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Discussion Starter · #1 ·
tomoorrow im going to look at a 2001 duramax that quit yesterday.

started but was running rough. now cranks but doesnt start.
owner said oil smells like fuel.

im not really familiar with the duramax. i have access to all the gm service manuals. and a good scan tool.

any idea where to start? high pressure fuel pump?
 

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IS THE OIL OVERFULL? WILL IT RUN ON A SNIFF OF EITHER ? TRY PRIMING PUMP MAKE SURE THERE IS PRESURE IN THE FUEL SYSTEM , pEOPLE ALSO SUCK AT CHANGING THE FUEL FILTER CAN COMPLETELY PLUG .
 

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DON'T spray either into your engine!! If you have fuel in your oil it's more than likely your injectors are bad! The lb7 engine was notorious for this!
 

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Check the fuel lines, check if they are slightly crimped or worn down. just replaced the one on my fathers 07
 

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Discussion Starter · #6 ·
i went to look at it yesterday.
all the fuel lines are rotted and cobbed together, leaking in multiple places.

it doesnt seem to be getting any fuel, what is there for a pump? i saw a fuel pump relay but never heard a pump coming on. i checked the connecter at the tank but thats only a 2 pin so i figured its just a fuel level sending unit not a pump. i looked at the fuel system diagram and didnt see a transfer pump anywhere just the injection pump. i can build pressure w the hand primer but still doesnt start and looses any prime i built as soon as i crank it.

theres also an active code for the cam sensor.
 

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Sounds like injectors lb7 injectors go bad at some point. The injector pump is on the right bank. I think the lift pump is along driver side frame rail.
 

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The pump is along the drivers side frame looks like a inline fuel filter as the other guy mentioned . You probably have bad injector or injectors but they all don't go bad at once so it should still run. You cannot have any leaks in the fuel lines in the fuel system before or after the pump it will not start or run with air in the system. If you pump the priming pump and it hold pres let it siit for a while recheck. If you crank and loose pres there is one injector stuck open or a leaky jumper line . Too see if the sensor is not letting it start I go back to the either . If you give a very light spray as someone is cranking the motor you will not damage anything . You just want to see if it gets fuel it will start . You dont want to run it on either . My experience 35 years with CAT, build a 2005, 12.5 sec 1/4 mile duramax .
 

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Discussion Starter · #9 ·
went back last night and replaced the leaking fuel line.
there is no lift pump on the frame, i can follow the lines from the tank to injector module.
primed it and bled the air at the shrader.
hit it with a sniff of ether and it started. ran for 5 min and died. never got it to start again. tried a few more times.
its loosing its prime after it runs up each time.
there is one more fuel line that looks suspect, it on top of the fuel cooler and looks to be flat/kinked. ill replace that one tonite.
any other ideas?
 

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Discussion Starter · #10 ·
theres also a connector to the rear of the injector module, kinda under the fuel filter thats not connected to anything. the wires are greened out and looks like it broke off but i dont see the other end.
 

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the prime pump has orings in it that fail after awhile, can still build pressure pumping by hand but air sneaks through and kills the motor, i seen this in deisel power mag a couple years back and just the other week on a show,looked like a really easy fix and they said it mimicks the bad injector symptoms, worth looking into maybe
 

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PROBABLE THE WATER SENSOR wire ON THE FILTER . mY SON SAYS THE PUMP ON THAT YEAR IS IN THE FUEL TANK. you may try turning the key on and listening or feeling the vibration at the tank. you could also crack the line going into the filter and see if it is pumping fuel to the filter.. If it is a old fuel lilter it could be the seal on the filter . It's hard to help if you don't see it or aren't there.
 

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sounds like your water in fuel sensor harness failed on ya man, if i remember right if you take out the right side wheel liner you should have a better view of that but they are known to break and fail and they make delete kits for this
 

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An 01 Duramax has a CP3 fuel pump w' lift pump built in. It is mounted in the valley of the engine under everything.

You said there was a cam sensor code? Being electronic controlled the ECM needs the cam sensor to decide when to fire injectors. It is located on the front of the engine low and left of water pump pulley.

If the oil smells heavy of fuel then it most likely needs injectors. I always recommend doing all at once because the new/rebuilt injectors have updated parts that reduce the failure risk. Get new sealing washers for the return lines too. But it should still run even if it has bad injectors.
 

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Discussion Starter · #15 ·
ya the cam sensor code came back so i did all the circuit tests and im getting a new sensor.
theres deffinitely more issues, im pretty sure ill be doing all the injectors soon. i saw smoke roll off the right bank a few times, down by the glow plugs, those all probably should be replaced while im at it.
 

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Discussion Starter · #16 ·
well the cam sensor broke off when i was trying to get it out.

any tips/tricks to get it out?
 

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Discussion Starter · #17 ·
changed cam sensor, still wont start. batteries are so dead that even with the charger on it i cant get it to spin fast enough to run up on ether. looses prime everytime i crank it. still throws cam sensor code. i ohmed the circuits between the sensor and the ecm, all good.

can anything else cause that code to go active?

im gonna have the owner grab me 2 new batteries today.
 

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Discussion Starter · #18 ·
installed 2 new batteries, still cranked slow. added new cables to starter. cranks good now, still wont start. noticed a puddle under the tank and found another leak, this ones in the return line.
is there a check valve for the return line? when i pump the primer i get a solid stream from the return line and loose my prime over a few minutes.
 

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Discussion Starter · #19 ·
would a stuck open FPR cause fuel to return to tank?

i have the return line disconnected and i can watch a stead stream come out when the primer is pumped.

i cant seem to get an answer as to what retains the pressure at the rails from returning to tank. ive got my district trainer calling his contacts at gm, i called the local chevy dealer today, ive checked the gm manuals. man i dont understand why this is such a hard question to answer.
 

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Discussion Starter · #20 ·
i called the gm tech line and the guy said my FPR was stuck open. replaced it and still nothing, still has a steady stream returning to tank when primed.

also it wont run up on a shot of ether, it did a few weeks ago, i had it running for around 5 min, thought i had it until it died.
 
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