Here goes. Installed a Koso ditigal speedo along with a new streetfigher-type headlight. Got all to function, but now the fuel pump wont prime. Here's what I've done to troubleshoot: put fuel pump directly on battery, it works. Switched out the fuel pump relay, no change. Switched out ECU, not change. Switched out entire wiring harness, no change. I can get her started with fuel in the carbs, but she dies out as soon as that's gone. What am I missing here?? I know my 98 F3 does not have a BAS, and I've disconnected the kickstand kill switch. What else could I try???

Any suggestions would be much appreciated as I'm getting to the point where I may have to just take her into the repair shop.

 

On an F3, the fuel pump does not prime. It only runs when the engine is running. If you want to test (which it sounds like you already have) you can disconnect the connector on the Fuel Cut-off relay and put a jumper between the Black and the Black/Blue wires. When the key is turned on, the pump should run.

 

Thanks for the reply!

I do notice that it "sputters" when I try to start the engine. I can feel that as I'm holding the pump and engine is cranking. if I get the engine to start by manually adding fuel into the carbs, shouldn't that be enough to start the fuel pump and keep the motor running?

 

You don't need the fuel pump for the bike to run. Bypass it and see if it runs well on a gravity feed (petcock to carb).

 

Thanks for the reply.


I went ahead and switched it to gravity feed and I can still only get it started if I put gas directly into the carbs, after which it dies within a few seconds. I'm going to check and make sure things aren't stuck/plugged some how. Any suggestions?

 

Maybe the breather tube for the tank is pinched off. Correct me if I'm wrong but doesnt air need to enter the tank in order for fuel to come out of the tank. I would think a quick way to check this would be to pop open the fuel cap and listen for a vacuum release. Or leave the cap open and try to start the bike.

 

I know this is a dumb question but is the petcock turned to the "on" position? Does it have the oem petcock? I ran into a similar issue with my f3 when I first got it, the po had fitted a different petcock not meant for the bike, had to output lines that merged into 1 then into the filter, so on and so forth. I removed around 9" of unnecessary fuel line that was hodge-podged together with kinks all over and capped one of the outlets now it works great. How is the inside of your tank? Dirty? Inspect the screen on top of the petcock? Sounds like a clog, I'm no mechanic by any means.. Do you have a service manual? There are tons of troubleshooting tips and such. Good luck.