Hello guys,

I have a problem with the fuel level reading in my truck. Sometimes as I turn the ignition the fuel gauge will move to where it should be but most of the time now the needle goes straight to full. While driving or sitting at idle for a while the needle will move from full to the correct level and stay reading correctly until I turn the engine off. I have recently replaced the fuel pump / sending unit assembly (2 months ago) as this was the problem before except it always read full. After the new install it read properly for about six weeks and now back to reading full and sometimes reading correctly and the thing I noticed when I filled the tank with the new unit it took about 10-15 mins for the needle to come up to full while driving, after that it read correctly until empty but every fill up it would take that time to register full. Any ideas?

Thanks

 

Most vehicles have some form of "slosh module" for the gas gauge, this prevents the needle from jumping around when you go around a corner and the fuel "sloshes" to one side and then back in the gas tank, causing float to go up and down.
This module is also why fuel level may slowly increase when you first turn on the key after filling up, these modules "sample" the float level(OHMS) from a few seconds before then re-adjust for new level, then "sample" level again and re-adjust, ect..................until level reading is not changing
10-15 min. of slowly rising would not be correct, 30-60seconds maybe, depends on vehicle, usually 15 seconds would show corrected level

Ford Ranger has a Slosh module in the instrument cluster, 1996 seen here: https://therangerstation.com/Magazin...gauge/gr-8.JPG

Upper right of the picture, green circuit board, it can be removed and replaced or repaired or even by passed

Google: ford ranger slosh module

loads of info on these

Can't say this is your specific problem, only testing can decide that, its just a place to look.
Ford Fuel gauge Sender uses 10 ohms Empty and 160 ohms Full, so a loose or corrode sender wire would cause High Ohms, so would read Full, shorted to ground wire would read Low Ohms so Empty.

Sender is Grounded with Fuel pump, but has its own ground wire, and then has a yellow/white stripe wire as signal wire that runs to the instrument cluster and slosh module
If you have instrument cluster out look for the Yellow/white wire, should be center connector(C215) last pin(pin 12), with connector removed use Ohm Meter, ground one probe and put the other on Yellow wire, should read between 10-160 ohms now Rock the truck, get gasoline sloshing around, ohms should change as float moves around, if this happens then sender and wiring are OK.
If sender ohms are jumpy or intermittent then wiring or new sender is the problem

 

Thanks RonD,

I will check the ohms with the meter as soon as I can. I still have a 03 Sport Trac cluster that I have to install just got to swap the odometers and that has the anti slosh module in it so will see how it reads with that one.

 

Hello again,

I finally got around to swapping the instrument clusters and now have the 03 Sport trac cluster in with the odometer from my old cluster. The fuel level again as the key is turned on the needle jumps straight to full and doesn't move. I don't think the slosh module in this unit would be bad as well and the pump and sending unit was replaced a few months ago so that should be good. I guess I have to do some testing now and try to see what the problem is.

 

1989 and up Fords use 10ohms Empty and 160ohms Full for the sender and gas gauge

If it goes to Full with key on then most likely the sender wire is not connected, infinite ohms, very high, lol

Ford used a Yellow/white stripe wire from instrument cluster back to the gas tank
It often ran over to passenger side of cab where inertia switch is and then out with the Ground and 12v wire for fuel pump

If cluster can be pulled out again you could test it there, or in the frame rail near the gas tank
In Rangers, 1996 and up Pin 12 in center connector(B) was fuel gauge, yellow wire, in 2004 it was changed pin 7

If you have Ohm meter hooked to good ground and the yellow wire(use a sewing needle to pierce yellow wire) you should see ohms between 10 and 160, then rock the truck, get gas in the tank to move, causing float to go up and down and you should see the OHMs change as it does

 

Thanks again RonD and yes I will pull the cluster again and do some testing to see what I find. Will keep you updated.

 

Hey,

I removed the cluster again and tested the wire but reading over the previous post I think I tested the wrong wire. I attempted an ohms test on the yellow / white wire and I see where I should have tested the yellow wire so I will pull it again and test. I got no reading from the yellow / white that goes into the cluster. I also removed the slosh module to see if it would changed the fuel level reading and it went back down beyond empty.

 

Yellow/white stripe IS the correct wire
NOT Yellow

It should read 10-160 OHMs depending on fuel level in the tank

If its HIGH ohms then wire is disconnected
If it 0 ohms then its shorted to ground

There are a couple of different just yellow wires, one will have 12v key on, the other is for Low Fuel Warning light, if dash has one

But only 1 yellow/white wire, for fuel sender in gas tank

 

Good, I was testing the correct wire. I used my cheaper multimeter out of the 2 I have because I couldn't find the other one and on the low ohms setting (200) the reading didn't change from the 1 reading on the screen at all so I guess it's shorted to ground. Time to start digging for chaffed wires now then.

 

On a OHM meter touch the probes together first should get 0 ohms, that shows the meter is working, then touch one probe to yellow/white wire and the other to a Cab Ground
Should see 10-160 ohms, I think 16-158 ohms is spec
Rock the truck and watch OHMs change a float goes up and down

 

 

I had some spare time this morning and I have removed the cluster again and did some testing. I tested the yellow / white wire in the black connector pin 12 which goes into the C2 port of the cluster top right hand side right next to slosh module when looking at cluster from the back. I used my better meter and same results, no reading or change from OL on the screen. When touching the leads I get a reading of 0.03 so the meter is also working. I assume since there's no reading from that wire it must be completely broken and not making a connection. I will check the connection at the inertia switch and go from there and I will keep the cluster out as I have another truck to drive while testing.

 

Yes, reads like broken or unplugged wire

You can test ground by just touching other probe to another ground, should drop to close to 0 ohms

 

I did some more testing and I have continuity on the yellow / white wire from the cluster connector to the big plug under the dash above the driver side kick panel so the wiring behind the cluster is fine. From the big plug does it then start going out and to the rear? If the sending unit is bad, would I get the reading I am getting on the meter? I've looked at the wire loom leading from the front to fuel tank and it's in good condition with no cracks or cuts.

 

Yes the sender can be bad, or the sender's Ground wire can be, its a Black/yellow stripe wire back by the gas tank, but changes to a Black/white stripe up by the cab
If your yellow/white wire is on clusters pin 12, then pin 2 on that same connector is the Black/white ground wire, test it for 0 ohms a good ground

Get a sewing needle
Leave cluster end disconnected

Use needle to pierce the Yellow/white wire anywhere you can find it to test OHMs to ground, 10-160 ohms
When you get to the tank area find the black/yellow wire and test it for 0 ohms, good ground

Not much to a sender, look here: https://www.fordification.com/tech/f...ding-units.htm
Just a variable resistor but they can and do fail

 

Hey,

just to update on this issue. I went ahead and replaced the fuel pump and sender assembly and the gauge now works again. This time the needle moves right up to full when the tank is refilled and seems to be working correctly so will update in a week or so on the readings.

 

Good stuff

Thanks for the update

 

Well the gauge is still reading but I don't think its accurate and some weird movements are occurring. First pic shows gauge in the morning, second is same day with no driving and the last is where it went down to after 10 miles of driving.