Help VF1000F fuel problems

[B80EBL]

Hi

I have just rescued a 1984 VF1000F. First problem is starting. Ignition on, no fuel pump - tested fuel pump -ok. No feed to pump. Traced wiring to a three pin relay. the relay has two feeds going into it (blue wire and black wire) and nothing coming out on the white. If remove relay and bridge the white wire to the pump and the black wire (I think goes to the stop/switch) the fuel pump bursts in to life.

Does anybody know if this is correct and I have a faulty relay? or is there a fault with the wiring (I don't think so but always listen) and what happens if the relay goes missing and it's just left bridged?

Thanks in advance

[RandyM]

Hi B80EBL, it sounds like your kill switch may be the issue. It seems to be acting as if the kill switch is engaged.

[masonv45]

The fuel pump cut off relay gets it's trigger signal from the coils. The Kill switch cuts power to the coils.

[JamieDaugherty]

This is actually pretty common (relay failure). Most of the time people just jumper the plug so that it's always "on". A good friend of mine had a 1000F that was used this way for several years and never experienced any issues because of it. The bike was that way when he bought it so there is no way to know how long it had been used like that. Give it a shot and I'll bet you are good to go.

[B80EBL]

The bike runs when relay bridged. Not tested kill switch, just switched off with key but will try tomorrow. It hadn't been started since 2000 (date of the tax disc anyway) the fuel stank so I changed that for some fresh petrol - does anybody know if these run on unleaded or need an additive? It cranked for 5 or 6 seconds and started. The Japs sure know how to engineer - I'll be swearing at them later when I can't get something off!! Thanks for all your help.

[JamieDaugherty]

If it runs with the relay jumpered then there is nothing wrong with the kill switch. I'd leave it jumpered and start riding!

[kevcov]

i am having the same problem on my 84 vf500. im going to to that to since i bridged it to do a flow test. but how is the fuel presser regulated? is it just by the fuel pump or is there a regulator down the line?

[masonv45]

The fuel pump is a low pressure pump. When the carb bowls fill, the float needles close and the pump cannot overcome the back pressure. As the fuel is being used by the carbs, the needles open, releasing the back pressure, and the pump starts pumping again.

Basically, the fuel pump is powered all the time the engine is running. It just pumps when it can overcome the back pressure from the float needles.