no power to fuel pump

[Tenmilsocket]

Those lines are the float bowl vent lines. The vacuum lines are found on the intake manifolds under the rubber mat. #2 & #4 on the left side go into a "T"



On the right side I'm not sure where #1 goes (this is a wreck I bought to strip parts off of) but #3 is supposed to go the the AFV

If you have the AFV bypassed you will need to find and plug this line or this cylinder will run lean.

 

[dwalby]

The only vacuum hose I see from carb 3 is the one for balancing. There should be another?

that's the one, there isn't another.

Before removing that valve and bypassing it, when I used to do carb syncs I put a Tee in that hose so the fuel valve would continue working while doing the sync. The service manual suggests pulling a vacuum on the fuel valve and clamping the line, but I never used that technique. Not that any of this is important to your current issue, just wanted to give you confidence that there's no other line to be looking for.

so now that you've bypassed the shutoff valve, plug the vacuum line you found and try starting the bike again.

 

[John OoSTerhuis]

Dean, that is the Purge Control Valve in your picture. The other valve on the other side up front is the Air Vent Control Valve (the #1 vac hose is connected to this valve). See the diagrams and descriptions in Chap 1 of the Honda Service Manual. CA and USA ABS/TCS models.

John

 

[DeanR]

The vacuum line from carb 3 for balancing is, and has been capped, connected to nothing. This would imply that this is not the source of the original problem of the fuel pump not running? It is also not long enough to have been connected to the fuel shutoff valve (petcock assembly) anyway, so I'm still left with the mystery connection to the valve. Next time I have some plastic off the perfectly running '99 I'll be able to compare. The 99 will be ridden on many winter days when the roads are not white.

This vacuum hose setup sure is confusing., as are the diagrams.

Really wanted to get this 91 running before winter, as it has just been sitting covered in the garage for a couple years. But not wanting to reinstall and refuel the just emptied fuel tank, I pretty much covered it up and likely will leave it till spring. Frustrated.
Thanks for everyone's help, as always.

 

[Uncle Phil]

If the fuel pump runs when connected directly to the battery with the all the suspect hoses connected and does not run 'normally' through the circuit with the all the suspect hoses are connected, why would you think the hoses would be a problem?
Or did I miss something?

 

[dwalby]

Hey Dean, why not at least trace out the electrical path, you can do that without actually pumping fuel. Disconnect the leads to the fuel pump and trace out the voltage through the schematic.

BTW, I went back and edited my earlier post on page 1 that shows some of the electrical path to clarify some things that I didn't word exactly right the first time.

 

[Ron]

"Would this vacuum problem prevent the fuel pump from even running? which is the original problem and why I need to jump it directly to the battery."

No. If the fuel stops flowing to the carbs, the fuel goes to a bypass route inside the tank.

I understand your frustration with winter coming on strong. Having everything disassembled makes it worse.

The fuel path for the 1100 is relatively simple with few components. The pump sends the fuel to the filter. From the filter to the vacuum operated fuel valve. From the vac.operated fuel valve to the carbs. When you get back to it, I would suggest trying the following.

Your pump is working.

Is the filter flowing fuel? Pull hose to verify.

Is the vacuum operated valve flowing fuel? Pull hose to verify.
If not flowing fuel, connect the output hose to the out put side of the filter, bypassing the valve. Run the pump for 20-30 seconds to fill carbs. Try to start motor.

I don't see how it could flow fuel if the vac. line isn't connected. I don't know of anyone around here modifying the valve to flow fuel without the vac. line. But, there is a similar valve on the 1500 Valkyrie. Those folks have figure out how to modify the valve for free flow fuel (by gravity) to an auxiliary tank mounted below the main tank. So possibly. But you said your carbs were dry, so probably not.

Here is an explanation with pictures. Takes less than 15 minutes when the plastic is removed.

Vacuum Fuel Valve Bypass Method ( ST1100 ) *

Vacuum Fuel Valve Bypass Method ( ST1100 ) *

www.st-riders.net

 

[DeanR]

Its my understanding that the fuel will gravity flow just fine, as in no pump needed
[/QUOTE
Is this true? (from another thread) For the 1100.
I have yet to solve my problem of fuel pump not running unless jumpered right to the battery. Have not returned to this problem for a while.
I would like to start it without having to do this.

 

[rwthomas1]

If you read the posts regarding fuel pump failure the bikes can be ridden 100miles or so without a functioning fuel pump, when the tank is full. Certainly not an ideal situation but you could get home like this if you had to. The gas cap is considerably higher than the carb bowls, so full to the top there will be head pressure.

 

[DeanR]

Getting back to my fuel problem of the thread below.

no power to fuel pump | ST1100 Related | ST-Owners.com

Could I hang a lawn mower fuel tank or such from above (or maybe an XS1100 tank with on/off petcock) and send a fuel line down to the carbs to run the bike in the garage?

From above thread … fuel pump only runs when jumped directly to the battery. I need to run the engine. It’s just been sitting ( = bad). There is no tank in the ST at the moment.

 

[TerryS]

Of course you can set up a gravity feed to run the bike in the garage. The carbs don't care where the fuel comes from.

 

[Ron]

Of course you can set up a gravity feed to run the bike in the garage. The carbs don't care where the fuel comes from.

I would go straight to the filter bypassing the aux. vacuum fuel valve. Maybe even bypass the filter.

 

[DannoXYZ]

You should test for spark as well.
The fuel-pump relay is driven off ignition ground-pulses from ECU for coil 2/4.
Fuel-pump relay not working may be due to lack of spark signal.