Problem with current so i want to replace the fuel tank system

[usar17]

So i currently have on tank. Previous owner ruptured the driver side tank, removed it, and just plugged the lines where the sending unit connected.  Passenger side is in place and Tank selector switch is still there (Haven't tested or messed with it).

Currently I believe there is an issue with the float on my passenger side tank. I'm only getting 8-10 gallons in it when the gauge reads empty. I measured the wide and length (but not the height) of the tank and it matches specs i found for original 16 gallon tanks. So i'm assuming the float is bad on the sending unit.

Current plan/what id like to do, is remove the switch and selector valve, replace the tank with a 20 Gallon and new sending unit.

Thoughts? Any issues you think i may run into? I don't need two tanks, 20 gallons is enough for this around town'er and lil off-roading.  As for new sending unit i know its a 3 tube connection, but i have seen them listed on some sites differentiating "w/ auxiliary tank" or "excluding auxiliary tank". whats that?


Thank you

[usar17]

Also ...maybe bc of sending unit, but is it normal for the fuel gauge to drop up to a quarter as i brake and come to a stop. It returns to previous spot after I settle or accelerate.

[1979C20]

The sending units on these trucks are not very accurate. I have dual 20 gallon tanks, but I only use the driver side. It can be completely empty, I put 10 gallons in it and the gauge reads full. I fill it to 20 and it goes a little pas full and stays there. When its almos empty, it sits on an 8th tank on the gauge when there's still like 5 gallons, and says a an 8th until empty. And the gauge moving when you brake is because the tank has no baffle in it, so the gas sloshes and moves the sending unit.

[bake74]

     Grounds are very important on these tanks to read right.  As far as replacement with a 20 gallon tank, have you checked to see if it will physically fit ?

[usar17]

ya i'll check all the grounds and wiring. as for fitment im gonna be measuring before i order. So removing the selector valve isnt a problem? any re-wiring to be done in regards to the sending unit through the selector? and has anyone seen baffled replacement tanks

[zieg85]

ya i'll check all the grounds and wiring. as for fitment im gonna be measuring before i order. So removing the selector valve isnt a problem? any re-wiring to be done in regards to the sending unit through the selector? and has anyone seen baffled replacement tanks

If your truck has the 8 foot bed either 16 or 20 gallon tank will fit.  If it is the short bed only a 16 gallon will fit.

[1979C20]

Tanks from fuel injected trucks have baffles. Is your truck a long bed or short bed? Long bed, the 20 gallon will fit no problem. I'm not sure about the short beds. And, no re wiring needed. All you have to do is remove the 1 wire from the switcher valve and make sure it won't ground out on anything and your good to go.

[usar17]

8 foot bed

Thanks, I'll look for some EFI tanks

[usar17]

Hows this parts list look??

1985 three port fuel sending unit
1985 tank straps for a 20 gallon tank
1987 fuel tank 20 gallons with baffles

All new replacements no salvage yard picks. Will this set up warrant any modifying?  Just worried about the 85 sending unit fitting the 87 tank since they were designed for sending units with fuel pumps. Will I have to modify the lock ring area or cut some baffles to fit the unit?

[Captkaos]

The baffled tank won't help with the accuracy of the gauge, it is all in the funky sweep the sending unit does at the top as it is on an arch.  It is mostly accurate  at 1/2 a tank or below...  All of them are like this.

[usar17]

I'm assuming that bc i haven't seen it posted before, you can't switch it over to a later model inside the frame tank

[Blazin]

Where would you put it inside the frame? Drive shaft, and exhaust is taking up all the space.

[usar17]

Will a 20 gallon tank fit on the passenger side where there is currently a 10-12 gallon axillary tank? Or do I need new brackets etc...?

[thirsty]

A 20 gallon tank will fit on either side.

where there is currently a 10-12 gallon axillary tank?

When you say auxiliary 10-12 gallon tank is that something that is not for the truck but added and made to fit or do you have a 16 gallon tank made for the truck?

[usar17]

well like i previously stated, i have an unknown fuel tank hanging on the passenger side. measures length and width the same as  16 gallon. But I only put around 10 in when the gauge reads E. so idk lol