Hi! I've got an 81 Ford F100 with a 300 i6, and I recently replaced my fuel sending unit (the gauge wasn't working) it would go up to full then after a few miles it would go down to E, So I installed the new unit and went on, from the word go the gauge still isn't working right. it works better than it did but while going down the road it changes positions and still isn't accurate. I ran a ground wire from the sending unit to a fresh spot on the frame and still no luck. anyone have any ideas of what I could check? any help is appreciated! Have a good day!

 

Pull it out again, and hook it up and move it up and down while watching the gauge.

 

You sure you got the right sending unit?
Did you get it thru LMC?
If not who thru and the part number so we can check it out.


You did not say what gal tank you have and where it is on the truck.
There are 2 different side tanks & senders. A 16 gal & 19 gal.
Only1 rear 19 gal tank but you see 3 tanks & senders.
Dave ----

 

It's the 16 gal tank on the driver's side, the sending unit was Spectra FG75A, Im pretty sure it was the correct one. I bought it thru Amazon.

 

First this is the 1 I went with after I was told of the 3 different senders, 2 for the side tanks.


http://www.1aauto.com/1980-84-ford-fuel-tank-sending-unit-for-lh-mounted-16-gallon-gas-tank/i/1afsu00159?f=436961&y=1981
I put your part number into Google and of the 4 or 5 I checked only 3 I could see it was for the16galside tank so I would have to say you are right it is the right one.


What is meant by "it works better than it did but while going down the road it changes positions and still isn't accurate."?
Does the gauge move up and down when driving the truck like going around corners or bumps?
As was said you could pull it and move it thru the arc and see if it follows right.


Now from what I remember on replacing mine there was a tab on the sender and this fit into a cut out on the tank opening to "index" the sender. This could be for 3 reasons the way I see it.
1) So the pickup tube sits in the lowest part of the tank.
2) So the float can move up & down freely without hitting the tank walls.
3) The last is with fuel sloshing around in the tank. It could move more front to back OR left to right.


Lets say the fuel moves more F/R and that is how you have the float set the gauge can move then. But if you have sender L/R (less fuel moving) the gauge would not move as much. Again this is based on the tab/cut out.


Just my .02
Dave ----


btw-I have not put my sender to work yet so cant say how it works.

 

What I meant was: It works better as it fills up and tries to read accurate but when taking off and driving normally in town or down the highway it starts slowly going down to E, but doesn't go down Completely. but it still is very inaccurate, I'm going to pull it later today and test it.

 

I have got the same issue, I replaced the sending unit and it continues to have the same issue

 

grounds, grounds, grounds....