I've pulled the fuel pump from my 87 and am trying to see if it works (Someone mentioned that I may have connected it wrong before and ruined the pump). I thought there was a thread explaining exactly how to hook it up directly to a 12V power supply, but I cannot find it now.

There is
- a black/blue wire that goes to the connector and runs straight into the body of the pump,
- a green wire that goes to the connector and attaches to what I think are called the "points" (? not sure if that is the right term),
- a black wire coming from inside the pump and connecting to the points,
- and a silver wire bridging two spots on the points.


The manual details a procedure to connect the pump to a beaker when it is connected to the bike, but not when the pump is removed from the bike. I found a few on repairing a pump but all he did was replace what he was calling the points.

Thank you !

 

The pump doesn't work like a motor. It's more like a solenoid and plunger. When power is applied to the pump, it energizes the solenoid which pulls a plunger up against a spring. That movement causes a diaphragm to create suction to pull fuel from the tank. On the other end, it causes the contacts to open up, which removes power from the solenoid. The solenoid turns off, the spring moves the plunger back in the opposite direction, causing the diaphragm to push the fuel out towards the carburetors. This then allows the contacts to close again which energizes the solenoid and the process repeats. One way valves allow fuel to only flow in one direction.

It should be noted that the fuel pump does not receive a full 12v supply. It receives a pulsed 12v that is tied to one of the ignition coils. Supplying 12v continuously for a long period could burn it up. There is a Fuel Flow test in the F3 manual that has you disconnect the connector from the relay and short the Black and Black/Blue wires. This will cause the pump to continuously run when the key is turned on. This pump is a low pressure pump and only takes a few PSI of back pressure to make it stop pumping. Having it stop is not a problem since it only has to keep the carburetor bowls full of gas.

 

Thanks @IDoDirt for the detailed explanation !. What I am taking from this is that I need to test the pump while it is hooked up to the bike. That means there’s a few things to sort out on that side.

 

Excellent explanation @IDoDirt . Thank you!