B4000 Fuel Gauge Problem after Replacing Sending Unit

[Walksnotruns22]

I have recently changed out the sending unit on my 1994 B4000 Extended cab because the fuel gauge was not reading at all. Since I put the new sending unit in, the gauge pegs out at full and never moves.

Any idea what I might have done wrong or what could be causing the problem. Taking bed off truck tomorrow to replace fuel neck off so would like to know if there is anything else I should look at since I will have access to the area.

Thanks in Advance.

 

[superj]

sounds like a wire is grounding somewhere.

 

[rubydist]

I believe that means that the gauge has ground but not power when it reads full all the time. I would be checking all the wiring connections to the pump assembly.

 

[Walksnotruns22]

Thank you. I will check all the wiring at the pump today.

 

[Walksnotruns22]

Ok. So now I am royally confused.



When the truck is on it either reads pegged full or empty but when the truck is off it reads correctly. It's like the wiring is backwards but the connector at fuel pump only goes one way.

 

[RonD]

It doesn't read correctly when off, the gauge just has a spring in it so doesn't stay on Empty with key off

1989 and up Fords use these OHMs
16 ohms EMPTY
158 ohms FULL

0 ohms is a short to ground, so below EMPTY
Disconnected wire is a million gazillion ohms so above FULL

Mazda may use the same wire colors as Ranger
Should be a 4 wire connector on the tank
Yellow/white wire is the OUT to fuel gauge in dash
Black/yellow is the ground for sender
Should see 16 to 158 ohms between the two connectors for sender, rock the truck a bit and float should go up and down and OHMs should change as it does
If so sender is OK

Test black/yellow wire to frame ground, should be 0 ohms, direct connection


1994 will have a Anti-slosh module on the back of the cluster, its a separate plug-in module
These can die, and show Empty or Full all the time and back and forth some times

Google: anti slosh module bypass

This takes it out of the circuit, you will notice gauge will go up and down when going around corners without this module in the circuit, but it will show correct level when driving straight
Or replace it if you can find another one

 

[Walksnotruns22]

Thanks for all the information.

Gonna ask neighbor when I can use his garage and winch to pull of bed again. I did do a quick look around when it was off and all four wires were connected but I didn't test any. While I was testing the passenger window with the key just in the on position it stayed at about 1/4 tank (which is about how much gas is in it) but once I started the truck it went back down to empty.

 

[superj]

instead of pulling the bed, just tilt it up and you will get access. that is how i did my mazda bed when i fixed the float on the old 98 b2300. tilted it up and put a 2x4 to hold it while i did the work. really easy and gives you lots of space

 

[Walksnotruns22]

So I was able to get back under there and start testing some wires. The plug in that goes into the sending unit seems to me intermittent. I don't think I will be replacing that.

I will go the old school way of just watching the amount of miles I drive or just turn the truck off and watch the fuel gauge go to the correct spot lol.

Thank you guys for all the help.

 

[superj]

when i used my old 98 mazda as a work truck, i would just fill up every 200 miles. worked for 250k miles that way and i never ran out of gas.

only later did i realize the truck had one of those lights that comes on when you are almost to the empty mark. i might have gotten in trouble using that as a gage though since texas used to have lots of miles between towns along the southern border.