Fuel Pressure

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Luwi67, Jan 19, 2014.

  1. Cetane+

    Cetane+ Road Train Member

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    Completely disregard my post. I forget your engine uses that extra fuel housing. I was referring to the newer filter base on later engines. Sorry to confuse.
     
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  3. wernertyrell

    wernertyrell Bobtail Member

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    Is there a difference with them?
     
  4. Cetane+

    Cetane+ Road Train Member

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    The C-15 does not use that extra fuel pressure housing. Its all in the secondary filter base.
     
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  5. Luwi67

    Luwi67 Heavy Load Member

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    What is under this 1" plug?

    [​IMG]
     
  6. Hurricane69

    Hurricane69 Road Train Member

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    It's not a plug. It's the fuel pressure regulator. You have to make sure you get the correct one for your motor. I say this because I have been given the wrong one before and not realized it. Ended up chasing a pressure problem that wasn't there. The number is across the face of the plug part.
     
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  7. Luwi67

    Luwi67 Heavy Load Member

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    So I have another fuel pressure related question. I had the truck out the other day taking a light load up to MA. and when the truck is at cruise rpm the fuel pressure is 70 (needle on gauge steady), when under load say pulling a hill the pressure will drop to about 60 and I can feel a slight vibration and see the fuel pressure gauge needle vibrating as well. Is that normal for the pressure to drop under load or is it indicative of a worn fuel pump?

    I also must say in the 10 years I have owned the truck it has never lost its prime no matter how long it sits (sometimes as long as 4 to 8 weeks)
     
  8. Hurricane69

    Hurricane69 Road Train Member

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    Yes it's normal for the pressure to drop on a long hard pull but your pressure is way to low. Did you change the pressure regulator?

    I change mine at least once a year. They run around $30. If that doesn't get your pressure up shim the pump. That spring also gets weak.

    What I've found if your gauge starts jumping on a pull you have a injector problem. Run a cut out test.
     
  9. Luwi67

    Luwi67 Heavy Load Member

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    Well it wasn't a long hard pull more like a short easy pull but, under load none the less.

    I've never changed the regulator but sounds like maybe I need to. Does the regulator have anything to do with holding prime on the engine while not running?

    Is there a way to test if the pump needs shimming?

    I wouldn't say my gauge is jumping, it's more like the needle is steady but looks blurry because it's vibrating between a few psi (only when under load).

    What's involved in a cut out test?
     
  10. Hurricane69

    Hurricane69 Road Train Member

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    Yes the regulator is what holds the prime. It can hold the prime and the spring in it can still be weak.

    The cut out test is run by plugging in to it and run the cut out test with cat et. They will probably charge you a hour labor to run it. Just takes a few minutes to do. They cut out one cylinder at a time to see if there is a change. You need to fix your fuel pressure issue first. Could be a slim chance the cam sensor is getting flaky but this has nothing to do with your low pressure.
     
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  11. Luwi67

    Luwi67 Heavy Load Member

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    Yeah, I have been suspect of the fuel pressure lately and do want to make sure my fuel system is working as best as it can because I was looking into a fuel air separator system and didn't want it to "mask" any prior [fuel system] shortcomings.

    I appreciate your input and will start out replacing that regulator. Do I just bring my serial number to cat and ask for the correct regulator?

    The engine has 250k on a cat opt overhaul.
     
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