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Fuel Pressure alarm

in General Tech Discussion 10 years ago

  • Re: Fuel Pressure alarm

    by » 10 years ago

    James
    Is the "T" for the fuel pressure sensor above or below the sensor. ie does the line from the "T" run uphill or downhill to the sender?
    Mike G
      
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  • Re: Fuel Pressure alarm

    by » 10 years ago

    Hi Mike,

    I have mounted fuel pressure sensors above and below and haven't seen any differences in pressure alone. My fuel pressure sender is mounted above the engine to keep it from clogging from 91 auto fuel sitting in the fuel line hanging downward and never getting any fresh fuel. The lines hanging down can get some pretty smelly old fuel over a years time.When mounted above and after the plane sits after a flight the fuel drains away from the sender and at start I always get fresh fuel and I never have to clean out the small orifice on the sender like I do other people.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Fuel Pressure alarm

    by » 10 years ago

    Roger
    On my previous 914 I fitted a fuel pressure/airbox differential pressure gauge and the sender was below the "T". It worked fine for some time and then I started to get lower than normal readings but it didn't seem to affect the engine performance. I thought that there was a problem with the fuel pressure regulator or maybe the pump and spent a lot of time searching and thinking that I had been smart to fit this gauge because it had detected a problem before it showed up as an engine problem in flight.

    Until I pulled the hose off the sender and it was clogged up with a black tar like substance. I cleaned it out and everything went back to normal. So I hadn't been smart I'd just created my own problem.

    Thinking about it further it occurred to me that all that was happening was that gasoline is a mixture of hydro carbons that is distilled in the refinery (I worked for an Oil company in the refinery division so should have seen this coming) from crude oil and gasoline contains minute amounts of everything from asphalt (tar) to the purest ethers. The gasoline that is static and sits in a vertical pipe will simply continue to be distilled by the heat in the engine compartment and the lighter ether like molecules will "boil off" and rise up to the "T" and be drawn into the engine, but the heavier "asphalt" molecules will remain and sink to the bottom and over a period of time simply block off the sender.

    That's what happened to mine and that's, perhaps, what is happening here.

    Mike
      
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  • Re: Fuel Pressure alarm

    by » 10 years ago

    Hi Mike,

    I agree that build up happens especially if the hose hangs down on the firewall below the balance tube and then it continually gets cooked inside the cowl and never gets fresh fuel replacement. The ones I have had like that did have low fuel pressure symptoms. It happened to me and that's why I started to mount senders above the balance tube. I have had mine like that for 5 years now without any issues from that sender.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Fuel Pressure alarm

    by » 10 years ago

    Roger

    I don't understand :(
    Are you saying that the sender below the "T"

    does
    " The ones I have had like that did have low fuel pressure symptoms. "

    or doesn't
    "I have mounted fuel pressure sensors above and below and haven't seen any differences in pressure alone"

    affect the fuel pressure readings?

    I don't follow your comment about being
    "below the balance tube "

    Are you talking about the carb balance tube or something else?

    Mike
      
    Report
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