Tech: 2003-2004 M45 (Y34) Fuel Sending Unit

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HondaCRX
Posts: 75
Joined: Mon May 31, 2004 7:25 pm

Tech: 2003-2004 M45 (Y34) Fuel Sending Unit

Postby HondaCRX » Mon Jan 24, 2011 8:27 pm

Disclaimer: This is only a partial fix to a fuel gauge that is incorrectly reading actual fuel level. This will NOT fix any gauge cluster issue you may have.

I initially had a perfectly working fuel level gauge, until one day I drove the car rather hard. The fuel gauge then started to read full ALL THE TIME. thinking that the fuel may have sloshed around and got the sender stuck, I decided to take it apart and figure it out. Here's what I found:


Tools:
- common screwdriver
- 8mm socket wrench or normal wrench OR a stubby phillips screwdriver
- two small bags with twist ties
- O-ring for fuel sender unit (~$7)

BEFORE BEGINNING: Work in a well vented area, and make sure you haven't started the engine or turned the key to the On position for at least an hour. this will relieve the fuel pressure.

1. Open trunk
2. Remove carpet, spare wheel cover, and the foam bits surrounding the wheel
3. Remove the push clips that hold the rear trim. There's about 6-8 clips. just pop the centre out towards you, then remove.
4. The top part of the trim is clipped to the trunk. Pull it towards the rear of the car, and the rest of the trim will come out
5. You'll see this:
Image
- Remove the electrical connection
- Grabbing both sides of the fuel line, as indicated by the arrows, pull the fuel line away. WARNING: FUEL MAY SQUIRT OUT... ESPECIALLY if you didn't listen to the "before beginning" bit.

6. Wrap both the fuel line to the engine, and the fuel pump line, in bags using the twist ties to tie them off. This will collect any fuel that leaks out.
7. Remove the six 8mm bolts (8mm socket or phillips screwdriver)
8. Slowly remove the fuel pump/sender assembly. I had to turn it 180 degrees counter-clockwise in order to full remove it. BE VERY GENTLE pulling it out.
9. Here's the fuel pump / sender assembly:
Image

Here is the sender unit components:
Image
Image
Image

In the first picture, the arrow points to a plastic clip that holds the sender unit's arm to the rest of the assembly. This arm is spring-loaded, which is soldered to the lower section in the photo. The picture shows what it would be if the gas tank was empty. Notice the lines behind the arm... the higher the arm goes, the more fuel is in the tank, the higher your gauge should read.

In the second picture, the arrow points to the metal tab that slides on the lines that completes the circuit and ultimately determines where your fuel gauge should read. This metal tab is what is soldered to the spring, and ultimately to the lower section of the first photo. This metal tab is made of some very very thin metal, and is highly prone to being twisted, bent, or otherwise altered from it's normal shape. More on this later...

The third picture shows the arm actually off the unit, only being held on by the wire that makes up the spring and metal tab.

From here, you'll need to do some problem-solving on your own... But, for mine there were two problems:
First, the arm of the sender had popped off, which caused no reading whatsoever.
Second, the metal tab that slides up and down was bent, so when it was reading, it was reading HIGHER than normal... because the metal tab was bent slightly up.

What I did was fixed the metal tab so it was much straighter, without any kinks/bends in it. This allowed for it to read properly.

To test to see if your fuel sender is toast, or to see if what you're doing is making any difference, disconnect the fuel pump from the assembly, by disconnected the electrical connection. This is the black plug near the rubber hose. This will prevent the fuel pump from running without any fuel in it (BAD, as fuel pumps use fuel as a lubricant).
Then, plug the whole assembly back into the chassis harness, turn the ignition to the on position, and adjust the fuel sender unit to go through it's range.
If it still doesn't work, check the wiring on the assembly to make sure there are no broken wires or bad soldering connections. You can also check resistance with a multimeter across the entire range of the sender, but I don't have any details regarding those tests.

So, if you got everything fixed... or unable to fix it, reassembly time!

10. Looking at the gaping hole for the tank, you'll notice a groove around the edge. You should have a gasket there that looks like this:
Image

This will sit perfectly in the groove...
Image
No o-ring

Image
O-ring!

If your old o-ring doesn't fit perfectly, replace it with a new one (About $7). Otherwise, you'll pop a SES (Service Engine Soon) light, explaining there's a small emissions leak :)

11. Replace o-ring!
12. Reinstall fuel sender unit, being very gentle when putting back into tank. You do not want to knock the sender arm off the post...
13. Bolt back down, connect the electrical connection and the fuel line.
14. Start the car to make sure everything is working as it should (hopefully better if you fixed it to start reading fuel levels!).
15. Shut car off and replace the trunk trim.

Viola. Should take 15-30mins from start to finish.


CAUG2
Posts: 127
Joined: Sat Apr 03, 2010 9:17 am
Car: 03 M45

Re: Tech: 2003-2004 M45 (Y34) Fuel Sending Unit

Postby CAUG2 » Tue Jan 25, 2011 6:28 pm

good stuff.I hope never do this.

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DRIPS
Posts: 385
Joined: Wed Oct 24, 2007 3:03 pm
Car: 2003 Infiniti M45

Re: Tech: 2003-2004 M45 (Y34) Fuel Sending Unit

Postby DRIPS » Tue Feb 01, 2011 6:43 pm

Just ordered a fuel filter, sending unit, o ring, and a few other random parts.

I will be doing this this weekend.

KIZITO22
Posts: 3
Joined: Fri Dec 02, 2016 8:24 pm
Car: 2003 INFINITI M45

Re: Tech: 2003-2004 M45 (Y34) Fuel Sending Unit

Postby KIZITO22 » Sun Jul 11, 2021 8:09 pm

I have bought and replaced a new sending unit. Gauge is still showing a full tank. I am missing a bolt and can't find it anywhere online. Does anyone know the exact size of the bolt that fits? Please help. I will probably end up taking the car to the dealer to fix the gauge.

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Tech: 2003-2004 M45 (Y34) Fuel Sending Unit

Postby VStar650CL » Sun Jul 11, 2021 8:37 pm

Can't help you with the screw, but full all the time generally means a shorted sender wire or a bad gauge. Nissan senders are all "negative coefficient", meaning the lower the voltage, the higher the reading. Since an open sender drives the voltage to maximum, a disconnected sender should make the gauge read flat empty. Try disconnecting yours and watch the needle. If it still reads full even with the connector loose, you either have a sender signal wire shorted to ground or the gauge in your cluster is dead.

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Re: Tech: 2003-2004 M45 (Y34) Fuel Sending Unit

Postby EdBwoy » Sun Jul 11, 2021 10:37 pm

KIZITO22 wrote:
Sun Jul 11, 2021 8:09 pm
I have bought and replaced a new sending unit. Gauge is still showing a full tank. I am missing a bolt and can't find it anywhere online. Does anyone know the exact size of the bolt that fits? Please help. I will probably end up taking the car to the dealer to fix the gauge.
I don't know the exact size of the 6 screws/bolts but I can provide the part number as they are pretty cheap.
01436-00291

For the fuel level showing as full while the tank is actually less than full in 2003-2004 m45s, there was/is a recall for it. I would call the dealership with your VIN to see what they have to say about it.

KIZITO22
Posts: 3
Joined: Fri Dec 02, 2016 8:24 pm
Car: 2003 INFINITI M45

Re: Tech: 2003-2004 M45 (Y34) Fuel Sending Unit

Postby KIZITO22 » Mon Jul 12, 2021 6:21 pm

Thank you both for the replies. My gauge still moves up and down but gets stuck on full or shows half a tank when it should be empty at times. It’s got worse over the past year. I will try unplugging the fuel gauge to see what happens. I won’t be a happy camper if that was the problem all along as I just spent money on a new fuel sensor. Oh, and the O-ring was also stretched. Pulled a error code but I replaced it with a new one. It appears the previous owner had worked on the fuel sensor because I found a bolt missing. I just ordered the bolts. Looks like they should be the right bolts I have been looking for. Thanks again.


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