Fuel Pump Woes

Check pump, vent, and relay before bypassing?

Okay, I am a newbie to bikes, but I was an auto mechanic for quite a few years, and I have a couple of questions before I run downstairs and bypass the pump.
1. What is the best way to test the cap vent? I found a pinhole on the shoulder of the cap and tried to blow through it with a length of tubing--no go. Any suggestions?
2. How can I test the fuel relay?
3. The pump. Yeah, I tested this, or think I did. I disconnected the outlet line at the joint where it connects to the line that feeds the carbs, cranked the motor over, and no fuel was driven through the line. The pump clicked once and held that position, no matter how long I cranked the motor.
Brief history might help. The bike is a 1984 V45 Interceptor (FV750) and it only has about 1300 miles on it. When it was given to me it kept dying, and I finally cleaned the tank (and lined it per the advice of the parts man at the local Honda store), drained the carbs, and all seemed well for the first 150 or so miles. Then it sputtered, died, and left along the side of the road. I have good spark to the plugs, but, according to my pump test, no fuel to the carbs.
I appreciate any advice and thanks for the time!

 

1) Spray carb cleaner through it. It's not uncommon for the vent to be plugged like you describe.
2) I use a volt meter. Check that voltage is coming in (to activate it) and it should have an output voltage. If not it's no good. That's really common by the way.
3) This could be your relay. The pumps are known to fail also, that's why I crap-can them on my bikes right away and switch to gravity feed.

Per my PM you should check to see if that liner has separated from the tank (like they all do). Let us know what you find.

 

My pump works every now and then and has left me on the side of the road a bunch of times now. I have to let the bike cool down and the pump will start working again. I got sick of messing around with it, so I just yanked the pump and put the lines together to complete the circuit.

Will this be ok, or should I make it more direct? Should I fabricate something to go straight from the petcock to a filter to the carb?

After I disconnected the pump and went to gravity feed, I took it for a 5 mile ride and went to redline a complete times and it ran like a champ.

 

Make sure to also remove the filter if you haven't already, then it should be good to go.

 

I notice ever since I eliminated the fuel pump the idle seems to be all over the place. It always stays between 900 and 2000 but I feel like I'm constantly adjusting it depending on the day. It is not bouncing up and down, but staying constant somewhere between 900 - 2000 RPM.

Don't get my wrong, the bike runs great and it will go to redline all day long, but the idle just seems weird to me.

 

I don't think that can have anything to do with the fuel pump (or lack there of). My VF's tend to be persnickety like that too, maybe not to that degree. I'd say it sounds like you have a vacuum leak somewhere, that's often the cause of idle problems like this.

 

Sounds to me like you need a carb sync...

 

Thanks for the info guys... The bike is running awesome now that I eliminated the fuel pump and I couldn't be happier.

As for the idle it was good yesterday and today staying around 1,400 give or take 100 or so. The carbs were just cleaned and synced in June, so I don't think it's that. The problem just recently started after I eliminated the fuel pump. Probably just a weird coincidence, but I'll keep my eye on.

The more I look back on it, the change in idle seems to be when the weather is extremely different. So in the cold mornings the idle will run higher and in the hot and humid afternoons it would run lower.

 

I too, seem to be running into that problem. Upper 80's in the afternoon and during my night drives, 60's or less, I to have to adjust the idle 200-+ for that perfect 1250rpm.

It don't matter to me, just as long as it runs right : )

But yours seems to be running really well. I never take mine up to WOT.

I've only tasted the power of 6k rpm. LOL!

LL

 

hey guys,
does anyone have a picture of how they routed their fuel line for gravity feed. I have an '85 VF700F and it seems like I would have to run my fuel line off of the tank outlet, down and around the rear shock bracket and then over the rear cylinder head to the carbs. If I got it right please let me know

 

Hey everyone,

just came across this thread when I was trying to track down a couple of unused connectors on my 85 VF500F. From what I've been able tell, the connectors were for the fuel pump and relay. Looked in where the pump should be and it's not there. So I was in a panic about having to find a new fuel pump and filter. Then I remembered that I had seen something on this forum about ditching the fuel pump and going to gravity feed. Now I can rest easier knowing that it looks like the previous owner had done this.

 

gravity feed on 84 vf700 intercepter

I was told that my carb inlet is higher than my tank outlet so gravity feed wont work also i was wondering if anyone has tried the vacuum operated pumps

 

Not true - the fuel outlet is higher is than the level in the bowls. Plus, the real driving force is the surface of the fuel in the tank, which is clearly much higher than the carbs.

 

Two reasons for the fuel pump.

IT can be shut of electrically and automatically with a mercury switch if the bike tips over.

The other reason is with a fuel pump if you do have a fire, it will keep spraying the gas on the fire.


You do not need a fuel pump on a carburated motorcycle engine.
It has a kill switch.

No fuel pump, no fuel pump relay, No fuel pump fuse, no fuel pump to drain your battery. if you have a leak fuel will not SPRAY all over you and your garage, lighting your house on fire.