Bridging The Fuel Pump Relay - Honda Shadow Forums : Shadow Motorcycle Forum

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Old 05-04-2008, 07:40 PM   #1 (permalink)
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Default Bridging The Fuel Pump Relay

If you have a Honda with a fuel pump relay, you probably know that the relay only energizes the fuel pump when the motor cranks. This can leave you stranded if the relay goes bad or you run out of fuel. Cranking the engine to fill empty carbs can drain your battery dead before the carbs fill. The options are to bridge the relay with a jumper or wire in a switch. Be sure to use a switch that will stand a minimum of 5 amps. I bought a Radio Shack 25 Amp 12V rocker to wire in.

Here is the relay.


This is how you bridge the connector with a jumper wire.
Black wire and Black w/Blue stripe wire on my '83.


New wiring soldered into the relay wires.


Insulated connectors crimped onto the wires.
Soldered joints taped up. Switch connected.


The switch sits neatly inside the side panel without needing a bracket.
If the switch gets bumped, the worst that could happen is that the pump would work when the key is turned on.
(Radio Shack supplied a bracket, but I elected not to use it. You might want to.)
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Old 05-04-2008, 07:52 PM   #2 (permalink)
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I did the same thing, except I used a momentary contact switch for mine.

The probability of it ever happening is slim, especially where yours is,
but I used a momentary contact just in case a toggle could get switched
during an accident.
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Old 05-04-2008, 11:36 PM   #3 (permalink)
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Thanks Rocksolid,

You Rock!
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Old 10-03-2008, 10:10 AM   #4 (permalink)
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Quote:
Originally Posted by litnin
I did the same thing, except I used a momentary contact switch for mine.

The probability of it ever happening is slim, especially where yours is,
but I used a momentary contact just in case a toggle could get switched
during an accident.
So do you hold in the momentary toggle while you ride it home? I ask because as soon as you release it the fuel pump would quit and I didn't think gravity would work.
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Old 10-03-2008, 01:27 PM   #5 (permalink)
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Quote:
Originally Posted by gelsbern
Quote:
Originally Posted by litnin
I did the same thing, except I used a momentary contact switch for mine.

The probability of it ever happening is slim, especially where yours is,
but I used a momentary contact just in case a toggle could get switched
during an accident.
So do you hold in the momentary toggle while you ride it home? I ask because as soon as you release it the fuel pump would quit and I didn't think gravity would work.
No! the switch is to bypass the ignition signal that makes the pump run normally. The switch is incase you run your carbs dry (run out of gas) you can turn on the switch long enough to PRIME the carburetors. So the switch is a way to install a priming circuit, once the carbs are full and the bike is running the priming circuit is to be switched off.
MarkC
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Old 10-03-2008, 01:43 PM   #6 (permalink)
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In addition to what Mark said, it is also useful if you lose the relay on the road. The fuel pump will only run till the carbs are full, and it will keep them full.
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Old 10-04-2008, 03:19 PM   #7 (permalink)
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I added bypass switches that activate the relay for the pump on our 1100s, so 5 amp contacts are not really a necessity. However, going this route also means that if the fuel pump relay died on you (As in the previous post stated), you wont be able to run the pump. It will help you diagnose the problem of a bad relay though!

Works like a charm to pump the bowls full after draining or if you run out of gas and need to fill the bowls again.

Mark
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Old 10-04-2008, 04:34 PM   #8 (permalink)
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Mark, I'm wired in beyond the relay. I can turn the switch on and run the pump w/o the relay.

Quote:
Originally Posted by zikzak
I added bypass switches that activate the relay for the pump on our 1100s
Mark
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Old 04-08-2010, 10:01 AM   #9 (permalink)
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Default Relay bridge = Lifesaver

Just got my hands on my brothers old Shadow VT750 1984.
It didn't start unless I used a charger/boost making it impossible to use the bike for commuting or errands...

Bridging the relay fixed it!
Thanks!
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Old 04-09-2010, 02:55 AM   #10 (permalink)
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drflex, I'm glad that bridging the relay got your bike going. Since you mentioned needing additional power, I suspect that you have work to do in the charging system and battery. The bridge merely eliminates the relay.
If you need a manual, here is a download.
http://www.carlsalter.com/download.a...08046112100102
For electrical diagnosis, I recommend this trouble shooting chart.
http://www.electrosport.com/technica...ng-diagram.pdf
There a couple of great guys (and gals), on this list that are very good with early 80's Shadows. Post a new thread on the technical area mentioning the 84 vt750 and some indication of your problem. I have a 83 vt750c, but won't be available to help much in the near future.
Good luck
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