All times are UTC - 6 hours [ DST ]




Ask A Question Reply   
Author Message
 

contributions: 3
Stumped!! I have a 89 ford 150 that has a fuel gauge reading incorrectly. Was advised to change the sending unit for which i did and the gauge started to read excessfully full instead of reading the way it should. Completely disconnected the wiring for the sending unit and the gauge still continues to read over the full mark. All wiring looks good but able to figure out what is going wrong. Any suggestions to what is going on would be great. Checked for power at the connector to the tank and found power going to the low pressure pump but no power to the sender unit. Traced wire back to fuel gauge and found that there is no power coming from the fuel gauge but the fuel gauge will read 3/4 full with no power and reads well over the full mark with the power on. Got me scratching my head.


Share on FacebookShare on DiggShare on DeliciousShare on TechnoratiShare on TumblrShare on Google+
   
Reply with quote  
* Search   
 
User avatar

contributions: 2076
Images: 37
Location: Oregon
since you didn't say anything about either tank I am going to assume that you have a single tank truck. The fuel gauge has a yellow and white wire that goes back to the sending unit in the tank. It connects to the A12 pin in the instrument cluster. with the wire open or disconnected it should make the gauge go to empty (or below empty). If you gauge reads anything above that with the sender disconnected I would look for a short to ground. Because it doesn't read full to the top I would look for a short that has high resistance. A short to ground will take away the voltage measured at the fuel tank sender connector at the tank. (because it is already completing a circuit)

If you can access the dash wire harness and remove the wire to the sender either by taking it out of the connector or cutting it where you can see the wire is not accessible to any ground, check if the gauge still reads high. If it reads over empty you probably have a bad gauge.

When you say it reads 3/4 with no power and over the full mark with power, are you talking about with the key on and with the key off? If your gauge doesn't go to empty when you turn the key off I would try another gauge.


   
Reply with quote  
 

contributions: 3
yes it is a single tank and i had ground the fuel gauge wire with power and the fuel gauge went to empty. took off ground and gauge went back to reading full, there is 8 volts at the fuel gauge wire. checked ohms at sender unit and is reading 14 ohms empty and 153 ohms full this was on a new sending unit, was told by another mechanic that i should only have 10 ohms at full and 70 ohms at empty. returned sending unit and got another did the ohms check and got the same readings. not sure what to think at this point. :cry:


   
Reply with quote  
 

contributions: 3
thanks 4 the help, solved the problem myself.


   
Reply with quote  
 
User avatar

contributions: 2076
Images: 37
Location: Oregon
that's great Bill. would you like to post your fix so others that have similar problems might be able to benefit from your findings?


   
Reply with quote  
Ask A Question Reply   

   Similar Topics   Author   Replies   Views   Most Recent 
New Articles View the first 95 ford fuel system 5.8 f350

in Ford Trucks

rick123458

1

574

Sun Jan 22, 2017 3:06 pm

carriedi View the latest

New Articles View the first f250 5.4 starts then stall no fuel , changed most fuel parts

in Ford Trucks

milkmandelight

4

1403

Sun Nov 13, 2016 12:09 am

Rachel View the latest

New Articles View the first 93 f150 fuel problem need answers

in Ford Trucks

Drewh

1

618

Sun Jan 29, 2017 3:10 pm

carriedi View the latest

New Articles View the first 92 Ford Escort

in Ford Cars

Tibo

1

1821

Fri Nov 28, 2014 10:53 pm

carriedi View the latest

New Articles View the first Ford F-150 egr problems

in Ford Trucks

earnie

1

1546

Thu Feb 12, 2015 12:04 am

carriedi View the latest

New Articles View the first Ford Car Milage - carprice se

in Ford Cars

carpricese

1

1239

Sat May 16, 2015 8:42 pm

carriedi View the latest

New Articles View the first 4x4 problems in ford truck

in Ford Trucks

fish

1

1385

Wed Nov 26, 2014 4:08 am

carriedi View the latest


All times are UTC - 6 hours [ DST ]



Search for:
Jump to:  
Contact Us