1994 K75S High-pitched chirping noise when hot?

[42906]

You have to blow VERY LIGHTLY.

That's what she said.

[Zagando]

I filled up the tank again today thinking that the fully submerged fuel pump might behave thus but that notion was quickly dispelled. Still as noisy as ever.

I think that idea of running a fuel line over to the pump is nonsense; yet I will be the first to apologize should/could I be proven wrong. No amount of fuel is going to cool it down enough to be quiet.

I suspect that my pump is beginning to die or wear out---nothing more or nothing less.

Hope that it's not a dangerous situation brewing as I ride around New Mexico in the 90+ degree heat and the pump (or something inside the tank, presumably) chirping like a canary on steroids. How do fuel pumps die?

Curious to hear any stories about other's going south and whether it is usually sudden or long and drawn out.

---Perplexed in ABQ

Anyone?

[98lee]

Usually the first symptom of a pump going out is the bike goes quiet and coasts to the side of the road never to start again. This entails the joy of trying to contact someone to come and get you and your bike. Just think of the hours of enjoyment you could have on the sunny side of the road listening to busy signals or being put on hold (if you can get a signal). Walking on a 90 degree day, leaving your "baby" in the middle of nowhere can lead to all kinds of surprises.

If you are SURE the noise is coming from the pump, why wait for the very inconvenient eventuality? Consider yourself fortunate that you are getting a warning while the bike is at home.

Have you pulled the pump and bench tested it? Have you inspected the lines inside the tank for leakage while it is running? Have you done a fuel pressure test to insure the regulator is working properly? Have you checked the filter again to insure it's not partially plugged again? Are all 4 hose clamps TIGHT?

I would not be out riding if I suspected my fuel pump was about to fail. The cost of a failure on the road is WAY higher than the cost of a new pump (if that's where you're SURE the noise is coming from and it's NOT a bad regulator or filter or hose).

[TED]

Have you checked your fuel hoses for kinks, especially from the FPR to the tank? Are these the original hoses that came with the bike?

[Zagando]

Have you checked your fuel hoses for kinks, especially from the FPR to the tank? Are these the original hoses that came with the bike?

The in-tank lines are fine as far as I can tell. I installed new lines three years ago even though the original ones were intact. I also installed a new pump sock which should (AFAIK) effectively filter the large bits of gunk (if any) floating around the tank.

I'm going to siphon the tank now and install another new fuel filter for one last check to see if a blocked or gunked up filter is causing the squealing. Thanks Ted for your input, too!

[Zagando]

Usually the first symptom of a pump going out is the bike goes quiet and coasts to the side of the road never to start again. This entails the joy of trying to contact someone to come and get you and your bike. Just think of the hours of enjoyment you could have on the sunny side of the road listening to busy signals or being put on hold (if you can get a signal). Walking on a 90 degree day, leaving your "baby" in the middle of nowhere can lead to all kinds of surprises.

If you are SURE the noise is coming from the pump, why wait for the very inconvenient eventuality? Consider yourself fortunate that you are getting a warning while the bike is at home.

Have you pulled the pump and bench tested it? Have you inspected the lines inside the tank for leakage while it is running? Have you done a fuel pressure test to insure the regulator is working properly? Have you checked the filter again to insure it's not partially plugged again? Are all 4 hose clamps TIGHT?

I would not be out riding if I suspected my fuel pump was about to fail. The cost of a failure on the road is WAY higher than the cost of a new pump (if that's where you're SURE the noise is coming from and it's NOT a bad regulator or filter or hose).

This is all pertinent and logical and brings me to the realization that I am almost looking too hard into the forest to see the trees.

Yes, Lee, I agree that it is crazy to be riding around New Mexico in this heat (91 today)waiting for a potentially costly situation to develop so I am taking your advice to heart.

I will install another new filter once I finish typing this to see if it makes any difference at all. The other new filter I installed a few weeks ago seemed to cure the squeal at the time---but it was back again after less than 250 miles. Hoping that it could be blockage I'll try it one more time.

No I haven't taken the pump out to bench test it but that is something I could probably do. I do have several 12v DC supplies on hand so it should be easy to try outside of the tank and far from any gas. One thing, though; isn't it bad to run the pump without gas running through it? Maybe it'll be OK for a few brief times.

I suppose I would be wanting to see if it's noisy or not as well as running it backwards (reversed polarity) a couple of times in hopes of dislodging gunk, heh?

The fuel pressure regulator is something I know nothing about. Heck, I didn't even realize that there is such a device---there again, can't see the forest for the trees, I guess. Maybe that could be the culprit, too. Is that what Don was talking about a while back; the device that relieves the pressure if the fuel line/pump gets blocked?

Sorry, but I've not much of a clue as to where to look for it, either. In the tank or tucked away somewhere else? Yikes. This is a bit daunting but I'll await your response before proceeding further than installing the new filter today.

As I told Ted above the in-tank lines are only three years old and are OEM so should be fine. The outside lines are old, though.

Pretty sure all the clamps are tight but I'll double check them, too.

Thanks very much for your helpful advice and insight into this annoying situation.

As if this wasn't enough to deal with, my electrical system is acting up with the ABS relay apparently faulty as well as my auxilliary lights are all out now, too.

At least the new battery seems like a good move and I'll be getting new fork seals and wheel bearings installed after this fuel system problem is resolved.

Cheers, Jeff

[ghyber]

I was on the US side two weeks ago and picked up a Craftsman automobile stethoscope; dirt cheap at Sears. We can't get that tool at Sears in Canada.

Maybe you could try that avenue and listen-in to ensure the noise is not originating from somewhere else.

[Zagando]

That's another good idea, Ghyber and I believe our landlord already has one in his enormous and well-equipped shop. He's sponsoring an Airhead Tech Day this Saturday and although I only ride my Brick I was planning to attend and check it out anyway (may be some brick riders there).

If the problem is still present I will try listening with it to pinpoint the noise but I don't expect that to be easy; the noise is very loud and obnoxious to the naked (unhelmeted) ear!

Just installed the latest new fuel filter and am now going for a quick test ride as the sun sets in ABQ. Will report back tomorrow after a 2nd ride assuming I don't hear the noise again now.

[Zagando]

A 25 minute test ride where the radiator fan came on and so far no screeching or other sounds emanated from my bike. Fingers crossed that it was just another clogged filter but will hold my breath until further test rides tomorrow.

[98lee]

Drain the old filter and let it dry out. Lightly blow through it. Is there ANY resistance?
More than the new filter?

[deilenberger]

The fuel pressure regulator is something I know nothing about. Heck, I didn't even realize that there is such a device---there again, can't see the forest for the trees, I guess. Maybe that could be the culprit, too. Is that what Don was talking about a while back; the device that relieves the pressure if the fuel line/pump gets blocked?

The FPR is an active device that works ALL the time the pump is running. The pump output is in excess of the pressure the injectors need. To regulate the pressure, part of the pump output is routed back to the tank from the FPR, the other (regulated) output goes to the fuel rail. The FPR also reacts to vacuum, upping the pressure when RPMs rise. Since the L-Jetronic is a "dumb" system (no feedback loop on actual mixture to the ECU), it relies on having the correct fuel pressure for the conditions the engine is running at.

Sorry, but I've not much of a clue as to where to look for it, either. In the tank or tucked away somewhere else? Yikes. This is a bit daunting but I'll await your response before proceeding further than installing the new filter today.

The FPR is not actually easily visible. It mounts to the back side of the throttle-body assembly, and can only be seen/touched/replaced by removing the bottom half of the air filter box, and going in from the starboard side of the bike.

They can go bad in several ways - a punctured diaphram in one will result in raw fuel being dumped into the rear most cylinder (where the vacuum line to the FPR connects.) Or if it sticks shut, fuel pressure will go up, mileage will go down, and there is a possibility that the pump may start chirping just like yours is.

The test is a fuel pressure test. Easy to do, requires a decent pressure gauge, a good fuel-line T and some hose and clamps. This test will show up problems with the FPR toot-sweet so to speak..

[deilenberger]

A 25 minute test ride where the radiator fan came on and so far no screeching or other sounds emanated from my bike. Fingers crossed that it was just another clogged filter but will hold my breath until further test rides tomorrow.

I believe I mentioned somewhere - that a brand new filter can be instantly plugged up, if the crap in the fuel that plugged the old one up is still in the tank. If you didn't drain and clean out the tank when replacing the old filter, it's entirely possible this happened. And also - a fuel filter can last about for eternity if it never sees a load of crap in the fuel (BMW and Porsche have removed the replacement interval requirement for fuel filters on their newer cars..)

And as far as a mechanic's stethoscope - HARBOR FREIGHT in the US, it's often on sale for $1.99 or $2.99 (regular price is around $3.99), wonderful tool.

[Zagando]

Been away from the bike all day but may check it further tomorrow---thanks for your suggestions and info---might be a blocked tank vent, too (something our housemate mentioned that's worth investigating).

[ghyber]

...And as far as a mechanic's stethoscope - HARBOR FREIGHT in the US, it's often on sale for $1.99 or $2.99 (regular price is around $3.99), wonderful tool.

The only thing that costs $1.99 in Canada is the federal sales tax, and only if you are lucky; then you add the provincial sales tax and then you pay $5.67 for one US gallon of high octane fuel.

[ghyber]

...The test is a fuel pressure test. Easy to do, requires a decent pressure gauge, a good fuel-line T and some hose and clamps. This test will show up problems with the FPR toot-sweet so to speak..

"toot-sweet" - wow, got to love thy French (toute suite).

However, do you have the fuel pressure parameters/range handy, eg. 10 - 12 psi?