fuel pump?

I've been having an issue where my '93 ST1100 either dies or gags going up a rather large hill (about 10 miles from home) on the way to work, 30 miles for the whole commute. After it dies, I can get it started after about 5-10 min. and it runs fine the rest of the way. On the way home, the same issue occurs at 65-70 MPH. I get it started again, take the side road, and runs fine all the way home.
I replaced the fuel filter and emptied the tank to put in fresh gas and a little dry gas, but I had the same problems. The air filter was replaced at the same time since it was a little dirty.
I suspect the fuel pump, but I wondered if anyone had had similar issues and discovered a different cause.

Thanks for any input you can provide,
Joe

Or the dreaded vacuum operated fuel shut-off. Have you by-passed it? A crack in the diaphragm could also cause this.

Thanks for the heads up.
I'm looking through my service manual but I don't see it listed. So I looked on the Honda parts website. I see this:Valve assembly, auto, #16970-MT3-D13. Is this the part?
You say bypass it. Is that something you done and do you have it bypassed permenently?

Joe

NRP is supplying a reasonable priced diaphragm replacement kit http://www.nrp-carbs.co.uk/honda_fuel_tap_repair_kit.htm

The debate of leaving it out permanently or rather keep that safety device in place and operational is kinda religious... ;-)
IMHO its there for a serious reason... and the ~150 Honda engineers who'd designed that incredible bike were seldom in the wrong...

Thanks.
So maybe I'll just bypass it temporarily to see if that's the problem.
Am I correct in thinking it's the assembly just after the fuel filter?

Running a temporary bypass is easy to do and back-out if you want it returned to service. It would be a good test. Lots of discussion here on the merits of doing it. I have it removed from my 97. Many people think it's just another point of failure, notwithstanding its designed purpose. The bypass is simple: Disconnect the fuel lines from the from the vacuum valve assembly. Connect the fuel line that runs back to supply the carbs directly to the fuel filter. You should have enough slack for this. Disconnect the vacuum line from the diaphragm assembly and plug it with a golf tee or something. If there is a split in the diaphragm, it could cause the engine to run rough. That will totally isolate this component from the system. Repair parts are available to replace the diaphragm if that's the route you want to take. Let us know what you find.

I'll give it a try.
Just to be sure I'm disconnecting the right piece, is it the assembly just after the fuel filter?

Have you tried opening the gas cap and trying to restart? Dying and restarting after xx minutes can also be a classic symptom of vent being plugged.

I did try that

JoeW said:

I'll give it a try.
Just to be sure I'm disconnecting the right piece, is it the assembly just after the fuel filter?

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correct

If there's a correlation between this problem and low fuel level in the tank...most likely the weak pump..... But the fuel bypass should be checked first. It doesn't cost anything but a lil time.

You were right, Eagle59, it was easy to bypass. Took it out for over 400 miles this weekend, no problems! Thanks so much for the heads up.

I'll look to get a diapharm and fix it over the winter. What is the real purpose of the thing anyway?

The vacuum shut-off's reason for living is to stop fuel flow if there is no vacuum... As in: engine not running, no fuel flow.

If there's a correlation between this problem and low fuel level in the tank...most likely the weak pump..... But the fuel bypass should be checked first. It doesn't cost anything but a lil time.

Click to expand...

Yes. The pump is cooled by the gas in the tank. A weak pump will overheat and slow/stop pumping. One option is to top off the tan when it drops below the 1/2 mark. I would definitely top it off by 1/4 mark.