac says.

 

same with me. one bad glow plug will not really make any difference in the way it starts except for the cloud of white smoke out of the exhaust until htat cylinder gets hot enough to fire. there are probably thousands of turbo IDI's out there with the glow plug under the turbo bad because it is a pain to change.

 

I'd be worried about an open glow plug in the engine bay as a fire hazard, plus you'd have to rig up a ground for it, but like others said, it should start fine off of 7.

 

The controller will still be fine with only 7 plugs? It won't start burning them out too? Or was that just the early controller?

 

i know of one 89 truck that has only had 7 glow plugs in it for the past 250,000 miles and 18 years.
only on its second set of plugs after the first ones burned out, and he will not replace the one under the ATS turbo because he claims it is too much of a pain in the *** to do.
still on the original controller too.

 

Push button to the relay, eliminate the controller. If only one is bad it shouldn't make a huge difference in starting.

 

As i understand it, the newer controllers are supposed to pick up the resistance and shut off based on that. 7 plugs just wont cook as long. Thats why when you get 3 or 4 burnt out, they only come on for 2-3 seconds, which isnt hot enough to do anything.

 

one glow plug bad will affect glow time, just screw a gp into a fitting of some kind under hood it will work...

 

the controller will still work fine with only 7 plugs connected. the only difference is you will loose a hair of glow time. instead of 15 seconds you may see 13.
you start running into issues when you have 2 or more plugs bad or disconnected.

 

It makes a prety big difference. My controller stays on for 20-30 seconds in 20-30f weather, if i disconnect a glow plug it only stays on for 15 or so. I should make a video of it. I made a new harness when i replaced all the glow plugs and one of the butt connectors had come look from the glow plugs, it started clicking in half the time it seemed

 

itll be fine with 7. just whatever you do.....do not leave a gp stuck somewhere under the hood exposed. you don't need a red hot gp burning thru wiring or a return line, and if left exposed it'll burn out in the first few glow cycles anyhow. if they are that worried, plug the block heater in for a hour or two before you start it.