Vboost & fuel pump not cycling upon power up

[wayne z]

Powered up my barnfind Vmax yesterday. Since it hasn't run in 4 years, I decided to spray some oil down the intakes and spin the motor up some, without plugs, to limber it up some before installing my freshly rebuilt carbs. I left the plugs plugged in and hanging and grounded them with clip leads, great spark wahoo!

Compression checked OK with my shadetree compression tester. PVC sink supply tube with cone rubber gasket jammed in the plug hole and my thumb over the other end, If it pops hard with spin over it's good enough to try to run it LOL.

I did discover 2 problems though, maybe related. Neither the Fuel pump or the Vboost cycles, when key is turned on. Checked all the fuses I think. Main 30 amp was blown previously and replaced yesterday. Other fusebox OK under left side of fake tank.

Anyone have ideas what to check next?

Thanks,
Wayne

 

[Miles Long]

The fuel pump will only cycle if the bowls are dry.
The v-boost control unit is tied in with the vacuum pressure sensor - see what happens once everything is buttoned up.
Cheers!
Edit - I'd also buy a manual, either Clymer or Haines. Best 30-35 bucks you will ever spend on the bike. Then trace out and find every connection you can, clean and reassemble using di-electric grease. Wiring and components are a weak point on this bike, especially the older ones. Four years sitting unused in a hot and humid climate probably didn't help either.
Good luck!

 

[wayne z]

OK, thanks for the info. I have genuine Yamaha service manual, but I've found some discrepancies in it about jet sizes, and about fuel pump wiring on my bike.

The electrical schematic shows one wire connected to the fuel pump with case ground.

My bike has 2 wires for the pump, one is hot with key on and one is ground i guess, but I got a slight millivolt reading on it.


I tried jumpering the pump various ways and got no spark or operation , so I assume it's bad.

I found that the Vboost controller's case was unsealed and a tiny mud dauber nest was in there. Everything looks to be potted very well, enough to handle this, but maybe not.

So, I prolly need a pump and boost controller.

I have cleaned and greased most all the connectors with copper grease.

Can anyone shed light on the 1 wire vs 2 wire fuel pump vs schematic discrepancy?

 

[wayne z]

OK, here's a follow up. The 2 wires are supply and ground and the ground may interface with the Vboost system. I dismanteled the fuel pump and found the armature plunger stuck. Worked it a little and put it back together and installed it.
Now it pumps fine and the Vboost started working too! All is good, now I will proceed with carb installation.