Glow plug relay question

[Ghuds]

Hi everyone, I’m new to the forum and to IDI motors. I have an 83 F250 6.9.
The glow plug controller is bad so I bought a new relay and a switch to manually control the plugs. My truck has a solid state module attached to the relay which doesn’t seem like it’s original. My problem is when I hooked up the switch and disconnected the module wires, the glow plugs work but the truck won’t start. Seems like one or more of the original wires still needs to be connected. I’m just not sure which one(s). Any help would be greatly appreciated.

 

[franklin2]

The starter won't spin when you turn the keyswitch? Or the engine is turning over but won't fire off?

 

[Ghuds]

It won’t fire.

 

[mblaney]

I think something else is wrong. Have you confirmed 100% that your glow plugs are heating? Cycle them and feel for warmth or use a clamp-on ammeter (preferred) or voltmeter. is your fuel shut off solenoid clicking?

 

[Ghuds]

Glow plugs are all working. Is the fuel shut off solenoid on or near the injection pump?
There is one red wire that was connected to a small terminal on the relay that when touched the power will make the injection pump click. If I hook everything back up like it was originally I can start the truck with either.

 

[mblaney]

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[franklin2]

Glow plugs are all working. Is the fuel shut off solenoid on or near the injection pump?
There is one red wire that was connected to a small terminal on the relay that when touched the power will make the injection pump click. If I hook everything back up like it was originally I can start the truck with either.

So with tbe new wiring, check this and see if it has power. If not, zero in on that part of the circuit. I believe that circuit is a key on power wire common to several things on top of the engine

 

[Ghuds]

I really appreciate your help, I’ll check it out this weekend. I think it’s got a later model set up for the glow plugs. Everything I’ve seen on an 83 does not have the module that the relay sits on.

 

[IDIBRONCO]

I'm sure that yours has been changed to the "7.3 style". The 6.9 controllers could be a HUGE pain. They were known for sticking on and burning out all of your glow plugs. Also, your glow plugs probably have bullet connectors on the tips where the wires hook on. The type that your truck came with had spade connector tips on them. If yours are bullet type, just buy glow plugs for a later model with a 7.3. That will save confusion.

 

[Ghuds]

You’re right, they are exactly as you say they are. I’m just trying to figure out how to make them work.
The guy I bought the truck from put in all new glow plugs and injectors, as well as replacing all the return lines. He said the glow plugs haven’t been working at all. That’s why I decided to put a manual control switch in. It works fine but the truck won’t fire when I disconnect the wires on the relay like the instructions say. I think I’ve narrowed it down to one wire that goes to the injection pump. It must be the fuel shutoff wire. I’m just not sure where to hook it up on the relay. Sorry for my ignorance, I’ve never owned a truck with the IDI motor before.

 

[IDIBRONCO]

That's OK. I'm not well versed on the 7.3 style controller myself. I've only owned a couple of 85 6.9s so I can't be much help on the manual control. The 6.9 style was easier (to me) to switch over to manual control. There's a separate relay on the passenger's side inner fender. There's a wire that you splice into with your power supple. You don't need to have a controller installed. These, by the way, screwed into the back of the driver's side head. I know, not much help, but just some more info. You never know, you may pick up another 6.9 truck and have the 6.9 style glow plugs.

 

[Ghuds]

The relay is on the passenger side fender, and there is a controller on the drivers side head. The controller is probably bad. That’s why the glow plugs aren’t working. I thought I’d bypass the controller with a manual switch (apparently like a bunch of others have).
I’ll mess with it tomorrow and see if I can figure it out. It’s got to be something simple, these things are pretty “low tech”.
Thanks for your advice, I appreciate it.

 

[rhkcommander]

if you have a pair of needle nose pliers and an old but good wire you can test damn near everything.

Take the wire straight from battery positive to the plug on the injection pump, Use the pliers to jumper the relay for glowplugs for about 8 Mississippis', and then use the pliers to actuate the starter relay. Should crank over and start.

You can take a test light to each glowplug head and if it don't light then 100% that plug is dead. These trucks can start with about 5-6 working minimum, in OK weather, if its close to freezing forget about it when under 6 working plugs unless your truck and batteries and starter are top notch.

Now if it doesn't start:
Doesn't crank: bad relay or starter, (hopefully the teeth on the flywheel are OK - I can't recall a case of that happening but I'm sure it has), or the cables are bad/dirty. Should hear something - relay noises, starter noises. If you hear something spinning/whirring, the starter is bad - the thing that makes it engage to the flywheel isn't working probably.

Testing relays side note: If you are ballsy you can bypass the relays with a big piece of metal - I've had to do this before. If it starts to crank the relay is shot or making poor contact (corrosion). This can tell you if the relay for starter/plugs is bad, and get you out of a jam if either fail when you're out and about especially with the factory glow plug controller that ***** the bed when 1 plug might be dead or corroded.

Cranks but wont start: keep cranking, see if fuel vapor is coming from the exhaust. Should be grayish white. No smoke means no fuel, either the fuel pickup in the tank is bad (so it isn't picking any fuel up - happens all the time on these old trucks), the fuel line is clogged (with rust, algae, or prior-mentioned fuel pick up), clogged fuel filter, or IP shutoff is stuck shut. Test the shrader valve on the filter head, see if fuel is gushing out when cranking. That'll help you find out if its before or after in this case. You can also try tapping on the IP gently to see if the shutoff was stuck shut. Should get a spark when giving power from a wire.

 

[Ghuds]

Thanks for the info!
The truck starts and runs fine. When it’s cold, you have to use starting fluid. When it warms up it fires immediately.
I’m just trying to get the glow plugs to work with a manual switch. I need to know where the fuel shutoff wire goes on the relay.

 

[rhkcommander]

Fuel shutoff wire is red with a green stripe. It's key-on power really.

I wired my glow plug relay to work without key on.

There's 4 posts on the relay, 2 fat, 2 small. One of those smalls is a ground, the other is the positive to actuate it. the fatties are the power in and out.

I wired mine like this - I use the ground to toggle them on and off so I only needed to run one wire into the cab to the switch, then ground it anywhere convenient.

I made a short wire that goes from the fatty post with power, and connected it to the S-post (I think that's what the other little one is labeled, switch activator). Just my 2 cents, you can run it either way, running a wire from the S-post to the switch, and a 12v positive to the switch, leave the big fatty posts alone, I believe you still have to ground the ground post unless the old harness is still used there.

I would skip the shutoff wire entirely because these trucks are stupid simple to steal if you are thinking it will stop anyone.