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Hard/No Start? Check here first.

375K views 82 replies 42 participants last post by  meador123 
#1 · (Edited)
Thought I'd post this as a sticky thread now that cold weather is on us.

How to check Glow Plug System

To check the Glow Plug Relay (GPR)
· Be sure the engine is cold, so that the PCM will tell the GPR to turn on. If the engine is hot, you won’t have as much time to check. (if oil temp is above 130F, it won't turn on at all)
· Locate the GPR – It's behind the fuel filter on top of the engine, a little bit toward the passenger side of the valley. There may be two relays there. If so, the rear one is the GPR. It will have two fairly large wires (yellow and brown) connected to the large post without the rubber boot.
157028

Another location photo here:
157025

Photo credit F350_6

With your multitmeter set to DC volts, and 15 V range (if not autoranging), clip the positive (red) lead to the output terminal (with yellow and brown wires connected), and the negative (black) lead to a good ground point (like the battery ground terminal or someplace metal directly on the engine block.)​
Turn the key to ON (do not start)​
If your GPR is good, it should click, and you’ll see 11 volts or so on your meter, then, depending on temperature, it will click off up to 2 minutes later. You should do this a couple of times to make sure it consistently makes the connection.​
If you don’t get voltage with this test, confirm by retesting as follows.​
Remove the two small wires from the smaller two of the four GPR terminals.​
With jumper wires, apply voltage from the battery across the two small terminals. If your voltmeter now reads voltage on the output terminal, your GPR is OK, and your problem is in the PCM circuit that tells the GPR to activate.​

GPR for 99 & up 7.3L
Ford F81Z-12B533-AC
NAPA GPR#109 (mounts 90 deg out of rotation from original)
Carquest #RY-175 (clone of GPR#109)
Autozone Sorensen MR-99 (also clone of GPR #109 I think)
International #1831646C1 (Identical to the one you'll get from Ford) ~$25-$30
[added on edit] A forever GPR - White Rogers/Stancor 586 902


To check Glow Plugs.
Remove the electrical connector on the inboard side of valve cover at the gasket. Press down on the top of the connector latch and pry gently with a screwdriver.​
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Disconnecting VC harness connector.
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Another photo of it loose.

There will be 9 pins on the valve cover gasket where you removed the connector. The two pins furthest forward and the two pins furthest back are for your glow plugs.​
With your multimeter set to resistance (ohms) and low range (single digits) if not autoranging, clip the negative (black) lead to a good ground point.​
Probe each of the 4 outer pins individually with the positive (red) lead, noting the resistance. Good glow plugs will have a resistance between 0.6 and 2 ohms. If you get infinite resistance on any glow plug, that one is either bad or the connector under the valve cover has come loose.​
 
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#3 ·
Oooohhhhh. This is awesome. We've had Ford diesels for years, and are just now trying to figure out what we can do on our own! (I'm sick of paying the "stealer" his crazy rates) This kind of troubleshooting is AWESOME! Please, please, please keep it coming!!
Is there any way to post diagrams? I know, I should just get the repair manual...... But I'm still looking for the fuel filter....
 
#4 · (Edited)
But I'm still looking for the fuel filter....
LOL /ubbthreads/images/graemlins/biggrin.gif /ubbthreads/images/graemlins/biggrin.gif

I know what you mean. The owner's manual on my 99 doesn't even tell you where the filter is. /ubbthreads/images/graemlins/mad.gif

I eventually found it under the "Powerstroke" cover on top of the engine. We were all noobies once. /ubbthreads/images/graemlins/grin.gif
 
#5 ·
[ QUOTE ]
[ QUOTE ]
But I'm still looking for the fuel filter....

[/ QUOTE ]

LOL /ubbthreads/images/graemlins/biggrin.gif /ubbthreads/images/graemlins/biggrin.gif

I know what you mean. The owner's manual on my 99 doesn't even tell you where the filter is. /ubbthreads/images/graemlins/mad.gif

I eventually found it under the "Powerstroke" cover on top of the engine. We were all noobies once. /ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]

This is information that needs to be added to the beginning of the otherwise great write-up in the "The TheDieselStop.com 1999-up FAQ" I copied this off and had it in hand when I went to R&R the fuel filter but my wife and I both looked for quite some time before I figured out where it was located.
 
#6 · (Edited by Moderator)
Here is a pdf I put together of glow plugs/gpr and the troubleshooting of them...hope this helps someone.

Streamload.com [link broken]
 
#81 ·
Here is a pdf I put together of glow plugs/gpr and the troubleshooting of them...hope this helps someone.
Unfortunately I can't include a copy of the defunct link from quoted post because I'm new here. Does anyone have a copy of the GPR Troubleshooting PDF nlemerise put together a decade ago? The link is no longer functional - instead cross links to an iDrive website requiring you to register, then only will back up your own system - it's not a file sharing site.

Thanks!
Garth
 
#7 ·
Thanks "klhansen" and "8V92TTA" for the great write-ups and the additional diagrams. I'll add all this info to my "book" of PSD knowledge for use in the future. /ubbthreads/images/graemlins/cool.gif
 
#9 ·
KLH, so how do ya know if your GPR is faulty? Thanks!
 
#10 ·
Will it still start in warm weather with a faulty GPR? Do they completely fail or get tempermental??? Good Stuff /ubbthreads/images/graemlins/cool.gif
 
#11 ·
What if you have a CA truck and have the Glow Plug Controller instead of the Glow Plug Relay? How would I go about testing this thing? It has 2 pigtail plugs goin into it...Thanks!
 
#12 ·
[ QUOTE ]
What if you have a CA truck and have the Glow Plug Controller instead of the Glow Plug Relay? How would I go about testing this thing? It has 2 pigtail plugs goin into it...Thanks!

[/ QUOTE ]

As far as I know, the GP Controller talks to the PCM and throw codes whenever it has a problem, so you best approach there would be to scan it with a good scan tool. You might be able to pull the GP harness off and monitor the GP pins on the harness (front two and back two) for voltage at first Key On similar to the GPR testing. I think the GP controller contains a series of solid state relays, one for each GP.

Sorry, don't have any direct experience with those animals.
 
#13 ·
To check Glow Plugs.
· Remove the electrical connector on the inboard side of valve cover at the gasket.
Ok, I probably picked the worst day to try to do this because it is COLD here. How in the #$!@% do you get the connector off? I was not able to get it off and was afraid of breaking it.
 
#14 ·
They are tough little buggers, and hard to get to.

Push down on the lump on the center of the connector to release the hooks just to each side of that lump and at the same time use a small screwdriver to gently pry the connector apart at each end. Stick the screwdriver in at the joint where the seal is and twist.

Hope that helps. I'll be getting at mine in the next couple of days and will try to post a picture.
 
#15 ·
They are tough little buggers, and hard to get to.

Push down on the lump on the center of the connector to release the hooks just to each side of that lump and at the same time use a small screwdriver to gently pry the connector apart at each end. Stick the screwdriver in at the joint where the seal is and twist.

Hope that helps. I'll be getting at mine in the next couple of days and will try to post a picture.
Mine was being difficult to get off, but I discovered I could just stick the multimeter's probe in next to the wire to get a reading, without unplugging the connector.
 
#17 ·
You can just take your multimeter put the leads in the top of the connector. You don't even have to take the plug off.
If you're talking about sticking the multimeter lead down beside the wire going through the seal, I think I'd avoid doing that. Those seals are there to keep moisture out of the connectors. If you damage a seal, you may find that the terminals will get corroded, causing at best a bad connection, and at worst a toasted external connector.

I've been trying to find a source for the external connector, but haven't been successful. About the only other way to repair that is a $500 engine harness. /ubbthreads/images/graemlins/eek.gif
 
#18 ·
You can just take your multimeter put the leads in the top of the connector. You don't even have to take the plug off.
I don't think that works anyway. All the leads come back to a common point so it won't really tell you anything unless all the plugs were bad.
 
#19 ·
You can just take your multimeter put the leads in the top of the connector. You don't even have to take the plug off.
I don't think that works anyway. All the leads come back to a common point so it won't really tell you anything unless all the plugs were bad.
Exactly right, I forgot about that. /ubbthreads/images/graemlins/crazy.gif

OTC makes a tool that's a connector with each wire brought out to a test point to check GP's and injectors, but they want $75 for it. Pulling the connector is much cheaper and works just as well.
 
#20 ·
Great write up! One quick comment, when my GPR went bad, it was intermittent.
I would turn the key on, wait to start, and try to start it. at first, once out of 10 times it wouldn't start right up, and I'd repeat the process.
Eventually, it wouldn't start no matter what.

Only reason I mention this, is using your great testing techniques, you might "luck in" and test it when it was working.
The 99 and up GPR is like 25 bucks at the local parts store, and the local parts store DOES stock them, and it takes under an hour to replace it.

Hint hint.

When in doubt, change it.
 
#21 ·
Would it be possible to convert my Glow Plug Controller to the Glow Plug Relay setup? Dont they do the same thing???
 
#22 ·
Just edited the original post to inlcude pics of getting the VC connectors loose. Also added a note on checking the GPR a couple of times to make sure the good connection isn't a fluke.
 
#23 ·
[ QUOTE ]
Would it be possible to convert my Glow Plug Controller to the Glow Plug Relay setup? Dont they do the same thing???

[/ QUOTE ]

They do the same thing, but go about it a little differently.

If you could determine which wires to your GPC come from the PCM to activate it, you could probably rewire the engine harness to install a GPR instead, but I doubt it would be worth the effort.

I believe the solid state GPC may be a litte more robust than a GPR, not having contacts to arc when it disconnects.

Sorry I couldn't be more help.
 
#24 ·
Ahh, I see whatcha mean. In my ongoing experience, the truck would start 50/50. Sometimes it would crank right up in the morn, starter would sound normal. Other times, Id put it in the on position in the morn and the batt. indicator on the dash would slowly go down to the 8 mark very erratically and then the stock headunit would flash on and off, as well as a bunch of clicking coming from the engine bay. When the truck is warm, it wouldn't have the problem. I'm thinking the ECU is bypassing the warming of the GPs and thus bypassing the GPC? /ubbthreads/images/graemlins/shrug.gif
 
#25 ·
[ QUOTE ]
Other times, Id put it in the on position in the morn and the batt. indicator on the dash would slowly go down to the 8 mark very erratically and then the stock headunit would flash on and off, as well as a bunch of clicking coming from the engine bay.

[/ QUOTE ]
That sounds like you are having a battery issue. How old are they?

[ QUOTE ]
When the truck is warm, it wouldn't have the problem. I'm thinking the ECU is bypassing the warming of the GPs and thus bypassing the GPC? /ubbthreads/images/graemlins/shrug.gif

[/ QUOTE ]
Yes, the GPR (and presumably the GPC) is controlled by the PCM to only energize the GP's when the engine is cold. If the oil temp is over a certain value, the GP's won't even be turned on.
 
#26 ·
[ QUOTE ]

That sounds like you are having a battery issue. How old are they?

[/ QUOTE ]

They were replacement Red Top Optimas. The first set, I had for about 6 mos., the second set was replaced in Aug. of this year. In the beginning they worked good, then I'd have to jump the truck every so often, especially after sitting more than a day or so...Now I'm jumpin the truck more than haveing it start on its own /ubbthreads/images/graemlins/mad.gif This gets old after about the second time. Now, I'm at about the 15th time I've had to jump the truck now /ubbthreads/images/graemlins/depressed.gif I'm thinkin about going to the dealer and getting their batts., cuz the stockers lasted for about 3 and a half years before they started to weaken. Probably because I never filled them up with distilled. Are the dealer batts worth getting? /ubbthreads/images/graemlins/shrug.gif I dont mind the build up on the terminals, as long as the darn thing starts!
 
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