Duramax Diesels Forum Truck of the Week
  #31  
Old 06-14-2018, 08:57 AM
Tylerrc34 Tylerrc34 is offline
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Originally Posted by 2004LB7 View Post
I had three solenoids short out on me over the time i had my LB7

First one I ended up replacing it with a new one for the dealership

2nd, and 3rd, I ended up purchasing a few used injectors on ebay and just swapped the coils out leaving the injector body in place.

I made a special socket for the solenoids being that they are somewhere around an 18 sided nut. Took a 1" emt and heated red and tapped it onto a bad injector solenoid so as to form it to the shape

All three shorted to ground and I believe two of them where #5 or #7. Dont remember but it was the same one twice

Just like any injector swap, you need to be meticulously clean and make sure you dont reassemble the high pressure lines if anything is in the injector fuel input conector.

I have no idea why they shorted out
How did you determine which injector was grounding? I have my passenger side valve cover open (dreading removing the driver side) and when measuring the continuity of the injectors they read...

#1 = .06
#3 = .00
#5 = .00
#7 = .00

I don't think .06 is a bad reading do you? Or is this a sign my #1 injector may be grounded?
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  #32  
Old 06-14-2018, 09:02 AM
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Originally Posted by Tylerrc34 View Post
Yes, all wires from the ECM to the FICM and from the FICM to injector harnesses have continuity.
Checking continuity doesn't tell you anything. A short is a wire rubbed through to ground or to another wire. You need to visually inspect the harness for this.

I got burned by this on my wifes old car. Threw an injector at it cuz the wires tested fine. It had a rubbed through wire that was intermittently shorting that was the actual problem though.
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  #33  
Old 06-14-2018, 09:11 AM
Tylerrc34 Tylerrc34 is offline
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Originally Posted by LBZ View Post
Checking continuity doesn't tell you anything. A short is a wire rubbed through to ground or to another wire. You need to visually inspect the harness for this.

I got burned by this on my wifes old car. Threw an injector at it cuz the wires tested fine. It had a rubbed through wire that was intermittently shorting that was the actual problem though.
If I use my ohm meter between the ground and a single wire and it reads 1.00 then that means there's NOT a short to ground but if it reads anything else like .77 or .90 then that means there IS a short to ground. Isn't that correct? And the smaller the number like .25 means it's a stronger contact.
Right?
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  #34  
Old 06-14-2018, 10:24 AM
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I disconnected the connection right at the valve covers for the injectors and measured there. There are four pins. It should be obvious but two go to one injector and the other two go to another injector. I measured the resistance from one of the pins to ground and it read continuity. The others did not.

After pulling the valve covers. I took the wires off the injector and measured there. It read to ground so I knew it was a bad injector.

Then I disconnected the fcim from the harness and measured the resistance to ground while moving the harness around. Everything checked out good

When it happened again, except this time on the passenger side, I did the same test but also opened up the harness to see if there was anything I could find that would cause it. Everything checked out good and no chafes or exposed wires.

Thats when I made the socket. I just replaced the coil as I had no clue what condition the bodies where in being that I got them on eBay for about $75 each.

I used break clean and a vacuum pump to make sure all of the ports on the injectors where spotless before reassembling it.

At one point before the injectors showed up, I dont recommend it but I needed my truck to get to work as it was my only vehicle at the time, I connected a small inductor in place of the bad injector to trick the FCIM into thinking everything was ok and drove it for about two weeks with one cylinder out. This was to keep it out of limp mode and get the other injectors back on so it had enough power to safely drive down the road
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  #35  
Old 06-14-2018, 11:11 AM
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Originally Posted by Tylerrc34 View Post
If I use my ohm meter between the ground and a single wire and it reads 1.00 then that means there's NOT a short to ground but if it reads anything else like .77 or .90 then that means there IS a short to ground. Isn't that correct? And the smaller the number like .25 means it's a stronger contact.
Right?
If you are using an old school sweeping arm ohmeter I suggest stepping up your game and getting a more accurate and easier to read digital multimeter.

Not sure what kind of meter your using but most digital meters read OL when measuring a wire that is supposed to be isolated from the ground side when measuring between it and the ground. Any other number means it is making contact with the ground. If checking the wire itself you should see 0. Numbers higher than that means it possibly has poor continuity for a variety of possible reasons including In-Line resistors, breaks, shorts and poor connections.
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  #36  
Old 06-14-2018, 11:29 AM
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Also, to elaborate a little bit on what LBZ said.

There shouldn't be any continuity between the injector studs and ground. It should read in the megaohms. Stud to stud is something like a half an ohm
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  #37  
Old 06-14-2018, 01:03 PM
Tylerrc34 Tylerrc34 is offline
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Thank you for taking time to answer the questions.

I'm opening up my drivers side valve cover now and I'll give you an update of what I find.
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  #38  
Old 06-16-2018, 08:46 AM
Tylerrc34 Tylerrc34 is offline
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I am so lost on this issue. Here's what I've done over the last couple days.

I pulled off the entire bale connector harness, brought it inside, took off every bit of electrical tape, inspected every wire, checked every connection with my digital multimeter, looked at every pin, there is nothing wrong with the harness. I put new tape and protective sleeves on it. I can say with certainty it is not the harness.

I pulled my driver's side valve cover off and checked the continuity of each injector, all read .00 and I also checked each stud on all injectors for continuity to ground, none are reading grounded. All 7mm captured nuts were tight.

I'm quite nervous about needing new injectors because my lower valve cover bolts are so incredibly tight that I don't think I can get them off without stripping. But maybe that's not an issue right now because I am not getting the sign that I need new injectors.

HELP!

Could it be that I need a new FICM? I was thinking if I got one from a salvage yard with a return policy then I could switch it out to see if that's the problem then return it if not.
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  #39  
Old 06-16-2018, 09:40 AM
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Did you check the injector pigtails that run through the valve covers?
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  #40  
Old 06-16-2018, 09:50 AM
Tylerrc34 Tylerrc34 is offline
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Quote:
Originally Posted by 2004LB7 View Post
Did you check the injector pigtails that run through the valve covers?
Yes, twice. All checked out fine.
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  #41  
Old 06-16-2018, 10:41 AM
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I would put it all back together less the upper valve covers and test the connections at the fcim. If all looks good test run it. If it still has issues take the ohm readings that the fcim connector for each injector and report what each one is here.

If everything still checks out but doesn't run then maybe it is the fcim
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  #42  
Old 06-16-2018, 11:06 AM
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I honestly leaned toward the FICM from his first post.
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  #43  
Old 06-16-2018, 12:06 PM
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I bet you are right Tom

I was just thinking of a few last steps to do that dont cost anything before braking down for an FCIM. The codes listed could be a number of things, one of which is a short to ground. Brakes in the wires, bad connections, too high or too low resistance, etc. All can cause the codes listed

By putting it all back together and testing it at the FCIM connector he can rule out the injectors and harness. This would give him a good idea if he needs another FCIM
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  #44  
Old 06-16-2018, 12:10 PM
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Oh no, don't take that wrong....I completely agree with your diagnostic tree.
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"BBT" -- 2003 GMC CC/SB 4x4 12.14@111.15
"Flyin' Brick" -- 1999 Chevy 1500 RC/SB 2wd -- stalled out, no motivation
"The Cruzer" -- 2014 Chevy Cruze Diesel -- the fun little DD
"The Bigger Boat" -- 2011 Workhorse P700 - 6.0LS/Allison - what I drive at work


Two wrongs dont make a right, but three rights do make a left.

Reality is a matter of perspective.

This forum isn't for the weak of heart.....or wallet.

"Lets build a race car they said. Itll be fun they said. I don't know who "they" are.........but they need a good punch in the face!" -- mufflerguy (yb)
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  #45  
Old 06-16-2018, 01:18 PM
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Here's a thought for Tylerrc34

Is your codes for injector 1, 3, 5 & 7? Or 2, 4, 6 & 8?

The original poster had codes for the injectors on the passenger side but I see that you have the drivers side open along with the bale connector. Are you sure you have the right bank of injectors?
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