25hp Yamaha (1987) fuel pump questiions

[over60pirate]

I'm trying to get my, new to me, 15 Yamaha, 1887, 2cyl/2cycle, motor, ready to use.
The motor runs on the stand, but the fuel just drips into the fuel filter. The filter doesn't fill up. What drips in the top, just goes thru. I don't think it's getting enough fuel, to work in the real world (on the boat, in the water)

I ran the suction line from the filter, directly into the tank, and it was the same.
I them took the fuel pump apart, and it looks ok. It was very clean.
Is there a way to check the vacuum/pressure form the crankcase, that makes the pump work?
I would like to check that, before replacing the diaphrams in the pump.
Thanks for any help.

 

[robert graham]

Re: 25hp Yamaha (1987) fuel pump questiions

I'm not sure I understand your question, but is your primer bulb O.K.?...it has ball check valves in each end that hand pumps gas up to the fuel pump, filter, then to carbs. The primer bulbs can get old or the ball check valves get stuck and don't work properly. Also check all fuel line connections and fittings for air leakage. Good Luck!

 

[over60pirate]

Re: 25hp Yamaha (1987) fuel pump questiions

I ran the suction line from the filter, directly into the tank, and it was the same.

Doing this, I eliminated the orig line, bulb and connection at the cowl.

 

[robert graham]

Re: 25hp Yamaha (1987) fuel pump questiions

If the motor "runs on the stand", what makes you think it won't run in the river?...maybe it's O.K.?....I believe that fuel filters sometimes have air in them...maybe not a problem?...

 

[99yam40]

Re: 25hp Yamaha (1987) fuel pump questiions

Never heard of testing the pulse to fuel pump, but if reed or crank seal is bad it probably would affect the operation of pump.
might try rigging up a pressure/vacuum gauge with rubber hose to hold against the pulse port to see how it reacts on your motor and the on a different motor to compare it to.
Does the motor run and idle well on the stand , and is the compression OK?

 

[over60pirate]

Re: 25hp Yamaha (1987) fuel pump questiions

The motor does run and idle ok on the stand. When revved up the fuel bairly drips into the filter. I'm sure out on the water, under load, it will starve for fuel.
I think I'l get a new fuel pump for it.