How does this fuel pump work?

Hoping someone can explain to me what the heck I'm looking at. :silly: I took these captures off a customers truck that's equipped with an aftermarket auxiliary fuel tank and transfer pump. Pump current is in yellow, pump power (then ground) is in green.





It's a low pressure fuel pump, 5.5 - 9 PSI, but the current waveform looks more like a coil current ramp. :huh: The pump IS working. There's some voltage drop in the power and ground, sure, but that's not the problem.

What's going on inside this pump? Why does the current waveform look like this?

If it helps, the pump is part of a Titan kit:

www.xtremediesel.com/titan-5410050-trave...uxiliary-fuel-system

That looks like an interupter style pump rather than a rotary pump , what you are seeing is a solenoid coil being switched on then off. Interrupter pumps have an iron core in the centre that shuttles back and forth to give a linear pumping action like a bike tyre pump

That looks like a Facet (Bendix) interrupter style pump rather than a rotary pump , what you are seeing is a solenoid coil being switched on then off.

Thank you, sir.

Forgive my ignorance, but what exactly inside the pump causes the solenoid to cycle? A circuit breaker of some kind?

These days they use a Hall-Effect switch, back in the day with the early larger ones and the SU diaphragm pumps it was contact breakers

www.fuelpumpsonline.co.uk/facet-posi-flow-pumps-12v-1819-c.asp

Then can be quite noisey I had one of the cube style pumps in my racers and it made quite a racket it was tiny but pumped a lot of fuel was very efficient

www.fuelpumpsonline.co.uk/facet-8-c.asp