Another Uncle Phil Interesting Running Mystery

[John OoSTerhuis]

 

[Uncle Phil]

John - That will be included in the next round.
I've got plenty of them in my 'spares'.
You ever had one go bad on you?

 

[Slydynbye]

I didn't see where you eliminated the fuel pump. If I had 2 bikes (or more) to play with I'd swap the whole fuel tank, pump and all.

 

[Uncle Phil]

I didn't see where you eliminated the fuel pump. If I had 2 bikes (or more) to play with I'd swap the whole fuel tank, pump and all.

See post #35
As I have said before, I don't part swap off one of the runners as then I have the potential for having two ST1100s that aren't running.

 

[Slydynbye]

Maybe check the connector on the ECU looking for corrosion or loose connector.
Although pulse generator sounds more likely

 

[SMSW]

Another thing we know -
9. It ain't the coils.

At this point, all I can do is start all over again and go through the stuff a lot slower and see if anything jumps out.
That is the joy of an intermittent failure - a bit like Big Foot hunting ...

Did you replace the plug wires and caps as @dwalby suggested?

 

[Uncle Phil]

Did you replace the plug wires and caps as @dwalby suggested?

Replaced the whole assembly with a known good one.

 

[dwalby]

sorry to hear you're still chasing it down. Maybe for the next step try swapping out the ignition black box. Since that's under the front fairing I suppose its fairly easy to access and swap out, but I've never had to do that so I don't know how easy it will be. Electronics are generally pretty reliable, but given the age of these 1100s nothing would surprise me at this point.

 

[IndyRob]

Sounds like the gas tank is not venting properly... creating a vacuum after a gallon or 2 of fuel have been used. Have you tried riding with a loose gas cap? I know mine will actually make noise while sitting in the garage after a ride, especially when I have 1/2 tank or less.... pretty sure it is the air trying to get past the gas cap because when I loosen it I get a whoosh of air into the tank. If that vent was clogged you would run lean/ "out of fuel" after about 50-90 miles.... until air can get back into the tank.

 

[kiltman]

If you’re starting over again, try a different fuel cap but don’t leave it loose, turn the cap till it locks.

 

[SMSW]

Did you check the electrical harness for corrosion? Back to basics - maybe an intermittent ground? How about the ecu? Maybe easier to just change bikes.

 

[St-Gerard]

Weirdest prank I have heard of was someone put clear plasic wrap in the tank,floats around then gets sucked up by the pickup screen and stalls the motor ,you can't see it in the gas . Nasty trick

 

[bdalameda]

I posted this earlier - perhaps a bad Bank Angle sensor. The sensor operates a relay that kills the ignition circuit. The BAS relay could also be suspect.
Also - is the side stand switch still active?

 

[St-Gerard]

Stupid question U. P. have you replaced the spark plug?

 

[John OoSTerhuis]

John - That will be included in the next round.
I've got plenty of them in my 'spares'.
You ever had one go bad on you?

Never heard of an ST1100 pulse generator failure. Mine had a long-time oil seep, hence the pictures.

John

 

[Uncle Phil]

Well where I am now -

1. Pulled the fuel tank, dumped it completely empty, rinsed it with 'real' gas and then reinstalled and added 'real' gas (to eliminate water in the tank).
2. While I had the tank out and since the 'smoking' motor had a working pulse generator easy to get to, I replaced it while I was at it.
3. Replaced the fuel pump relay (up on the left side of the fairing stay - requires removing the upper left fairing).

Now she seems to be perking as she should - but I won't really know until I take her for a 300-400 mile shake down ride.
That will be a bit since I am off to the Mansfield RTE tomorrow.

Here's what is interesting -
I jumpered a switched hot to the fuel pump and put a meter on the fuel pump 'hot' while it was running to see if I saw anything.
You had to look close but several times the voltage dropped from 13-14+- volts to .6, stayed there and then came back.
So I changed the relay - which is what my original hunch was the problem.
This is not the first time I've run into this as I had one go bad on BlueBelle.
If it is fixed my money is on the fuel pump relay because as John said, I've never heard of a pulse generator going bad on a ST1100.

 

[DeanR]

Sounds like good news Phil.
So the fuel pump relay is what Honda calls the "RELAY, FUEL CUT" 36100-MN5-000 ?

 

[Uncle Phil]

Sounds like good news Phil.
So the fuel pump relay is what Honda calls the "RELAY, FUEL CUT" 36100-MN5-000 ?

Yeppers that would be the one - hangs in a rubber holder on the fairing stay under the left upper fairing.
There's another smaller relay beside it but I think it controls the fuel gauge.

 

[Uncle Phil]

Well, I went to pull her out of the workshop this morning and the problem returned like a bad check.
I guess it's back to the 'drawing board' ....

 

[ChriSTian_64]

Keep going on, Phil.