Gas Tank Sizing

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Nov 21, 2023 | 04:24 PM

#16

Brother Les

Cargo Master

Joined: Oct 2007

Posts: 2,712

Likes: 107

From: BoCoMo

Quote:

Originally Posted by Ted722

Is the fuel warning light coming on?

Same config here, V10 Supercab Shortbed. Have run mine(several times) until the warning light just comes on and I can put 24.5 to 25 gallons in. Haven't run it out of gas, but I've read and believe I have about 4 gallons left once the light comes on.

Sounds like your fuel gauge / sending unit might need some troubleshooting. Regardless, only way to know capacity is running it dry and filling it back up.

With the 7.3s, the last 5 gallons have to be slowing dribbled into the tank as there are breather tubes in the tank that foam up the diesel to get the full 29 gallons instead of the shut off at 25gal.. There is a mod that is called the Harpoon mod. The harpoon mod is easier to look up than ask about. Basically, the fuel vent on the fuel filler neck, that shuts the pump off because fuel backfills it when getting full, is trimmed off higher in the inside of the tank to allow for a more filled fuel tank.

Nov 21, 2023 | 04:56 PM

#17

Pickupmanx2

Lead Driver

Joined: Jun 2006

Posts: 5,653

Likes: 978

From: Near Yosemite CA

Quote:

Originally Posted by oat_stormtrooper

My fuel light comes on and I’ve driven for a bit and fill about 20 gallons.

Had this issue years ago on my 99 w/7.3, gauge was showing mt, so I would fill it and it would only take like 20 gals or so, filled it full full, parked on level ground, disco'd batteries for about 15 mins, reconnected, was always good after that...

Nov 21, 2023 | 05:43 PM

#18

super 6.8

Fleet Mechanic

Joined: Oct 2004

Posts: 1,394

Likes: 104

From: Southern KS

You could always convert to the Excursion tank that goes in place of your spare tire. I think it is 42 or 43 gallons.

Should be a pretty straightforward swap from junk yard parts.

I have thought about doing that but have never got around to it.

Nov 22, 2023 | 06:00 PM

#19

WE3ZS

Moderator

Joined: Jul 2010

Posts: 12,050

Likes: 1,549

From: Media PA

Quote:

Originally Posted by super 6.8

The Excursion tank is listed as 44 gallons but there are some owners who have done the harpoon mod that report near empty fill ups close to 50 gallons, the most that I’ve pumped into mine was about 43 gallons, but I try to not let it get that low.

Nov 27, 2023 | 12:03 PM

#20

Ted722

Tuned

Joined: Mar 2022

Posts: 304

Likes: 192

From: Northern California

Quote:

Originally Posted by oat_stormtrooper

My fuel light comes on and I’ve driven for a bit and fill about 20 gallons.

Just FYI. Had an opportunity to test it again this past weekend on my '03 SCSB V10. Fuel light came on between 1/8th of a tank and E on the gauge. Drove another 12 miles to my primary go-to gas station...gauge was now on E when I got to the station. Let it fill up(on slower gas nozzle notch like I always do) to first "click", no topping off. Put in 25.4 gallons.

Nov 27, 2023 | 05:34 PM

#21

oat_stormtrooper

Thread Starter

Cross-Country

Joined: May 2023

Posts: 51

Likes: 9

Mystery solved. If I fill my tank super slowly I can get close to 29 gal on an empty tank. Gauge reads about an 1/8th over full when I do this as well! I had tried filling until it clicked off then topping off, but I really have to wait for it to bubble back down before topping off with super slow pump.

Nov 28, 2023 | 07:30 PM

#22

super 6.8

Fleet Mechanic

Joined: Oct 2004

Posts: 1,394

Likes: 104

From: Southern KS

In the very few cases I have let my low fuel light come on I can only get about 25 gallons into the 29 gallon tank.

I wouldn't make a habit of getting any lower than that. Your fuel pump will not like it at all.

Nov 29, 2023 | 09:52 AM

#23

Pickupmanx2

Lead Driver

Joined: Jun 2006

Posts: 5,653

Likes: 978

From: Near Yosemite CA

Quote:

Originally Posted by oat_stormtrooper

Yes, diesel has always had bubbly, but when they changed to ulsd it really foams up now, depending on which truck, I can usually get another 2-4 gals in after it clicks off and waiting a min or so for it to subside.. glad ya figured it out.