I have a 1985 F250 4x4 with a 7.5L and a T18. Ive had it for about 3 months now and i love the truck, and i love working on it and fixing it up. However i have hit a bit of a road block.

My gas gauge was not working properly when i bought the truck. it was usually hovering around 1/4 to 1/2 tank despite a recent fill up or being bone dry. this is the 19 gallon tank in front of the rear axle. So after talking to the previous owner and finding out that the fuel pump was less then a year old and under warranty i decided to drop the tank and pull the pump, then bring it to the parts house and get a warranty replacement.

Before reinstalling the new pump i crawled under the truck and plugged the pump into the wire and manually moved the float up to 1/4 tank, then 1/2, then 3/4, and so on and so on several times while a friend was in the truck watching the gauge and it worked perfectly the pump even has a little gauge built into it so that depending on where the floats at, it tells you if its half or full or whatever.

So i went ahead and installed it and bolted everything back together and went and filled up, and it never got above 3/4's of a tank. i can fill it up and thats the highest the gauge gets, and then it will be on E for a long time, because there is obviously fuel in the tank still but the gauge isnt showing it.

So my question is does anyone have any advice on what i can do to try and fix this problem? i am 100% stumped. thanks in advance, and im excited to be apart of this forum and get to learn more about these awesome trucks!!!!

 

You tested the gauge before installation and it worked good. Not sure what you mean about the fuel pump having another gauge? Are you sure you assembled the sender/pump correctly? I'm wondering if you oriented the unit properly. If it didn't go in straight into the sump the float might be hanging up on the side of the tank maybe and then it doesn't get to the top of the stroke when full?

BB2

 

I mean exactly that. The fuel pump assembly had an actual gauge on it. So when you moved the float arm, it pointed at the gauge to tell you if it was at half, full, whatever. And while doing that I had a friend in the truck looking at the actual gauge and confirming that what the pump gauge was saying was what the truck gauge was showing. That’s one of the reasons I am so dang stumped! Just like a little mini gauge on the side of it. I bought the complete unit so I didn’t do any assembly myself. I’m hoping I didn’t get two fuel pumps in a row that were both bad but I guess it’s possible.

The only part I’m worried about is what your saying about the way I put it in. The pump has two metal tabs sticking out where it fits into the tank. They are at say 11 o’clock and 2 o’clock, so from what I was seeing there was only one way to put it in the tank. But I dont know if there was a certain way that you were suppose to slide the unit in before you twist it to line the tabs up. Maybe I missed something on that step?

Thanks for the reply! I appreciate the help.

 

Sure glad to help. Is this a plastic tank you are working with? Post a pic of the sender you're working with. I'm a IDI guy so not familiar with all the variations in gas tanks.

 

Fuel guage units are not perfect and are never 100% accurate. Yours is off a little more than usual though. All you have to do is take the unit out again, bend the arm on the float down just a little bit, and re-install it. That way when you have a full tank, with the float being bent down some, it will push the sending unit higher, giving you a higher reading on the gauge.

You will always have fuel left in the tank when empty. If you study the sending unit, most of them have a stop on the arm, and it stops above the pickup screen assembly. The empty side is the most important, knowing when you are going to run out is more important to know than how full you are. If you mess with this thing, run around with a 5 gallon can of fuel till you are sure where it's going to run out. If you get to "E" and then fill it at the station and get about 16 gallons in it, that is about perfect. You have a 19 gallon tank (I am assuming you have a 8ft bed since it's a f250) and if you have 3 gallons left in the tank that is considered empty.

 

Ok so the problem has been fixed and it was a little more of an issue then what i was expecting it to be.

The float was actually hitting the filler neck/breather house spout where they entered the tank. There is obviously the part that sticks out where the actual filler neck fits over the little pipe sticking out of the tank, but that doesnt just stop on the outside of the tank. It extends inside the tank about 3-4 inches. The float was lined up perfectly with that, and after about half a tank of fuel the float would come into contact with the underside of the fillerneck/breather hose and be prevented from rising to a full tank, even if the tank was 100% full.

So after some advice from you helpful people i got it all fixed up so that now it reads totally empty at 3 Gallons, half tank is roughly 9.5 - 10.5 gallons, and a full tank is when the bottom of the breather hose connector in the tank first has water touching it. Which i believe would be when the gas pump would first start kicking off.

My main question now is whats the best way to go about getting all the moisture out of a fuel tank? I already dumped all the water out, but there is obviously still some remaining inside, and some moisture on the metal. I need to get all that out so i can reinstall it and start driving this puppy! Thanks for all the info guys!

 

I am trying to figure out where the water came from, I am guessing you used water for testing? Shake it around and get all of it that you can out, and then just re-install it and during your first fill-up go buy a bottle of dry gas. Any little bit of water remaining, the dry gas will let it be picked up and burnt through the engine. With a full tank of fuel and a little bit of water, the ratio will be so high that you won't notice it. And the dry gas will let the water be pulled through the system. If you don't use something like dry gas, the water will sit at the bottom of the tank and roll around down there for a long time before it gets sucked up, if ever.