2003 Glow Plug Harness Trials

Hi Gang,
I just replaced my injectors and glow plugs on gen 1 6 liter in September and it was running and starting great. Now it will not start and I discovered there wasn't continuity to glow plugs 1, 5, & 7. When I re-installed the glow plug harness in Sept, I squirted di-electric grease into each of the cups and everything checked out.

I am perplexed why these harness's fail but I would think it would be the cup end, but that is a guess? Has anyone pulled one of these 'hard line' harnesses apart and fixed the issues why they fail?

I ordered replacements but in a time crunch and curious if I could place some tin foil in the cup connection on the glow plug? Also, can I cut off the hard housing and make the lines flexible? I need to get this rig working so I can get back on the road. Or am I missing something else totally?

I use the Torque App and will get a misfire code when trying to start it and all the other critical pieces appear to fine - like FICM power, HPOP psi, and so on. Plus my fuel pump appears good and the fuel is treated. The only way my rig starts is if I plug it in for 2 plus hours and it is cold here in NW Wyoming.

Curious what others have to say?

Please post the misfire code number.

Have you checked the resistance on each glow plug wire? On each of the glow plugs?

I don't remember the codes when I cleared them as it has been sitting for a couple of weeks. On the resistance, I will have to figure out how to check that when I get it apart. What 'numbers' should each glow plug have and the wires?

Thanks

The glow plug should read about 1 ohm on the tip to ground. The wires should not have any resistance and should read 0 ohms.

Hope to close this thread with this post.

After I dove under the hood, confirmed zero connectivity from 3 glow plugs and determined the wire harness was in tack and passing current just fine to all 8. Pulled all the glow plugs and replaced them with new Ford units and new wiring harnesses for both sides. Checked the ohms and all were about the same as they flickered some but the numbers were between 0.7 and 0.8 on my meter from the plug connection at the glow plug control module. Buttoned everything up and it started like it SHOULD.

The previous glow plugs came from Diesel Care and Performance and were half price but they said they have never had an issue like I did. It makes both parties wonder what happened but they were really great to work with and refunded the cost of these glow plugs plus sent me a return label. The 5 working glow plugs had ohm reading of 0.5 to 0.6 and are an alloy material which a magnet does not work on. So I taped a little piece of shop towel in my 10mm socket to create a tighter fit to pull them out.

What did I learn? Lots, this second time around. Things like - how to check the wiring harness, what other spec's are needed for the rig to start (like HPOP and FICM numbers and more). AND to use MOTORCRAFT or FORD glow plugs.

The rig starts great and I hope it continues for many years as I cannot afford a replacement.

Thanks again and I am grateful for everyone who contributes to help those in need on this forum-
MuleMan, Ken

Glad it is resolved! When you have been helped, hit the "like" button. Especially for a "regular" like DaveBen who gave you the actual resistance values!

I never wanted to pay for a harness, i build my own with insulated 12 AWG wire. also i always put antiseize on everything that threads into the block or head.

Mule man. Thanks for post. Makes me aware of what to at least consider with my trk issue.