K11 Owners Group

[R1200HACK]

Hi- I have an 93 K1100RS with 16k miles. I've replace the original fuel pump a while ago because is started to get real noisy. I replaced it with a factory pump and the new pump is still making a loud pitch winning noise. the tank is not low on fuel and the only thing I can think is, could it be a vapor lock? when I open the fuel cap you can hear the pressure release and the noise seems to go away. could it be a clogged up vent hose in the tank?
Any help would be greatly appreciated.
Thanks
Sergio

[Jim]

Not vapor lock.

Easy enough to get the hoses kinked when putting the tank back on.

Are you building pressure, or vacuum?

If you haven't installed an air accumulator, you might want to do that - it's an inexpensive plastic part - then you won't have to think about a kinked hose when you put the tank back on. Use the Search button at the top to search for air accumulator.

If you want to go to the trouble, empty the tank, take it off and blow through the two nipples on the bottom - one is the rain drain, the other is the tank vent. If they are both free, and you still have the hoses off the bottom of the tank, check the hoses. I don't know if your bike has the check valve in the vent hose from the tank to the engine. I think that was a US only California emissions thing.

You may need to rebuild the gas cap, too.
_________________
Jim
1997 K1100LTSE 94,000 - still has gremlins!
1995 R100RT Classic 16,650 crashed - repaired!
1992 K75RTP 46,000

"We shall not all die, but we shall all be changed."

[Ted]

The fuel system is closed in these bikes - here is my understanding how it works, please correct me if I am wrong (a definite possibility...)

Basically the pump pushes gas out at between 40 to 50psi, but is capable of over 100psi when there is some resistance and the pressure builds. The fuel goes from the pump, through the gas filter to a fuel pressure regulator which meters the correct amount to the injector rail (about 35psi) and bypasses the rest back to the tank. When there is a blockage from something like a kinked hose, improperly installed fuel filter or a failing fuel pressure regulator the pressure builds and the pump psi climbs. At 65psi there is a pump bypass valve that should activate that releases the excess pressure from the pump back into the tank.

What you could be hearing and noticing is the pump bypass valve activating because of excess pressure in the closed system. This as mentioned could be caused by a kinked, blocked or degraded gas hose or fitting, or by a failing FPR.

Basic diagnostics would be to test the fuel pressure with an inline testing gauge (harbor freight, about $30 - check threads here for tutorial). You might also take a very close look at the entire fuel path to look for kinked or failing fuel hose. As Jim mentioned in his excellent post, also check the tank vent that empties into the air accumulator (aka shed cup) and the gas cap.
_________________
Ted
KOG#1

[R1200HACK]

Thank you for all your help. I removed the tank today and checked the fuel and vent lines underneath the tank. One of the line was kinked, it was the one that drips fuel and fumes from the other end. The pump is still making the noise at times and it seems it does it more when is warm out (I live in Miami 85 today). Also I noticed as I sat on the bike and removed filler cap assembly that forward of the cap hole hanging from under the inside of the tank there is an aluminum canister that fuel drips from back into the tank. Next to that canister there is a a small metal tube hanging down with nothing attached to it. Should there be a hose or something attached to this?

Thanks for your help guys!
Sergio

[Jim]

[Ted]

Just a note that your fuel pump will scream angrily if you run the bike in hot weather with a very low tank - it is cooled by the fuel and tends to let you know quite audibly if the bike (and fuel) is hot and there isn't much in the tank.
_________________
Ted
KOG#1