Holley Sniper Stealth EFI - Part 12 (Sending Unit Adjustment)

This evening after work, I decided to add a little fuel to the gas tank and confirm the fuel gauge reads properly.  This is one of the few points that you have such a controlled situation you can determine exactly how much you have in the tank when the gauge reads empty or close to it.  I wanted to take advantage and set it up so that I had two gallons or so when it reads empty.

I added probably just under wo gallons to the tank and then checked the gauge but it had hardly moved.  I then added about a third gallon but didn't want to add any more.  At this point, the needle pointed to the lowest point of the E which is far below the empty hash mark.  I checked the sending unit and don't remember the exact ohm reading but it was below 70 so the sender was registering fuel in the tank.  

I pulled the sending unit, which is exceptionally easy since it is now on top of the gas tank.  It was at this point I was exceptionally thankful that I decided to use the rubber gasket on the sending unit instead of the cork gasket with sealant.  What I didn't know the first time I removed it was that I would remove it another 9 times before I decided to leave it alone.

The first adjustment was just to make sure that I had full movement of the arm where it would just touch the bottom of the tank when empty and would just touch the top when full... no change.  I then decided I would move the pivot point down just a little (1/8)" from the recommended setting... almost no impact.  This continued time and time again with little impact.  The sender is working as it reads 52.5 ohms with the three gallons it just doesn't correlate too much on the gauge.

I contemplated it all for a while and decided the gauge should really be set to read empty with three gallons.  Any more and it simply doesn't make sense to call it empty.  This time, I took it apart and confirmed the float would need to be about half under water before it started to move.  This really didn't change my approach much but confirmed that the two inches of fuel in the tank should be enough to move it reasonably.

I ultimately dropped the pivot a total of about 3/8".  I adjusted the arm so it would still just contact the top of the tank when full.  On the low side, it would initially attempt to hang lower than the bottom of the tank.  I adjusted the lower arm stop to match the bottom of the tank.  I then put it back in and the gauge pointed to the middle of the E.

I decided at this point that I was going to put just a bit more gas in thinking that I was perhaps at the tipping point of it moving rather rapidly to the empty hash mark.  I put about another gallon so I expect to have about 3.5 gallons in it.  With this amount added, the sender read 45 ohms and it is now pointing at the E hash mark.  

When the gauge is off or disconnected, you can see in the picture above the needle stop well below the E.  This is the beginning of the needle movement.  I expect that is where it starts when it is at 70 or so ohms.  This makes sense when you consider it but really empty is considered the bare minimum rather than what appears to be a quarter tank below it.  

I think when I actually fill it up, I should put in 4.5 gallons which would put me around 8 total and see what the gauge reads.  While I don't expect it to read a half a tank, that is what I'll have and it will be good to know what it reads.  I'll then do the same at 12 and then 16 gallons.  I'll try to take pictures each time just so I validate the gauge a bit more and know what I'm working with.