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Thread: Fuel Pressure Regulator - R1100RT - What Symptoms if bad?

  1. #1
    Registered User m_stock10506's Avatar
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    Fuel Pressure Regulator - R1100RT - What Symptoms if bad?

    My 2001 R1100RT (105,000 miles) had a sudden running issue six weeks ago. Suddenly lost power, wouldn't idle, ran like crxxxp.

    I spent 3 weeks attacking fuel delivery; replacing fuel tank hoses, filter and fuel pump. Then I pulled, examined and replaced the Hall Effect Sensor with a new HES. Still not fixed, so I threw in the towel and had my dealer pick it up.

    So far they have done a little bit of diagnostics and found that fuel pressure isn't holding; it goes up to 43 psi but when they check it later it has dropped. So they're suggesting replacing the fuel pressure regulator. They also found extremely low compression on the left side, 155 on the right. They still have to do a leakdown test but it looks like a valve is broken.

    It seems unlikely that both the FPR and the valve failed at the same time and it's most likely that running on one cylinder was the immediate cause of the running problem.

    My question is, what symptoms would one see if the FPR was not holding pressure properly? Not total failure, just not holding pressure. R&R the FPR means a few hours to put the tail at least partially in the air. I've probably been running the bike this way for a while - and before the loss of compression it was running great. What's the thought of just repairing the valves and not splitting the bike in half? I'm good with regular maintenance stuff; valve work and splitting the bike are beyond my abilities.
    Michael Stock, Trinity, NC
    R1100RT, R100, R60/6

  2. #2
    Pepperfool GSAddict's Avatar
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    Quote Originally Posted by m_stock10506 View Post
    My 2001 R1100RT (105,000 miles) had a sudden running issue six weeks ago. Suddenly lost power, wouldn't idle, ran like crxxxp.

    I spent 3 weeks attacking fuel delivery; replacing fuel tank hoses, filter and fuel pump. Then I pulled, examined and replaced the Hall Effect Sensor with a new HES. Still not fixed, so I threw in the towel and had my dealer pick it up.

    So far they have done a little bit of diagnostics and found that fuel pressure isn't holding; it goes up to 43 psi but when they check it later it has dropped. So they're suggesting replacing the fuel pressure regulator. They also found extremely low compression on the left side, 155 on the right. They still have to do a leakdown test but it looks like a valve is broken.

    It seems unlikely that both the FPR and the valve failed at the same time and it's most likely that running on one cylinder was the immediate cause of the running problem.

    My question is, what symptoms would one see if the FPR was not holding pressure properly? Not total failure, just not holding pressure. R&R the FPR means a few hours to put the tail at least partially in the air. I've probably been running the bike this way for a while - and before the loss of compression it was running great. What's the thought of just repairing the valves and not splitting the bike in half? I'm good with regular maintenance stuff; valve work and splitting the bike are beyond my abilities.

    Fuel pressure should be 43 psi running at idle and the flow (return to a bucket) should be 2 litres in 1 minute.
    If the bike is not in running condition (disassembled) you can easily unplug the tank plug and power the pump with 12v directly and use a stopwatch.
    I just checked mine this way as my machine is higher mileage and I wanted to confirm correct function.

    I doubt it is fuel pressure as the bike would idle ok at low pressure and not act up until high rpm when higher flows/pressure is required.

    Your problem is elsewhere, possibly valve related. I have seen burned ex valves, the bike will run at higher revs but be extremely lumpy at idle and stall
    '
    Ufda happens..........

    It's all about the details.

  3. #3
    Registered User m_stock10506's Avatar
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    Quote Originally Posted by GSAddict View Post
    .....
    I doubt it is fuel pressure as the bike would idle ok at low pressure and not act up until high rpm when higher flows/pressure is required.

    Your problem is elsewhere, possibly valve related. .....
    Bingo! No compression on one side. The shop pulled off the head; I saw it today. There is a quarter-inch chip missing from one of the input valves. The fuel pressure doesn't appear to be an issue.
    Michael Stock, Trinity, NC
    R1100RT, R100, R60/6

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