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Discussion Starter #1
I'm doing some research on fuel pump diagnostics and I came accross an article on popular mechanics website. and it suggests that a fuel pump will have more amp draw from a clogged fuel filter.

As far as I know, all fuel pumps are not pulse width modualted. which means they get a constant supply of voltage all the time. what's controlling the pressure is the regulator. so the voltage is system voltage minus the resistors. so the only thing that would change the current flow would be charging voltage and the pump heating up and causing resistance.

lets say the filter is clogged. it would build 100 psi at the filter and heat up which would make amp draw go down. what's changing is the pump is working harder. and it's not persay putting any more of a load on the charging system. technically less.
 

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Discussion Starter #3
Which fuel filter are they talking about: pre-pump, post-pump, or in-pump?

Also, when the say "the pump is working harder", what do you mean? To me, that implies that it's using more energy, which means the current draw has to increase.

post pump, cause they where talking about neglect of replacing it. I didn't about this scenario for the in tank.

work harder as in it's being ask to maintain 100psi ( just say) if the post filter was completely clogged. as opposed to running a system at 35-40psi.

yes more energy, but we can't ignore the ohm's law. the volts are given, and the restence is the pump and all the wiring ( and heat). The way the pump is setup the computer is not allowing more or less power go to the pump to control pressure. it's a constant flow of power. and the pump doesn't have a computer with a set of resistors.
 

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Discussion Starter #7 (Edited)
normally, the pump is supplied with constant system voltage. the pump runs at 35-40 psi because of the regulator. If you install a b&m fpr or block off the return line the pressure goes up to max with out changing the amount of electricity going through the circuit. so technically the pump is flowing at it's max capacity all the time. the pressure is changing. if you raise the pressure by completely blocking off the return line the pump works harder at maintaining 100 psi ( it's at it's redline). ie the flow and PR of a turbo. different effeciency at different pressures.
 

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If you install a b&m fpr or block off the return line the pressure goes up to max with out changing the amount of electricity going through the circuit.
Are you sure? Have you confirmed this with measurements? I always thought current draw increased with fuel pressure.

I'm still not sure what you mean by "working harder" in terms of physics. What is the metric for "working harder"? Is more torque required from the pump, is it consuming more energy, etc.
 

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Discussion Starter #9
Are you sure? Have you confirmed this with measurements? I always thought current draw increased with fuel pressure.

I'm still not sure what you mean by "working harder" in terms of physics. What is the metric for "working harder"? Is more torque required from the pump, is it consuming more energy, etc.

I haven't confirmed this, it just doesn't make sense to me if you consider ohm's law. where are the amps coming from?


well, I dunno the specifics of working harder, but I would think it would be. does a pump not have a Pressure ratio and flow where it's at it's max efficiency?
 

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Discussion Starter #10
ok, maybe not working harder, but it's efficiency is going down or its getting hotter.

heat = resistance. resistance = less current.
 

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Why does more heat mean more resistance? It just means less efficiency. If anything, heat would mean more power. Since power increases exponentially with current and linearly with resistance, more power/heat would be created with less resistance and more current. That might be what's happening with the fuel pump.

To answer your previous question, yes, pumps have efficiency maps.
 

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ok, maybe not working harder, but it's efficiency is going down or its getting hotter.

heat = resistance. resistance = less current.
What kind of winding does the pump have inside it?

Remember, if something is wired in parallel, more resistance doesnt necessarily mean less flow. Depending on the type of windings (delta, "y" etc.) This could possibly effect how it draws current vs. its resistance.
 

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Discussion Starter #13
really this is getting away from my main point that the pump is connected directly to the battery and stays connected while the cars running. the power flow doesn't stop or change ( it's an electric motor, not belt driven or anything) The only way to increase current would be to connect the pump directly to the battery or use a higher volt battery. we know battery voltage and we could measure resistance on the ground and positive side. A=V/R. Where are the extra amps coming from?
 

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where is lkaiburn,rrussel,shifty35, or the others. to quell all this unsubstantiated theory or take on said subject
 
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