# Duramax troubleshooting



## 1gr8bldr (Aug 29, 2012)

Here is the story; I loaded about 3 ton of old brick on my dump trailer and took it to a spot on my hunting land where we usually have problems crossing. I tought I would back it in the mud a little and then dump. But once it reached the mud, it sank to the frame and the truck quickly dug 4 holes trying to pull it out. I did not dog it at all. With an 8000lb truck, once stuck, your stuck. No sense in trying over and over. But we dug out in front of the wheels and I was going to give it one more try and it cut off. It was like someone hit a kill switch somewhere. It can't be anything mechanical. Must have throwed some safety code. So, I got it pulled out in neutral and now it's being towed to local mechanic. But I really need to get this thing back to work. I don't wish for this thing to set in a lot for several days before they get a chance to look at it. Anybody have any ideas???


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## willc2412 (Aug 30, 2012)

Water could have gotten in exhaust


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## rjcruiser (Aug 30, 2012)

How deep did the truck go?  You mentioned that the trailer went to the frame, but what about the truck?


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## bluemarlin (Aug 30, 2012)

I guess you don't have a tuner? Mine reads codes and lets me know what's up on the display... What year is your truck?


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## 1gr8bldr (Aug 30, 2012)

rjcruiser said:


> How deep did the truck go?  You mentioned that the trailer went to the frame, but what about the truck?


The truck would have never got stuck if it was not for the trailer. The trailer was in the mud, not the truck. But the ground was soft.


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## 1gr8bldr (Aug 30, 2012)

bluemarlin said:


> i guess you don't have a tuner? Mine reads codes and lets me know what's up on the display... What year is your truck?


2004.


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## 1gr8bldr (Aug 30, 2012)

willc2412 said:


> Water could have gotten in exhaust


No water, I could walk across it and sink up a little in my shoes. The main problem was the weight in the trailer. I unhooked the trailer, but at that point, I had dug 4 holes that it would not climb out of. A shovel could have fixed that but then It died


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## rjcruiser (Aug 30, 2012)

1gr8bldr said:


> No water, I could walk across it and sink up a little in my shoes. The main problem was the weight in the trailer. I unhooked the trailer, but at that point, I had dug 4 holes that it would not climb out of. A shovel could have fixed that but then It died



Sounds interesting.  I have no clue, but it almost sounds as if something else was about to go and the strain pushed it over the edge.

I'm guessing something simple.  Battery maybe?  Ignition coil?


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## bluemarlin (Aug 30, 2012)

1gr8bldr said:


> It was like someone hit a kill switch somewhere. It can't be anything mechanical. Must have throwed some safety code.



Fuse?


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## Showman (Aug 30, 2012)

When you turn the key on, do you hear the fuel pump run?  If not, check for a blown fuse or circuit breaker.  If the pump is running, then for how long (longer than usual might mean a clogged fuel filter or air getting in somewhere).  If it ain't that, man, you got big problems.


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## JpEater (Aug 30, 2012)

Showman said:


> When you turn the key on, do you hear the fuel pump run?  If not, check for a blown fuse or circuit breaker.  If the pump is running, then for how long (longer than usual might mean a clogged fuel filter or air getting in somewhere).  If it ain't that, man, you got big problems.



A Duramax doesn't have an in tank electric fuel pump. Or any electric fuel pump at all.


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## 1gr8bldr (Aug 30, 2012)

JpEater said:


> A Duramax doesn't have an in tank electric fuel pump. Or any electric fuel pump at all.


Mine has some sort of pump in the tank. If I let it get below 1/8 of a tank, it runs out. So it seems, but what they say is that little pump has gone bad. Expensive fix so I just never let it get that low. It is a pain when it does because I have to bleed the fuel pump/lines. Then pump the primer. But this time I have plenty of gas [correction, fuel]


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## 1gr8bldr (Aug 30, 2012)

JpEater said:


> A Duramax doesn't have an in tank electric fuel pump. Or any electric fuel pump at all.


One year ago this friday it broke down with the same symptons. Only that time I had the 4wheeler in the back with the boat hooked up, dead in the middle of a blinding rainstorm, sitting in the middle of a busy hwy. Whew, I just knew someone was gonna rear end me. But that time it was a fuel pump relay


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## bluemarlin (Aug 30, 2012)

1gr8bldr said:


> But this time I have plenty of gas



I'm confused... Diesels have lift pumps and don't use gas.


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## 1gr8bldr (Aug 30, 2012)

They hooked it up and the code showed it to be the glow plug module circuit. This does not sound correct. It cut off and never crunk back. Not that it would not crank. Something caused it to shut down


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## 1gr8bldr (Aug 30, 2012)

bluemarlin said:


> I'm confused... Diesels have lift pumps and don't use gas.


LOL, I meant to say fuel. That would be a problem. But sadly, I have done it. Long story. I got distracted


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## Showman (Aug 30, 2012)

Only has a manual Fuel Pump?  That don't sound right.  What do you do if the Prime is not at it's peak?


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## 1gr8bldr (Aug 30, 2012)

Showman said:


> Only has a manual Fuel Pump?  That don't sound right.  What do you do if the Prime is not at it's peak?


I'm sure it has a fuel pump. But it also has a primer button on top of the fuel filter housing. To bleed it, there is a nut to loose, someone turns the motor over until all the air is out and then after tightening, you pump the button until it gets hard.


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## devin25gun (Aug 30, 2012)

Expert:  Tim West replied 850 days and 3 hours ago. 
Thanks for visiting Just Answer,
this is usually due to bad wiring to the fuel injection control module.
There is a TSB on the issue that reads:Condition/Concern:
Some owners may comment of a SES MIL on and if DTCs are checked with the Tech 2 a U0100, U0101, U0105, and/or U0106 will be set. The ECM, TCM, FICM, and Glow Plug Controller communicate between each other on circuits 2361 and 2362 (CAN Buss), the Tech 2 does not communicate on these circuits. 

Recommendation/Instructions:
In most cases, if all the DTCs set it could be caused by the Can Buss circuits shorted to ground. Cases for either of these circuits shorting to ground at the FICM/Alternator bracket have been reported. Before replacing any parts perform a thorough visual inspection of this wiring harness near the FICM/Alternator bracket and repair as necessary if shorted. 


Check this first   Seems to be a issue on the 04 model duramax's


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## JpEater (Aug 30, 2012)

1gr8bldr said:


> Mine has some sort of pump in the tank. If I let it get below 1/8 of a tank, it runs out. So it seems, but what they say is that little pump has gone bad. Expensive fix so I just never let it get that low. It is a pain when it does because I have to bleed the fuel pump/lines. Then pump the primer. But this time I have plenty of gas [correction, fuel]




A Duramax does NOT have an electric fuel pump. It does't have anything more than a fuel sending unit in the tank. However, it does have a fuel pump. It is built into your C3P injector pump mounted in the front of the engine valley on top of the engine. It is a mechanically driven pump that "sucks" fuel from the tank, through the fuel filter and into the pump. Thats why there is a primer on top of your fuel filter housing. Without the primer your would not be able to bleed all the air out of your filter and supply your fuel pump. Everytime you press the primer, your sucking fuel from the tank.


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## JpEater (Aug 30, 2012)

1gr8bldr said:


> I'm sure it has a fuel pump. But it also has a primer button on top of the fuel filter housing. To bleed it, there is a nut to loose, someone turns the motor over until all the air is out and then after tightening, you pump the button until it gets hard.



Do not turn the engine over untill all the air is bled out of the system. 

Proper bleeding procedure for a Duramax Diesel of ALL year models.....

Step 1: Open plastic slotted bleeder screw on top of the filter housing a few turns. 
Step 2: Prime the primer until you get a steady stream of clean diesel fuel with no air bubbles present. 
Step 3: Lightly snug bleeder screw. 
Step 4: Prime the primer a few times. After 2-3 pumps, you should notice it firm up. 
Step 5: Crank up the truck. 

Note: Plastic bleeder screws are very prone to cracking. The engine will NOT run if its cracked and sucking air. Merchant Automotive sells a machined Bleeder screw that will not break.


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## bluemarlin (Aug 30, 2012)

Def get rid of the plastic bleeder screw and replace it with a machined one. Also it's a good idea to get yourself some type of code scanner. It will pay for itself and you'll know what's going on... Most can read and erase fault codes.


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## JpEater (Aug 30, 2012)

Always start with the basics....

First thing is Fuel. A Duramax will not run with any type of an air leak in the fuel system due to the fact that there is no electric fuel pump to pressurize the system. The fuel system is 100% mechanical with NO relays for a fuel pump. It works off of vaccum. It "pulls" fuel to the engine. 99% of all fuel problems are caused by either an improper fuel filter installation sucking air, a cracked or stripped out water in fuel sensor (bottom of fuel filter), a cracked bleeder screw, or leaking seals in the primer assembly. Start by checking for air in the system. You can loosen the bleeder screw and prime is a few times. If you have air bubbles present in the fuel stream, you have an air intrusion caused by one of the above mentioned places most likely. If you don't have air bubbles when priming, you likely have another issue. 

One thing that you didn't state was how it shut off. Where you on the throttle when it died? Did it just shut right off or kinda sputter out. Feel free to PM me a number and I'll be more than happy to walk you through some things to check. Normally a Duramax won't just die unless its a fuel problem. There are other circumstances obviously, but they are pretty uncommon on a duramax. 

You didn't state which model engine you have. Is it an early 04 (LB7) or a late 04 (LLY). You can determine that by looking at the 8th VIN digit and seeing if its a 1 or a 2.

Keep in mind, these are just the first of many steps involved in diagnosing it. There are many more...


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## M80 (Aug 30, 2012)

My question is does it spin over and not crank, or does it not spin over at all, you turn switch over and nothing or?

If it doesn't spin over at all, maybe something is up with your 4x4 and not allowing it.  Need more info.


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## 1gr8bldr (Aug 31, 2012)

mwilliams80 said:


> My question is does it spin over and not crank, or does it not spin over at all, you turn switch over and nothing or?
> 
> If it doesn't spin over at all, maybe something is up with your 4x4 and not allowing it.  Need more info.


It spins over


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## 1gr8bldr (Aug 31, 2012)

JpEater said:


> Do not turn the engine over untill all the air is bled out of the system.
> 
> Proper bleeding procedure for a Duramax Diesel of ALL year models.....
> 
> ...


Interesting, so I don't understand how if it is not a pressurized system how the air will get out.


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## 1gr8bldr (Aug 31, 2012)

JpEater said:


> Always start with the basics....
> 
> First thing is Fuel. A Duramax will not run with any type of an air leak in the fuel system due to the fact that there is no electric fuel pump to pressurize the system. The fuel system is 100% mechanical with NO relays for a fuel pump. It works off of vaccum. It "pulls" fuel to the engine. 99% of all fuel problems are caused by either an improper fuel filter installation sucking air, a cracked or stripped out water in fuel sensor (bottom of fuel filter), a cracked bleeder screw, or leaking seals in the primer assembly. Start by checking for air in the system. You can loosen the bleeder screw and prime is a few times. If you have air bubbles present in the fuel stream, you have an air intrusion caused by one of the above mentioned places most likely. If you don't have air bubbles when priming, you likely have another issue.
> 
> ...



If I remember right, I had my head out the window, was goning to give it some throttle so that I could see if the front wheels were going to spin. I gave it a little, saw the wheel spin and if shut down


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## 1gr8bldr (Aug 31, 2012)

JpEater said:


> Always start with the basics....
> 
> First thing is Fuel. A Duramax will not run with any type of an air leak in the fuel system due to the fact that there is no electric fuel pump to pressurize the system. The fuel system is 100% mechanical with NO relays for a fuel pump. It works off of vaccum. It "pulls" fuel to the engine. 99% of all fuel problems are caused by either an improper fuel filter installation sucking air, a cracked or stripped out water in fuel sensor (bottom of fuel filter), a cracked bleeder screw, or leaking seals in the primer assembly. Start by checking for air in the system. You can loosen the bleeder screw and prime is a few times. If you have air bubbles present in the fuel stream, you have an *air intrusion *caused by one of the above mentioned places most likely. If you don't have air bubbles when priming, you likely have another issue.
> 
> ...


I have the early model, whichever that is, LLY, I think. You must be right about "air intrusion", because the mechanic bleed the system and it fired right up. If I had suspected this, I would have done it in the field. You got me thinking, last year when they claimed they put a fuel pump relay on it, I wonder if this was all they done to it but wanted to justify a higher charge for their trouble. ???


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## 1gr8bldr (Aug 31, 2012)

As Willie would say "On the road again". Thanks for all the help


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## bandit819 (Sep 1, 2012)

If you had air in the lines it will happen again and more frequent. It did for me. I would get a new bleeder screw. bleeding and priming are a pain.


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## 1gr8bldr (Sep 2, 2012)

bandit819 said:


> If you had air in the lines it will happen again and more frequent. It did for me. I would get a new bleeder screw. bleeding and priming are a pain.


I think I will. Did you order yours or just match it from the hardware store?


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## JpEater (Sep 2, 2012)

1gr8bldr said:


> I have the early model, whichever that is, LLY, I think. You must be right about "air intrusion", because the mechanic bleed the system and it fired right up. If I had suspected this, I would have done it in the field. You got me thinking, last year when they claimed they put a fuel pump relay on it, I wonder if this was all they done to it but wanted to justify a higher charge for their trouble. ???



You likely have a cracked or leaking bleeder screw, a leaking fuel primer, a leaking fuel filter or water in fuel sensor. I would start by replacing the fuel filter. Be sure to replace the O-ring for the filter and replace the o-ring for the water in fuel sensor on the bottom of the fuel filter. The water in fuel sensor is plastic, so be careful not to overtighten and strip it. If you still have an issue with it loosing prime, I would rebuild your primer assembly or replace it. The complete fuel filter head can be bought from the deal and replaced with two bolts, on wire connector and two fuel lines. Super super easy to replace. If your mechanically inclined and want to save money, replace the seals in the primer assembly with a kit available from Merchant Automotive. 

An FYI for you. The fuel system on a duramax works on vaccum because fuel is "pulled" from the tank to the engine. If there is a leak, it will not show itself because the system is not under pressure. It will instead suck air in and cause stalling and no start situations.

And yes, I believe the shop took advantage of you to be able to charge you more. Thats blatantly obvious due to the fact they charged you for a fuel pump relay on a truck that does not have an electric fuel pump.


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## JpEater (Sep 2, 2012)

Here is a link for the billet aluminum bleeder screw to replace the plastic one. 
http://www.merchant-automotive.com/bleederscrewforfuelfilterhead.aspx

Here is a link for the primer seal kit. 
http://www.merchant-automotive.com/completefilterheadrebuildkit.aspx


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## bandit819 (Sep 3, 2012)

I would get the one above, I didn;t know they made one. I got mine from a chevy dealer, $15, they said they sell about 100 a month. I would also change the fuel filter. I remember a mechanic told me last year that someone had a bad batch of filters and it and it was causing the same thing. My money would be on the bleeder screw.


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