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Thread: Fuel pressure at 0 PSI

  1. #1
    Junior Member
    Join Date
    Jun 2015
    Posts
    4

    Fuel pressure at 0 PSI

    I've seen a lot of fuel pump posts around here, but I haven't found one that fits my case. I have a 2004 XB12R. I think that my fuel pump is bad, but I wanted to see if anyone else has ideas.

    Symptoms:
    Idles fine while cold, but hesitates or stalls under load. Seems to stall slightly less at high RPM; stalls more when warm. I have to rev high and feather the clutch to get down the block. Usually starts back up after stalling, but may just stall again soon after. The pre-start fuel pump whine has been sounding a bit sickly for a while, but after replacing the battery, it sounds about as normal as I remember.

    Testing:
    I picked up a Ford CFI adapter for my fuel gauge. My gauge doesn't have any fancy valves or levers like the one in the service manual; when I hooked it up to my car, it Just Worked(tm), so I figured it would do the same here. But when I hooked it up with the bike idling, the needle didn't even move. Revved to 3000rpm, and the needle still didn't move. I thought maybe the adapter was faulty, so I turned off the bike and pressed the schrader valve with a rag, and a little fuel leaked out. No high-pressure spray.

    Other interesting bits:
    - After the bike has been off for a while, if I disconnect the fuel pump power and try to start it, there is no catch at all. Just cranks.
    - Directly after turning off the bike, if I disconnect the fuel pump power and try to start it, I do get a catch, and the bike idles for 2-3 seconds, no more.

    Questions:
    What I don't understand is, the gauge shows 0 PSI. Not low PSI, but 0. And yet the bike will still idle and, usually, rev. Does this sound feasible? Could it be that the gauge requires something like 5 PSI to begin to move the needle, but the pump puts out less, albeit somehow still enough to run at idle? Or does it sound like I'm doing something wrong?

    While I wait for a new fuel pump to arrive, is there anything obvious that I'm missing?

    Thanks!

  2. #2
    Senior Member lunaticfringe's Avatar
    Join Date
    Feb 2011
    Location
    AmishLand, PA.
    Posts
    7,491
    While I wait for a new fuel pump to arrive, is there anything obvious that I'm missing?
    NO.

    you've just described a faulty pump in totality. you do NOT need any sort of pressure gauge to point out the obvious which is:
    excessive crank-to-start time.
    odd/unusual/loud pump motor noise.
    excessive stalling during cold-start mode.
    lazy motor response to throttle inputs.
    acceleration lag....engine shudder during throttle roll-ons in higher gears.
    alarmingly high AFV values when checked with software AND you have ruled out faulty intake seals after testing them.

    the XB fuel pumps are a sound, solid and nicely designed piece. they were great right out of the box but are now aging and causing problems. the pump does NOT always have to be replaced. in most instances a full rebuild restores it to new.

  3. #3
    Junior Member
    Join Date
    Jun 2015
    Posts
    4
    Thanks, Fringe. This makes me a bit less concerned about the idea that i might have some fault in the gauge hookup. I'll check pressure again after installing the new pump to see the difference.



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