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Discussion Starter #1
Truck sat at an idle for about 20 minutes, I got a call where my son was hurt, I hammered down to get there and after about 300 feet it felt like it went into neutral and will NOT start without pumping primer. BTW, son is fine, poked himself in the eye while climbing a dirt pile and its healing good. The truck however, will start about half the time after priming to solid, and will only continue running if you pump the primer. Seems to do better when I put air hose with blower and rag in fuel cap and use regulator to let 10 psi through. Runs about 5-8 seconds on its own, then needs about 8 fast pumps to go another 5-8 seconds. Will prime up and hold. I've become very familiar with this over the past 140k miles I've put on it. Installed new AC Delco filter, bled at filter housing and valve with cap by FICM, even put on a clear line between the fuel filter and pump...no air at all coming through that line while it's running. Hose is pretty stiff and does not collapse. Is it the fuel pump? Either failed or wiring? Other ideas? Getting these codes no matter how many times I clear.
P0670 - glow plug module control circuit
P1093 -
P1621 - control module long term memory performance

I farm and this is my work truck with all my tools so it really needs to get going. Any help is much appreciated, thanks in advance.
 

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Discussion Starter #2
I should add that the truck has 218k miles. It used to get 18-22 mpg, depending on temp and wind direction, gets about 12-14 now. Have a new primer assembly on the way if I get to that level of desperation. The entire assembly is $170 at GM, 125 at XDP.com
 

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I should add that the truck has 218k miles. It used to get 18-22 mpg, depending on temp and wind direction, gets about 12-14 now. Have a new primer assembly on the way if I get to that level of desperation. The entire assembly is $170 at GM, 125 at XDP.com
If you're trying to do the primer pump on a budget there's a rebuild kit that's around $20 Basic Filter Head Rebuild Kit (O-Rings Only) | DMAX Store
this worked for me but some people report that that theirs was cracked and needed a new whole assembly to fix the leak.
 

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Discussion Starter #4
Last time I priced the rebuild kit (around 150k miles) it was more than the whole assembly so I didn't even price it this time. That would've been a cheaper option to keep on the shelf tho.
 

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As you know the Duramax does not have a lift pump to push the fuel from the fuel tank to the engine, it uses the injection pump [CP3], to draw/suck the fuel from the fuel tank through all the fuel lines, filter, FICM and then into the CP3. So any small leak in the filter or fuel lines it will suck air and affect the running of the engine.

Common for the fuel filter housing seals to loose the seal. Probably because of the high heat in that part of the engine compartment. Some have been successful in rebuilding the housing [be sure to replace the o-ring under the fuel heater] . Several of the Forum Supporting Vendors have a new housing and that has corrected the problem. Be sure to inspect all the fuel lines, and as you stated, a regulated pressure will help show the problem areas.
 

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Discussion Starter #6
As you know the Duramax does not have a lift pump to push the fuel from the fuel tank to the engine, it uses the injection pump [CP3], to draw/suck the fuel from the fuel tank through all the fuel lines, filter, FICM and then into the CP3. So any small leak in the filter or fuel lines it will suck air and affect the running of the engine.

Common for the fuel filter housing seals to loose the seal. Probably because of the high heat in that part of the engine compartment. Some have been successful in rebuilding the housing [be sure to replace the o-ring under the fuel heater] . Several of the Forum Supporting Vendors have a new housing and that has corrected the problem. Be sure to inspect all the fuel lines, and as you stated, a regulated pressure will help show the problem areas.
Wouldn't the clear line going from filter housing to pump show any air? Or is it just the lack of fuel getting to the pump?
 

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What happens is the fuel filter housing seals leak- so when the truck sits, the seals allow air into the system and fuel drains back into the fuel tank. You start the engine and there is a little fuel in the injection pump [CP3] and it starts and dies, because there is no fuel in the supply line, it does not keep running. Sometime if you pump the primer on the filter housing before you start it, it will continue to run.

Moved to LLY
 

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Discussion Starter #8
What happens is the fuel filter housing seals leak- so when the truck sits, the seals allow air into the system and fuel drains back into the fuel tank. You start the engine and there is a little fuel in the injection pump [CP3] and it starts and dies, because there is no fuel in the supply line, it does not keep running. Sometime if you pump the primer on the filter housing before you start it, it will continue to run.

Moved to LLY
Wouldn't that result in air in my clean fuel line?
 

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Discussion Starter #9
Clear, not clean. The housing bolts to the block with no other connections. I'm not understanding how there would be fuel leaving, meaning replaced with air, the filter via seals, etc, and not show up in that clear line.
 

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Yes, you would have air in the "Clean Fuel Lines" Sometimes extended cranking of the engine will push the air through the lines, but the batteries may die before it starts, and that much cranking is hard on the starter.
 

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I hate when people ask for help, get advice, then never come back to tell what fixed it, SO HERE'S WHAT HAPPENED. I installed clear fuel lines going into the filter and out of the filter, basically the 2 you remove to replace filter housing. Also cut out the flex part of the fuel supply and return lines under the driver's seat next to the transmission and put on clear hose. Primed lines, problem persisted but none of the lines had ANY air in them after the truck ran for a few minutes. So to keep this somewhat short, I put in a 12 volt diaphragm pump with a valve to control the fuel output, and it will start and run perfectly, no problem. Bought an Edge Insight that I've been wanting for awhile, and confirmed fuel rail pressure was great as long as the pump was on. When I turned the pump off, PSI would drop until the truck died. Turn pump on, truck starts and maintains fuel rail pressure. So I have an airdog 100 mounted to frame and I believe it will solve my problem.

Thanks to those who have e advice
 

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I hate when people ask for help, get advice, then never come back to tell what fixed it, SO HERE'S WHAT HAPPENED. I installed clear fuel lines going into the filter and out of the filter, basically the 2 you remove to replace filter housing. Also cut out the flex part of the fuel supply and return lines under the driver's seat next to the transmission and put on clear hose. Primed lines, problem persisted but none of the lines had ANY air in them after the truck ran for a few minutes. So to keep this somewhat short, I put in a 12 volt diaphragm pump with a valve to control the fuel output, and it will start and run perfectly, no problem. Bought an Edge Insight that I've been wanting for awhile, and confirmed fuel rail pressure was great as long as the pump was on. When I turned the pump off, PSI would drop until the truck died. Turn pump on, truck starts and maintains fuel rail pressure. So I have an airdog 100 mounted to frame and I believe it will solve my problem.

Thanks to those who have e advice
You still have a fuel problem the lift pump is just masking this. The lift pump suggest supply promblems other than that I have no idea what it could be at this point sorry for that. As with most things you'll just have to check every part of the fuel delivery system, hopefully your problem is obvious. In the case it is not you'll have to be very detailed in your investigation testing and examining every part from the tank--to engine.
 

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I been having the same problem as well, the truck would die while drive and not start with priming the primer. I replaced the fuel filter housing and it has been better still once in a while it will die while driving and i would have to prime it to start.

I am looking to get a Fass lift pump to help solve the problem.
 

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I hate when people ask for help, get advice, then never come back to tell what fixed it, SO HERE'S WHAT HAPPENED. I installed clear fuel lines going into the filter and out of the filter, basically the 2 you remove to replace filter housing. Also cut out the flex part of the fuel supply and return lines under the driver's seat next to the transmission and put on clear hose. Primed lines, problem persisted but none of the lines had ANY air in them after the truck ran for a few minutes. So to keep this somewhat short, I put in a 12 volt diaphragm pump with a valve to control the fuel output, and it will start and run perfectly, no problem. Bought an Edge Insight that I've been wanting for awhile, and confirmed fuel rail pressure was great as long as the pump was on. When I turned the pump off, PSI would drop until the truck died. Turn pump on, truck starts and maintains fuel rail pressure. So I have an airdog 100 mounted to frame and I believe it will solve my problem.

Thanks to those who have e advice
When the truck dies after you turn the lift pump off do you start getting air in the lines again?

If so you probably still have an air leak in the supply line so may be worth checking from lift pump to tank as well for leaks.
 

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I hate when people ask for help, get advice, then never come back to tell what fixed it, SO HERE'S WHAT HAPPENED. I installed clear fuel lines going into the filter and out of the filter, basically the 2 you remove to replace filter housing. Also cut out the flex part of the fuel supply and return lines under the driver's seat next to the transmission and put on clear hose. Primed lines, problem persisted but none of the lines had ANY air in them after the truck ran for a few minutes. So to keep this somewhat short, I put in a 12 volt diaphragm pump with a valve to control the fuel output, and it will start and run perfectly, no problem. Bought an Edge Insight that I've been wanting for awhile, and confirmed fuel rail pressure was great as long as the pump was on. When I turned the pump off, PSI would drop until the truck died. Turn pump on, truck starts and maintains fuel rail pressure. So I have an airdog 100 mounted to frame and I believe it will solve my problem.

Thanks to those who have e advice
I'm wondering if you traded one problem for another with the clear fuel lines. Like maybe there was a leak before with the original lines and replacing them with clear lines fixed the air leaking into the line but is collapsing under the pull of the high pressure pump without a lift pump running. Just a shot in the dark, you may have big burly clear line in there and this guess isn't even close. I'm just imagining a flimsy clear line that is getting sucked closed.
 

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Discussion Starter #16
It's a pretty heavy clear hose, very hard to crush with your hands.
 

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It's a pretty heavy clear hose, very hard to crush with your hands.
Usually you'd see the hose getting crushed if that was happening and it wouldn't have bubbles, likely another issue IMHO.
 

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Discussion Starter #18
Well I put on an Airdog FH100....pumping good clean fuel out the "to engine" port, but the truck is acting exactly the same. I've ran 2 gallons of fuel from the hose that comes out of the stock fuel filter with NO AIR. So 1) the airdog is pushing fuel to the engine. 2) there is no air in the system. 3) the engine will run ONLY while manually pumping primer button 4) will NOT run UNLESS the primer button is being pumped.....*smacks forehead*

Now what? Injection pump? ?

I have been watching fuel rail pressure while running. After I pump primer button, it will run up to 8-11k psi, gradually drop to 5, up to 6, hover around 5.5, then drop until it dies. It has done this exact sequence at lease 40 times. All the while watching the clear fuel line going from fuel filter outlet port to inlet behind alternator. Not a single air bubble has passed through this hose.
 

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Ok if your confident the supply side is good that leaves us with 4 things to check: fuel injectors returning to much fuel, fuel pressure relief valve bad bypassing to much fuel, cp3 weak/worn out, or fuel pressure regulator bad this one usually causes a surging erractic idle.
 

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The clear fuel lines you installed may not be compatible with the high engine/under hood heat. They can get hard and not flex like regular fuel hose and develop a leak, and possible fire.
 
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