Need quick help- injectors not passing ohm test
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Hotshot
Joined: Jul 2003
Posts: 12,177
Likes: 40
From: Newport, WA
Need quick help- injectors not passing ohm test
I just installed the new GP's in the passenger side head, hooked up the wires, and busted out my multimeter. The GP's passed, but the injectors didn't- ALL of them. Front front to back I got 8,15,8,8 for ohm readings. Am I screwed? Truck was running fine when I parked it to do this job. Only thing I can think that may have caused me a problem is I unhooked the lead on the alternator to get it out of the way while working on the driver's side and I was trying to move it to a safe spot and wrap it in tape when it briefly touched the housing on the alternator- I decided to just leave it alone after that (stupid thing to do I know). If I've got 4 dead injectors I'm majorly screwed...
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
Now I remember what I forgot to do when I had my valve covers off.
Since you didn't remove your injectors, and the odds of you breaking all of your injector wires but not your glow plug wires seem slim, check the center ground pin. I meant to take a closer look at this to see how the common is wired up. I'd pay close attention to the center pin and make sure your problem isn't there. From the pictures I do have, I don't see where the center pin wire leaves the UVCH connector.
You can also unplug the inside and outside connectors and ohm the pins to make sure there aren't any issues there.
Since you didn't remove your injectors, and the odds of you breaking all of your injector wires but not your glow plug wires seem slim, check the center ground pin. I meant to take a closer look at this to see how the common is wired up. I'd pay close attention to the center pin and make sure your problem isn't there. From the pictures I do have, I don't see where the center pin wire leaves the UVCH connector.
You can also unplug the inside and outside connectors and ohm the pins to make sure there aren't any issues there.
Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
What do you mean? I am sure you are referring to the fact that we are ohming the harness connections.
To check the harness ohm it at the Valve cover connector on the outside.
Pin Out
G G I I C I I G G
G=Glow Plug +
I = Injector +
C= Injector Common
***The injectors fire with a 115VDC signal from the IDM do not pierce to wires to test.***
Ohm between "I" and "C" to test the injectors, should be less than 5.0 Ohms
To check glow plugs Ohm between "G" and battery ground should be between 0.1 and 2.0 Ohms
Pin Out
G G I I C I I G G
G=Glow Plug +
I = Injector +
C= Injector Common
***The injectors fire with a 115VDC signal from the IDM do not pierce to wires to test.***
Ohm between "I" and "C" to test the injectors, should be less than 5.0 Ohms
To check glow plugs Ohm between "G" and battery ground should be between 0.1 and 2.0 Ohms
Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
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Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
Umm Kris, you feeling alright tonight? Mike's right on this. Ohming the glow plugs wouldn't help us diagnose a rough running truck or a P1316 IDM code while we're looking for the infamous loose UVCH connector.
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Thread Starter
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Hotshot
Joined: Jul 2003
Posts: 12,177
Likes: 40
From: Newport, WA
I went out and checked it again... same results. I didn't feel like sitting here very long, so I went out and threw the valve cover back on and fired it up... it runs and starts fine. Drink more beer and don't worry about it?
Postmaster
Joined: Dec 2005
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How does the truck run? If its running fine like it rip.
When you ohm the injectors that way you are ohming out the internals of the injector along with the harness, a bit different that a glow plug. The glow plug operates like a resistor or a light bulb, its an element that heats up. When you ohm it out, you are grounding out through the head(this is where the GP grounds out), which will just tell you how much resistance that glow plug had. Higher ohms = less heat/ poor connection, infinite ohms = no connections. With the injectors you are dealing with a lot more chit, than a simple circuit such as glow plugs, if you are getting different ohm readings, it could be way more than a simple wiring harness problem, but if your not experiencing a problem not worry about it. The mileage of the truck will wear out certain parts, but if they wear equally, you won't notice a different. How I am understanding it anyways, I can always be wrong.
When you ohm the injectors that way you are ohming out the internals of the injector along with the harness, a bit different that a glow plug. The glow plug operates like a resistor or a light bulb, its an element that heats up. When you ohm it out, you are grounding out through the head(this is where the GP grounds out), which will just tell you how much resistance that glow plug had. Higher ohms = less heat/ poor connection, infinite ohms = no connections. With the injectors you are dealing with a lot more chit, than a simple circuit such as glow plugs, if you are getting different ohm readings, it could be way more than a simple wiring harness problem, but if your not experiencing a problem not worry about it. The mileage of the truck will wear out certain parts, but if they wear equally, you won't notice a different. How I am understanding it anyways, I can always be wrong.
Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
Drive on bro.
