86 K75 Fuel Pump issues

[WesFont]

I'm trying to get my K75 running after sitting for 2 yrs. I am starting with the fuel pump. I purchased a new fuel pump, filter, hoses. Cleaning the old tank out and saw that the "relay" with the wires that were powering the fuel pump were connected to, was pretty corroded. I cleaned it pretty good. None of the wires seemed to be frayed or disconnected. I installed the relay and floater back and installed the new pump and filter. Everything looks good, added fuel and tried to start. Nothing, I didn't hear the whirl of the fuel pump. So I'm guessing there is no fuel getting to the engine. So i'm not sure what to do now.


How do I know if its the pump or the wiring? (The pump was bought brand new, so I'm pretty sure its good)   
Is there a way to test the pump thats not in the bike? I do not have any electrical testers. (If it needs something like that)
And if its the the relay, do I need to replace the whole thing or can i bypass it some how?

Straight Newbie
Thank You for any help

[Kontoboy]

Did you hook up the wire harness from the tank to the bike?

Do you know if your fuel level sending unit is working?  My understanding is if the if the sending unit indicates the fuel level is tool low it will shut off the pump to protect it.

With the pump out of the bike you can jump your 12 volt battery across the electrical connectors at the top of the pump.  Check the polarity though--probably not a good idea to run the pump in reverse. And don't run the pump dry for too long.

You can also run your voltmeter to the connectors inside the tank to see if you are getting 12 volts when you try and start the bike.

As always exercise caution around fuel.

Kontoboy

[Inge K.]

You have checked the fuse?.......the fuel pump only runs when the starter button is pressed (and when the engine is running, of course).

[WesFont]

Yes the wire harness from the tank to the bike IS hooked up. Not sure about the fuel level sending unit, if it's working of not, how would you check that?

[WesFont]

Fuse is good. I don't hear anything from the pump. At least it doesn't seem like it, the starter is pretty loud.

[Inge K.]

I don't hear anything from the pump. At least it doesn't seem like it, the starter is pretty loud.

It's enough with a short momentary push on the starter button, the fuel pump should run ~1,5 sec after
the starter have stopped. To narrow it down measure if you got power at the fuse while pushing the
starter button.

If no power is present, the relay don't close its contacts. The relay is managed from the ignition ECU,
which grounds the relay coil when it reads a signal from the starter button or hall sensor.

The other side of the relay coil have constant power as long ignition switch and kill switch is on.
Could be a idea to remove the relay and measure at the contacts in the socket.

[WesFont]

My pump is working fine. I tested on the battery. Is there a work around for the plug. I am having a hard time finding a replacement Fuel Level Sender.

[rbm]

Do you know if your fuel level sending unit is working?  My understanding is if the if the sending unit indicates the fuel level is tool low it will shut off the pump to protect it.

This is an incorrect statement. There is no output from the fuel sending unit that provides a signal to the ICU or ECU to shutdown the pump. The fuel sending unit has two outputs.  One is a resistance proportional to the level in the tank.  That output goes to the Additional Instruments Connector under the tank.  The second output is a ground signal that comes on when the fuel passes a predetermined level in the tank.  This output goes directly to a light in the instrument cluster. 

Attached to the same passthrough connector on the sending unit are two additional terminals for power to the fuel pump and ground.  These just pass directly through and have no connection at all with the fuel level sender.  Often, the wiring inside the tank becomes hard and brittle.  The insulation with crack and break off, exposing bare copper wires.  If yours is in such a state, it could be reconditioned if you can find wire with fuel resistant insulation.

Yes the wire harness from the tank to the bike IS hooked up. Not sure about the fuel level sending unit, if it's working of not, how would you check that?

Check the tutorial I wrote on the K100-forum about reconditioning the fuel sender.  If this procedure works, then you don't need a new sender.

[WesFont]

Ok, I am definitely a newbie, I replaced the relay, found one on ebay for $45, unfortunately it was for a 75s and I have a 75 c I think. Anyway the connectors were different at the end. Look for that if anyone else has this problem. I ended up splicing all the wires. The relay works now. I have the correct fuse and the fuel pump is working now.

I try to start it now, It still doesn't quite turn over. When I try to start it now, right after releasing the starter, I hear loud bang like a back fire, but the engine doesn't start. When I checked the spark plugs, they had a bit of oil on the tips. So my next plan was to take the valve cover off and see if there was excess oil. Clean it out and try again. Would that prevent the engine from starting?

[rbm]

I don't see any reason to remove the valve cover.  Are you sure the residue on the plugs is oil and not fuel?

If the bike was sitting for some time and the owner did not put fuel stabilizer into the system, it is possible that the injectors are plugged.  You might want to test the injectors on or off the bike.  One method off the bike is to hook them to a battery source to make sure that they function (they should click for each contact with the battery).  On the bike, it is possible to remove the injectors as an assembly from the bike still connected to the fuel rail (make sure the engine is very clean around the injectors beforehand; don't want dirt in the inlet ports).  Turn the engine over and they should all spray fuel.  Use a bucket to collect the fuel for this test and observe strict safety rules since you'll be playing with gasoline.

Have you followed Bert's "bike won't start" flowchart?

[K75RT Keith]

Had the same issue with mine.  2 Options: 1.Pull the injectors and send them out for cleaning (Mr. Injector in Idaho does a good job at a reasonable price).  2, Get a container of high quality fuel injector cleaner (not the buck a bottle crap) and put a heavy dose in the tank. 

Just remember, the more you get big backfires the more likely you are to end up replacing the exhaust.