Engine quit - request for diagnosis assistance

Dang! Feel for ya. Wish I had the answer so this would all go away. I keep thinking of the bike computer, though. These instances are seemingly so random. Sometimes you get the same result, sometimes you don't. Is there something funky in the computer? Or what is it that is randomly giving the computer a reason to shut off the fuel. What about a bad/faulty tip over sensor?


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im going to say that u have a connection point that is going bad or corroded. it might be a pain but might want to pull all connections plugs and take a good look at both ends. was thinnking vapor lock but after reading more i dont think that now.

Not totally familiar with the 1100 but doesn't it have a vacuum controlled petcock? If it does I'd check there and see if any fuel lines maybe clogged or have debris in them that could limit fuel flow.

As familiar as you should be with the wiring, perhaps a long pair of wires with a small LED taped where you can see it. Then attach the far end to your fuel pump to verify when you do/don't have power when this happens and not just rely on the sound. Depending on where/when you have power when this happens, I gather you have enough knowledge about the wiring path to trace back with your new "test light" to see if you have power from the relay to the pump....to the relay and so on. It's not a lot, but sometimes more unusual methods help find more unusual problems.
That's where I'd be headed if I had your problem. That and maybe a clear inline gas filter to see if you are out of gas to the carbs when it happens, if you have fuel pump power when it does fault.
I may have missed some of your fix attempts along this thread, but have tried to keep up with your problem. I'm almost as curious as you are to the solution, but not as frustrated.:

I'm assuming you've already bypassed the petcock, as Byron has mentioned.

Haven't followed ALL your thread, but suggest running with fuel cap loose(cap vent restricted). Also, vacuum fuel shut-off next suspect(and a common one). This can easily be temporarily bypassed, even if failure happens while on the road. Remember to cap off the vacuum line when bypassing re-attaching existing fuel line

justin_sabre said:

im going to say that u have a connection point that is going bad or corroded.

Click to expand...

+1...
The fault appears just too random/irregular for being a fuel petcock issue (which symptoms usually start at high revs/more fuel drawn)

Could be the crimp connectors at the ignition coils...
Contacts in the ignition lock...
Connectors/contacts of the RHS switch assy (located behind steering head)
Somewhere else down the line...
A spark plug "leaking" (cracked isolator)

I would make sure you don't have a funky connection at the ground & power connectors at the top of the fuel tank. Sometimes there can develop broken strands right at the slip-on connectors. The wire insulation hides the defect. Hold the connector and pull a little on the wire and see if it starts "creeping" or it separates completely. Even if it seems OK, I would cut back about a quarter of an inch & replace the connectors just to eliminate a connection problem as the cause of the problem.

I suspect this may be your problem because early on in your post, apparently messing around with one of those connectors seemed to solve the problem.

If that doesn't solve your problem, I would remove the pump and either make sure the clamp wasn't overtightened ( it only needs to be snug ) or just replace the pump to be sure it's not intermittent.

For $15, you can tee off the fuel pump with a harbor freight fuel pressure gauge to see if the fuel pump is dropping out on you. Here's a link to the pressure tester.
http://t.harborfreight.com/automotive-motorcycle/diagnostics/fuel-pump-and-vacuum-tester-93547.html

John

I have not read through the entire thread again so if this has already been done I apologize. It seams that this all started after you changed the fuel pump. Have you opened up the fuel tank and made sure there is nothing foreign in the tank? Before anti-siphon screens in car fuel tanks, if you forced a ping pong ball into the fuel tank you could really mess with their head. The car would run fine until the suction of the fuel pump would suck the ball down to clog the fuel intake. The car would run like crap then die. After it sat for a few minutes it would run fine again. (the ball would float to the top). I would pull your fuel tank, open it up and inspect very carefully for anything that is in the tank. Something loose or something foreign that could be working its way to clogging or restricting the intake to the fuel pump.

Tony

Great thoughts everyone - really appreciate it.

The vacuum assembly has been bypassed. Not vapor lock either as there isn't any type of abnormal rushing of air when I pop the tank cap after it dies.

I am going to pull the pump/assembly and take a peek...then if I don't see anything abnormal I'll pull the tank as Tony suggests to take a look. Hoping I find a ping pong ball. Then if all looks ok there I'll go back to focusing on the electrical connections to the pump.

Because the bike acts starved for fuel running with less and less power until it finally dies, I don't think the sidestand switch is an issue because that would cause it to cut out and lose power immediately, right? I'm pretty sure I inspected it visually and didn't see any issues...

Man, I feel your pain. I'm running an open thread now about the bank angle sensor relay that somehow got dismounted and was swinging in the wind. That was causing an intermittent total shut down of the bike, not a slow fuel starvation issue like you are experiencing. I agree with your assessment of the side stand switch. That would be all or nothing. I know you mentioned the vapor lock question but have you had a chance to try cracking open the fuel cap then immediately attempting a restart? The pressure may be slight enough to cause a vapor lock but not enough to cause a hiss when you open the tank. The next time this happens try this. Crack open the cap to equalize pressure. Turn off the ignition and turn it on again. Verify the fuel pump is humming for a few seconds. Can you see fuel flow through the filter sight glass? Do this a few times to pump fuel into what is probably empty or starved bowls. Attempt a restart. Just curious, have you drained the carbs into a clean container? I've never done that myself and I know you need a long 14" flat blade screwdriver to get in there. It is possible there is crud in the bowls that may be clogging the jets? Draining it all out may show something.

Any updates to this?? Do you ever find anything that solved your problem?

Long overdue update!

After my last ride in late May 2014 I pulled the fuel pump assembly back out and took a look. For 8 months.

Finally got around to troubleshooting a few months ago. Took the Airtek replacement pump off and it appeared to be ok and then when I went to reinstall it in the assembly I over tightened one of the nuts on the small stud used to make the electrical wire connection and it snapped off. So I ordered another Airtek pump, installed it and while I was at it I ran across this thread talking about hacking the fuel pressure regulator off the OEM pump and plumbing it inline with the Airtek to ensure the correct fuel pressure was being delivered to the carbs. Seemed to make sense to me so I did that and reinstalled the assembly.

https://www.st-owners.com/forums/showthread.php?89040-ST1100-Fuel-Pump-Replacement/page13

(Especially posts 122 & 136)

Side Lesson: When placing the assembly back into the tank take extra care to ensure the rubber gasket that gets tightened down on the top of the tank is aligned correctly and doesn't get pinched. Because if it does and you fill the tank completely full with new gas and take it for your first ride on it in nearly a year, the fuel you smell isn't "just the way you remember it" - it is slowly seeping out of the top of the lower portion of the tank where you pinched the gasket. Thankfully you had a fuel siphon handy when you rolled back into the garage and were able to suck enough fuel back out of the tank to get the level below where the pump assembly is inserted into the tank - right? Right.

Anywho....I did notice that the Airtek pump sounded "stronger" (if that is possible) than the other one when it was primed by the relay when I turned the key on for the first time. Might just be me. But I did take it for a 90 minute test ride earlier this week and then a 2 1/2 hour ride followed by a 3 hour ride this weekend and didn't have any issues. On each ride I did shut the bike off after running it for awhile and then restarted with it running ok afterwards - which was the only consistent order of events when I was having the fuel delivery issue previously.

So I'll keep riding and see if the issue pops up again...but so far so good...

Good to hear it may be resolved!

Sounds like you need a road trip to Springville, to check it out, and have some pretty good BBQ!! :eat1:

Glad to hear your ride is up and running again. I went on my first ride today in four months, basically glorious.
I rode my wife's bike to pick up some brake fluid for redoing all of my lines brake and clutch.

I hope your new fuel pump has finally solved this issue. It's been a PIA for you for a long time. Also seems to be a not too uncommon problem - that is - install a new part and it turns out to be faulty. Years ago a friend had his timing belt replaced just before an out of town trip. After all, he didn't what to breakdown out in the middle of no where. Well it did just that, broke the belt and smashed some valves on I5 half way between Manteca and Coalinga.