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Discussion Starter · #1 · (Edited)
Ok guys I'm a long time reader and first time poster here. I did read the sticky and know how to work a search engine. I apologize if this is a dumb question but I'm not finding what I need.

So the condensed version of my story is I have a bad fuel knock and lots of black smoke (no diesel in oil). I understand there is most likely one or more injectors stuck open. Now being a broke college kid logging part time to work my way through college, I don't have the funds to buy a Tech2 or EFI right now.

Is there any way to check cylinders through glow plugs? I think I read something somewhere about pulling glow plugs and FICM fuse and turning over the engine. If that make any sense, could some one explain to me a little more detail what the proper procedure is?

Also do injectors go bad like this overnight? The injectors where checked and resealed with new lines not 2K miles ago when the head gaskets where done. The truck ran fine with no issues not 6hrs before It started knocking. I did forget to plug in the block heater that night and I had to prime it by hand to get it to start in the morning. I changed fuel filters and let it warm for the whole day. I also have been running the white Diesel Kleen in every tanks. I got balancing rates jumping to 11 on cylinders 1,2,3,7 if that means anything.

This is my first diesel truck so I'm learning as I go. I have a bit of experience wrenching on gassers and heavy diesel equipment. Sorry for the long post. Any and all info is much appreciated.
 

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Discussion Starter · #3 ·
Im in Morgantown WV right now. If that's the case would trying to run GM injector cleaner through the quick disconnects be worth a try?
 

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Discussion Starter · #5 ·
OK I'll try that today and let yall know how it goes, thanks
 

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You can pull the glowplugs and disconnect the FICM harness'. This allows the truck to crank over without injecting fuel to start. The injectors that are stuck open will still allow fuel to enter the cylinder. This fuel will spray out the glowplug hole. All this test will do is show you which injectors may be sticking. You may see the glowplug saturated when you remove it.
 

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Discussion Starter · #7 ·
Ok that what I was thinking, just wanted conformation. I unfortunately had it towed to the dealer on Wednesday morning so they could use there scan tools to determine for sure which injectors were bad (my mistake) its now Saturday and they haven't touched it yet. I hate going to the dealer for anything. So ill start tearing into it after Christmas. I'm glad i have AAA free towing up to 20 mile.
 

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Discussion Starter · #8 ·
Anyone in the Morgantown WV area DO NOT go to Premier Chevrolet they are to incompetent to check my injectors for the past 2 weeks they have had my truck. I'm losing money waiting. Tonight I will be towing the truck to my garage and doing the glow plug test. I know its not the best solution but you got to work with what you got.
 

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Discussion Starter · #10 · (Edited)
I'm on my lunch break now. I had an idea that might be stupid but i need some insight from yall. So each injector is controlled by two wires. The 4 wire connectors above the head control 2 injectors at a time ex: (1/3,2/4,5/7,6/8). If i were to put quick disconects on each injector wire. I could in theory pull the 2 wires each injector individualy until i had the fuel knock disappear?
 

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Theoretically that would work. Wait for an expert in case that would F something up. Aside from timing I wouldn't see why not. But like I said, wait for somebody that knows what they are doing. I'm a mechanic but not a duramax mechanic :)
 

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Maybe and maybe not. If the Injector is stuck open (firing) all the time, removing one or two wires
to the injector won't do anything. (You should only have to remove one wire from the Injector to
disable it versus both.) But, remember the FICM is creating 48 Volts to fire the Injector, and is looking
at the Current through each Injector as it fires, and also re-capturing the High Spikes from the Injector's
Solenoid's Collapsing Field to store that energy for another Injector). I wouldn't be removing wires
and troubleshoot that way, because you could possibily smoke something.

Aarons suggestion of removing the Glow Plugs would be the best idea to pinpoint the Injector.

Larry
 

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Discussion Starter · #13 ·
I just did the glow plug test as recommended I pull my FICM plugs and all glow plugs. I found no saturated plugs and there was no diesel spraying out as the motor was cranked over. I also checked my rail pressure with my PPE tuner before and after rail pressure was 5600psi (I have a small fuel leak at the filter housing).
So now I'm thinking if the injector was hung it would not be able to close and the cylinder would be flooded. If my rail pressure remains the same and there was no diesel in the cylinders. Then I can conclude all the injectors were closed. That leads me to think I have a FICM problem telling an injector to stay open. Now could a bad FPR cause fuel knock and black smokeing lope at idle?
 

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Are you sure its a fuel knock?
 

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Discussion Starter · #16 ·
UPDATE: i went to go swap my buddies FICM from his 02 to my 01 and he had talkd to a tech that afternoon and said that the FICM are vehicle specific and wont work with my truck. he said it had to be reflashed. I checked the Part number on thee FICM mine ends with 772 his is 773. Is this true?
 

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yup its true, not a plug and play... and if you try to disconnect 1 injector at a time as soon as your ficm sees a circuit issue (which you will be creating by disconnecting injector wires) it shuts down that entire bank and will make even more knocking

i suggest finding a good technician, maybe try another dealer an ask them is they have a good diesel tech, also try caling local independent shops.
 

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Discussion Starter · #18 · (Edited)
Thats what I was afraid of. Im about out of options now. I have read about people buying FICMs off ebay and pluging them in. Do i need a dealer to reflash a new FICM if i go buy one new?
 

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Discussion Starter · #19 ·
Pulled the injecter line #7 tonight to beiging the process of camping off one line at a time to narrow down which injecter is hung. After takeing a break and a few more beers i figured this is the best way to proceed. Im suprised to find some crud on the injecter line with only 2k miles on it. Maybe a new lift pump with filters should be in the future on top of the cat filter.
 

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Anyone in the Morgantown WV area DO NOT go to Premier Chevrolet they are to incompetent to check my injectors for the past 2 weeks they have had my truck. I'm losing money waiting. Tonight I will be towing the truck to my garage and doing the glow plug test. I know its not the best solution but you got to work with what you got.
All the new dealerships are incompetent around here, welcome to Morgantown :thumb
 
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