Sometimes fuel disappears

[BadOlHoe]

Hey all. Did a search and there is a similar post but not exactly so here goes.

About 2 months ago my fuel gauge suddenly started to stop at and around the 3/4 line with every fill up. Every few fill ups it seems that I can almost watch the needle move towards empty while driving (an exaggeration but you get the point), it really does need to be filled up again a lot sooner than normal when that happens. I don't smell a gas leak anywhere and there are no spots underneath that I can see.
Alao once in a while after filling up and taking some turns the needle will go towards full but never all the way. The needle never jumps around so couldn't be the sending unit could it? Any suggestions would be much appreciated

 

[swathdiver]

A leak cannot always be detected by smell. It is probably time for a complete new fuel pump and sender assembly.

Before you break out your wallet, check for leaks above the tank, wet spots and such, might have to stick a phone up there and take some pics.

 

[rockola1971]

I would stick a bidirectional scanner like a tech 2 on the vehicle and run the manual test for the gauge to verify the gauge is working correctly first since it is the easiest to do and the stepper motors that move all the needles on our instrument clusters do not have the best reputation for long life or trouble free.
Also might want to verify your MPG average in your display in the cluster and also take a look at total range once tank is filled up.

 

[Fless]

I would stick a bidirectional scanner like a tech 2 on the vehicle and run the manual test for the gauge to verify the gauge is working correctly first since it is the easiest to do and the stepper motors that move all the needles on our instrument clusters do not have the best reputation for long life or trouble free.
Also might want to verify your MPG average in your display in the cluster and also take a look at total range once tank is filled up.

x2 on the gauge check before replacing a fuel pump. But tell us a little more about your rig: year, model, Flex Fuel, miles, etc.

 

[exp500]

Late night fun after Dad goes to bed?

 

[rockola1971]

Late night fun after Dad goes to bed?

Fuel gauge stops at 3/4 tank immediately after "Filling up".

 

[Fless]

How do we know it's getting filled completely?

 

[rockola1971]

How do we know it's getting filled completely?

He likely doesnt or he runs down to fumes and then fills a 23gal tank roughly with 23gals or slightly less? Thats how I would check. The range would show when you are on fumes since range will work even if gauge does not work correctly. Then again he may not be able to physically fill the tank and the gauge isnt lying to him which Is why I say do a manual check with a bidirectional scanner on the fuel gauge since it is so quick and dirty and requires no parts to be thrown at the vehicle from the start.

 

[MassHoe04]

He likely doesnt or he runs down to fumes and then fills a 23gal tank roughly with 23gals or slightly less? Thats how I would check. The range would show when you are on fumes since range will work even if gauge does not work correctly. Then again he may not be able to physically fill the tank and the gauge isnt lying to him which Is why I say do a manual check with a bidirectional scanner on the fuel gauge since it is so quick and dirty and requires no parts to be thrown at the vehicle from the start.

Tech 2 (or other bi-directional scanner) can make for quick work on something like this for sure.

If there is no Tech 2 or bi-directional scanner available, this might be another way for the OP to see if the issue can get narrowed down without one.

My gauge is off maybe 1/8 due to PO installing a cluster decal set.
But I have been able to rely, pretty accurately, on the range displayed on the DIC.
On a full tank, mine shows about 325-330 miles remaining.

After complete fill-up (stopping after the first click on the pump to avoid overflow to the EVAP canister), OP can see what the trip information shows for range. Unless he drives 100% in congested city and no highway, I would expect his computed range should be in the 300+ range on the "miles remaining" trip information display.

If tank is full, computer says range is 300+ miles remaining and gauge is saying only 3/4... Very good chance the stepper motor is no good on the cluster.

When tank is full and computed range is 250 miles (or less), then the float on the pump assembly might be sticky or the sending unit no good.

Keep us posted on the situation.

 

[Fless]

My gauge is off maybe 1/8 due to PO installing a cluster decal set.
But I have been able to rely, pretty accurately, on the range displayed on the DIC.
On a full tank, mine shows about 325-330 miles remaining.

You could reseat the gauge needle so it's accurate, comparing what your Tech 2 reads for fuel level % now and the gauge, then adjusting the needle. Usually when the ignition is off the needles rest a little below their zero point. When powered up with no input they'll bump up from that slightly due to the stepper motor moving from its resting point to its zero point. You could also install an accurate gauge face while its apart.