Fuel tank only fills halfway

[penguinc00]

hi guys,

The other night I was getting some dino juice in my 99 528i touring. I let the tank fill by itself until the pump clicked off, signaling that the tank was full. It wasn't, however, and in fact was only halfway full (I know because I only had about a gallon of gas left in the tank). I waited a bit and tried to fill again only to quickly hear the click again. I tried yet again and this time a bit of fuel spilled out of where the nozzle inserts.

After that odd experience I fired up Test #6 in the low OBC and noticed that the sender was showing 000310 (unsure of last three digits) signaling that there was no fuel in the left bank of the tank. After driving around for a while it started to show something like 060270 -- I guess a bit of sloshing around filled up the left bank a bit.

I'm wondering why fuel isn't being transferred from the right side (where the filler is) to the left side of the tank. It seems so odd. It's not a matter of the gauge not showing the right amount of fuel (because it shows that the tank is half full), but rather that the fuel isn't always going to the other side of the tank.

This only happens intermittently by the way. There are days where I can fill up the car without any trouble.

Any ideas?

Thanks!

[fragzem]

wtf is dino juice? that's what I'm hung up on

[76papa]

Sometimes I fill up my '99 528i with "dino juice" and the gauge doesn't show it. the next day the gauge is reading normal.

[Flybot]

I dont see how it can not fill the left half. Fuel should just run over the top of the right side. Sounds like a vent problem.

[Geoff.T]

I dont see how it can not fill the left half. Fuel should just run over the top of the right side. Sounds like a vent problem.

This.

Did you try to continue filling the tank at a slower speed? It's possible the fuel gun you were using was defective as well to back pressure. Try another gas station.

[penguinc00]

I dont see how it can not fill the left half. Fuel should just run over the top of the right side. Sounds like a vent problem.

That's what I thought too. It didn't make any sense to me either. What was even more confusing was that the digital gauge as part of the low obc gauge was showing the left bank as completely empty (ie. the 000 part of the 000310 reading).

Why would the fuel overflow, causing it to spill out of the latch though? Something is odd...

[bimmerfiver]

There is a port side fuel sensor and a starboard side fuel sensor. Inbetween there is a mechanical syphon jet (pump).

You got an issue:

http://www.realoem.com/bmw/showparts...09&hg=16&fg=15

http://www.realoem.com/bmw/showparts...25&hg=16&fg=05

I also had to replace my failing 'Leak Diagnosis Pump' # 12...a freaky uber method of krazy Kalifornian Emmisons freaks getting their hands into our cars:

http://www.realoem.com/bmw/showparts...96&hg=16&fg=10

[Flybot]

That's what I thought too. It didn't make any sense to me either. What was even more confusing was that the digital gauge as part of the low obc gauge was showing the left bank as completely empty (ie. the 000 part of the 000310 reading).

Why would the fuel overflow, causing it to spill out of the latch though? Something is odd...

If the vent is clogged, air cant get out as you fill the tank. Then the fuel pump (gas station) will shut off.

[penguinc00]

If the vent is clogged, air cant get out as you fill the tank. Then the fuel pump (gas station) will shut off.

Any way to unclog said vent?

[Aussie528iT]

Could be a faulty fuel level sensor.
Go to test 6. There are more parts to test 6 beside the fuel levels.
L, R and total fuel, next part of test 6, 1.6.1 tells you both sensors are good, 1.6.2 tells you if one sensor is bad but doesn't tell you which one, 1.6.3 tells you both sensors are bad or the Kombi can't access the information IIRC.
Hope this helps as I don't have my car with me at present to check accuracy of above info.

RonR
99 528iT M52TU

[Alpina540i]

I would like info on this vent as well.

I have to pump gas at 3/4's speed to make it not stop at around 8 gallons.

-Anson

[SailingFool]

Any tips or procedures for clearing this vent?

[bmwhiteman]

I get the same problem, but only at shell

[TriniSpeC]

is dino juice not gasoline?

[Qsilver7]

1. ...I fired up Test #6 in the low OBC and noticed that the sender was showing 000310 (unsure of last three digits) signaling that there was no fuel in the left bank of the tank.

2. After driving around for a while it started to show something like 060270 -- I guess a bit of sloshing around filled up the left bank a bit.

3. I'm wondering why fuel isn't being transferred from the right side (where the filler is) to the left side of the tank. It seems so odd. ...

I recognize that this is an older thread that has been brought back to life...but there's some misconceptions that should probably be cleared up so that others reading this now (and any future searches) won't react to incorrect info.

Clarification for #1 & #2

See the info below on how OBC TEST #6 should be interpreted for the LOW instrument cluster. As someone mentioned...TEST 6 has 3 sub-tests which overall gives a lot of detail about how the fuel level sensors are working:

click this link for instruction on how to UNLOCK the high or low OBC...plus the description of what all 21 OBC TESTs represent:

• http://www.cardomain.com/ride/313409...-series/page-6

Clarification for #3

Our fuel tanks are kind of "semi-bifurcated" or "saddled" (has two parts but not completely separated) but the fuel on the LEFT side is syphoned over to the RIGHT side (not the other direction as the OP presumed). You can see the two fuel level sensors in the diagram below. The data that they send to the instrument cluster (IKE) will read that the left side empties first (will go to ZERO liters)...although the fuel in the tank is really going down evenly, then when the fuel on the left side falls below the saddle/hump...it relies on the syphon jet pump to transfer it over to the right side where the fuel pump is located that sends it on to the engine:

[chiefwej]

My bet would be that the problem is the fuel sensor. Are you sure that the tank is not filling, could it just be gauge error? If it is the sending unit then a bottle of Techron added at each fill up will cure it, after a few treatments.

BTW: This is a common problem among those who don't use Top Tier gasolines or regular Techron treatments. Deposits build up on the sending units and cause error in readings. Techron helps remove the deposits.

[bmwhiteman]

It's not my fuel level sensor. I get 10-11 gal in when I'm on empty before it clicks. It clicks every half gallon until 18.5 gal. It must be some sort of vent problem.

[Qsilver7]

It's not my fuel level sensor. I get 10-11 gal in when I'm on empty before it clicks. It clicks every half gallon until 18.5 gal. It must be some sort of vent problem.

Perhaps it can't handle the length of the nozzle. Are you shoving it all the way in...or do you back out the gas nozzle a bit so that you can continue to fill the tank?

I can't stick it all the way in on either of my BMWs...I always have to just stick the tip of the nozzle (like the first 4-5 inches) in if I don't want to have the gas pump click off before the tank is full.

[bmwhiteman]

It started doing this about a month ago. I've had the car for 2 years and it had never done it before. Now it does it every time without fail regardless of pump or station.
It's also CA so I can't back the nozzle out, it shuts it off if the vapor seal isn't compressed, I've tried holding it back and keeping the nozzle out a bit but it still clicks

[E39540i62000]

I also had a similar problem with my car when I purchased it, it had to be re-fueled slow or the pump would click off. I found that my tank purge valve electrical connector was covered in a green slime substance, cleaned this off with contact cleaner and gave the pins a scratching, re-connected it and have not had any problems re-fueling since.
http://tis.spaghetticoder.org/s/view.pl?1/02/33/21