93 F-150 Fuel woes
04-12-2015, 12:59 PM
#1
93 F-150 Fuel woes
Hello everyone,
First, let me say I have tried to research this topic but I'm still not 100%, so I would really appreciate it if you could help clear this up for me!
I have a 1993 F-150 4x2 with the 302. The truck has been fantastic, and I drive it more than I do my MKZ. It only has ~84,000 original miles.
The dual fuel tank system, however, is a royal pain. Let me explain what is going on.
We have been running it on the front tank for a long time (previous owner, I don't remember why they did), and I decided to switch it to the rear to burn the old gas out. The only issue with that was the old gas caused it to stall once, but after a bottle of B12 chemtool it was fine. I about ran that tank dry!
I switched it to the front tank with no problems. A few days later, I stopped and filled both thanks up. The rear tank took about 13 gallons, and I had only burned one or two gallons from the front tank. The fuel gauge worked fine for both.
But now, I have been running it off the front tank for about 65 miles, and the fuel gauge has not moved off the "F." In fact, is is far to the right of it. I switched it to the rear tank, and it while it is on the "F" also, it looks as if it has burnt some from that tank (only a gallon or so, it was on a slight angle.)
I guess the only way to find out what is going on is to fill the truck up tomorrow and see which tank accepts it.
Here are my questions:
Is the front tank larger than the rear?
Is the fuel somehow transferring from one tank to the other?
Is there a selector valve that needs replacing, or is it something else?
I really don't care if it does this, I can just leave it on one tank, but I don't want to be left stranded. I have no idea where this thing is drawing fuel from!
Thanks,
Andrew
First, let me say I have tried to research this topic but I'm still not 100%, so I would really appreciate it if you could help clear this up for me!
I have a 1993 F-150 4x2 with the 302. The truck has been fantastic, and I drive it more than I do my MKZ. It only has ~84,000 original miles.
The dual fuel tank system, however, is a royal pain. Let me explain what is going on.
We have been running it on the front tank for a long time (previous owner, I don't remember why they did), and I decided to switch it to the rear to burn the old gas out. The only issue with that was the old gas caused it to stall once, but after a bottle of B12 chemtool it was fine. I about ran that tank dry!
I switched it to the front tank with no problems. A few days later, I stopped and filled both thanks up. The rear tank took about 13 gallons, and I had only burned one or two gallons from the front tank. The fuel gauge worked fine for both.
But now, I have been running it off the front tank for about 65 miles, and the fuel gauge has not moved off the "F." In fact, is is far to the right of it. I switched it to the rear tank, and it while it is on the "F" also, it looks as if it has burnt some from that tank (only a gallon or so, it was on a slight angle.)
I guess the only way to find out what is going on is to fill the truck up tomorrow and see which tank accepts it.
Here are my questions:
Is the front tank larger than the rear?
Is the fuel somehow transferring from one tank to the other?
Is there a selector valve that needs replacing, or is it something else?
I really don't care if it does this, I can just leave it on one tank, but I don't want to be left stranded. I have no idea where this thing is drawing fuel from!
Thanks,
Andrew
04-12-2015, 01:34 PM
#2
Drive like you stole it
No selector valve. The switch in the dash just switches which fuel pump is powered. Each pump/sending unit has a check valve that is intended to stop the cross feeding, they often fail. Also, don't read too much into the gauges at "full" most of the time gas gauges are more accurate below a half tank where it matters, hope that helps ease your mind a bit.
04-12-2015, 01:37 PM
#3
1994 F150 XLT 5.8L 2wd
Front tank on mine is 19gallons and rear is 18. They also had a 16 gallon tank as well.
The check valve in the pump assembly is what allows the fuel transfer, it transfers to the tank with the bad valve. The best way to fix it is to replace the pump assembly. Check valves failing are usually the first step in pump failure, though some have used a cross filling pump for an extended period of time with no pump failure.
If you decide to replace the pump, fairly easy to drop the tank and swap the pumps out, also replace the tank straps as they are most likely corroded and in need of replacing. Also, using both tanks regularly is the best way to keep both pumps in good working order. Mine has both original pumps and 300k+ miles, the previous owner (also the original owner) told me how he would use his tanks and I continue the practice as it seems to work great:
Run tank to the E (you will still have a gallon or two left in it), switch to the other tank, when you get gas fill both tanks but remain on the other tank and use it to the E, switch to the first tank and repeat process.
He said he never let it run completely out of gas and always switched when the needle would touch the letter E. Following this not only do both pumps get evenly and regularly worked but you also use up the oldest gas first so you are never running gas that is months old.
The check valve in the pump assembly is what allows the fuel transfer, it transfers to the tank with the bad valve. The best way to fix it is to replace the pump assembly. Check valves failing are usually the first step in pump failure, though some have used a cross filling pump for an extended period of time with no pump failure.
If you decide to replace the pump, fairly easy to drop the tank and swap the pumps out, also replace the tank straps as they are most likely corroded and in need of replacing. Also, using both tanks regularly is the best way to keep both pumps in good working order. Mine has both original pumps and 300k+ miles, the previous owner (also the original owner) told me how he would use his tanks and I continue the practice as it seems to work great:
Run tank to the E (you will still have a gallon or two left in it), switch to the other tank, when you get gas fill both tanks but remain on the other tank and use it to the E, switch to the first tank and repeat process.
He said he never let it run completely out of gas and always switched when the needle would touch the letter E. Following this not only do both pumps get evenly and regularly worked but you also use up the oldest gas first so you are never running gas that is months old.
The following users liked this post:
bus12 (04-12-2015)
04-12-2015, 02:12 PM
#4
Thanks to both of you. Forgive me, but I'm not vehicle savvy.
Is the check valve a part of the actual pump? If I had both replaced, would that do it?
EDIT:
fltdriver, thanks. I should have read your post more carefully. Looks like two new pumps and straps. Does not sound like a bad fix at all.
Is the check valve a part of the actual pump? If I had both replaced, would that do it?
EDIT:
fltdriver, thanks. I should have read your post more carefully. Looks like two new pumps and straps. Does not sound like a bad fix at all.
Last edited by bus12; 04-12-2015 at 02:21 PM. Reason: Re-read post
04-12-2015, 04:37 PM
#5
Also, what brand of pump? Motorcrafts are high, and I have heard awful things about airtex. How is delphi or bosch?
https://www.rockauto.com/catalog/raframecatalog.php?ck here is the rockauto link. What about the Hella or delphi? Do those come with everything I need?
https://www.rockauto.com/catalog/raframecatalog.php?ck here is the rockauto link. What about the Hella or delphi? Do those come with everything I need?
Last edited by bus12; 04-12-2015 at 04:41 PM.
04-12-2015, 04:43 PM
#6
1994 F150 XLT 5.8L 2wd
You wouldn't need to do both if it's only filling one tank-figure out if it's actually cross-filling, if it's only into one tank or if it goes both ways, also check out the condition of the tanks, if they are rusted or just basically look hit you may consider an entire replacement. They sell them with the pumps already installed and with straps online and it's just bolt and go. I've never had to deal with new pumps, or heard how those brands are on ford pumps.
04-12-2015, 04:53 PM
#7
You wouldn't need to do both if it's only filling one tank-figure out if it's actually cross-filling, if it's only into one tank or if it goes both ways, also check out the condition of the tanks, if they are rusted or just basically look hit you may consider an entire replacement. They sell them with the pumps already installed and with straps online and it's just bolt and go. I've never had to deal with new pumps, or heard how those brands are on ford pumps.
Sounds good. I'll fill it up tomorrow (and see which tank takes it.) Maybe the gauge is just lazy and the system is ok. Both pumps sound great, never whine.
By the way, the truck has been in west TN all its life, so hopefully the tanks are in good shape!
Trending Topics
04-12-2015, 06:52 PM
#9
1994 F150 XLT 5.8L 2wd
I already responded to your PM but this is for anyone else with the same problem:
Rule of thumb is which ever tank is receiving fuel, from the other tank, is where the bad check valve is. It's not closing properly when the other tank is working so it allows fuel to be deposited. This is drivable but the other pump works harder to supply both the engine as well as the affected tank, using just the bad tank (rear in this case) will eliminate any cross-filling and is the ideal course of action as it won't wear out the "good" pump. The bad side to this is the "good" pump goes unused for a length of time which can be just as bad as it being overworked.
Rule of thumb is which ever tank is receiving fuel, from the other tank, is where the bad check valve is. It's not closing properly when the other tank is working so it allows fuel to be deposited. This is drivable but the other pump works harder to supply both the engine as well as the affected tank, using just the bad tank (rear in this case) will eliminate any cross-filling and is the ideal course of action as it won't wear out the "good" pump. The bad side to this is the "good" pump goes unused for a length of time which can be just as bad as it being overworked.