NICK JONES
Cadet
- Joined
- Aug 9, 2002
- Messages
- 29
Problem with fuel starvation. 135 V6 Mariner. Boat has a 20 gallon aluminium bow tank, don't see any anti-siphon valve unless it's inside the fully welded tank. The fuel pick up is 3/8" bore aluminium tube welded into the top of the tank, so I don't know what it looks like inside the tank. The tank vent is working fine, and there is plenty of fuel delivery but it comes with air bubbles (fitted a section of clear fuel hose to see). Don't know if it happens with a full tank but it does with 5 gallons or less. Thought it must be a leak in the fuel line / water separator connections / bulb so applied a vacuum test from the motor to the end of hose at tank which held up fine with no leaks. When disconnecting fuel pipe from the motor and letting the fuel siphon out of the tank there is no air content but every time the priming bulb is squeezed and released the fuel contains lots of air.Tried a new priming bulb same thing happened. Also the same thing happens when the motor is running above 2000 rpm with subsequent loss of power until the "soft" bulb is squeezed. The fuel only seems to contain air when drawn through the line by vacuum pressure. (I also connected a "Mityvac" vacuum pump and this drew air bubbles from the tank).Could it be that the aluminium fuel pick up pipe is fractured inside the tank ? If it is it seems odd that it will hold up to siphoning okay ,with no air, but not a small amount of vacuum. Any ideas anyone ? 