no power to fuel pump

[Andrew Shadow]

So, backing up to your first post:


I would think that statement points to a bad battery or a loose connection at the battery terminal. If it is starting and running just fine with external voltage (a jump), then there shouldn't be any issues with your wiring, relays or components. Everyone is giving you advice and test procedures based on the assumption that you have a working/good battery. A loose battery connection will sometimes give good voltage, but then drop to nothing once any amps are pulled. Normally, this is most noticeable on a starter that draws a lot of amps (it will just "click" once and never turn the starter).

Can you confirm that if jumped there are no issues, and it will remain running once the external battery is disconnected? If that is the case, look closer at your battery connections and possibly take your battery in to any auto shop for a test.

Ryan

I think that he is referring to jumping the fuel pump, not the battery.

 

[Ryan_B]

When you 'jump' the hot wire on a ST1100 pump, you are bypassing all relays, circuits, etc.
I would bet he jumped off the bike's battery.
The key is does 'runs fine' means the bike or the pump or both.

I think that he is referring to jumping the fuel pump, not the battery.

Haha - whoops, looks like I am the one assuming here... You are good hands, proceed as directed.

Good luck, I hope you find the issue quickly! Electrical gremlins are frustrating, but just post your progress and let these good folks help direct.

Ryan

 

[DeanR]

When you 'jump' the hot wire on a ST1100 pump, you are bypassing all relays, circuits, etc.
I would bet he jumped off the bike's battery.
The key is does 'runs fine' means the bike or the pump or both.

Yes, + pump connector to + bike battery post. Key not on. Pump will run.
That's how I empty the tank when needed.

Assuming this bypasses any fuse as well? (don't know which fuse is for the fuel pump anyway)

 

[Uncle Phil]

Yes, + pump connector to + bike battery post. Key not on. Pump will run.
That's how I empty the tank when needed.

Assuming this bypasses any fuse as well? (don't know which fuse is for the fuel pump anyway)

Yes, that bypasses any fuses.

 

[Ron]

I ran my 1100 with the fuel pump "hot wired" for about 6 months. On the back of the fuse block are several slots that a male spade lug fits into. This gives you a switched power source. I put an inline fuse holder with fuse in the line. No problems.

The pump relay runs the pump for a short period if you only turn the key "on". If you switch the key on and start the bike, the pump runs non-stop. A bypass is built into the pumps plumbing.

 

[afrymoyer]

Dean... If you get in a jam, hot wire/bypass the pump circuit and ride it up to my shop. If the bike is stripped, put it on a trailer and run it up to me. I have everything here....

 

[DeanR]

update ... it's not the relay. It works in my everyday '99. None of my three relays work in the 91 and they all work in the '99.
By 'work' or "runs" I mean I hear the pump activate briefly when the key is turned. That only happens when the pump + is jumped to the battery +.

Not the fuse. ( the 10A IGN, STARTER, ACG per the manual )

 

[Uncle Phil]

Check the ground and hot at the pump?

 

[DeanR]

Check the ground and hot at the pump?

ground check key on - test light bright / 12.3V
hot check key on- no light / 0V

Have not yet done Andrews process.

 

[Uncle Phil]

Then I'd start at the fuel pump end and trace hot wire back to the relay to see where the break is.

 

[dwalby]

ground check key on - test light bright / 12.3V
hot check key on- no light / 0V

Have not yet done Andrews process.

Not sure how to interpret this data Dean, the ground should be 0v with key on, and the hot should be 12v with the key on, you're reporting the opposite.

Agree with UP that you're just going to have to trace the wiring backwards through the system to find where the problem occurs. If you need help with that process just ask.

 

[Uncle Phil]

I think he meant that on the ground wire with the test light connected to the hot post on the battery, he got 12 volts - which he should.

 

[DeanR]

It would be nice if I could talk intelligently about electrons, but sadly that's not the case.
I followed Uncle Phil's direction ....
ground check - key on, ground on pump to battery + ... bright test light , 12.35 V
positive check - key on, pump + to battery ground .... no light, 0 V

Haven't yet plunged into Andrew's instructions.

 

[DeanR]

Is it ok if I jump the fuel pump directly to the battery, then start the bike to run in the garage or driveway?
Pump would be running constantly, not sure how that compares to its usual operation?

 

[Uncle Phil]

Is it ok if I jump the fuel pump directly to the battery, then start the bike to run in the garage or driveway?
Pump would be running constantly, not sure how that compares to its usual operation?

If you can, I would put a inline fuse in the wire directly from the battery just to be safe.
Or if you have a fuseblock that is hot when the key is on, run a wire from a fused circuit.
It should be fine.

 

[Ron]

Is it ok if I jump the fuel pump directly to the battery, then start the bike to run in the garage or driveway?
Pump would be running constantly, not sure how that compares to its usual operation?

Yes but like Uncle Phil says, I'd add a fuse.

See my post #25 above.

 

[DeanR]

Finally getting back to my no start problem.
With fuel pump jumped directly to the battery and running ... no start.
Fuel is getting through the fuel filter.
Opened the carb drains once I found em, and they were empty. Just as I had left them last year.
So no fuel flow between the filter and the carbs.
So I just did the fuel valve bypass to eliminate that, and noticed no vacuum line was connected. Can't even find it to plug closed. I see the vacuum lines for carb balancing, but I do not see one for the bypass valve? Where should this be located and could this be the problem all along?

 

[Ron]

... could this be the problem all along?

Yes. The fuel valve needs the vac. hose to open the valve. You can bypass the valve to verify the fuel is flowing. Hook the filter to the hose going to the carbs. Click link below. It has pictures and description on how to do it.

Vacuum Fuel Valve Bypass Method ( ST1100 ) *

Vacuum Fuel Valve Bypass Method ( ST1100 ) *

www.st-riders.net

I believe the vac. hose is from carb #3. It should be on the valve or plugged.

 

[dwalby]

as Ron said the vacuum hose is from cylinder #3, but it must have come loose recently or you'd never been able to pump fuel without it being attached to the vacuum shutoff valve.

After you bypassed the shutoff valve, which shouldn't care if you can't find the vacuum hose, did you get fuel to the carbs?

Eventually you'll have to find the vacuum hose from cylinder #3 and plug it.

 

[DeanR]

as Ron said the vacuum hose is from cylinder #3, but it must have come loose recently or you'd never been able to pump fuel without it being attached to the vacuum shutoff valve.

After you bypassed the shutoff valve, which shouldn't care if you can't find the vacuum hose, did you get fuel to the carbs?

Eventually you'll have to find the vacuum hose from cylinder #3 and plug it.

The only vacuum hose I see from carb 3 is the one for balancing. There should be another? Without pulling the carbs I can't see from where it would originate. Doubt it is hiding under the rubber mat.

Fuel tank is out Doug, as is the air cleaner now for a better view.. So I have not yet tried it with the valve removed.

The attached photo (extra carbs, '94 if I remember correctly. The 91 is what I'm working on) maybe doesn't help because it is a different configuration, I think. All 4 vacuum hoses from the carbs collect at the round black thing (whatever that is) at the front of the carb bank pictured.

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.