26 to 36 gallon fuel tank swap

[rustyrider]

New member here, purchased a carbonized grey '21 f150 Supercrew stx fx4 5.0l about six weeks ago. Since that time I've decided to upgrade the fuel tank from the current 26 to the 36 gallon tank. I've been hanging around one of the other forums and have conflicting information regarding fuel pumps for this swap. Some say my existing fuel pump can be transferred to the new tank and it will work fine, however there's a different part number for the '21 fuel pumps for the standard tank and the extended range tank. I searched this site (perhaps I used bad terminology) and didn't get any hits on anyone around here doing this swap.

Can anyone confirm that the extended range tank takes a different fuel pump....and why?

No guesses please, I need someone who has actually done this swap.

Thanks

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[Bocephus]

New member here, purchased a carbonized grey '21 f150 Supercrew stx fx4 5.0l about six weeks ago. Since that time I've decided to upgrade the fuel tank from the current 26 to the 36 gallon tank. I've been hanging around one of the other forums and have conflicting information regarding fuel pumps for this swap. Some say my existing fuel pump can be transferred to the new tank and it will work fine, however there's a different part number for the '21 fuel pumps for the standard tank and the extended range tank. I searched this site (perhaps I used bad terminology) and didn't get any hits on anyone around here doing this swap.

Can anyone confirm that the extended range tank takes a different fuel pump....and why?

No guesses please, I need someone who has actually done this swap.

Thanks

Have not done it and I am not guessing. It is not just a pump, it is a sender and pump assembly. Different part numbers from a standard tank to extended range tank. Heat shield and skid plate (if equipped), fuel vapor cannister and lines are also different. The list will go on and on. It is not a practical modification.

 

[xtraman122]

If you want your DTE to be accurate you'd then also need to modify some things with Forscan to get that updated to the bigger tank. Seems a lot more work than it would be worth and not really a practical thing to like was mentioned.

 

[rustyrider]

Have not done it and I am not guessing. It is not just a pump, it is a sender and pump assembly. Different part numbers from a standard tank to extended range tank. Heat shield and skid plate (if equipped), fuel vapor cannister and lines are also different. The list will go on and on. It is not a practical modification.

Actually no, this isn't the case. It's been a fairly common swap on another forum I frequent. After doing a lot of research, the fuel pump is different along with the float assembly and basket as the extended range pump is a taller pump, since the 36 gallon tank is not only 8" longer than the existing tank but also 1/2" deeper.

The fuel vapor canister and lines stay in tact and aren't part of the swap.

Couldn't figure out the multi quote

 

[rustyrider]

If you want your DTE to be accurate you'd then also need to modify some things with Forscan to get that updated to the bigger tank. Seems a lot more work than it would be worth and not really a practical thing to like was mentioned.

What a difference it makes from one forum to another. Since this is a gen14 forum and fairly new, there's not much history regarding this swap (on this forum). It's neither new or out of the ordinary among many different trim levels of F150's. I had heard there was a lot of information on this site so I gave it a try. There was some debate on the other forum and a disagreement over which is the correct pump to use so I joined up and asked the question here.

I'll have about $400 in this swap when complete. Can't see how it's detrimental or not worthwhile, especially since we tow a camper frequently with this truck and it's much more beneficial to have to purchase gas perhaps only every 300 miles instead of every 200.

Perhaps I could have ordered a truck with a 36 gallon tank...but good luck with actually getting one anytime soon. I did find 1 with the extended range tank, however it was about 8 grand more than the truck I bought.

Since I posted this thread, the Forscan details have been pretty much worked out for this swap also on the '21YM trucks.

 

[Bocephus]

What a difference it makes from one forum to another. Since this is a gen14 forum and fairly new, there's not much history regarding this swap (on this forum). It's neither new or out of the ordinary among many different trim levels of F150's. I had heard there was a lot of information on this site so I gave it a try. There was some debate on the other forum and a disagreement over which is the correct pump to use so I joined up and asked the question here.

I'll have about $400 in this swap when complete. Can't see how it's detrimental or not worthwhile, especially since we tow a camper frequently with this truck and it's much more beneficial to have to purchase gas perhaps only every 300 miles instead of every 200.

Perhaps I could have ordered a truck with a 36 gallon tank...but good luck with actually getting one anytime soon. I did find 1 with the extended range tank, however it was about 8 grand more than the truck I bought.

Since I posted this thread, the Forscan details have been pretty much worked out for this swap also on the '21YM trucks.

Well I guess you have answered your own question - Good luck.

 

[rustyrider]

Well I guess you have answered your own question - Good luck.

Yes, but thanks anyway. I posted here a couple of days ago before I found the answers I was looking for. I found a couple of examples of the swap I'm planning to do and was able to learn enough to go forward. Thanks again.

 

[Bocephus]

Yes, but thanks anyway. I posted here a couple of days ago before I found the answers I was looking for. I found a couple of examples of the swap I'm planning to do and was able to learn enough to go forward. Thanks again.

Would you mind posting those links here?

 

[rustyrider]

Would you mind posting those links here?

I found this thread to be the most helpful regarding the fuel pump question. It's not for a '21, however the gas tanks are the same all the way back to '15.

fuel pump differences

There are litereally dozens of threads at the same site with tank swap write ups. Too many to list. As said earlier, there is some disagreement about fuel pumps among them however.

Also I was able to finally find the correct part numbers for a '21 fuel pump with the standard tank, and the extended range tank. The poster I was discussing it with disagrees that a new pump is necessary, however I think he's not getting the benefit of his larger tank because he has the wrong fuel pump.

 

[Missmy3/4ton]

Does anyone know if they modified the reserve on the 2021s? I looked this before when I first got my truck, but everyone said the reserve was +/-5 gals. Anyone confirm? I'd hate to do the swap and fill up with 100 mile DTE but the gauge saying the tank is "empty."

 

[rustyrider]

Does anyone know if they modified the reserve on the 2021s? I looked this before when I first got my truck, but everyone said the reserve was +/-5 gals. Anyone confirm? I'd hate to do the swap and fill up with 100 mile DTE but the gauge saying the tank is "empty."

There's only one fuel tank, and no actual reserve tank. Perhaps when the DTE trips the light and shows 50 miles to empty there's actually quite a bit more gas, but it's a single tank and not a saddle tank or anything like the dual tanks on 05-10 mustangs.

 

[Missmy3/4ton]

There's only one fuel tank, and no actual reserve tank. Perhaps when the DTE trips the light and shows 50 miles to empty there's actually quite a bit more gas, but it's a single tank and not a saddle tank or anything like the dual tanks on 05-10 mustangs.

I was a bit confused when I first started reading about the larger tank. Marketing got "auxiliary" and 'reverse' confused. Reserve means the "Reserve Fuel Level" which is the buffer between the light coming on the engine actually running out of fuel. The gauge is at or near "E" but you still have fuel remaining...That is the reserve. An auxiliary tank is the 'dual tanks' you mention.

I'm just trying to confirm with a '21 when the low fuel light comes on, how much fuel is required to be back at Full. If it's like the 20's and before... 30 gallons would mean a reserve of +/-5 gals. There no reason (to me, at least) to swap the tank if there's 100+ miles DTE, but the gauge saying the tank is "empty" and your DTE is reading "0."

 

[rustyrider]

I was a bit confused when I first started reading about the larger tank. Marketing got "auxiliary" and 'reverse' confused. Reserve means the "Reserve Fuel Level" which is the buffer between the light coming on the engine actually running out of fuel. The gauge is at or near "E" but you still have fuel remaining...That is the reserve. An auxiliary tank is the 'dual tanks' you mention.

I'm just trying to confirm with a '21 when the low fuel light comes on, how much fuel is required to be back at Full. If it's like the 20's and before... 30 gallons would mean a reserve of +/-5 gals. There no reason (to me, at least) to swap the tank if there's 100+ miles DTE, but the gauge saying the tank is "empty" and your DTE is reading "0."

I don't know how many miles are actually left when the DTE is at 50. I can tell you when towing, that number subsides very quickly.

The reason (for me) for a tank swap is pretty simple. When towing a camper, the truck will net between 8 and 11 mpg. I've already experienced in a different vehicle the difficulty a small gas tank causes when towing long distances. I think most folks who tow on a regular basis would confirm that a larger fuel tank is a benefit. In a previous vehicle (2019 Ford Ranger; at times it got 6mpg towing), there were instances that I could make only 120 miles to a full tank of gas, depending on conditions. Having to stop and more than that, making sure gas is available every 2 hours was a bit much, so I made the switch to the f150 for towing. There were other reasons also, such as the white knuckle driving a lightweight tow vehicle causes. Again, if I could have sourced an f150 with the trim level I wanted and having the 36 gallon tank, it would have been ideal. I paid $42k for my '21 stx fx4 supercrew. The only truck I found with the 36 gallon tank was an xlt and it was $50k. 8 thousand dollars makes a $400-$800 tank swap look pretty desirable to me.

I learned to carry a couple of 5 gallon jerry cans for an emergency, however the convenience of carrying that extra 10 gallons in the tank instead of the bed of the truck is obvious.

 

[Missmy3/4ton]

I get what you're saying, Im in the same position. I DO want to do the swap myself, if I can get the DTE corrected.

I don't know how many miles are actually left when the DTE is at 50. I can tell you when towing, that number subsides very quickly.

That's my point. The DTE is volume based (gallons), NOT miles. DTE/gas light come on when you hit X gallons...on the <20's, it's 5 gals left; to your point, is that 100 miles or 80 miles (unloaded)? The usage could be even more extreme when you look at towing with or without a headwind.

Maybe Im not explaining this well enough....Yes, you wont know how many miles are left, because your truck is going to read 0 miles remaining once you have used 30 gallons. Which is why Im asking what the reserve is on the 21's. If it's 32 or 33 gals that makes more sense than needing to fill up with 100 miles left in the tank.

 

[rustyrider]

I get what you're saying, Im in the same position. I DO want to do the swap myself, if I can get the DTE corrected.



That's my point. The DTE is volume based (gallons), NOT miles. DTE/gas light come on when you hit X gallons...on the <20's, it's 5 gals left; to your point, is that 100 miles or 80 miles (unloaded)? The usage could be even more extreme when you look at towing with or without a headwind.

Maybe Im not explaining this well enough....Yes, you wont know how many miles are left, because your truck is going to read 0 miles remaining once you have used 30 gallons. Which is why Im asking what the reserve is on the 21's. If it's 32 or 33 gals that makes more sense than needing to fill up with 100 miles left in the tank.

We aren't connecting. I view the tank as either a 26 gallon tank or a 36 gallon tank. I don't think in terms of reserve amount of fuel left. I'm not brave enough to run the truck to zero miles to empty and then see how much further it will actually go (and it would vary anyway, depending on conditions). I do know however how to figure what's left if the tank if starts from full and I'm getting 10mpg.

edit: I missed the part about you saying you would like to do the swap yourself. It appears one of the members on the other forum may have figured it out. Even if he didn't, someone will shortly, I'm sure. They're figuring out pretty much everything in Forscan.

BTW, if you need part numbers, I was able to get mine locally from two different dealers. They confirmed the part number for the fuel pump independently from each other. Also, my truck is a 5.0l coyote truck. If you need a part number for the extended range fuel pump for that, I can give it to you.

ML3Z-9H307-B

I found the best place (with some searching) to buy the pump was at Blue Springs Ford. Even though the pump was a little more than tasca parts or levitown parts, shipping was half the price as the other two so the price came out less. I ordered the pump and a new lock ring and gasket so the new tank will be ready to go without breaking down the old tank. That way, if I have a shop do it, the labor should be a little less. I've done a fuel pump change before on an F150 and while I can do it, it's hard to do laying on the driveway, at least for a 64 year old guy.

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