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Fuel pump fuse keeps blowing......*#$%!@


Got_Poi?

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Alright. I just finished lubing the splines and replacing a clutch plate on my 99 R1100rt. It ran fine before except for the slipping clutch. Well I just got it back together and the fuel pump fuse (#6) keeps blowing when I turn the ignition on. It even blows when the fuel pump is disconected and I turn on the ignition.

 

Now correct me if I am wrong but I am asuming that somewhere in the wiring harness from the connection under the tank to the fuse box I now have a short.

 

If someone knows of something I am missing please pipe in before I split the frame again to find it. Any ideas?

 

Erich

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BucksTherapy

You have a short to ground.

 

You may have pinched a wire or the connector under the tank may be corroded and pulling it apart and plugging it back together. It is more then likely the former.

 

If you have volt meter and ohm meter the pull the fuse for the fuel pump, disconnect the plug under the the tank and measure the voltage on each of the posts that the fuse would normally bridge. You should have 12 volts on one post. This is the side going to th epositive battery and we know the short isn't there or you would have significantly more problems.

Now switch to ohm meter and measure the ohms between the other post for the fuse and the negative side of the battery. If the ohms approach zero then you know you have a short to ground between the fuse connector and the connector under the tank. This is most likely.

 

Another possibility is a short in the connector going to the tank or the wiring going to the tank. With the connector still apart measure the oms between each post in the connector and ground. If any approach zero then you have a short in the wiring going to the tank.

 

Now check the connector visually. If it is relatively clean with no breaks or burns then it is highly unlikely that is the problem. If you can find the pin out for this connector you could measure the ohms between the positive fuel pump wire and any other if there are any approaching zero then you have a short in the connector or between two wires going to the tank.

 

It is more likely you have pinched, scraped, crushed, burnt the positive wire between the fuse box and the connector under the tank. You need to look very carefully for a bruise of the wiring harness between the fuse box and the connector. Pay particularly close attention to the areas that is near the frame or transmission. It is most likely a pinched wire that is causing a ground to through the frame. When found, cut out the wire where it is bruised, solder in a short peice of same or thicker wire having slid heat shrink tubes on first and out of the way, cover the open wire with dielectric grease then slide the heat shrins in place and shrink them. If done this way you will never have to worry about moisture or corrosion in the splice.

 

Good luck and keep us posted.

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BucksTherapy

 

Here's what I found:

 

Ign on. Fuse+ to the conector ends -

#1 12.13 V

#2 12.13 V

#3 4.3V

#4 0.31V

 

Ign on. Neg Battery to the conector ends -

#1 0.0 V / .02 Ohm

#2 0.0 V / .02 Ohm

#3 8.03V / 1.0 Ohm

#4 11.81V / 1.0 Ohm

 

Fuse - to the Neg on bat

1.0 Ohm

 

Am I to assume that wires #1 and #2 are the culprits because of their ohm readings?

 

Thanks

 

Erich

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Bill Dennes

Got_Poi: Your last post makes me think that the fuse does not blow when the four-prong plug under the tank is disconnected.

 

If I got that part right, and if the fuse blows when the plug IS connected, we could be onto something. The something could well be "downstream" from the plug.

 

Does anybody have the resistance info for a good fuel pump? I think that the wires that run the pump are Green and Brown. Maybe there is a short in the pump or wiring problems in the fuel tank's part of the harness?

 

confused.gif

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BucksTherapy

Did you take these measurements with the plug under the tank disconnected? If so I would trace out both of these wires to see if there is any damage. If not then disconnect it and take these readings again. If you get zero ohms between the fused side of fuse 1 and fuse 2 and ground with the connector disonnected then we will know the short is between the fuse box and the connector.

 

You have already told us that the fuse still blows when the pump is disconnected and you have 12.13V on the battery side of the fuse box so we know we have a problem between the fuse box and the pump. When you said it still blew when the pump was disconnected, how did you disconnect the pump?

 

If it does not approach zero then the short is in the wiring between the fuel pump and connector. At this point you should pull the pump and wiring and give the wiring a thorough inspection.

 

I have an 1150 so I am not sure which fuse on your bike powers up the fuel pump. Can you tell me that?

 

Have you given the wiring harness a thorough visual inspection? Pay particularly close attention to areas where the frame moved during the spline lube that are in close prximity to the wiring harness. It is most likely you pinched, crushed or stretched, one or more wires where they can touch the frame.

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I'm surprised that nobody caught that he used an ohmmeter on a hot circuit. Any voltage at all present when using an ohmmeter will give a false reading. All resistance readings should be taken on circuits with absolutely no voltage.

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BucksTherapy

 

Here's what I found:

 

Ign on. Fuse+ to the conector ends -

#1 12.13 V

#2 12.13 V

#3 4.3V

#4 0.31V

 

Am I to assume that wires #1 and #2 are the culprits because of their ohm readings?

 

Thanks

 

Erich

 

Is this Fuse #5? If so, trace the wiring, you have something shorted to ground. The same 12V powers both injectors, the charcoal cannister purge valve and the O2 Sensor.

 

As was mentioned, do NOT measure Ohms with the circuit powered up (unless you have one of those new (almost worthless) meters that switch automatically.)

 

Mick

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BucksTherapy
Did you take these measurements with the plug under the tank disconnected? If so I would trace out both of these wires to see if there is any damage. If not then disconnect it and take these readings again. If you get zero ohms between the fused side of fuse 1 and fuse 2 and ground with the connector disonnected then we will know the short is between the fuse box and the connector.

 

The readings you just gave are volts. I was looking for ohms of resistance as outlined above. As mentioned make sure you pull the each fuse before measuring the resistance between the post in the fused side of the circuit in the fuse box and ground. Do this and we will go from there.

 

I am not going to offer anymore "if" statements because I think I am confusing the issue.

 

Can anyone tell us what fuse feeds the fuel pump on the 1100RT and what else is on that fuse?

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BucksTherapy
Both injectors, cannister purge valve, O2 sensor Heat circuit.
That's fuse 6, fuse 5 is the Motronic.

 

You are not going to like this but the short could be between the fuse box and any of the following:

Either injector,

cannister purge valve,

O2 sensor Heat circuit,

Fuel pump relay, or

It could be between the fuel pump relay and the fuel pump.

 

The only way you can use a meter to find the short is if you isolate the positive side of these circuits. When you indicate the fuel pump fuse keeps blowing even with the fuel pump disconnected all you can rule out is the fuel pump and the wiring harnes between it and where you disconnected it.

 

To isolate these circuits you need to measure the resistance between the fused side of Fuse 6 and the positive lead into each of the devices with the actual device disconnected if possible. I would do this with both the negative cable disconnected from the battery.

 

I would encourage you to first do a thorough physical inpection. Look and feel for bruised, flattened, pinched, stretched or severed wires. This may mean sone deconstruction to put yourself in a position to really inspect each wire.

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I think I found it! The oxygen sensor assy on the exhaust that plugs into the harness was pinched by one of the frame assy bolts. It crushed the shroud and grounded the wire on the frame. I fixed it and reassembled it and it doesn't blow fuses anymore so that may be it. I will know for sure later this weekend when I finish reassembly and actually start the thing.

 

E

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