• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-

Stupid gas gauge!

  • Thread starter Thread starter asecretfile
  • Start date Start date Mar 17, 2009

asecretfile

New Member
Feb 11, 2007
228
0
0
Mar 17, 2009
#1
  • Mar 17, 2009
  • #1
Got tired of guessing how much gas was in the car so after 2-1/2 years I said time to put this issue to bed

I know...who cares....Im off for the week because of the economy so I figured I'd make myself useful lol

View attachment 265980

View attachment 265981
 

Darkwriter77

Resident Ranting Negative Nancy
5 Year Member
Jul 1, 2005
314
281
134
Apache Junction, AZ
Mar 17, 2009
#2
  • Mar 17, 2009
  • #2
You have more motivation than me. I've had a brand new sending unit for my notch sitting in the closet for like 2 years now, and I still haven't convinced myself to get off my lazy duff and just drop the tank and put it in. I've just been waiting for the fuel pump to fail ... but I'm pretty sure the pump in there is still fairly new, so the freakin' motor will probably wear out before the damned fuel pump in there ever does.

Was your gauge reading full or empty all the time? Mine pegged out above Full when I first bought the car, and it's stayed there ever since then.
 

mob

the guy who hits on his mom
20+ Year Stangneter
Oct 3, 2003
2,566
136
104
Dallas, TX
Mar 18, 2009
#3
  • Mar 18, 2009
  • #3
damn took you 2 and a half years? It took me a 3 days to get sick of it. I also put in a new fuel pump while I was in there. Lowering that tank is a pain in the ass, I did it by myself with a full tank of gas, I was wrestling that thing to stay level on the jack and not lose all my gas!
 

strtrcr50

New Member
Jun 21, 2006
0
4
0
Previously from Dirty Jerzey exit 7a
Mar 18, 2009
#4
  • Mar 18, 2009
  • #4
Dropping the fuel tank isn't bad. I did it in the street with 1/4 tank and no jack. IIRC, I put one set of tires on top of the curb and didn't even need jackstands. Using hand tools working in the street and drinking beer the whole time, I think it took me 40 mins or so to change the fuel pump.
 

asecretfile

New Member
Feb 11, 2007
228
0
0
Mar 18, 2009
#5
  • Mar 18, 2009
  • #5
Darkwriter77 said:
You have more motivation than me. I've had a brand new sending unit for my notch sitting in the closet for like 2 years now, and I still haven't convinced myself to get off my lazy duff and just drop the tank and put it in. I've just been waiting for the fuel pump to fail ... but I'm pretty sure the pump in there is still fairly new, so the freakin' motor will probably wear out before the damned fuel pump in there ever does.

Was your gauge reading full or empty all the time? Mine pegged out above Full when I first bought the car, and it's stayed there ever since then.
Click to expand...

it would say full until it got to 1/4 tank and then start working lol then it just quit working completely and stayed on full
 

DocG

5th graders > me. They're not bant
Sep 25, 2005
8,297
1,358
194
Cincinnati area
Mar 18, 2009
#6
  • Mar 18, 2009
  • #6
Hmmmm....my gauge always reads empty. I really need to test the connections and probably replace the sending unit too.

Didn't realize I'd have to drop the tank.
 

mob

the guy who hits on his mom
20+ Year Stangneter
Oct 3, 2003
2,566
136
104
Dallas, TX
Mar 18, 2009
#7
  • Mar 18, 2009
  • #7
asecretfile said:
it would say full until it got to 1/4 tank and then start working lol then it just quit working completely and stayed on full
Click to expand...

Did the sendunit fix it? Some people say the anti slosh module can cause that.
 

jrichker

StangNet's favorite TOOL
In Remembrance. Thank you for your contributions
Mar 10, 2000
27,512
2,813
234
Dublin GA
Mar 18, 2009
#8
  • Mar 18, 2009
  • #8
Here's some tips on diagnosing fuel gauge problems...



The red/yellow wire (power supply to gauge & sender) should have 12 volts when the ignition is in the start or Run position.

Troubleshooting the gauge and sender circuit:
Since the sender uses a variable resistor, sum the resistor values of 22 Ohms (empty value) & 145 Ohms (full value). That gets you 167, which you divide by 2: that gets you 83.5. So in theory, 83.5 ohms is 1/2 full. A trip to Radio Shack for the closest combination of resistors to make 83.5 ohms gets you one 68 Ohm (Catalog #: 271-1106) + one 15 Ohm (Catalog #: 271-1102) for a total of 83 Ohms at the cost of $2 plus tax. Wire the resistors in series to make a resistor pack and cover it with heat shrink tubing or electrical tape. The 83 Ohms is close enough to the 83.5 Ohm figure that it shouldn't matter. Disconnect the electrical connector shown in your for the tank sender unit. Connect one end of the resistor pack to the yellow/white wire on the body side fuel sender electrical connector and the other end of the resistor pack to ground. Make sure nothing is touching that isn't supposed to and turn the ignition switch to Run. If I am correct, the fuel gauge will read 1/2 full, or very close to it. If it does not, then the odds are that the gauge or anti-slosh unit are bad.

How and why the test works…
Most of the fuel gauge failures give a stuck on full or stuck on empty as a problem symptom. Using a resistor combination that mimics 1/2 tank allows you to decide if the gauge and anti-slosh module are the problem source.

If the gauge reads about 1/2 tank with the resistor combination, that points to the sender as being the culprit.

If the gauge reads full or empty with the resistor pack in place of the sender, then the gauge or anti-slosh module is at fault.

Fuel gauge sender testing and replacement
The next steps require dropping the fuel tank and removal of the fuel level sender. Here are some useful tips...

I have done the tank removal three times, and the main issues are getting the car up on jack stands and getting the gas out of the tank. DO NOT try to do this job without jack stands. Becoming a pancake is not part of the repair process.

Pumping out the old gas:
If the old pump still works, you can use it to pump the tank out.
1.) Separate the pressure line (the one with the Schrader valve on it) using the fuel line tools.
Look in the A/C repair section for the fuel line tools. They look like little plastic top hats. You will need the 1/2" & 5/8" ones. The hat shaped section goes on facing the large part of the coupling. Then you press hard on the brim until it forces the sleeve into the coupling and releases the spring. You may need someone to pull on the line while you press on the coupling.


Use a piece of garden hose to run from the pressure line to your bucket or gas can. Make sure it is as leak proof as you can make it. Fire and explosion are not part of the repair process...

2.) Jumper the fuel pump test point to ground.

Turn the ignition switch to the Run position. the fuel pump will pump the tank almost dry unless the battery runs down first.

Some 5 gallon paint pails lined with garbage bags are good to hold the gas. The garbage bags provide a clean liner for the pails and keep the loose trash out of the gas so you can reuse it. If you decide to use a siphon, a piece of 1/2" garden hose stuck down the filler neck will siphon all but a gallon or so of the gas.

Remove the filler neck bolts and put them in a zip bag. Disconnect the supply & return lines by removing the plastic clips from the metal tubing. If you damage the clips, you can get new ones form the auto part store for just a few dollars. I have used tie-wraps, but that is not the best choice. Then you remove the two 9/16" nuts that hold the T bolts to the straps. Put the nuts in the zip bag with the filler bolts. Pull the plastic shield down and away from the tank. Once the tank drops a little bit you can disconnect the wiring for the pump & fuel quantity sender.

The fuel gauge sender assembly comes out by removing a large metal ring that unscrews from the tank. There is a separate mounting/access plate for the fuel pump and fuel gage. You are supposed to use a brass punch to tap on the ring so that you don't make sparks. Look closely at the rubber O ring gasket when you remove the fuel gauge sender.
When you install the metal ring that holds the sender in place, watch out for the gasket O ring. Some RTV may be helpful if the ring is not in excellent condition.

The tank to filler pipe seal is a large rubber grommet. Inspect it for hardening, tears and damage. At $20 from the Ford dealer, it might be a good idea to replace it.

I used a floor jack to help lift the tank back in place. You may find that it is the only time you really can make good use of a helper.

All resistance measurements should be made with the power off.

Note from bstrd86 - 86 and older fuel tank sender units are 73 ohms empty, 8-12 ohms full.


The yellow/white wire will show a voltage that varies with the movement of the float on the sender unit. To test the sender, set your Ohmmeter or DVM on low Ohms. Then disconnect the sender and connect the Ohmmeter or DVM to the yellow/white and black wires from the sender unit. Move the float arm while watching the Ohmmeter or DVM. You should see the reading change from 22 to 145 ohms +/- 10%.

If the Ohmmeter or DVM resistance readings are way off, replace the tank sender unit.

Use extreme caution if you do the next step. Fumes from the gas tank can easily ignite and cause a fire or explosion.
With the sender unit out of the tank and connected to the body wiring harness, turn the ignition switch to the Run position. Move the float arm and the fuel gauge indicator should move. If you are very careful, you can use a pair of safety pins inserted in the connector for the yellow/white and black wires to measure the voltage as you move the float arm. The voltage will change, but I have no specs for what it should be.
Do not short the safety pins together or to ground. If you do, you may damage the anti-slosh module or crate a spark. A spark with the fuel tank open could cause a fire or an explosion.

If the voltage does not change and the tanks sender passed the resistance tests, the anti-slosh module or gauge is bad.

Anti-Slosh module pictures courtesy of Saleen0679

 

asecretfile

New Member
Feb 11, 2007
228
0
0
Mar 18, 2009
#9
  • Mar 18, 2009
  • #9
mob said:
Did the sendunit fix it? Some people say the anti slosh module can cause that.
Click to expand...

yea it fixed it, I tested it while I still had the tank dropped and it was the first time I'd ever seen my low fuel light come on lol
 

asecretfile

New Member
Feb 11, 2007
228
0
0
Mar 18, 2009
#10
  • Mar 18, 2009
  • #10
DocG2828 said:
Hmmmm....my gauge always reads empty. I really need to test the connections and probably replace the sending unit too.

Didn't realize I'd have to drop the tank.
Click to expand...

does it ever move even a little or just stay there?
 

TOOLOW91

If you're the village idiot what's that make me?
20+ Year Stangneter
Nov 29, 1999
8,483
8,682
234
S.I.NY
Mar 18, 2009
#11
  • Mar 18, 2009
  • #11
low fuel light? where is this am i missing something?
 

asecretfile

New Member
Feb 11, 2007
228
0
0
Mar 18, 2009
#12
  • Mar 18, 2009
  • #12
toolow91 said:
low fuel light? where is this am i missing something?
Click to expand...

yea my GT lights up a picture of a gas pump when its at like 1/8 or so
 

Beasty306GT

Active Member
Dec 19, 2002
671
4
28
Oxford,Mass
Mar 18, 2009
#13
  • Mar 18, 2009
  • #13
i got a gas light to on my 89 about 4 gallons left in the tank it turns on
 

mob

the guy who hits on his mom
20+ Year Stangneter
Oct 3, 2003
2,566
136
104
Dallas, TX
Mar 18, 2009
#14
  • Mar 18, 2009
  • #14
What years came with a gas light? Why would late 80's car have and my 93 doesn't?
 

DocG

5th graders > me. They're not bant
Sep 25, 2005
8,297
1,358
194
Cincinnati area
Mar 19, 2009
#15
  • Mar 19, 2009
  • #15
asecretfile said:
does it ever move even a little or just stay there?
Click to expand...


Doesn't move at all....just stays on E.

 

LiquidGT

Member
Oct 8, 2007
368
0
16
Near STL hell
Mar 19, 2009
#16
  • Mar 19, 2009
  • #16
My gas gauge is a liar, the mark below half a tank is 7.7 gallons (tank is 15.4). This caused me to run out of gas once; luckily a nice cop came with a gas can.

mob said:
What years came with a gas light? Why would late 80's car have and my 93 doesn't?
Click to expand...

The information center with the gas light was gone in '90 I believe. I guess they had to save money for the airbag and three point rear seat belts.
 
You must log in or register to reply here.

Similar threads

H
Fuel starvation issues, 91 EFI to carb swap. Car dying after 1-3 gallons used. EFI tank, electric fuel pump, bypass regulator. Dual fed carb
  • hassler
  • Oct 11, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
8
Views
714
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Oct 12, 2025
nickyb
Hard to start when engine is cold
  • 86_Capri
  • Mar 11, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 2
Replies
32
Views
822
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 21, 2026
CAMTWO1070
O
SOLD FS: 18" FR500 chrome wheels and Toyo tires
  • optionizerSS
  • May 21, 2026
  • Other Classifieds
Replies
1
Views
76
Other Classifieds Jun 2, 2026
optionizerSS
O
Fox Xtremely high fuel consumption
  • PonyGTrider
  • Apr 11, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 9 10 11
Replies
213
Views
3K
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- May 9, 2026
PonyGTrider
S
Need help and Advise - 89 Problem Child
  • Sheela
  • Oct 28, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
1
Views
139
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Oct 28, 2025
evintho
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?