Fuel Gauge Inaccuracy?
 

My car had been in the bodyshop for 3-4 weeks and driven a total of 3 miles during that period. I go to auto-fill my tank today (it was on 1/16) and the when the pump stopped (when it's supposedly full), the gauge read 11/16. i'm confused because when i pump gas and i set the handle, it stops when it's full and i usually see a full 16/16 gauge. the pump charged me for 16.765 gallons and only shows 11/16.

is it possible there is something wrong with the pump? or is it my gauge? it looks like i have space for another 6 gallons but i know my tank is 19 gal so i at least expected the 14/16 if i had a completely empty tank.

i feel like i paid for a full tank but only see less than 3/4 on the gauge. the accident i was in caused me to get a new bumper, hood, fenders, and a few new front-end things. i wouldnt think the fuel sensor is up there somewhere so im out of ideas. i just want to make sure it's accurate so i dont get stranded somewhere.

this post was longer than i expected but my head is sorta all over the place right now. lol. thanks in advance for any suggestions/ideas.

Probably a little corrosion on the sender contacts from sitting. Throw a bottle of techron in the tank. Often that will help scrub them clean..

Woah woah mod, only Shell gets in this machine! Lol

I pour in a bottle of Techron fuel system cleaner each oil change. Its great stuff, the company I work for does testing on all kinds of oils/fuels/filters/additives and those guys rave about how it actually worked compared to the others claims. For the op I also use shell but a bottle of Techron is good for your fuel system on occasion. Just my 2 cents.

I heard Chevron 91 is better than Shell 91

Ooo, I thought you guys were talking about chevron gas. Didn't know they had their own cleaner. I'll get some tomorrow.

Look at this exploded view of the fuel tank.

172 Fuel Tank :: Fuel & Engine Control :: Genuine Nissan Parts :: 370Z Parts (Z34) 2009+ :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

The sender has a float on the end of a metal arm. This arm can get bent, and a hard impact from a collision could certainly be enough to do that.

I doubt they can get bent...The floats are very light and would not have enough momentum to bend the arm. What typically happens is the contacts on the reostat get gummed up or corroded especially when the fuel level is low. This isn't a Z sender, but is similar to what is used in most cars these days. As the arm, moves up it causes the contact wiper to make contact with the various pc board contacts. Further up (more fuel), more LEDs lit on the gauge. Techron is proven to clean these contacts. I've had plenty of Audi buddys who have brought their senders back from the dead with a few applications..Techron even covers this on their website..

http://www.chevron.com/products/ourf...tives/tcp.aspx

http://images109.fotki.com/v775/phot...SCN3954-vi.jpg

Believe me the Nissan ones can get bent, they aren't as sturdy as the one you show. It happened to me with my G35.

In my '04.5 Touring Coupe, it's a gas tank issue, not the fuel gauge. I read somewhere that the fuel vapors in the tank "fool" the shut-off mechanism in the fuel nozzle, which stops dispensing the gas. When you get into your vehicle, the fuel gauge is slightly below the "F". Weird Nissan bugs.

I've had that too with my G35 but that's a different issue than here, you can usually tell the difference by how many gallons were dispensed.

True. Still, they're Nissan bugs that mess with your mind! Little annoyances that aggravate you 'cause you KNOW that Nissan could and should do better on those minor-but-irritating issues. I do admit, though, that the engine, cooling system, AT, electrical system, body integrity, etc., are very reliable.

it was weird seeing more dots light up today. lol. i was driving the car hard and saw two dots light up.

driving hard improves fuel economy...:ughdance:

Ha! Yeah, right!

Well....sloshing the fuel around in there with some Techron does work...He's not wrong! ....:tup:

update: i thought the issue fixed itself but today i thought i had 1/4 tank (4 dots) and the car shut off. had to get a friend to hook me up with 2 gallons of gas to get outta there. im buying that techron tomorrow. if that doesnt work then i guess i'll be going to the dealer for a new fuel sender unit or whatever the problem is. ugh, id hate to take it to a dealer! hopefully this techron does the trick!

Guess I was wrong there in assuming you acted on that...Just sloshing, No techron. If you'd taken my advice from 2 weeks ago it might be fixed by now!......:ugh2:

i thought it fixed itself when i saw more dots magically light up. no worries, i sloshed it around PLENTY of times with the techron in there today. i mustve looked like a maniac.

This is usually what happens. The issue has to do with sulfur building up on the sending unit contacts.

Shell is known for having sulfur problems actually.

This is correct.



Also, guys, you should also know that if you're going to use the auto-fill on the handle of the pumps, you should use the lowest/slowest setting. The reason for this is that modern pump handles have a vapor evacuation channel that sends fumes back to the pump. When pumping at full speed, some of the gasoline will return through that channel and you will be charged for that gas that you're not actually getting. So your MPG calculations (if you do them by hand) will be inaccurate and you will over pay.

Using the slowest setting on the pump does not guarantee that none of the gasoline run back to the pump through the vapor channel, but there's far less chance of it.

BTW, you'll notice that many times the VERY bottom auto-fill setting (the slowest) is either cut off or disabled. They do this because they know that even if they get you for $0.01/gal more, they're going to make a significant gain in profit. Some gas stations know this and go out of their way to prevent you from using the slowest auto-fill setting. Some pumps will not let you pump that slow as well. (Greedy jerks. LOL)

good info. thanks!

ive already actually had problems with the fuel level sender. thew a code for circuit voltage too high. seems like nissan has a new replacement part # out too.

hmmm... tell me more. did it just happen randomly? what is different about the new part?

Techron ftw! The stuff is amazing. I've even used it to clear clogged fuel injectors.

+1 rep :tup:

I heard that Nissan fixed that problem on the '05 Touring coupe, dude! :tup: You missed it by six months............:ugh2:

It happened after i topped off the tank. never had a problem doing so in my spec v but the 370 did it on my 3rd fill up. nissan is looking into the part for me.

How did they diagnose it? Do they just take your word for it? I assume they take voltage readings from somewhere.

obd2 scanner/trouble codes.

Basikly they messed up your CPU chip

Well I don't have a CEL. Probably a stupid question but is it possible to have a trouble code if there's no CEL? If so, I'll scan tomorrow to see if I have anything.

Had thus happen on my 09g and it was the file sending unit. It now is happening on the 09 fx too. Dealer will replace under warentiy

If it's a simple dirty contact issue it's unlikely to throw a code or CEL..

Whats a cpu chip?
how did you get this AMAZING conclusion?