I just bought a 94 F350 with the 7.3. It has 177K miles and I didn't pay much as I got it as part of a package deal.

The guy has been starting it with starting fluid. I checked voltage to the glow plugs and there isn't any. I haven't pulled the glow plugs and have no idea if they are good. I assume that there should be some voltage to them for X seconds with the key in the on position. Is that the case?

Basically, I want to make sure this truck isn't an "ether baby" before I throw any money at it to fix it up.

Can I just wire the glow plugs in a circuit, run a wire through a fuse to a switch to the battery to test it out? I've used this solution on an old Isuzu diesel and an old Mercedes diesel.

Alternately, is there a way to check a relay/switch that would fix the voltage to the glow plugs? I've never had a 7.3 (or any Ford diesel) so I'm unfamiliar with the motor at this point.

Thanks for any help/suggestions.

Jason

 

Jason,
can you post the 8th digit (it happens to be a letter) of your VIN please?

 

The 8th digit is M.

I did find some helpful threads here since posting, but any advice is appreciated.

I did the test light glow plug test and they all passed.

Where is the WTS light on the dash?

 

out of the 3 available diesel options for 1994,you have the 7.3l IDI (indirectly injected) N/A (naturally aspirated/non turbo)
here ya go:
Glow Plugs 101 Tutorial

the WTSL location:

 

Thanks. That entire panel ( where the wtsl is) doesn't seem to work. I'm assuming there are other indicators on that panel?

 

wait to start light lamp diagnoses can be found in the provided link above in post #8.
direct link:
https://www.ford-trucks.com/forums/1...l#post12967785

yes.there are other indicators there as well.this is where the fuel filter (plugged/restricted filter) and water in fuel lights (self explanatory) are located too.
you can remove the bezel and make sure the plug is firmly inserted there.once you remove the bezel,you can't miss it.

 

Thanks. I'll check the fuses as well in the morning. And I'll go through those threads you provided.

 

OK, I finally got a few minutes to get back to the truck. I followed the instructions to bypass the controller (by removing the white wire #4 and grounding that connection). I did not get any power to any other terminal on the relay (other than the battery cable #3 that is always hot).

If I provided power directly to 5A, I do get power to the glow plug wire at the plug (at least the one I tested). Given that, my guess is that (at least) the relay is bad? OReilly's wanted $70 for the relay. That seems high?

I wanted to make sure I understand the layout of the controller/relay, so I removed it and put the picture below:



Here's my best guess. Am I correct?

1. Signal to WTSL
2. Ground for the controller
3. Power from battery
4. Ground signal from controller telling relay to close (white wire from controller)
5. (a & b). Power to the glow plugs? (yellow wire from controller to 5a, green wire from controller to 5b, two brownish wires from harness attach to 5b)
6. Ignition Switch (red wire from controller, two red wires from harness attach as well). There isn't any power to this terminal at any time in my testing.

Is there a good way to diagnose the controller and/or relay while it's off the truck?

Thanks,

Jason

 

OK, I think I got the answers from here:

https://www.ford-trucks.com/forums/9...le-system.html

I didn't test with the ignition switch in the "on" position. I probably should have? Would that stop the relay from working?

 

I replaced the relay (with the 86 6.9 version for $19.99 thanks to the threads on this forum). The relay is now clicking. When I have the front two glow plugs on the driver side connected, the relay stays on. When I connect any of the other 6 glow plugs, it immediately cycles.

Does this mean that those 6 glow plugs are likely bad? They all passed the test light test (hooking the test light to the positive side of the battery and touching them).

Is my controller likely good?

The WTSL still does nothing. I put the test light on the WTSL connector on the controller and got nothing when I turn the key on. Is this supposed to put out 12 volts or should I connect the multi-meter and look for a lower voltage?

I also tested the connectivity (using the OHM setting on my multi-meter) of each glow plug wire and I have it, i.e. no breaks in the wires.

Thanks,

Jason

 

what glow plugs are in it? if anything other than motorcraft ZD-9's, just replace them.
have you removed a glow plug and manually tested it?

and you need to have the key on to test the glow plug relay and controller.

 

I went ahead and ordered a new set of ZD9s yesterday. I'll have them by wed and I'll post an update

 

I just received the shipment of new ZD-9 glow plugs. What is the proper torque?

 

snug.
i use a 1/4 inch ratchet.
book is 10 to 14 foot lbs torque

 

thanks for the torque spec