Fuel Gauge isnt reading correct level

have an 04 jetta tdi and my fuel gauge constinantly reads 1/4 tank even after i fill it up (have done so 3 times since this started happening). I've never run into this issue and have no experiance working or diagnosing this..does anyone have any advice? Also, the needle does move when the key is turned on

anyone? I know there are some bright people on here when it comes to bew/alh engines. is there one sensor in the tank near the pump? could it be up front in the engine bay? can anyone just point me in the right direction? thanks

cfm56 said:

have an 04 jetta tdi and my fuel gauge constinantly reads 1/4 tank even after i fill it up (have done so 3 times since this started happening). I've never run into this issue and have no experiance working or diagnosing this..does anyone have any advice? Also, the needle does move when the key is turned on

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__. One thing that happens fairly frequently is that the float either doesn't float anymore or the float lever arm gets caught on something. Both are in the tank. If *could* be wiring or guage but not likely.

Are you venting the tank? If not then your gauge will always read 1/4 tank low. Have you done the Ventectomy mod?

Havent done the ventectomy yet (plan on doing so). I know venting it wont help since it reads quarter tank no matter what i have in there. THe first time i found out was the hard way...i had quarter tank showing on the fual gauge when the engine died while on the freeway...and the needle hasnt moved above quarter tank on the gauge ever since. I plan on yanking the fuel pump out and check the floater assembly to verify its not sticking in place. Thanks for the help so far, i appreciate it. Also if there's anyone in the seattle/bellevue area up in washington that wants to help it would be great. I currently am up in this area with work and dont have a garage/tools here which sucks...if anyone in the area can help i would appreciate it. Thanks

cfm56 said:

(snip) I plan on yanking the fuel pump out and check the floater assembly to verify its not sticking in place. (snip)

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__. Yeah. There are a couple of different failure modes. The "floater assembly" can get stuck because there is a problem with the pivot or if it starts rubbing one part against the other. On the other hand, you can get an "external stuck" if the mechanism rubs up against the inside of the tank -- sometimes it's hard to check these out because when the mechanism is out of the tank, it's not stuck any more! Also, check out the float itself - if it gets "fuel-logged" it won't float anymore.

__. And there's another place you could have a problem, that's the electrics inside the tank. Dunno if the VW system is similar, but a type I have a lot of experience with had what they called a "card". It's the resistance part - the moving mechanism part moves a connection on the card and that provides the differing electrical signal to the gauge.

__. It's really not too hard but there are quite a few items to check out. Having said that, I'm pretty sure that the problem is inside that tank (although it could be wiring or gauge problems).

__. (Also, if you haven't pulled the mechanism out of the tank before, do a search. It's easy but there are some tricks -- and you're very likely to spill a lot of fuel in the back seat of your car if you don't get the tricks right.)

I had a problem with my B4 when I got it. Under hard acceleration, the indicator would drop to 0, but slowly return to an accurate level.

After using B99, the guage 'fixed itself'.

Not even going to try to say that I know why, or that it will fix yours though.