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Old 12-17-2013, 07:20 AM   #198
Trrrex92
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Re: codes P0171, P0174 Lincoln LS V6"

Quote:
Originally Posted by shorod View Post
Yep, a modern fuel pump consists of an electric motor. The electric motor can fail to run randomly. Kind of like how a starter motor can sometimes fail to run, yet a tap with a broomstick (etc.) can get it to work again for some amount of time.

To confirm whether or not the fuel pumps are getting power you can remove the rear seat bottom cushion and check for voltage at the connectors. For the main fuel pump module, I'd suggest making two measurements. First, confirm you have power to the Green/Orange wire at the pump using a known good ground. If so, connect the ground lead of the meter to the Black/Red wire and see if you still have voltage.

I didn't notice the wiring schematic for the transfer/jet pump when scrolling through this morning, but the voltage checks would be similar to the main pump.

The computer uses PWM modulation to power the fuel pumps so you may not see full battery voltage when measuring across the wires for the fuel pump. Also, be aware that the pump does not run constantly when the key is off and engine not running so you'll need to have the test light/multimeter installed when you turn the key on. You'll probably need to make several iterations of "key off, wait several seconds, turn key back on and record measurement."

-Rod
Do I use the wires on the battery side of the connector or fuel pump side? The wires on the fuel pump side are black, red, yellow, and black and red.
I also have no idea what to set my multimeter on.
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