1986 F250 6.9l Fuel Capacities?

[stangclassic66]

Hey Fellas, this is my first post. I have a 1986 F250 with a 6.9L w/ATS turbo and Gear Vendors Under/Overdrive unit. I've owned it for a few months and i'm still learning a ton about it. This site rocks and has a ton of info, thanks!!

One question I have is, what are the fuel tank capacities?

My fuel gauge is acting funny and reads half tank when i've burned about 10-11 gallons and after about 10 more miles it drops all the way to EMPTY. So I took the mileage down and increased the distance I drove after every fillup. I pushed the limit a few weeks ago and the truck died after I started it up one evening. (I switched to the rear tank and it took 3 cranks of about 20 seconds each crank to fire up). I drove it to the gas station and filled the tank up about 19 gallons topped off. I recorded 327 miles on that 19 gallons which turns out to be 17.2 miles per gallon.

In any case, I just wanted to know if the tank is 19-20 gallons or if it's bigger and my pickup tube is broken.

How about the rear tank? I've never pushed that to the limit but it always shows half tank for a few miles then drops to EMPTY just like the front tank. I fill that tank to about 11.4 gallons on average.

Thanks in advance.

 

[Ironman03R]

My Front tank is 16 and the rear is 14. I have smaller tanks than most do for some reason.

 

[82fordtruck]

wow, my front is 18 and rear 19 on my 94, and on my 82, it's 18 and 20.

 

[stangclassic66]

Wow, the sizes fluctuate quite a bit through the years. Is this hard information or fillup information.

 

[The Warden]

IIRC, both the front and the rear tank are 19 gallons from the factory...I thought that all '80-'97 trucks except for SWB F-150's were set up this way. I've never gotten more than 19 gallons into either tank...and, for the record, my old E-series van had a 18 and a 22 gallon tank.

Ironman, how certain are you that your tanks are actually that size? It is very common for the fuel puckup tube (part of the sending unit assembly) to break off, resulting in the tanks having 4 to 5 gallons of unusable fuel each, and if the sending units are working (not a common thing in these trucks), it'll show that you have 1/4 of a tank left when the truck starts sputtering and acting like it's out of fuel (which, for all practical purposes, it is...and the fuel pickup is sucking air instead of fuel). Furthermore, the venting system for these tanks leaves a LOT to be desired...unless you modified them or allow them to sit and burp the air out (a process which can result in it taking almost an hour to fill both tanks ), you may not be filling the tanks up all the way.

 

[towcat]

here's the issue. unless you are really patient, you won't get a full load of feul due to the tanks filling up with foamy diesel. If you don't think you got a full load, go fill up the other tank for a little bit and let the first tank breathe a little. also, if you are basing your fillups on the fact you are sucking air, you may have the dreaded feul pickup foot problem. find the thread where f350camper is talking about dropping the tank.
As far as the gauge reading wonky, don't worry about it too much. That is a common problem on our diesels. diesel feul likes to attack the plating on the sender contacts and you will be replacing them again soon if you do put in new ones. drive by ODO and remember to reset when you change tanks and filling up.

 

[stangclassic66]

No reset on the ODO on these older trucks.

Do you guys think it's the sender that is bad or the instrument voltage regulator? I get the same reading on both tanks when they have burned 10 or more gallons.

 

[towcat]

No reset on the ODO on these older trucks.

Do you guys think it's the sender that is bad or the instrument voltage regulator? I get the same reading on both tanks when they have burned 10 or more gallons.

drop by the oakland pick-n-pull every couple of weeks, soon enough there will be a XLT truck with a trip ODO on the speedo. You will have hit the holy grail if you ever come across a diesel with a tach and trip ODO in the whole package.
its possible that you may be the first to have a bad instrument voltage reg. i have yet to see one equiped with that animal. but there's always a first. more often than not its the senders that are no good.

 

[Ironman03R]

When I fill up the truck I stop when the fues spits out or the auto shutoff clicks. Then I give it 2 or 3 more times then go to the next tank. My fuel gauge reads exactallt on E when it runs out. The time I did let it run out it took 16 on the front. Every fill up its about 15.8 and 13.9 or so to fill the tanks.
Is it possibe that the pickups are broke on this truck? I've never really thought about it since the gauge is allways acurate. I just thought that it was ordered with small tanks for some reason.

 

[The Warden]

When I fill up the truck I stop when the fues spits out or the auto shutoff clicks. Then I give it 2 or 3 more times then go to the next tank. My fuel gauge reads exactallt on E when it runs out. The time I did let it run out it took 16 on the front. Every fill up its about 15.8 and 13.9 or so to fill the tanks.
Is it possibe that the pickups are broke on this truck? I've never really thought about it since the gauge is allways acurate. I just thought that it was ordered with small tanks for some reason.

As far as I know, a small rear fuel tank wasn't even available as an option. If you've got smaller than 19 gallon tanks, you're the first person I've ever talked to with a diesel who does.

I'm pretty sure that you have broken or clogged fuel pickups (if the fuel pickup gets clogged, the fuel is instead pulled through a second opening a little over 1/4 of the way up), coupled with fuel tank sending units that aren't reading properly (which is actually the rule rather than the exception on these trucks; my senders both read pretty accurately but I'm in the very small minority there). I wouldn't call this a critical problem; as long as you have a working trip odo, you can keep operating like this. Just, if you ever have to remove the bed or pull the fuel tanks for any other reason, you could then correct this problem and increase your cruising range.

Also, if you're "only" go 2 or 3 more times after the pump clicks off, you may still have a gallon or so's worth of air in the tanks (probably a bit more in the rear tank due to its shape; I've always found it more difficult to get air out of my rear tank than my forward tank). I usually bring the fuel up until I can see fuel (and not foam) in the fillneck, then shake the truck some to get the tank to "burp" (while trying to not spill fuel out the fillneck), and keep going until the fuel level's right at the brim and shaking the truck doesn't bring the level down any. It takes a long time, but it increases my time between fuelings somewhat, and allows my fuel mileage calculations to be more accurate. The most fuel I've ever gotten into my forward tank was 20.126 (surprisingly enough, the tank wasn't empty), and 20.351 into the rear tank (this tank was just about bone-dry at that time).

 

[ramon f350]

I agree with everyone else all of the trucks that I have ever seen have 2 19 gallon tanks i know that is what both of mine had.

Ramon

 

[Mojave Red]

I really pushed it today and was able to get an even 20 gallons in my front tank today . I have an after-marked 38 gallon tank in the back that I don't use any more because it's too expensive to fill up .

Hey Strange... what gear ratio and transmission are you running? I've got a GV overdrive behind a C6 with 4.10s - I only average 15-16 MPG. I'd love to get over 300 miles on my 20 gal tank...

Brian

 

[h2odrx]

what is the mod to vent the tanks? or is there a link to a thread?
thanks