RE: which ELECTRIC 6v PUMP to buy for homade GASOLINE fueler??
Put a candle or a lit cigarette next to the plane when filling it. Move it around until "something" happens.
Let us know which locations were more likely to ignite the vapor.
The problem with gasoline isn't that it is flammable in the open air, it is that the liquid will readily evaporate and reach the combustible vapor density when heated by a flame. Gasoline always makes me wary.
The Sullivan smoke pump is sealed, isn't it? If so that would (could/should) contain any spark from the motor. If it isn't sealed, put some capacitors on the motor like an RC car and then seal the case with silicone. As I recall your switch is mounted inside a PVC box, which should contain any spark from that location. Be sure to plumb the vent line from the plane back into the fuel tank to minimize the amount of escaping vapors, which also keeps gas off the ground (where it kills the grass or destroys the asphalt, depending on the surface).
Those two steps should counteract nearly potential issues.
FWIW I met a guy who was nearly incinerated at work. He was working on a pipeline that was pumping some light aromatic hydrocarbon (I forget which). It was cold outside, he was nearing the end of his shift before going on vacation somewhere warm, and out of laziness (and against company policy) he left his work truck idling when he went to work on a pipe fixture. When he opened a valve he was sprayed with the liquid, covering his hemet and face shield, and his protective clothing. He turned an ran toward the emergency shower and while running, he heard his truck engine idling. His path top the showers took him about 20' away from his truck, and no closer. The vapor from the fluid ignited when it hit his truck (either hot exhaust or something electrical) and immediately engulfed him in a fireball, which then ignited the fluid on his clothing and then his finally skin.
He spent many weeks in a coma and endured many surgeries. More than two decades later he is still alive and works as a motivational speaker preaching the value of safety.
We have the potential for a catastrophic event if we have a) air, b) gasoline vapor, and c) ignition source. Eliminate one and a fire cannot occur. If the electrical system is sealed to contain any and all potential spark sources (motor commutation and back EMF, and at the switch), that will eliminate MOST of the fire potential.
Again the problem is not a combustible vapor forming and remaining around the switches, it is just that the ignition of the vapor will cause liquid gasoline to evaporate into the atmosphere, where it will ignite. The potential risk is extraordinarily high, so we need to be careful with the design (enclose all switches, etc) and take care to be clean and wipe any spilled gas off the plane, pump, fuel can, filling lines, etc.
Finally (and I apologize for this long post) be sure the hook a return line from the vent line back into the tank. Odds are the vapor blowing out the vent line is going to be the source of the problem.