Let's talk fuel pumps

[boscoe99]

A while back it was reported that resistance in the wiring to a fuel pump can result in greater current draw by the pump. I recall that when people were having fuel pump fuses blow this was stated as being a possible reason.

Do any of you recall this?

I have a fuel pump from a Yamaha SHO motor. The motor is running continuously and is pumping gasoline out of a container, through about a ten foot length of 3/8ths ID hose, and back into the container. When wired directly to a battery the current draw is 2.9 amps. When running the battery is indicating 12.3 volts so the resistance is calculated to be 4.2 ohms.

I decided to put a one ohm resistance into the circuit to see what happened. The current diminished to 2.3 amps. Consistent with ohms law that if the voltage is a constant then as the resistance increases the current flow will diminish. The ohms law math adds up.

I got this idea from seeing that the Yamaha OX66 uses a resistor to decrease the fuel pump flow when the motor is running at low RPM's and obviously does not need as much fuel flow.

Do my findings make sense to ya'll?

Where in the hell is fairdeal aka mr. pratt who eats no fat.

[rodbolt17]

the OX66 motors use about a .53 ohm resistor.
yes Ohms law works and works very well.
I understand Ohms law due to 6 yrs as an FC in the USN.

BE&E,FC (A) and FC (C) school.
the C school was on the CIWS mod 15 block 1.
plus a lot of other electronic and electronic test equipment schools.

[boscoe99]

the OX66 motors use about a .53 ohm resistor.
yes Ohms law works and works very well.
I understand Ohms law due to 6 yrs as an FC in the USN.

BE&E,FC (A) and FC (C) school.
the C school was on the CIWS mod 15 block 1.
plus a lot of other electronic and electronic test equipment schools.

I know. All I could get was a 1 ohm resistor. In the form of my old and tired 100 foot extension cord. Only thing I had that could handle 3 amps.

My newer 50 foot cord had too little resistance.

[99yam40]

My thoughts are that as the voltage available at the motor drops, the RPM drops also. this would reduce the output pressure/flow.

I always delt with AC motors that wanted/needed to run at a designed speed. if you lowered the voltage(increased resistance) to them they would draw more amps trying to get up to that RPM they were designed to run at.

I believe Rod is the one that corrected me on the types of DC motors and what they did.
may have been on starter motor we were talking about though

[rodbolt17]

you simply CANNOT compare an A/C motor with a D/C motor.
they work way way different.