E46 BMW Social Directory E46 FAQ 3-Series Discussion Forums BMW Photo Gallery BMW 3-Series Technical Information E46 Fanatics - The Ultimate BMW Resource BMW Vendors General E46 Forum The Tire Rack's Tire Wheel Forum Forced Induction Forum The Off-Topic The E46 BMW Showroom For Sale, For Trade or Wanting to Buy

Welcome to the E46Fanatics forums. E46Fanatics is the premiere website for BMW 3 series owners around the world with interactive forums, a geographical enthusiast directory, photo galleries, and technical information for BMW enthusiasts.

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.

Go Back   E46Fanatics > E46 BMW > General E46 Forum

General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 12-06-2012, 03:13 PM   #1
crazzy88ss
Registered User
 
Join Date: Nov 2007
Location: CA
Posts: 78
My Ride: 05 330 ZHP auto
MPG / fuel gauge inaccuracies - SULEV issues?

Ok, so there's some issues going on here that I started noticing a few weeks back.

1.) The fuel gauge is not accurate. It's a 16.# gallon tank, so each of the markers should roughly be at 1/1, 3/4, 1/2, 1/4, 0/0. I've always got about 300 miles out of 11.5 gallons (I always try and get gas at the 1/4 marker due to SULEV fuel system) but lately the tank has been going to about 1/8th to get to 300 miles.

If you see from the picture of the fuel pump, I used 12.75 gallons, which does not correctly match where the needle is on the fuel gauge. The final picture shows the fuel gauge showing a full tank after 12.75 gallons.








2.) Somewhere, something's not adding up. If you take 316 miles divided by 12.75 gallons, you get 24.78mpg and NOT the 26.7mpg that the computer shows.

I've ALWAYS been getting 26-28mpg and 300+ miles out of 12 gallons of fuel but now the numbers are not adding up in anyway.

Any ideas of what's going on?
Attached Thumbnails
Click image for larger version

Name:	photo 1.JPG
Views:	224
Size:	93.6 KB
ID:	481177   Click image for larger version

Name:	photo 2.JPG
Views:	159
Size:	95.1 KB
ID:	481178   Click image for larger version

Name:	photo 3.JPG
Views:	187
Size:	100.9 KB
ID:	481179  
crazzy88ss is offline   Reply With Quote
Ads by Google

Guests, get your FREE E46Fanatics.com membership to remove this ad.
Old 12-06-2012, 03:15 PM   #2
WDE46
Registered User
 
Join Date: Sep 2012
Location: Old Greg's Cavern
Posts: 8,997
My Ride: 2004 330Ci OBM
Quote:
Originally Posted by crazzy88ss View Post
Ok, so there's some issues going on here that I started noticing a few weeks back.

1.) The fuel gauge is not accurate. It's a 16.# gallon tank, so each of the markers should roughly be at 1/1, 3/4, 1/2, 1/4, 0/0. I've always got about 300 miles out of 11.5 gallons (I always try and get gas at the 1/4 marker due to SULEV fuel system) but lately the tank has been going to about 1/8th to get to 300 miles.

If you see from the picture of the fuel pump, I used 12.75 gallons, which does not correctly match where the needle is on the fuel gauge. The final picture shows the fuel gauge showing a full tank after 12.75 gallons.

2.) Somewhere, something's not adding up. If you take 316 miles divided by 12.75 gallons, you get 24.78mpg and NOT the 26.7mpg that the computer shows.

I've ALWAYS been getting 26-28mpg and 300+ miles out of 12 gallons of fuel but now the numbers are not adding up in anyway.

Any ideas of what's going on?
Have you ever changed your fuel filter? I don't know if this is possible on SULEV cars. Maybe your O2 sensors are going or your MAF sensor is dirty.

3/4 of a tank is 12 gallons so with 12.75 it should be past the 1/4 marker like it is. That might be a little far, but fuel gauges aren't that accurate ever anyway.

Oh and if that 26.7 MPG has been established over a couple thousand miles, then 300 at 24.7 is not going to move the average much. Reset the meter for this next tank and then compare the values.

Last edited by WDE46; 12-06-2012 at 03:19 PM.
WDE46 is offline   Reply With Quote
Old 12-06-2012, 03:20 PM   #3
Andy2108
Registered User
 
Join Date: Nov 2009
Location: U.S.A.
Posts: 8,039
My Ride: E46 M3, '67 Cobra
Read up on the fuel level sender. I think it may be contributing to your issue.
Andy2108 is offline   Reply With Quote
Old 12-06-2012, 03:32 PM   #4
crazzy88ss
Registered User
 
Join Date: Nov 2007
Location: CA
Posts: 78
My Ride: 05 330 ZHP auto
Quote:
Originally Posted by WDE46 View Post
Have you ever changed your fuel filter? I don't know if this is possible on SULEV cars. Maybe your O2 sensors are going or your MAF sensor is dirty.

3/4 of a tank is 12 gallons so with 12.75 it should be past the 1/4 marker like it is. That might be a little far, but fuel gauges aren't that accurate ever anyway.

Oh and if that 26.7 MPG has been established over a couple thousand miles, then 300 at 24.7 is not going to move the average much. Reset the meter for this next tank and then compare the values.
The fuel filter can't be changed on SULEV (that's why I don't go below 1/4 tank).

The 26.7MPG is over just one tank of 316 miles; I reset it every single tank.

My gauge/MPG has always been deadly accurate (i'm a #s person, and often calculate it manually. That's why I picked up on this issue "quickly").

I found another thread here (http://forum.e46fanatics.com/showthread.php?t=592414) that might be related to my issues. Can anybody else confirm/deny they're related?

Last edited by crazzy88ss; 12-06-2012 at 03:42 PM.
crazzy88ss is offline   Reply With Quote
Old 12-06-2012, 03:54 PM   #5
WDE46
Registered User
 
Join Date: Sep 2012
Location: Old Greg's Cavern
Posts: 8,997
My Ride: 2004 330Ci OBM
You should just sell your SULEV before the warranty expires and get a normal M54. Sounds like something may be about to break.
WDE46 is offline   Reply With Quote
Old 12-06-2012, 04:44 PM   #6
crazzy88ss
Registered User
 
Join Date: Nov 2007
Location: CA
Posts: 78
My Ride: 05 330 ZHP auto
Quote:
Originally Posted by WDE46 View Post
You should just sell your SULEV before the warranty expires and get a normal M54. Sounds like something may be about to break.
That's the plan. I still got a few years on it, though.
crazzy88ss is offline   Reply With Quote
Old 12-06-2012, 06:14 PM   #7
jfoj
Registered User
 
Join Date: Nov 2009
Location: Fairfax, VA USA
Posts: 10,114
My Ride: '06 330CiC, '03 M5
DISA, VANOS seals, O2 sensors??

Suggest you also check to see if you can use the 3rd link below in my signature to determine if your tank levels and sucking jet pump are working correctly.

I do think the fuel filter may be part of the tank on the SULEV, hopefully it is not as fine a filter as the regular cars??

Suggest you also perform a pressure & volume test on the fuel pump assuming the SULEV actually has a test point on the fuel rail?
__________________
Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299

Last edited by jfoj; 12-06-2012 at 06:17 PM.
jfoj is online now   Reply With Quote
Old 12-06-2012, 06:48 PM   #8
crazzy88ss
Registered User
 
Join Date: Nov 2007
Location: CA
Posts: 78
My Ride: 05 330 ZHP auto
Quote:
Originally Posted by jfoj View Post
Suggest you also check to see if you can use the 3rd link below in my signature to determine if your tank levels and sucking jet pump are working correctly.
I don't have access to a windows-based laptop at work or home or school.

VANOS is an interesting thought... the power is fairly weak at low RPM, but would VANOS impact fuel consumption/reporting?
crazzy88ss is offline   Reply With Quote
Old 12-06-2012, 07:58 PM   #9
WDE46
Registered User
 
Join Date: Sep 2012
Location: Old Greg's Cavern
Posts: 8,997
My Ride: 2004 330Ci OBM
Quote:
Originally Posted by crazzy88ss View Post
I don't have access to a windows-based laptop at work or home or school.

VANOS is an interesting thought... the power is fairly weak at low RPM, but would VANOS impact fuel consumption/reporting?
You could check your DISA. That helps provide low end torque. It won't affect fuel economy much though.
WDE46 is offline   Reply With Quote
Old 12-06-2012, 08:31 PM   #10
jdstrickland
Registered User
 
Join Date: Apr 2010
Location: Murrieta, CA
Posts: 6,871
My Ride: '94 325iC & '00 323i
YOU DON'T HAVE ANY ISSUES.

The fuel gauge is nothing more than an indicator of the difference in F and E. The tank is larger at the top than the bottom, so you can go 200 miles on the first 1/4 tank of gas, and 100 miles on the last 3/4 tank. This is normal.

When the gauge says 1/4, it is safe to say that you need more gas soon. When it says 1/8, then the urgency is increased. But just because you can drive for three days on the first 1/8th tank and only three hours on the last 1/8th does not mean there is something to be fixed.

Last edited by jdstrickland; 12-06-2012 at 08:33 PM.
jdstrickland is offline   Reply With Quote
Old 12-06-2012, 09:07 PM   #11
jfoj
Registered User
 
Join Date: Nov 2009
Location: Fairfax, VA USA
Posts: 10,114
My Ride: '06 330CiC, '03 M5
Quote:
Originally Posted by crazzy88ss View Post
I don't have access to a windows-based laptop at work or home or school.

VANOS is an interesting thought... the power is fairly weak at low RPM, but would VANOS impact fuel consumption/reporting?
Link for Hidden OBC Menu - http://forum.e46fanatics.com/showthread.php?t=239619

VANOS and DISA can impact lower RPM performance and likely can reduce fuel economy due to lower torque availability.
__________________
Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299

Last edited by jfoj; 12-06-2012 at 09:08 PM.
jfoj is online now   Reply With Quote
Old 12-07-2012, 11:03 AM   #12
crazzy88ss
Registered User
 
Join Date: Nov 2007
Location: CA
Posts: 78
My Ride: 05 330 ZHP auto
Quote:
Originally Posted by jfoj View Post
Link for Hidden OBC Menu - http://forum.e46fanatics.com/showthread.php?t=239619

VANOS and DISA can impact lower RPM performance and likely can reduce fuel economy due to lower torque availability.
Oh those are built into the car's computer; ok thanks.

I'm not familiar w/ DISA; where can I read up on that?
crazzy88ss is offline   Reply With Quote
Old 12-07-2012, 11:13 AM   #13
jfoj
Registered User
 
Join Date: Nov 2009
Location: Fairfax, VA USA
Posts: 10,114
My Ride: '06 330CiC, '03 M5
See first link below in my signature.
__________________
Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
jfoj is online now   Reply With Quote
Old 12-07-2012, 11:24 AM   #14
WDE46
Registered User
 
Join Date: Sep 2012
Location: Old Greg's Cavern
Posts: 8,997
My Ride: 2004 330Ci OBM
Quote:
Originally Posted by crazzy88ss View Post
Oh those are built into the car's computer; ok thanks.

I'm not familiar w/ DISA; where can I read up on that?
You can inspect the DISA very quickly. You only need a T40 torx socket and a 10mm socket. You remove the airbox, MAF sensor, and then the DISA. 4 bolts total and a hose clamp.

Last edited by WDE46; 12-07-2012 at 11:24 AM.
WDE46 is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Censor is ON





All times are GMT -5. The time now is 02:30 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
(c) 1999 - 2011 performanceIX Inc - privacy policy - terms of use