Why does 1986 Volvo Penta Bayliner 125hp IO not run after replacing mech fuel pump with electronic one when you hook to main tank yet runs great with the feeder hose just stuck down into a gas can?

make sure the old pump is not restricing flow of fuel, by completely removing any fuel lines to old pump. then check to make sure fuel tank cap is venting to allow air to displace fuel that is pumped from tank, easiest way to check this is to just remove fuel tank cap and see if engine runs

You should also be aware that most fuel tank connectors (plug and receptacle) have automatic shutoff systems. You may be missing the actuator pin in the plug part that opens both shutoffs. Look at a new plug in the store that is similar to yours to see if anything looks different. You could also check this by removing the hose that exits the primer bulb (and feeds to the motor), then pump the bulb with the remaining hose attached to your tank and see if you get a healthy flow of fuel (into a clean catch cup or back into your tank filler cap, not on the ground!!!).

• How do you change gear oil in my 60 horse power evinrude outboard motor?
• What year is a mercury 35 hp outboard serial number 9420742?
• Where are battery ground wires for twin mercursier 5.7 engines?