Correct Glow Plug Resistance
Hotshot
Joined: Jan 2010
Posts: 10,060
Likes: 491
From: Bristol, TN.
The reason for fuses is to protect the circuit against a short, so a direct short should take out the fuse. In my experience it is more typical for circuits to fail in the direct of an "open" rather than a "short, so I most often see ohm readings increase as the circuit or winding is failing. If ohm readings are higher (moving towards "OL"), the likelihood of a short is decreasing.
Steve
Steve
Elder User
Joined: Sep 2011
Posts: 979
Likes: 4
From: Vancouver
When you measure from the GPR, you send current through the glow plugs that are still somewhat operational. If there are one or more GP's that are blown open, the reading obtained will be a higher resistance, since you are measuring the resistance of a parallel circuit. When a glow plug goes bad, it usually burns through the heater element. This eliminates that parallel path for current.
A garden hose with 8-1/4" holes drilled in it is a way to visualize. If you tape up the holes one by one the amount of flow through the hose reduces, similar to electrical current. When measuring glow plugs you are measuring the resistance to the flow of current or how easy it is for it to move through the wire.
A garden hose with 8-1/4" holes drilled in it is a way to visualize. If you tape up the holes one by one the amount of flow through the hose reduces, similar to electrical current. When measuring glow plugs you are measuring the resistance to the flow of current or how easy it is for it to move through the wire.
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Mountain Pass
Joined: Nov 2016
Posts: 153
Likes: 2
From: Front Range
I found this
I guess the easiest way to tell if they are Beru or not is to pull one.
Glow Plug Wiring Diagram, Testing, & Troubleshooting
The glow plugs are located in the cylinder head, one for each cylinder. They stick out of the head about an inch, and are fed by a small brown wire with a bullet style electrical connector. The best way to test the glow plugs is to check the resistance in each one. To test the resistance in a glow plug with a digital multimeter, first disconnect the negative battery terminal from both batteries. Select the resistance setting of the multimeter (the settings on multimeters vary by model, but set your range for under 1k ohms). With the positive lead of the multimeter, probe the top of the glow plug. With the negative lead of the multimeter, probe the engine block at the base of the glow plug. The reading should not exceed 1 ohm. Most good glow plugs will read 0.1 to 0.5 ohms when resistance is checked (to provide a baseline, our testing indicated that a brand new Motorcraft glow plug had 0.3 ohms of resistance through it). Additionally, all 8 glow plugs should have relatively close resistance readings. If 7 glow plugs read 0.3 ohms of resistance and 1 glow plug reads 0.7 ohms of resistance, this is an indication that 1 glow plug is, at the very least, performing at a reduced capacity than the rest of the system. A single bad glow plug can cause the glow plug controller to malfunction. If you detect that 1 or more glow plugs is faulty, replace all 8; never replace a single glow plug, always change them in complete sets.
The glow plugs are located in the cylinder head, one for each cylinder. They stick out of the head about an inch, and are fed by a small brown wire with a bullet style electrical connector. The best way to test the glow plugs is to check the resistance in each one. To test the resistance in a glow plug with a digital multimeter, first disconnect the negative battery terminal from both batteries. Select the resistance setting of the multimeter (the settings on multimeters vary by model, but set your range for under 1k ohms). With the positive lead of the multimeter, probe the top of the glow plug. With the negative lead of the multimeter, probe the engine block at the base of the glow plug. The reading should not exceed 1 ohm. Most good glow plugs will read 0.1 to 0.5 ohms when resistance is checked (to provide a baseline, our testing indicated that a brand new Motorcraft glow plug had 0.3 ohms of resistance through it). Additionally, all 8 glow plugs should have relatively close resistance readings. If 7 glow plugs read 0.3 ohms of resistance and 1 glow plug reads 0.7 ohms of resistance, this is an indication that 1 glow plug is, at the very least, performing at a reduced capacity than the rest of the system. A single bad glow plug can cause the glow plug controller to malfunction. If you detect that 1 or more glow plugs is faulty, replace all 8; never replace a single glow plug, always change them in complete sets.
Hotshot
Joined: Jan 2010
Posts: 10,060
Likes: 491
From: Bristol, TN.
It is easy enough to calculate the change in heat by calculating, where necessary, your amps and volts and multiple to get watts. 3.41 BTU per watt. I think you will see the change in heat is likely not significant.
Steve
Steve
Posting Guru
Joined: Oct 2012
Posts: 1,910
Likes: 2
From: Hat Creek Ca
"So what I'm getting is that the low end resistance reading isn't that critical, just so it isn't zero and that it's in close range with the other glow plugs."
You are way over thinking this. Just get the correct Motorcraft glow plugs for your truck and move on to the next project.
You are way over thinking this. Just get the correct Motorcraft glow plugs for your truck and move on to the next project.
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Mountain Pass
Joined: Nov 2016
Posts: 153
Likes: 2
From: Front Range
"So what I'm getting is that the low end resistance reading isn't that critical, just so it isn't zero and that it's in close range with the other glow plugs."
You are way over thinking this. Just get the correct Motorcraft glow plugs for your truck and move on to the next project.
You are way over thinking this. Just get the correct Motorcraft glow plugs for your truck and move on to the next project.
I do have a new set of Motorcraft glow plugs coming. Just trying to decide in the meantime if I needed to wait for them. As it was, I pulled one and it was a Beru. I'm gonna leave them and put the new ones on the shelf when they arrive. I'll check the torque on everything else and put it back together.
I have new O rings for the breather and will probably turn it around and do a mod on it.
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Hotshot
Joined: Mar 2014
Posts: 10,750
Likes: 1,065
From: Douglassville, PA
Beru is the manufacturer of the Motorcraft glow plugs. I think that they moved from Germany to Ireland so newer ones should say, "Beru, Ireland" on them and older ones will say, "Beru, Germany".
Isn't it nice to pull one and see that rather than an off brand?
Isn't it nice to pull one and see that rather than an off brand?
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Mountain Pass
Joined: Nov 2016
Posts: 153
Likes: 2
From: Front Range
I sorta figured they'd be right. From what I've read and seen, everything else has been done right on this truck, even the aftermarket bling. I paid a lot for an 01', but I don't regret it. I can't begrudge a loose connector.
This sure beats the old days, working out of a Chilton/Haynes manual with no internet. I'd still be at square one.
Post Fiend
Joined: Mar 2015
Posts: 5,277
Likes: 32
From: Blairsville, Pennsylvania
The guy I bought the truck from probably read your forum. I did get a good feeling about him.
I sorta figured they'd be right. From what I've read and seen, everything else has been done right on this truck, even the aftermarket bling. I paid a lot for an 01', but I don't regret it. I can't begrudge a loose connector.
This sure beats the old days, working out of a Chilton/Haynes manual with no internet. I'd still be at square one.
I sorta figured they'd be right. From what I've read and seen, everything else has been done right on this truck, even the aftermarket bling. I paid a lot for an 01', but I don't regret it. I can't begrudge a loose connector.
This sure beats the old days, working out of a Chilton/Haynes manual with no internet. I'd still be at square one.
The net has really been a plus for automotive work
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
Yeah... as mentioned, OEM. Once you are in possession of the Motorcraft glow plugs with the VCs off, they will be installed in minutes. You'll probably feel like "wow... that was much ado about nothing".
The wiring harnesses between the valve cover gaskets and the components under the valve covers (UVCHs) are a much bigger concern, and the root of many evils. Any flaky readings to the GPs are more than likely UVCH related.
The wiring harnesses between the valve cover gaskets and the components under the valve covers (UVCHs) are a much bigger concern, and the root of many evils. Any flaky readings to the GPs are more than likely UVCH related.
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Mountain Pass
Joined: Nov 2016
Posts: 153
Likes: 2
From: Front Range
Originally I read that the ohm reading should be between 0.6 and 2.0. Not knowing, I had to question it.
I ordered the parts before removing the valve covers. Didn't want to wait. Unfortunately, the GPs were sent to an old address in another state and had to be retrieved and forwarded. I did receive new new VC gaskets and new wire harnesses.
The wire ties on the harnesses were brittle plus I broke one of the inside connectors on removal. It may have been my fault, but I believe that it was brittle to start.
There was a loose connection and I may have been alright using the quarter trick, but I had the new parts and a broken connector.
My theory is that not being a great mechanic, I can replace parts cheaper than getting a diagnosis.
My existing GPs are fine and OEM, so not having the new ones in hand, I decided to leave them for now.
The hardest parts were removing the back VC bolt on the driver's side, removing the VC from the engine bay on the passenger side, and reattaching the wire harness to the GPs and to the injectors. Short stubby fingers, lack of dexterity, and poor eyesight didn't help. Once they were on though, they were on.
I wish that I had read a little more, I would have gotten the Dorman VC single piece gaskets and harnesses, but I'm not really concerned, just a note for the next guy.
Now that I know what's going on, it will be a simple process if I ever do decide I need to replace the glow plugs.
I ordered the parts before removing the valve covers. Didn't want to wait. Unfortunately, the GPs were sent to an old address in another state and had to be retrieved and forwarded. I did receive new new VC gaskets and new wire harnesses.
The wire ties on the harnesses were brittle plus I broke one of the inside connectors on removal. It may have been my fault, but I believe that it was brittle to start.
There was a loose connection and I may have been alright using the quarter trick, but I had the new parts and a broken connector.
My theory is that not being a great mechanic, I can replace parts cheaper than getting a diagnosis.
My existing GPs are fine and OEM, so not having the new ones in hand, I decided to leave them for now.
The hardest parts were removing the back VC bolt on the driver's side, removing the VC from the engine bay on the passenger side, and reattaching the wire harness to the GPs and to the injectors. Short stubby fingers, lack of dexterity, and poor eyesight didn't help. Once they were on though, they were on.
I wish that I had read a little more, I would have gotten the Dorman VC single piece gaskets and harnesses, but I'm not really concerned, just a note for the next guy.
Now that I know what's going on, it will be a simple process if I ever do decide I need to replace the glow plugs.
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Mountain Pass
Joined: Nov 2016
Posts: 153
Likes: 2
From: Front Range
Thanks to an old post by F350-6 and all you guys, my truck is running better than ever. Thank you!!!
https://www.ford-trucks.com/forums/8...shakes-19.html
https://www.ford-trucks.com/forums/8...shakes-19.html
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