Baffled by fuel feed, anybody been there before?

1995 VFR750F, I've had lots of old Hondas and three VFRs and I knew I was going to have to get around the "no more parts" and charging system issues. And I have, at least the charging issues, with a mosfet hard-wired into the harness with heavier gauge wiring and located on the swingarm for air flow.

But THAT FUEL!!
I bypassed the petcock with a plate of steel brazed to a threaded pipe, which I then plumbed to a very good fuel filter (since the in-tank filters are gone now), and then plumbed to an electric brass valve, powered to the "on" position when the key is on. From there it goes to the fuel pump and then to the carbs as stock.

So hoping for the best, I rode it all over the neighborhood and waited for problems, all good. Rode it to the nearest ethanol-free gas station and filled it up, all good. Picked up some speed on the way home, all good. Got 5 miles from the gas station to my street, and it choked and died three doors down from the house. Pushed it home.
I know we're all thinking "fuel vent" but how did it go five miles from the gas station?
After an hour of sitting, it started right up, of course. So...not enough fuel from somewhere in the system, but I sure as heck can't find out where.

Any ideas?

 

It takes awhile for enough vacuum to build up to shut off the flow of fuel. Pop the cap and see what happens. If there is a big whoosh as air rushes in you have found the problem and the bike should start up after it fills the float bowls. Clean the vent on the cap and all is good.

 

I'm looking for a vent hole but don't see one. The overflow vent for the tank is clear, but is there a vent hole for the cap itself that I don't see?

 

yep, it's a small coin -sized bit of black plastic under the filler cap. blow through the hole to be sure it's clear.

 

I don't have that...my cap looks stock and the keys match the ignition, but I don't have that rubber plug that I can see in this photo of a new cap:

 

that probably means you have a california emissions cap. black bit in photo is the vent.

 

Here's mine.

 

i see no vent there.

 

Well I'm sitting on the side of the road... Got the problem to replicate easily lol.
There was no woosh of air when I opened the cap immediately when it cut off.
Now I think maybe I'm losing a coil ass the engine barely gets warm?

At very near the same mileage/time on the bike.

Ideas?



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try bypassing the unreliable fuel pump relay as illustrated in the honda service manual. just one jumper wire may cure the problem.

 

When I get this whale pushed the last mile to the house, I will is the city traffic don't get me first

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not fun pushing a heavy bike. good luck. have a beer or two when ya get home.

 

I pushed the bike as far as the nearest bail bonds place, which is staffed all night. Then I walked home with my gear. Then I rode over on my RELIABLE SUZUKI and locked it to a pole. Every time a little while would go by, I would try to start it. It would turn over fine, and every time when I first tried it, it would fire up like it was going to start, but then just go back to spinning over.
I'm pretty perplexed. I'm going to have to jumper the pump and see if that's it, and ride it without the tail fairing on so I can see the fuel in the filter...unless it's spark after all. Is that a thing with these bikes?

 

it's not

 

ok, thanks...next is to try it again (in daylight). When I jump the solenoid, what do I jump to? won't if flood if I hook it straight to the battery?

 

pump quits pumping when it senses that carbs are filled. find the fuel pump relay (not the solenoid) and add the extra wire. you need the shop manual.

 

Thank you, I appreciate the help.

I have a manual with wiring diagram.

I think I'm asking where to jump from, and to. I've replaced fuel pumps but I never had to mess with their relay before.


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Like this guy did?



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It was the fuel pump itself. After work I went to where I locked the bike and jumped the fuel pump straight to battery. Nothing. Then I removed the fuel pump from the fuel system and from the bike completely and jumped it to the battery. Nothing. Then, since the tank was almost full, I routed the fuel lines back together some kind of way long enough to fill the bowls with fuel, and rode it home like that with the fairing just hanging on.

So I'm not mad if a fuel pump almost 30 years old quit, I'll get another on there. But could someone tell me about this relay? How do I source one to keep with the bike at all times for when the original fails?

 

avoid replacing it with any $16 chinese pump.

when the original relay fails just use the jumper wire at the relay plug.

sometimes the original pump can be fixed by cleaning the moving points under the black cap.