78 F150 fuel gauge
 

Fuel gauge not working.Grounded out wire from connector at tank and gauge crept up to full, eliminating gauge.Replaced level sending unit, still the same problem.Good ground to sending unit.Checked both wires from sending unit for continuity...good. I have only put 5 gal. of gas in tank from bone dry and gauge does come up to just above the empty mark.Shouldn't it show at least a quater tank?

For,
__a 19.5 gal. tank,yes.
Where did you get your sending unit?
It may need final adjustment.

Got it from rock auto parts.

How is the final adjustment made?Please tell me I don't have to drop the tank again.

Put,
__that adjustment on hold.
You just may hust have to clean/correct your pigtail contacts.

Go to thread: https://www.ford-trucks.com/forums/7...ml#post6854822

If that don't work just look up thread: Gas gauge reading correctly??

Thanks Crazed, I can get the plug on and off without dropping the tank thank God.Actually the pins on the new sender were larger then the old.I'll check gauge and chasis ground.I'll keep ya updated on progress.

Ok,
__don't forget to clean the pigtail's contacts & chassie ground.
They need to be clear of any corrosion, use a good flashlight.
Good-luck.

OK...there was no body ground,there is now.Cleaned the pigtail contacts, cleaned engine ground, but am unable to find the chassis ground.Do you know where it's located?
Thanks for all your help.

There,
__was no manufactured chassie ground.
You have to put one in. Two ways of doing this.

1. run batt.cable (no smaller than 6-ga.) from ground on battery to a bare metal spot on chassie, use a spiked washer (makes a more correct contact.) inbetween cable & chassie. Don't forget to put DIELECTRIC sillcone grease on the parts & chassie. (This grease is the same stuff you put in your spark-plug boots.)

2. run ground from engine block to chassie. Don't forget your spiked washers & D-grease.

TIP: your original ground should be going from your battery to your Engine block,
Directly to your block.

NOT to a bracket, intake bolt/nut, exsast manifold nut/bolt, Or even to the engine head.
Only, Directly to your block.
This the one & best soild route to grounding the block.

I have no less than 3 grounds on my own trucks & cars. (one to engine, one to chassie, & one to the body.)

Thanks Again Crazed.I'll run that ground this evening.I was also told by someone that 5 gallons in a bone dry tank may just take the level just above empty to act as kinda like a reserve.
Take Care

Oh,
__yah! (slap's forhead") How could I forget about the 2 gal. rule!, Duh...

There's the 2 gallon rule, that there is at least 2 gallons in the tank when the gage hits E.
About 1 gallon to run on, the anthor gallon that keeps sediment/water from reaching the fuel-pickup.

I ran out of gas one time with the gauge showing a 1/4 tank.

Other times I have easily ran directly on E

Josh

Pardon my ignorance but how does running a ground wire from battery to chassis fix his broken fuel gauge? My fuel gauge just went yesterday on my 78 f150 two days after getting it on the road. I have little idea how to fix it.

Basically what he's saying is, the sending unit is grounded to the chassis. To ensure a complete ground circuit back to the battery, there should be a wire from the chassis back to the battery.

Tis the season for fuel gauge problems I guess... I just posted the other day on my experience. Just a quick recap: I fill mine up, gauge reads full. Gauge on empty, fill back up, tank only holds 10 gallons. I dropped the tank took out the sending unit. I observed the position of the float in the angle that it would be in while installed in the tank and noticed that it was about 3 inches above the pick up tube. I bent the arm float arm so that the float was about an inch over the pick up tube. Reinstalled everything and the fuel guage now reads closer to what the level in the tank. It might not be 100% accurate but close enough.

I see...... I'll double check the wires on the batt. I'm pretty sure there's some wire attached to the negative already but I'm not sure where it goes yet. As for dropping the tank, I sure hope it don't come to that....prolly wont get it back together with the same straps. If only I could just tap something with a hammer and have it work for a few more months till I'm better off lol