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Discussion Starter #1
Im gonna cry...

Not really, Im actually to the point of raging and crushing this bike..



My used fuel pump came in today. I put it on the test bench and put voltage to one of the wires and it ran. Sounded good too.


I hooked it up to my bike to see if it would prime and nothing. I of course had it in neutral, clutch in. (I am gonna go put the kickstand up too see if it helps any.) I took a test light to it and I have two wires that make the light barely come on at all. Those wires go to the side of the motor of the fuel pump.

Then i have two wires that have no power at all.

One i assume is a ground wire of course and the other is the wire that is supposed to have the 12v rail. (I assume).

If I am wrong would someone please tell me so.

So, basically what im asking is do you all know of anything that is causing this? Is it possible that either my neutral, clutch, or kickstand switches are net letting power to the 12v rail?

Are those two wires going to the side of the fuel pump just meant for communication to the computer and Odometer? Are they supposed to have low voltage like that?

I have so many questions i believe its confusing me, and I am hoping some you vets can calm my nerves a bit.

:eek:utcold:


Thanks in advance.
 

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Did a simple test on my 2005 C50. In neutral, kickstand down, clutch NOT in, just turned the key to ON and the headlight came on and the pump primed. Get a multimeter ($10 at walmart) and check the voltage on those two wires for the pump to confirm you are getting proper voltage (probably 12V, but check the spec for the pump if possible). The test light you are using does not give enough information.
 

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Discussion Starter #3 (Edited)
I just checked the voltage on the two wires going to the outside of the pump motor and they are both getting 8v.

EDIT: I did what you did also. I left the kickstand down, and didnt pull the clutch. I just made sure it was in neutral.

I turned the key to ON and the head lights, parking lights, and neutral light all came on. I heard a really high pitch whine. It stays on till i either flip the kill switch, or put it in gear, BUT BUT BUT I am holding the pump in my hand and it does nothing at all. Only time it has done anything is when i put 12v power straight from the battery to the Yellow/red wire and then it runs till i take the power off.

Nothing else other than that.
 

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Don't despair!!! You do know that there is a relay that supplies the power to your fuel pump right??? I would make it a point to find it and pull it out, and make sure that the connections on it are good. If you can easily obtain another fuel pump relay I would swap it out as an easy way to prove it out either good or bad. Relay contacts can fail and make a poor connection and that would give you that weak glow on your test light that you experienced. Most people don't realize but your fuel pump pulls a substantial amount of current and that can pit out the contacts in a relay like that. Also check the fuse for the fuel pump as well for bad connections etc... Trust me, you are a long way from the point of giving up hope... If you can get one, get a Clymer manual for your bike. Having a color wiring diagram is well worth the price of the book alone... Good Luck, I think you will get it fixed if you just be persistent and check the things I have mentioned. Also wouldn't hurt to clean your battery connections while you're at it...
 

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Check the voltage at the battery so you will have a baseline of what to expect. Expect the voltage you see at the pump leads to be 5-10% less.

Sounds to me like you have some corrosion or something else causing resistance.
 

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Discussion Starter #7
I have twelve volts at the battery terminal.

This pump has four wires going to it. Two have 8v and two have nothing. One of the two that have nothing is a ground. The other wire that has nothing is the wire that makes the pump run when I have the pump completely disconnected from the bike and hook a twelve volt leg to it straight from the battery. The two 8v wires only light up the odometer when I put twelve volt to them. Hopefully this clears somethings up.
 

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Sounds like a short to me I'd start tracing the positive back to the sorce checking for shiners (little bare spots missing insulation) also checking fuses and relays along the way.Also check all the safty switches.
 

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Sounds to me like the relay is probably not functioning. Did you find the relay and check it?
Have you tried unplugging the fuel pump and putting 12V+ onto (it appears from the schematic) the yellow with red tracer, with the 12V- onto the black with white tracer? It should run at that point. One of the other wires (yellow-black) appears to be the fuel level sender, from what I can tell (the schematic is pretty sketchy, but it's drawn as a resistor, which I would guess is the fuel level to the gauges). This could be 8V, measured to the black-white. The schematic I'm using shows only 3 connections.
 

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Discussion Starter #10
Sounds to me like the relay is probably not functioning. Did you find the relay and check it?
Have you tried unplugging the fuel pump and putting 12V+ onto (it appears from the schematic) the yellow with red tracer, with the 12V- onto the black with white tracer? It should run at that point. One of the other wires (yellow-black) appears to be the fuel level sender, from what I can tell (the schematic is pretty sketchy, but it's drawn as a resistor, which I would guess is the fuel level to the gauges). This could be 8V, measured to the black-white. The schematic I'm using shows only 3 connections.

I havent found the relay yet. I just got done ordering a Clymer manual so that i can have a good reference before i get in this bike and mess something up.


I also posted this earlier about what i have dont to test the fuel pump.

"I turned the key to ON and the head lights, parking lights, and neutral light all came on. I heard a really high pitch whine. It stays on till i either flip the kill switch, or put it in gear, BUT BUT BUT I am holding the pump in my hand and it does nothing at all. Only time it has done anything is when i put 12v power straight from the battery to the Yellow/red wire and then it runs till i take the power off.

Nothing else other than that."


So basically im not getting any power to the Yellow and red wire. So, a bad relay is highly possible. I just havent found it yet and I did want to start cutting the wire harness to trace it when i can get a Clymer manual to show me right where it is at.
 

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Discussion Starter #14 (Edited)
Ok, I just got my Clymer book in. Found the Fuel Pump relay. Tested ohms and voltage. Everything checks out. It even cycles like the fuel pump is supposed too when i first turn the key on.

I have also check the Tip Over sensor and its resistance, and voltages are all within the range they are supposed to be.

Im at a loss...

Edit: And the battery was fully charge too.
 

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When you tested it, you saw voltage on the output side of the relay (when it tried to cycle the fuel pump)? Was this with the pump hooked up? What about at the pump connector?
 

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Not sure of this, but it may be possible the fuel pump won't run unless immersed in liquid (gasoline).

Or, if the fuel system is full, perhaps the pump won't run until the injection system is partially emptied.

When You directly hook up the pump, that by-passes the fuel system completely.
 

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The prime should always happen at key on.
It might be that the ground circuit is open to the pump. Have you put an ohm meter from the - wire on the pump connector to battery - ?
 

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This circuit is really not that complicated. The battery power is fused through the 10A fuel fuse. It goes to the relay. The relay is switched by the ECU. The power from the switched relay goes to the fuel pump.
Keep in mind that measuring battery voltage in the circuit when the pump is not connected does not always tell the whole story. If the circuit is not loaded and there is a resistive connection or relay contact, the meter will not load the circuit enough to pull the voltage down, and it will look good. When the pump is connected in that situation, it has a heavy load (low resistance) on the circuit and a resistive connection will drop voltage and not let enough current flow to the pump to drive it. That could be what is going on here.
 
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