• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

Fuel Level Sending Unit Ohms/Troubleshoot and Fuel Gauge Swap Info


gungfudan

Member
Supporting Member
Joined
Feb 22, 2011
Messages
475
Reaction score
19
Points
18
Location
Mississippi
Vehicle Year
1994
Make / Model
Mazda
Engine Type
3.0 V6
Engine Size
3.0
Transmission
Manual
2WD / 4WD
2WD
Total Lift
N/A
Total Drop
N/A
Original Poster: Daniel Inbinett (gungfudan)

Dificulty: 4 out of 10

The time depends on how experienced you are.

Disclaimer: The Ranger Station.com, The Ranger Station.com Staff, nor the original poster are responsible for you doing this modification to your vehicle. By doing this modification and following this how-to you, the installer, take full responsibility if anything is damaged or messed up. If you have questions, feel free to PM the original poster or ask in the appropriate section of The Ranger Station.com forums.

This is an explanation on how to trouble shoot you fuel level sending unit and what the ohms you need (depending on the year of you truck) for a new aftermarket fuel level gauge or to use a your factory gauge with a new fuel cell that has an after market sending unit. Note: the reason is if you do not have the correct ohm range your guage will not work.

Tools Needed:
an electricians meter (that reads ohms)
flat head screw dirver

Parts needed:
(All parts in list are based on if parts are bad or need repair.)
possibly new sending unit
auto wire
butt connectors

IMPORTANT!!!!!!!
Things you need to know before you start:
The fuel gauge is a fairly simple electronic. The fuel gage circuit consists of the sending unit in the fuel tank, the gauge in the dash, and the wiring and dash wiring (or circuit board) between them. It's power source comes from a voltage regulator that is 5 volts. (NEVER HOOK THE SENDING UNIT OR GAUGE TO A 12 VOLT BATTERY) Here is a picture of a sending unit on a 1988 Bronco II wiring diagram:
View attachment 8476

How It works:
The sending unit is a variable resistor. It resists the flow of current from the ground to the gauge depending on the position of the float within the tank. When the float arm is at the full position It decreases the resistance between gauge and ground.(basically there is shorter distance for the current to flow) The more current that flows through the meter, the higher the gauge needle moves.
The gauge uses a 5 volt pulse supplied by the instrument cluster's voltage regulator.

Troubleshooting:

Problem; The gauge does not work.(the needle does not move)

Turn the key to the on position for this operation. If you can get to your sending unit wiring harness without dropping your tank(s) go ahead and pull it. If not then drop the tank(s) and pull the harness. Get a piece of wire (jump wire) to connect to the possitive of the harness and the negative of the sender housing. This should make the gauge jump to full.

If the gauge's needle moves:
It means that the wiring is fine and it is your most likely your sending unit. You need to remove the sending unit from the tank for inspection and testing.

Here is a picture of a 1985-1988 sending unit.
View attachment 8474
The red arrow(the male connection), The black arrow (is the main part of the sender), The blue arrow (is the float that is attached to the sender arm).

After removing the sending unit inspect to make sure the float, float arm, wires, and the sender it self is intact and functioning properly. There is a possibility that the arm is binding so move it up and down to make sure. Hook up an ohm meter to it to check the ohms. To hook the owm meter to your sender follow the from the sender to the bottom of the plate and locate on the top which prong it is.(to see prongs go to picture below) now the groung is the one with no wire attached to it. Now move up to full and down to empty to check reading.

View attachment 8475

It should read depending on the year; pre-1989 empty 73 ohms/10 ohms full or 1989-on empty 16 ohms/158 ohms full. If it does not it could need repaired or replaced.

I have an 1988 Ford Ranger and my sending unit was not working. The guage worked so I knew there had to be something wrong withe the sended. Now if you have a mechanical fuel pump like mine then you can not get the sending unit for that year because they stoped making it for that year. Which to me was stupid it just is one metal tube on the sender plate and a two prong connection. So I had to get a sending unit for a 2.3L ranger and modify it. And it works great.

Back on topic.

If the gauge does not jump to full:
Ground the sending unit wiring to a good chassis ground (instead of the sending unit housing) and watch the gauge. Does it now jump to the 'Full' side?The power supply to the gauge has been interrupted, (check fuses), the gauge is defective, or the wire from the gauge to the sending unit is open or has a break in it.

To check the voltage regulator for proper funtion use a tester. Probe the connector with the tester, it should flash on and off.

Note: If you are installing an after market fuel gauge you need to make sure that the gauge is the same ohms as your sender. It will not work if they are not the same. The same goes for after market sending units that you might get with a fuel cell. Check your instructions or call manufacturer for information.

Manufacturer of Gauges:
Auto Meter (have fuel gauges for ford)
Equus (have fuel gauges for Ford)
Sunpro
there are many others.

I hope this was helpful

I want to thank http://www.fordification.com for the information I read about.
 


Mark_88

Well-Known Member
Joined
Aug 11, 2007
Messages
18,554
Reaction score
240
Points
63
Age
68
Location
Ontario, Canada
Vehicle Year
2007
Make / Model
Dordge
Engine Size
3.3 Fuel Injected
Transmission
Automatic
My credo
Love Thy Neighbor
Good writeup Dan! You seem to have a knack for this sort of thing...keep up the good work...I've never seen my sending unit and now I know what it looks like...and what to watch for if I decided to actually change things...:icon_thumby:
 

Tominator

New Member
Supporting Member
V8 Engine Swap
RBV's on Boost
Joined
Aug 12, 2007
Messages
661
Reaction score
24
Points
0
Age
69
Location
Cahokia, Il.
Vehicle Year
1995
Make / Model
Ford
Engine Size
5.0 S-Trim 450HP
Transmission
Manual
Yup! Great job...that's a keeper!:headbang:
 

adsm08

Senior Master Grease Monkey
Supporting Member
Article Contributor
Ford Technician
TRS 20th Anniversary
Joined
Sep 20, 2009
Messages
34,623
Reaction score
3,613
Points
113
Location
Dillsburg PA
Vehicle Year
1987
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Tire Size
31X10.50X15
This is a great write up. I would like to add that if you have a concern about the gauge's ability to work in a specific spot you can get resistors from Radio Shack and put them inline to test the gauge at different spots.
 

gungfudan

Member
Supporting Member
Joined
Feb 22, 2011
Messages
475
Reaction score
19
Points
18
Location
Mississippi
Vehicle Year
1994
Make / Model
Mazda
Engine Type
3.0 V6
Engine Size
3.0
Transmission
Manual
2WD / 4WD
2WD
Total Lift
N/A
Total Drop
N/A
Yeah i built a 5 volt regulator for my new fuel gauge. Thanks guys
 

svtcards

Active Member
Supporting Member
V8 Engine Swap
Joined
Sep 4, 2017
Messages
826
Reaction score
137
Points
43
Age
46
Location
Lyman maine
Vehicle Year
1987
Make / Model
ford
Engine Type
V8
Engine Size
302
Transmission
Manual
2WD / 4WD
2WD
Total Drop
3'' front 4''back
Tire Size
245 35 18
I know this is an old post but the ohm readings he mentioned for pre-89 ranger. Is the ohm readings correct? 73 ohms empty 10 ohms full.just curious?
 

svtcards

Active Member
Supporting Member
V8 Engine Swap
Joined
Sep 4, 2017
Messages
826
Reaction score
137
Points
43
Age
46
Location
Lyman maine
Vehicle Year
1987
Make / Model
ford
Engine Type
V8
Engine Size
302
Transmission
Manual
2WD / 4WD
2WD
Total Drop
3'' front 4''back
Tire Size
245 35 18

Sponsored Ad


Sponsored Ad

Staff online

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Kirby N.
March Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top