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FPR Advice...preventative replacement...


Zero Knievel

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I've noticed a number of people seeming to have problems that go back to the fuel pressure regulator failing.

Is there a recommended age (years from manufacture) or miles on the clock that the FPR should be replaced as a preventative step or are they prone to go without warning at any age...or perhaps never?

Also might want to know if those with problems kept bike garaged or outdoors. Not that the FPR is exposed to sunlight, but it would get more accumulated head from the bike sitting in the sun all day.

Edited by Aunt Sylvia
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I believe mine took a dump in 2008 I believe (99 model.) Some people say it's the ethanol, but I had put in some fuel system treatment not too long before mine failed, so that may have accelerated it. It really doesn't give a warning to be honest. Mine was fine and I used to ride to work every day. Went to go home one day, and it was hard to start (almost like it had too much fuel but fired off.) Next morning, gas was all over the ground under the engine, fuel coming out of the throttle body throats.

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Anecdotally, they seem to last 5-10 years... I know that's kind of vague, but the common denominator is, as logic seems to indicate, most likely the fuel itself. Of course, there may be too many variables (and actual variations of the alcohol percentages) in the mix to get a better picture. Different locations typically have different fuel blends, and even that will fluctuate by seasons.

Since this is an known issue (one of the few for the XX) and an easy fix, it might be prudent to acquire a replacement FPR and keep it in stock.

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That's what I'm thinking. I don't see ethanol affecting the FPR as it's been around a long time, but I know the actual percentage of ethanol in the gas has been varied in some places (poor QC?), and once you're pushing 15%, that'll damage many fuel systems over time because 10% is supposed to be the limit for non-specially-equipped fuel systems (i.e., FlexFuel).

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That's what I'm thinking. I don't see ethanol affecting the FPR as it's been around a long time, but I know the actual percentage of ethanol in the gas has been varied in some places (poor QC?), and once you're pushing 15%, that'll damage many fuel systems over time because 10% is supposed to be the limit for non-specially-equipped fuel systems (i.e., FlexFuel).

You are wrong, of course. :) . It has more to do whether or not ECU can readjust AFRs for higher content of ethanol. E10 fuel requires 3-4 % enrichment vs. E0. Older vehicles might not to be able to compensate for E15. As far as durability of fuel lines, fuel pump, injectors, etc. it really does not matter e10 or e15. E 85 is whole another story.

Going back to your OP. I have nearly 200k on original FPR, and my bike has seen E 10 from day one. If you worry about FPR going south on the trip I would pack new one with me. Replacement is easy, just remove fuel tank and everything is wide open.

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I believe mine took a dump in 2008 I believe (99 model.) Some people say it's the ethanol, but I had put in some fuel system treatment not too long before mine failed, so that may have accelerated it. It really doesn't give a warning to be honest. Mine was fine and I used to ride to work every day. Went to go home one day, and it was hard to start (almost like it had too much fuel but fired off.) Next morning, gas was all over the ground under the engine, fuel coming out of the throttle body throats.

Now that you mention it, I just always assumed there was a relay that definitively stopped gas flow when de-energized. I was thinking a piston sort of shut-off. Guess I thought wrong. Seems like you'd want something like that when the gas tank is the highest part of the system.

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I can tell you the answer is "NO." The system isn't pressurized when off, but gravity still works.

I wonder...those with FPR failures, did you proactively change the fuel filter or were you still on the OEM fuel filter? I don't think that should matter unless the filter media was compromised.

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I believe mine took a dump in 2008 I believe (99 model.) Some people say it's the ethanol, but I had put in some fuel system treatment not too long before mine failed, so that may have accelerated it. It really doesn't give a warning to be honest. Mine was fine and I used to ride to work every day. Went to go home one day, and it was hard to start (almost like it had too much fuel but fired off.) Next morning, gas was all over the ground under the engine, fuel coming out of the throttle body throats.

Now that you mention it, I just always assumed there was a relay that definitively stopped gas flow when de-energized. I was thinking a piston sort of shut-off. Guess I thought wrong. Seems like you'd want something like that when the gas tank is the highest part of the system.

Carbed bikes have a vacuum controlled shut off, not the EFI.

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I can tell you the answer is "NO." The system isn't pressurized when off, but gravity still works.

I wonder...those with FPR failures, did you proactively change the fuel filter or were you still on the OEM fuel filter? I don't think that should matter unless the filter media was compromised.

I can tell you that you continue to be consistent. The system is pressurized after shut down, assuming there are no leaks. With a leak the pressure will drop off then gravity continues to push the fuel. Mine failed but it was a slow leak; slow starts and a low speed stumble that slowly got worse. The fuel filter, like any other filter, does a better job as it's used as long as it doesn't become damaged.

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Mine failed but it was a slow leak; slow starts and a low speed stumble that slowly got worse.

I'm not exactly sure what that is like, but there is this "stumble" I hear at idle on a regular basis. I might just play it safe and replace the FPR this winter and see if it goes away.

Penny's worth of prevention, right?

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One could keep one in stock, or just replace it if you're worried. Having one lay around 'just in case' degrading and possibly getting lost or damaged isn't a great idea, just replace it. Assuming mine was original-it went about 13 years and almost 50k. The bike appears to have been stored outdoors a long time in the AZ heat/sun, the frame is faded. The bike had a period of inactivity which may also play a role in the FPR's death, it started leaking when the bike started being used again. Ethanol is a factor in degrading fuel system components, including metal ones if there's any water in the fuel which is common. Ethanol's ability to hold water in suspension is good and bad. Most fuel hoses have been alcohol rated long before E10 was common, not sure when other rubber parts joined in.

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Mine failed but it was a slow leak; slow starts and a low speed stumble that slowly got worse.

I'm not exactly sure what that is like, but there is this "stumble" I hear at idle on a regular basis. I might just play it safe and replace the FPR this winter and see if it goes away.

Penny's worth of prevention, right?

Pull the vacuum line off, if there's any fuel in it the FPR has failed. If it's original it would make sense to just change it before it becomes a problem since it's at that age where it's just a matter of luck now.

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