ezjamm

My wife's 2005 350z has never accurately reported fuel volume. Has always under reported. She finally put her foot down (either fix it or the couch). I got the message loud and clear.

At any rate, before purchasing a new fuel pump, I figured I would mess with it. I removed the fuel pump from the tank and manually moved the float. The ohms ranged from:

• 2.7 ohms when at the full position (top)
• 81.6 ohms when at the empty position (bottom)

I left the pump on my bench and went to the car and shorted out the corresponding wires. When shorted, the gauge read around 3/8 of a tank.

This leads me to conclude that the issue is NOT the pump's sensor. I am hoping it's it not the gauge as every once in a blue moon, it will read full.

Next steps, I was going to measure the amperage through the sensor and the open voltage. I recently got my paws on the service manual (thanx to "Heel Til I Die"), I'm going to see if those values are buried in there somewhere. But if anybody knows what they are, I would appreciate the info.

ezjamm

ezjamm

I have checked the gauges using this document: Meter/Gauges Self Diagnosis Procedure. No joy. All meters appear to be working properly.

Voltage across the leads when disconnected is 11.1 VDC.

OldManZFL

It's not the gauge and although it seems like the float is good, it's not. The pump itself is probably fine. Replace both the passenger side and driver side fuel sending units and be done with it. Even if you clean the floats and get them working correctly, from past experience, the problem will reoccur.

karlt

ezjamm,

OldManZFL alluded to part of your problem. There are two fuel level sensors wired in series; the main sensor attached to the fuel pump and a sub unit behind the driver's seat. You need to check them both.

ezjamm

I did not know there were two. I did not find any reference to it from the repair manual. I'll look again.

Thanx

ezjamm

karlt

Removal and installation procedures for both units are described in the Fuel System section of the Service Manual, starting on page FL-4. Diagnostic procedures are in the Driver Information Section starting on page DI-20 and again on page DI-23.