Lathehand, I don't know the answer, but simple physics says that the ONLY way that the primer ball collapses is if it is under a vacuum That means that the engines' fuel pump is working properly and you can probably eliminate everything engine wise from where the fuel line connects to the engine up to the carbs. Sounds to me that somewhere a vent is not open or there is a clog. When you switched fuel tanks, did you make sure that the new tanks vent was open? Does he have a fuel filter and if so where is it located...before or after the primer bulb? 
__________________
1987 V20 w/1987 150HP Yamaha on a Shoreland'r Trailer
1978 16.5 Airslot w/1996 120HP Force on a Four Winns trailer
1996 V21 w/1993 200HP Mercury on a Shoreline Trailer
All towed by a 5.7L Hemi Durango.
If God didn't have a purpose for us we wouldn't be here, so
Live simply, Love generously, Care deeply, Speak kindly.
(Leave the rest to God) 
Silence, in the face of evil, is itself evil. Not to speak is to speak, not to act is to act. God will not hold us guiltless.
|