Fuel Pressure

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

  1. Luwi67

    Luwi67 Heavy Load Member

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    I have a 97 379 with a 3406E 550, the truck runs great but, lately I have been concerned about the fuel pressure. Seems everyone I talk to says when they first fire their truck up the fuel pressure is about 85psi, and when they are running down the road it's 90 to 100, when I first fire mine up it slowly climbs to 60psi and running down the road it's 70 to 75.

    I have new fuel filters, Cat 175-2949 primary and Cat 1R-0749 secondary.

    I just put brand new fuel lines from the tanks to the pump, but haven't ran it on the road yet, just at idle in the yard (it s-l-o-w-l-y climbed to 60psi).

    I've had this truck for 11 years and have to admit that I don't recall what the fuel pressure was a few years ago just that it was in the green zone on the gauge.

    The fuel filter gauge is a little above 2.

    Is fuel pressure effected at all by the ECM or the tune that programed in?

    Again, the truck runs well (it seems to be a little down on power pulling hills but, that might just be all in my head), just wondering why my pressure is lower than everyone else I talk to.

    Any insight would be appreciated, thanks
     
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  3. Cetane+

    Cetane+ Road Train Member

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    You could start by changing the check valve, relief valve in the filter housing, stop to the dealer with the serial number and screw them in. Under 100psi is where you want to be for an E model, a little higher for the C-15. If those two dont "do it" change the gear pump that supplys all the fuel, under $200. If its original, wow you got your moneys worth.
     
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  4. little cat 500

    little cat 500 Road Train Member

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    i think thats normal for a 5ek
     
  5. Flightline

    Flightline Road Train Member

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    What is slow to climb on fuel pressure?

    Also depends alot on rpm's. I run an airdog seconday fuel pump system which really helps on starting but with it turned off, mine is slow also.
    I only run 65-75 psi at 1300rpms going down the road without the airdog assist and all of my system is new. But now at 1550 I'm running at 102psi. So rpms can really effect it.
    I'd change the releif valve at the filter, mostley cause it's cheap and easy to change. But the top end fuel pressure is actually set by the releif valve in the mech. pump on the front of the motor. And it can be shimmed to increase pressure.
     
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  6. TwinStickPeterbilt

    TwinStickPeterbilt Heavy Load Member

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    The last three averts I drove where 60 at idle.
     
  7. Luwi67

    Luwi67 Heavy Load Member

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    Long island
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    serial number is 6TS03404.

    When I first start it, it will take a good 40 t0o 60 seconds for the pressure to reach 60psi

    I will look into getting the valves in the filter head or, I was thinking of getting a Davco 382 filter/water separator, just have to fab a mounting bracket to keep it in the same spot.

    I'm not sure how old the fuel pump is. The truck has 1.1 million and the engine was rebuilt 260k ago. I couldn't find in the massive work order that the fuel pump was replaced which is odd because everything else was replaced for the OPT warranty.
     
  8. Oscar the KW

    Oscar the KW Going Tarpless

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    That's a long time for the fuel pressure to come up.
     
  9. bull hauler

    bull hauler Medium Load Member

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    My 5ek ran at 78 psi at 1450 rpm, i shimmed it with a 1/4 spacer and added 10 psi, 1/8 spacer adds bout 5 psi, ive got the newer fuel pump with the hex bolt facing the frame rail, thats the one u screw out to shim, its got a spring in there so when u back it out dont let it just shoot out.

    My fuel pressure builds in like 5 sec so id say if urs is taking that long might be having either a bad fuel pump or sucking air.

    I did swap out my factory water separator head and filter and went to a racor 3150r head and filter that flows 150 gal/hr and really really like it. Low restriction, pulls bout 2 when new an ive got 18k on it and its still only pullin 4 1/2 restriction.

    one more thing, ive got a teltek in dash fuel pressure gauge, running the normal cat fuel filter the fuel pressure was all over the place going down the road, like jumping up and down 6-9 psi, kinda by accident i tried a luber finer fuel filter and no more fuel pressure jumpig around rock steady 1-2 psi variance at the most up and down. I wont run another cat filter again...theyre junk imo. My fuel restriction gauge was showing no issues on the suction side.
    Fwiw
     
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  10. bull hauler

    bull hauler Medium Load Member

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    U can tell by looking at the bolt on the lower third of the pump, if the bolt facing the frame rail if it takes a hex bit to remove its newer pump if it takes a socket its an older pump, mine when new still only ran 78 psi till i shimmed it up 10
     
  11. Luwi67

    Luwi67 Heavy Load Member

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    Long island
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    Thanks, I'll pop the hood tomorrow and check that out.

    I just thought of this, when I replaced all the fuel lines from the tanks to the pump the truck started right up. Was I supposed to bleed the system of air or does it do that automatically.

    When I shut the engine off the fuel pressure gauge drops to zero pretty quickly, is that normal?
     
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