Ok. It's another "loose nut behind the keyboard" scenario... otherwise known as "user error".

I went out and played around with my DVM, and learned that somehow, I either did not have it set properly or wasn't making a solid connection when I tested the GPR on Monday morning.

I do, in fact, have a solid 12+ volts on the supply wire, and the other smaller wires are also working as they should, but no voltage is getting through the relay to the glow plugs.

Therefore, I only got about 8 years life from this Stancor GPR, which is less than I had hoped for. Still, it's a simple fix.

Now knowing the above, I just ordered 2 of the Trombetta relays; the first one to install, and the second one to go in my tool bag as a spare, right beside my spare CPS.

 

I didn't think the Stancor would fail that soon. Good to know. Those Trombetta's should take care of you for at least that long I would think.

 

Yep, and they are 1/3 to 1/4 the price!

 

Glad it was simple, my Stancor is going on 12 years now but my truck is not my daily driver.
Talking about meters, a few weeks ago I was talking to a fellow sparky and I mentioned that "the meter was lying". He responded "The meter never lies, you just didn't ask it the right question"

 

I spoke too soon.

Yesterday, with it being an unusually warm 60°, I noticed the distinctive click of the GPR kicking off before I left the house, which made me wonder if I am looking at an intermittent GPR issue.

Got up this morning did the following:
- checked the old White Rogers relay and it switched on as it should, but chose to replace it with a new Trombetta due to suspected intermittent issue
- removed the Stancor and installed the new Trombetta relay
- ohmed the GP's, all good at 0.6-2.0 ohms
- cleaned both positive battery cables, reinstalled tight, and re-snugged the grounds on each battery
- verified that the new GPR was switching on as it should
- No start! Crank-crank-crank-sputter-crank... would not start.

Below are pictures of the install. I could have flipped the orientation around and sort of tucked it under the top flange of the fender, but that would really complicate getting to the top for maintenance, and it's really not in the way with how it is in the pics below.
Being vertically oriented like the OEM, the Trombetta is much more maintainable than the Stancor it replaced (took me a stinking hour to get the Stancor out just due to its tight sideways arrangement). Now, I just need to get a protective boot over the 12v battery post.

Replaced the Stancor with a Trombetta. The vertical orientation is a much more accessible and maintainable installation.

Overhead view of bolt/nut accessibility with the Trombetta in place of the Stancor.


New Find! NOW, the clicking I was previously so certain as being from the GPR has ended up being "transmitted sound"... the actual clicking is coming from somewhere near the DS fender, underneath the air intake/battery housing (or so it now seems).

Here's what I now know:
- good communication from PCM (otherwise, the relay would not switch on)
- Both the old and the brand new relays switching on as they should
- the 12v from the ignition switch is also working
- I received good glow plug resistance for each of the 8 GP's
- I have solid voltage from the battery to the relay

What next? I am beginning to lean towards just dropping it off at the shop and let them sort it out, but I hate to spend that kind of troubleshooting money if I can find it and fix it simply on my own... I'm just not sure what the next steps should be.

 

The only part under the air box is the ABS module. Perhaps unplug it (triggering the ABS light) and see if the clicking goes away.

 

Maybe check the voltage sent to GP’s at the valve cover harness while GPR is energized? It’s possible the relay is good but there’s a broken circuit between it and the engine.

You could probably ohm out the wire from the GPR (glow plug side) to ground and get an idea if it’s open or “normal”. I assume it would show 1/8th of the resistance of each individual GP since they would be checked as a whole in this case.

 

I do have a periodic ABS light issue, but it's because the sensor on the DS suspension is just resting in place without being bolted in which allows it to slip out far enough to not pick up a reading off the reluctor ring in the rotor (I stripped the bolt threads and then broke off my tap while working to install a Helicoil kit). I'll check it out a little further.

I did have a random thought of checking voltage on each of the harness pins before I plugged the harnesses back into the valve covers, but clipped them in without doing so because I must have had some squirrel brained distraction. I'll try both that and the resistance check, but some of the GP's can ohm as low 0.5 ohms, so, 1/8th of that might not be a very reliable reading.

 

Your Stancor failed early because it didn’t like being on the fender.

 

At this point, though, I'm not convinced that it has really been a GPR failure at all.