Progress Thread Goofy fuel gauge on slow progress

7991LXnSHO · Aug 9, 2022

General karthief said:
After checking 'the magic book' it refers to using a ford tool that likely nobody has, I really want to collect some of these test tools, they are out there someplace but the book gives resistance readings for the sender so a VOM can be used for that:
145 ohms at full
22.5 at empty
Question #1 (GT model only) does the low fuel light work?
Note: GT model only, not sure if this is all GTs, mine is an 89.
#2 does the gauge stay in place when key is switched off?

#2. Pretty much. It stays where it is as long as I want to sit there and watch. It might not read right next time I get in though. Is that good or bad?

The gauge was in the middle when I got in the car this AM (not right, I had 3/4 of a tank). I tuned the key to the on position and the needle did not move. After it ran a bit, I turned the ignition switch on and off twice and the needle moved the second time.
And this afternoon the needle stays in place when off.
The reading drops a bit when the ac is blowing and the engine is off, and a bit more when the starter is hit, vs. when the when the engine is running. So now it’s moving when on instead of stuck.

General karthief · Aug 9, 2022

Well I would guess either a bad connection or the sending unit in the tank is faulty but in order to test it accurately you have to drop the tank

7991LXnSHO · Aug 10, 2022

General karthief said:
Well I would guess either a bad connection or the sending unit in the tank is faulty but in order to test it accurately you have to drop the tank

So the gauge is supposed to stay out when off? I have not seen the Ford magic book for this car and should get one.

General karthief · Aug 10, 2022

As I read it, the needle should stay in place when key is turned off, I can't test this as the Junk Pyle is still waiting it's turn.

Mustang5L5 · Aug 10, 2022

You should be able to access the wiring at the rear of the car without dropping the tank. There is a connection for the fuel pump and fuel level sender that you can reach and unplug. You can then read the resistance off the sender and ground out the wire to the cluster to see what the needle does.

I’ll have to get the wiring diagram for 91 but it’s similar to this. Remind me later

Mustang5L5 · Aug 10, 2022

Here’s the 91 diagram

I think C400 is the connector at the rear that you can access that does fuel pump and sender. Black and yellow/white wires are what you want. If you check them from the sender, you should have 22.5-145 ohms depending on how much gas.

If you ground the yellow/white, it should max out the fuel guage.

Bad slosh module also a possibility

7991LXnSHO · Aug 10, 2022

Mustang5L5 said:
Here’s the 91 diagram

I think C400 is the connector at the rear that you can access that does fuel pump and sender. Black and yellow/white wires are what you want. If you check them from the sender, you should have 22.5-145 ohms depending on how much gas.

If you ground the yellow/white, it should max out the fuel guage.

Bad slosh module also a possibility

Thanks!!!
This is next- after the yard projects and recovery. Help finally showed up, but this is likely to get in progress sooner than that anyway. I should have some resistors or potentiometers in my electronics cabinet to set up a test with.

Progress Thread Goofy fuel gauge on slow progress

7991LXnSHO

wanna catch the space herp

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General karthief

wonder how much it would cost to ship you a pair

7991LXnSHO

wanna catch the space herp

General karthief

wonder how much it would cost to ship you a pair

Mustang5L5

That is…until I whipped out my Bissell

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Mustang5L5

That is…until I whipped out my Bissell

7991LXnSHO

wanna catch the space herp

Similar threads

Progress Thread Goofy fuel gauge on slow progress

7991LXnSHO

wanna catch the space herp

Sponsors (?)

General karthief

wonder how much it would cost to ship you a pair

7991LXnSHO

wanna catch the space herp

General karthief

wonder how much it would cost to ship you a pair

Mustang5L5

That is…until I whipped out my Bissell

Attachments

Mustang5L5

That is…until I whipped out my Bissell

7991LXnSHO

wanna catch the space herp

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