This may be a dumb question but i cannot find the answer after scanning many posts…

i removed my rear signals and brake lights etc as my f4i will be track only. The wiring to the undertail was a mess so i snipped the wiring. Following the bikes wire diagram the green taillight wires also ground the fuel pump…do i need to ground out these wires on the frame now that they are just hanging? My fuel pump will not prime and i have gone through almost every other part (besides replacing the pump itself).

 

Why don't you just touch the green cut wire to the frame and see?

 

No, you don't need to ground those cables. The other end of them is already connected to ground.

I'm afraid you'll need to find another source of your problem.

Two come to mind that are super simple - please don't be offended if you've already checked them - I only mention them because I've been guilty of forgetting them:

1) Your emergency cutoff switch
2) The tilt sensor in the front fairing (the pump won't prime without the front fairing connected

Good luck

 

Thanks for the suggestions. I have removed the tip over sensor, kickstand sensor, swapped out the fuel pump and ignition relays, swapped ecu’s etc etc….still no prime. I guess the next step will be to test the fuel pump and then go through the entire wire harness 🤦‍♂️

 

Having done that much, my next step would be to see if you’re getting 12v at the pump when the priming should be happening. That will tell you if your problem is the pump itself.

It’ll be very satisfying when you finally nail it!

 

eer - if you removed those sensors, it's not going to work at all?

 

Was bike starting OK before you removed taillight?

If so, undo everything you've done to wiring and restore wiring back to 100% OEM condition. Bike was working fine when it left showroom floor and will function like that again when wiring has been restored to 100% stock OEM configuration. Simple.

How to restore cut & snipped wiring back to OEM condition with straight-through junction like continuous wire. No need to pre-tin thicker stranded wires, too difficult to knot.

Proper way to reduce wiring for track use is to depin wires from connectors of unneeded circuits. Can restore back to OEM condition by plugging them back into connectors.

Here's stuff removed from harness with not cutting or snipping of wires. Only saved 1.5-lbs. Wasn't really worth it for effort involved.


Remaining minimal harness. No wires were cut, just de-pinned terminals from connectors to remove un-needed circuits.


Also put original working fuel-pump back in. OEM Mitusubishi pump is better than any fuel-pump you can buy. If pump really is bad, only replace with brand new factory OEM pump assembly from authorised Honda dealer. There's so many crappy 3rd-party aftermarket parts on market, that any 3rd-party part, especially electronics, must be tested and measured to confirm functionality before using.

 

Exactly!!! Without working tilt-sensor or kickstand switch, ECU will refuse to prime pump or fire sparks.

Let's get started with basics of troubleshooting: testing and measuring.

1. on original fuel pump, apply power and ground to its connector pins using test-leads with mini alligator clips. Does pump run?


It's same process as figuring out why headlight doesn't work. Immediate 1st thing many people do is replace bulb, but it still doesn't work. First step should've been to apply power directly to bulb to test bulb itself. Then you'll find that bulb is fine, but not getting any power from bulb socket. Won't waste time and money replacing perfectly working parts with brand-new perfectly-working parts and nothing changes.

So, when you're ready to actually test and measure to identify real problem, follow my guide here. It's 5-minute repair, I've fixed this no-start problem hundreds of times for people in remote parking lots in middle of night. Many times in pouring rain by phone as well!

https://cbrforum.com/forum/f4i-main-...1-06-a-163487/

Post ALL your measurements in order. DO NOT skip steps, you may hop right over wiring fault and end up at dead end.

 

I should have said that i bypassed both sensors, not just removed them.

 

The pump would not prime when i picked it up. As far as i can tell the bike had sat outside with no gas cap for close to 2 years. The original tank is completely rusted with a number of holes. I picked up a parts bike and swapped the tank/fuel pump over. The bike will turn on and attempt to start but no priming.

As for the taillight wiring it had been cut by previous owner to wire in the undertail. It was a complete mess and easier for me to just snip the wires. So now ive been working my way back through the bike testing everything that could possibly be the issue (except the fuel pump). Probably not a bad place to start! 🤷🏼‍♂️😆