Testing Electric Fuel Pump Problems with A Voltage Drop Test

Incorrect testing an electric fuel pump can give the impression that the fuel pump is bad. This can be avoided with a voltage drop test.

[ssss-dfqz]

So what exactly is going on here for it to show that drop?

The way I'm imagining it (as a noob) is that when the pump pulls current down the main wires, if there's any resistance because of a bad connection or frayed wire, the voltage will try to pass through the multi meter circuit?

[ahmedmahomed]

Excellent, easy to understand .Well explained.Thank you Sir.

[joaquinaguirre]

Thank you so much. I replace the fuel pump and still have no power when I turn on the engine. I will do this test!!!!

[aamirghanchi]

When i do positive voltage drop, the meter is showing 12+ volts without even cranking the engine. Does this make sense? Shouldn't it be showing zero volts?

[melkerekstromer]

I have 12.5 volts in my battery, and when i measure voltage back on the fuelpump positive terminal i only receive 12.3 volts, at this Point the ignotion is at it`s off position, is this normal, or should there me the same voltage back in fuelpump as in the battery?

[maxwebster]

Hi, a quick question. At the pump connector, 12+, 12v ground. No problem. Reconnect at pump, pull relay out. Relay measures 12v +, when I go from batt 12v+ in series to pump side ground I get 5.98v through the NEW pump. Pump measures 0 ohms R now that it is cold. Bad brush? New pump measures 0 ohms, and no volt drop from batt+ in series.
I changed pump, vehicle runs. Retest pump, 0 ohms res, no voltage drop. Was the 6v drop due to R from a hot / defective pump or did I miss something? Original pump was changed due to rotten tank as routine due to high mileage. I feel like I missed something!!!

[hectorivan]

Hello i was wondering, when you do the voltage drop at the power wire at the fuel pump, do you need to disconnect the connector or leave it connected and just probe into the circuit? How about the negative side?

[Viper]

Backprobe with t pins and alligator clips attached to the meter leads.

[philh]

How do you do this test on a duty cycle pump??

[Headshothorror]

U didn't show the wire from pump u talking about like wtf man

[alb]

Too bad to get to the connector on many cars you pretty much have to drop the tank.

[marccantin]

Appeared to be a quality video until he failed to address meter connections at the fuel pump in detail. moving on down check....

[chantellemockable]

How warm should fuel pump relay get while vehicle running?

[mknight]

Uh...I'm getting negative 8 Volts at the pump connector

[LizZyRocKZSwaG]

My 2001chevy express stops while driving what can cause that the engine light does not come on