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Discussion Starter · #1 ·
Thought it would be easier to just start another topic, my question is I decided to plug the fuel pump relay back in , start the bike and let it run while I tested the volts going to the fuel pump while it was unplugged. Don't think it would matter if it's plugged in or not but I was only an reading 4.5-5 volts . When I jumped the relay while the bike wasn't running I was getting almost 12 volt. Shouldn't the relay be sending 12+ while the bikes running to the pump? I don't know if that's normal or not.

I'm really just trying to figure out if I'm making a bigger deal than it is or maybe I have something else goin on. I would hate to install the pump and relay and have it go out when we I start it back up or a week later. If that makes any sense.
 

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1983 Honda vt750 Shadow
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Not sure what the amp draw on a pump is, but the relay may have gone bad from an old pump overloading the transistor circuit.
Does the pump work fine on 12 volts?
 

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Discussion Starter · #3 ·
Swifty. No the pump doesn't work at all. Like I said earlier , I did run 12 volts directly to the pump and nothing happened with it. So it's safe to say that's bad.. at least I would call it bad. When I run the bike it's from a funnel, straight to the carbs.well from the to hose I should say, you know what I mean. And it runs fine, everything else works,high low beam,turn signals,brake lights,speedo light plus all the idiot lights. Haven't run it long enough to kick the fan on it but it was working fine last time it was running before all this happened.
 

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Discussion Starter · #4 ·
I'm m still trying to figure out what this is , it wasn't hooked up to anything , it looks like it's factory but why would it be there. I haven't unwrapped it to see what color wires are there. It's a 3 pin connector I'm pointing at ,does hoes Honda use any tape in there wiring harness at all?
16266531728303316962371009354859.jpg
 

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That gob of tape doesn't look factory but see what the wires look like.
The plug looks factory, however.
 

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Discussion Starter · #6 ·
I been thinking about it , but it's taped so good it's gonna be a real pain , doesn't look like it was just thrown on there real quick. Might just leave it for now until I get the new pump and relay and see what happens with that. If I had other issues goin on our would definitely check it out now. I will say the picture makes it look a lot worse then it is. Tomorrow I'm gonna pull the relay back out , jump the wires,start it up and check the voltage going to the pump again. See if it's got 12+ or only the 4.5-5 whatever it was when I had the relay plugged in. Maybe that can give me a better idea on if the relay is going bad. Other than that I'm out of ideas until the new parts come in lol
 

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If you want to peek at the wires run a single edged razor blade down the tape in the same direction as the wires.
 

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Hard to say what you may actually see regarding voltage at the pump, since the relay is electronic and is triggered by the coil firing pulses. On a scope the trigger may look like a 6 to 8v ac signal with varying frequency depending on rpm, the output is constantly turning on/off with it running. Your meter may be giving you a dc average. Jumper it and try running. You can drain the float bowls, jumper it and turn the key on, should click fast, then slow and stop in a few seconds as the floats shut off fuel. If the bowls are full, it may not come on with the key... It is a pulse type pump vs an electric motor pump. And a few taps with a screwdriver handle or small hammer on the pump may wake it up... (Worked on my wife's Mercedes until I got around to changing the pump.,,,)
 

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Just for kicks I went out and measured my 1983 750 .
With it running, It had a voltage of 9 to 10 volts out of the relay, with the pump plugged in or disconnected. Not sure if that is the way it was new, but I never run out of fuel anyway.
 

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Discussion Starter · #10 ·
Oldguy,,, I have tried tapping on it a lil bit earlier today, probably not enough to do anything since it was a lil awkward getting to it. I was going to try again tomorrow on the other side where the wires come out.i got distracted and forgot about it or I would have grabbed something to get on it better. Give it a few good taps , I don't think I can hurt it any. Lol

As the days go by , thinking about gravity feeding it for a few days is making it hard to say no right now , at least I could get just a lil seat time . 10-15 min and back on the road !!! But that's just a temporary fix , it's not going to fix the issue or tell me anything. Just 3-4 more days , I hope
 

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Discussion Starter · #11 ·
Swifty... Well that's more then I have , like 4-5 more , now that I think about it the rubber mount the relay uses to hold it in place was broke. I wonder if it's possible to if that thing was to bounce around to much if that could damage it. Probably not but thought I would throw it out there. I'd say my relay is starting to go bad and my pump just gave up .
 

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Keep in mind, the relay's purpose is to stop the pump if it doesn't see the ground pulses the ICM uses to fire the coils. (as in you crashed and the motor died,,,) that yellow/blue wire comes from an ignition coil negative side and the relay and goes to the ICM.

Edit: The 83 may be using a signal from the stator instead of the coils
 

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No, that’s a solid-state relay tightly packed in that little black box. I was going to just twist-tie it on, but that would be purely cosmetic. If you fed 12v straight to that pump, with the tubes disconnected from the fuel system, then it’s dead. Feel free to disassemble it and check it out. I brought one back to life that was clogged, but it didn’t last long before something electrical failed inside of it.
 

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The contact points in the pump do go bad, KLSupply.com sells the replacement points kit for the fuel pump..

Edit: requires soldering...


And I've always wondered if a person couldn't use a regular old-fashioned points file on them and just clean them up?
 

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This is a very informative topic for me
 

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Discussion Starter · #16 ·
So far so good, haven't run it on the highway yet but seems like it's good to go. Guess my other post was to old and didn't pop right up without searching for it.
 
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