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Fuel Pressure

Discussion in '6.9L IH & 7.3L IDI Diesels' started by catbird7, Jul 28, 2020.

  1. catbird7

    catbird7 Full Access Member

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    Can fuel pressure be measured at the Schrader valve? Is the Schrader valve pressure reading "before" or "after" the filter? And what is the acceptable pressure range? I'm having an issue with the filter light coming on. Obviously the first thing I did was replace the filter however the problem continues. I'm guessing the electric pump is dying and hoping to confirm with pressure reading. Any help / info will be appreciated.
     
  2. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    That will be pre filter, only port that is post is the vacuum switch. I sell a kit that converts the ip feed line to -6 an fittings and adds an inline pressure gauge. You want about 5psi feed pressure, but the filter light comes on with any vacuum seen at that port. image.jpg
     
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  3. Cubey

    Cubey Full timer RVer

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    On my RV, that is where I have tested to troubleshoot problems since I converted to an electric fuel pump. I remove the core with the proper tool and shove the test gauge hose on the fitting. 5-7psi is too much pre-filter on there for some reason. I guess it was timed at some point with a weak mechanical fuel pump, so I'm gonna install a low pressure regulator to further drop the pressure to like 2-4 psi to ee if that helps, until I can get the motor timed properly at 5-7psi without the regulator. I can't safety drive it on busy (even in rural areas) 75mph TX interstate with a top speed of 55-60 with the pedal to the floor, as it's acting currently without a pressure regulator. It had no speed issues with the old weepy mechanical pump. I stupidly never checked the pressure of that for comparison before I did the conversion.

    If that's your only good place to test, it's better than nothing.
     
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  4. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Why does my want list grow almost daily with you?;Poke
     
  5. catbird7

    catbird7 Full Access Member

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    Thanks for the info guys! Just checked my records and found this Holley red pump was installed 10 years ago so it likely is the problem. I have a new spare that I take with me when traveling so I guess it's time to install it and buy another spare.
     
  6. catbird7

    catbird7 Full Access Member

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    Should have also mentioned that sometimes the engine surges and the filter light does not turn on.
     
  7. Cubey

    Cubey Full timer RVer

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    Red is what I put on my RV. Glad to know they seem to last 10 years. I think I'll carry a spare rebuild kit instead of a spare pump, at least for the first many years. They cost a heck of a lot less and it's not that much more work to do since you have to pull the pump off anyway if you were to swap it. It's down on the frame, so it should run nice and cool.

    https://www.holley.com/products/fue...nd_service/fuel_pump_repair_kits/parts/12-805

    20200213_175701.jpg
     
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  8. catbird7

    catbird7 Full Access Member

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    Think I may have solved \ identified the problem. Friend suggested it might be clogged tank pickup and told me to add full bottle of Power Service "Tank Cleaner", so I tried it on the front tank and so far ( knock on wood), no filter light! I'm going to run this full tank of fuel through it and pending success, do the same thing with the rear tank.
     
  9. riphip

    riphip Supporting Member Supporting Member

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    The Holley Red has a very fine screen mesh inside the pump feed chamber that will stop up, restricting flow.
     
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  10. catbird7

    catbird7 Full Access Member

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    Thanks for the info I'll have to look up an exploded view of it and check that out. At this point however I'm fairly certain this clogging issue is in my tanks. Recently took the truck on a fairly long road trip and the problem occurred shortly after returning. Possibly picked up two tanks of bad fuel??? Front tank now seems to be functioning properly after treating it with a full bottle of tank cleaner. Problem still exists on rear tank, hoping same product does the job on it as well.
     
  11. Cubey

    Cubey Full timer RVer

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