87 F150 4x4 302

I recently put new pumps and senders in both tanks. The fuel gauges both work fine. I disassembled and checked the gizmo fuel switch thing, no problems with o-rings. I have no fuel leaks. I've been running each tank to empty, and not filling the other until the tank being used is nearly empty. I'm not getting transfer of fuel from either tank to the other.

Any ideas what's going on?

Thanks.

 

I thought it was just me... my 90 F250 is the same way.. front tank lasts a long time, the rear tank on the other hand is gone before I know it..and once the guage says empty.. its EMPTY..

 

My rear tank is hard to fill all the way up.......when the front shuts off....it's full........but I have found that the rear will take a lot more after it shuts off on it's own. It reads full by the gauge too.

First few times I checked mpg I was getting different front to back.......now that I make sure the rear is full......real close.

Good Luck

 

possibly the rear fuel pump getting wacky...not pushing through at the right flow rate... ?? just a thought.

 

Well how are you guys judging your mileage? Sounds like you are judging by the time it takes for the tank to be emptied, which is not the correct way because one tank is larger than the other. I don't remember which because I only have 1 tank

-Chris

 

Also if the tank is a 10 gallons, you can squeeze in more since all tanks must be 10% larger than stated capacity... Also mileage Can only be accurately determined by what was bought, burnt and replaced... My pop taught me with his 18 wheelers to pump fuel until it touches filler neck so we knew we were measuring as close to exact as possible.
For passenger vehicles with a filler hose I pump til the nozzle clicks off, remove until only the tip is in the neck and nurse in real slow until the gas sits in the neck... ROCK THE TRUCK!!! Likely it will go done and allow this procedure to be repeated a few more times.... It is also a good time to look for a leak in filler hose...
DO NOT DO THIS IF YOU WON'T BE DRIVING AT LEAST FAR ENOUGH TO BURN A GALLON!!!
Brent

 

This is what I do to be sure I calculate an accurate mileage number. But why do you say that you should not do this if you don't burn a gallon right away?

-Chris

 

It is not advisable to over fill for 2 reasons... one is the 10% over size is for heat expansion. Air can be easier compressed than can liquid, also the possibility of a little leak in the filler hose allowing a puddle to accumulate under the vehicle and thus a possible fire hazzard.
I recently swapped a filler hose on a fellers ranger cuz he was sure he had a problem with the low fuel economy of his 4 cylinder motor...
It was split all to heck!
Brent

 

the only way you could burn more gas frome one tank than the other is if one is delivering higher presser than the other. I think first you need to learn how to calculate your MPG to see if you realy have a problam. and if you do then check your fuel presser at the fuel rail on both tanks. and change the pump for the one that is out of specs.

 

Allow me to elaborate. Follow Brent's advice for filling the truck to MAX CAPACITY, and write down the mileage on the odometer. Then drive the truck for as long as you want (preferably until the tank is close to empty for a more average/accurate number). Refill that same tank to MAX CAPACITY, but this time get a receipt that shows how many gallons you pumped, and again write down the mileage on your odometer. Now take the difference between the 2 odometer readings and divide that number by the number of gallons that you have just pumped into the tank. This is roughly your average mileage per gallon.

-Chris

 

I have a bulk fuel tank at home. No meter. But I understand that the front tank cap is 19 gallons and the rear is 18 gallons.

Depending on how much Hwy vs. putting around I do in this work truck, I can go 220 to 280 miles on the front tank, but only 175 to 200 on the rear.

It's not transfering fuel, or leaking fuel.

It seems I've seen comments like this occasionally on this board. Like mebe2K above. I was wondering if anybody ever found a fix or explanation.

I appreciate the "There's no way this can happen" side of the argument, but that doesn't really help me any because it is happening to me.

Thanks.

 

For the record Chris, if you fill a gas tank to the same point each time, and if you divide the miles traveled by the gallons consumed, as described in your post above, it does not "roughly" equal your miles per gallon.

It is precisely your miles per gallon.

The only way it could be "off" is if your odometer was inaccurate or the gas meter was inaccurate.

Thanks.

 

The method I mention is to rule out tight turns in the fuel filler hose and even nearly kink hose... I think you really hit the proverbial nail on the proverbial head... NO METER!!!
So you have no clue how much gas is actually getting in the tank? YOU WILL NEED to buy metered gas to KNOW your MPG... I actualy did mapquest searches to get a GENERAL IDEA of mpg once on a truck with no functioning odometer... Not accurate! You just gotta know gallons in versus gallons out over a known mileage to have even a clue...
Brent

 

I used to have this problem when I burned from the front tank first on the highway. Turns out fuel was being sucked out the cap of the rear tank at highway speeds. I figured it out after a trip to Texas when I switched tanks and the rear tank was below 3/4 tank before I ever used it. I started burning the rear tank first and don't have the problem any more.

BTW, my front tank will hold 18 gallons and my rear tank will hold 21. The rear tank is highly sensitive to how level the truck is when I fill it. If I can find a pump that lets it sit a little nose down and tilted away from the pump it fills much easier.

 

But you do not know you are getting the same amount in the tank... A one degree difference in either side ways or fore and aft angle could change that figure by several gallons
Brent