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Thread: fuel turning black

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    fuel turning black

    Anybody have any insight on what could be turning my fuel black? It's not bad fuel. Went to change filters on my air dog165 and the fuel was black. Dropped tank cleaned it and put clean good fuel in it. Trucks been hard starting and I opened the water drain on the filter and now the good fuel is black again. I have no idea what's going on. Abd I need some help.


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    I'll clear up one point. I noticed they black fuel when I went to change filters. Then I dropped the tank and cleaned it and put new filters abd good clean fuel in it. Then recently it's been hard starting so today I opened the drain and fuel is black again.


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    Old & Grumpy! Polaraco's Avatar

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    The only thing I can think of is engine oil getting into the oil, but I don't know how it can unless you have an issue with the cylinder head or gasket.

    As a standard rule, we ask for the year of the truck and what mods you have. Also any recent work done to the truck.

    Run the tank down low. Change the oil and run that tank. Check it again. See if it's as black.

    Bemore specific about the hare starting. 10 minutes, or 10 more revs?


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

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    Either oil getting in it, or idk LOL, after first drain and re fill it could've turned black again from what fuel was left in lines and returned to fuel tank. Something in injector pump that could break down and cause fuel to go black? Cuz if it was oil it really shouldn't change how truck started or runs a whole lot(depending on year/engine anyway) just smoke more. To piggyback on Grumps questions, any and what fuel additive? How long ago did the hard start show up? How long ago when noticed black fuel? Any other symptoms or strange things the truck is doing?


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    Truck has twin CP3s and 250hp injectors. Last month had a new head gasket and studs installed. Not noticing any low oil. I'm thinking if oil I'd noticed it on dipstick. Engine is an 07 6.7. Has an air dog2 165. Far as cranking I'd say 10 more revolutions. Abd the studs are arp625s. Also the fuel is producing a vapor in the tank as well.


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    Old & Grumpy! Polaraco's Avatar

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    Quote Originally Posted by thewildkarrd@doublerdiesel View Post
    Either oil getting in it, or idk LOL, after first drain and re fill it could've turned black again from what fuel was left in lines and returned to fuel tank. Something in injector pump that could break down and cause fuel to go black? Cuz if it was oil it really shouldn't change how truck started or runs a whole lot(depending on year/engine anyway) just smoke more. To piggyback on Grumps questions, any and what fuel additive? How long ago did the hard start show up? How long ago when noticed black fuel? Any other symptoms or strange things the truck is doing?
    Quote Originally Posted by Kisner93 View Post
    Truck has twin CP3s and 250hp injectors. Last month had a new head gasket and studs installed. Not noticing any low oil. I'm thinking if oil I'd noticed it on dipstick. Engine is an 07 6.7. Has an air dog2 165. Far as cranking I'd say 10 more revolutions. Abd the studs are arp625s. Also the fuel is producing a vapor in the tank as well.
    I don't think so Drew. To have a pump turn fuel black it's got to be beating the death out of the fuel before returning it.

    I never saw a dual CP3 setup. Is the remote pump pressure lubed from the engine like a turbo?

    The head gasket just done is a big clue. I assume you noticed the fuel turning black after the gasket and studs?


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

  7. Top Of Page | #7

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    Well I found my problem. An injector sealing washer was not sealing. Got smashed during this last install during the new head gasket installation. Basically since it was nut sealing I was putting combustion gas into the return fuel casing heat and high pressure. This too was causing my fuel tank to hold pressure. But to answer your question on the twin CP3, the CP3 isn't cooled by oil. It's cooled by diesel fuel itself. Abd the secondary pump gets its supply fuel from the original CP3 supply abd the return works the same way.


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    Old & Grumpy! Polaraco's Avatar

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    OK That makes sense. You saw where I was going. . .Head gasket install


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

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