[straightshooter412]

I am having problems with the glow plugs system. Have checked plugs and found #3&5 not working. New relay and still no power to plugs. Had it scanned showing PO 562 & 605. New batteries showing 14.4 vt. Running.
Key off - checked voltage on solenoid - 12 vt. To left big post, constant power. Two smaller posts no power. Large post, no power.
Key on, constant power to left large post. Power to both small posts. No power to plugs. Pulled PCM , checked pins, no problem noted. Replaced about 2 years ago. Truck runs great after start. Average cold morning temp has been in upper 30s. Very hard to start. Block heater is out, can not use.
If I have skipped any info please ask and I will try to answer. I also have had a very good diesel mechanic look at it and pulled the codes for me. He advised me to take it online for answers.
Thanks in advance.

 

[NoRalPh]

You've ended-up in a funny place, the "Tech Files Forum" is where "techs" post files to help others.

You've seemed to have gone in a pretty strange direction too, pulling the PCM to check pins because you have 2 plugs out? With a simple relay system (you have a GPR (relay) not a GPRM (module))? There's really very little control of the plugs by the PCM (with a relay, it's job is only to supply a ground path, from the power in the relays coil (sm wires) that creates a magnetic field inside to move an iron slug to connect the two big wires together). No "individual" plug control from the PCM. Have you checked for Power at 3&5 or is it possible they're just burnt-out?

The right direction , would be to look at the wiring harness that plugs into the valvecover gasket (called the UVCH) as having burnt pins in it (if you know that the plugs themselves are OK). A common issue that often needs replacement (Do Not Buy Dorman or any other Aftermarket UVCH - FORD Only or you'll have problems with it). In a 20yr old truck, you'd be smart to replace them both.

Pull the pass side valvecover and inspect the pins that go to both the Injectors and the plugs, 3&5 are in the middle (heavy wires are for the plugs, I'd expect to find corroded/burnt connections).

 

[straightshooter412]

You've ended-up in a funny place, the "Tech Files Forum" is where "techs" post files to help others.

You've seemed to have gone in a pretty strange direction too, pulling the PCM to check pins because you have 2 plugs out? With a simple relay system (you have a GPR (relay) not a GPRM (module))? There's really very little control of the plugs by the PCM (with a relay, it's job is only to supply a ground path, from the power in the relays coil (sm wires) that creates a magnetic field inside to move an iron slug to connect the two big wires together). No "individual" plug control from the PCM. Have you checked for Power at 3&5 or is it possible they're just burnt-out?

The right direction , would be to look at the wiring harness that plugs into the valvecover gasket (called the UVCH) as having burnt pins in it (if you know that the plugs themselves are OK). A common issue that often needs replacement (Do Not Buy Dorman or any other Aftermarket UVCH - FORD Only or you'll have problems with it). In a 20yr old truck, you'd be smart to replace them both.

Pull the pass side valvecover and inspect the pins that go to both the Injectors and the plugs, 3&5 are in the middle (heavy wires are for the plugs, I'd expect to find corroded/burnt connections).

I pulled the PCM to check for bent pins because I had one mechanic install it and ran terrible. I pulled and checked, found pins bent. Straighten and worked fine. Just to be sure. I checked the 3&5 by connecting a working harness from another engine and tested each plug with a test light. 3 & 5 did not light up. Trying to find rule out a blown PCM causing the GPR not powering up the glow plugs.
How do I test to see if the GPR is getting ground from the PCM.

 

[NoRalPh]

Remove both sm wires from their terminals on the GPR.

With the Key On, you'll find only One has 12v in it (the coil in the GPR connects them both together, that's why you see 12v in each when connected).

The Other sm wire is what the PCM uses to supply the path-to-Ground. To test if that path is present, put a meter between the two removed wires (+ the wire w/12v in it and - to the PCM's wire). If you see 12v flowing between the two then the PCM is doing its job. But, again, it's an All-or-Nothing thing with the GPR, it couldn't send power to 1&7 without going to 3&5 too if the wiring between them (UVCH) was good.

The PCM will supply the ground anytime the oil temperature is low so, a faulty EOT can cause the PCM to not "Know" it needs to supply that ground.

Good info here -> Troubleshooting GPR & GP's

 

[straightshooter412]

Thank you for the info. I picked the tech area because in my professional life, I tried to get knowledge from the brightest and smartest in areas of research. I will try you suggestion tomorrow.

 

[straightshooter412]

Remove both sm wires from their terminals on the GPR.

With the Key On, you'll find only One has 12v in it (the coil in the GPR connects them both together, that's why you see 12v in each when connected).

The Other sm wire is what the PCM uses to supply the path-to-Ground. To test if that path is present, put a meter between the two removed wires (+ the wire w/12v in it and - to the PCM's wire). If you see 12v flowing between the two then the PCM is doing its job. But, again, it's an All-or-Nothing thing with the GPR, it couldn't send power to 1&7 without going to 3&5 too if the wiring between them (UVCH) was good.

The PCM will supply the ground anytime the oil temperature is low so, a faulty EOT can cause the PCM to not "Know" it needs to supply that ground.

Good info here -> Troubleshooting GPR & GP's

As suggested, I tested the small wires and found 11.84 vts. across the two. Thus, the PCM is putting voltage across the GPR. Suggestions as to the course of action? I have replaced the ETO.

 

[NoRalPh]

Sure Go back to post #2 and inspect the UVCH connector.

Did you read the Troubleshooting Link? Did you test for a Voltage Drop across the Lg terminals when activated?

 

[straightshooter412]

Yes, I read the post from the link. There is no voltage between the two large terminals with the key on. Only between the two smaller terminals and large post coming from the battery.

 

[straightshooter412]

My apologies, I misunderstood your message. I went back and placed the small wires together, with the key on, I got 12.08 volts across the two big posts. Where to from here?

 

[NoRalPh]

Well then the GPR isn't activated or it's contacts are so bad it can't activate.

Let's review,,, you find 11.8v flowing between the sm wires WHEN DISCONNECTED from the GPR (that voltage is too high to have the plugs all working). You can't do measurements with those sm wires ON the GPR but you Can with the Lg terminals. The Voltage Drop test is to get voltage readings from each Lg terminal, to Ground, and compare them when activated. If the contacts inside are good there should be very little difference between the two. If you find No voltage on the other side, it's not working al all.

 

[straightshooter412]

This is the third relay I have tried. The last one was for the International engine. I am now at a total loss.

 

[straightshooter412]

Will two of the plugs being out prevent the system from working?

 

[NoRalPh]

Again, no it's a dumb system and has no idea if Any plug works or not.

And here I want to say that the 7.3 will start just fine (except at Really Cold maybe below 20F) without the plugs working at all. You shouldn't need them otherwise, you'd just have to crank a bit longer and see a lot of white vapor from the tailpipe until it warms-up.

 

[straightshooter412]

Thank you for your help. I appreciate it very much.