Dual Tank Troubleshooting Questions
#1
12-17-2003, 05:22 PM
Dual Tank Troubleshooting Questions
I've read many, many reports from people having various problems with dual tanks. I don't believe I've seen one that is the same as the problem I'm having, so I'd like to see about getting some troubleshooting advice. I have a '93 F250 with the 351W and E4OD automatic.
When I bought the truck, it was using the rear tank, which was full. After 200 or so miles, it was down to a bit under 1/4 tank, at which point I decided to fill up. I asked the attendant (no self serve in OR!) to fill the rear and put $5 in the front. When the pump kicked off on the rear tank, she put the hose back on the rack. I asked her about the front tank, and she said she had done that one first. My Rear tank shows full, but the front tank is still below E. I have switched to the front tank and driven for a short period (a couple of miles), but am afraid to leave it there for any extended period of time. Is there any danger in sucking sediment up into the filter / pump if I run it dry?
I took a total of 16.5 gallons of gas. I believe it was roughly $1.60/ gallon, so about 3 gal were pumped into the front, with the remaining 13.5 pumped into the rear.
From what I have gathered, I can have one of three things going on:
1. The gas from the front tank was pumped into the back tank immediately. I don't think this is too likely as the vehicle was off during the fueling. Also, I think my rear tank is 19 gal (?) and I had roughly 1/4 tank (5 gal). So, this tank probably had ~14 gal of capacity, which is consistent with what I figured was pumped into the rear.
2. Even though I flip the tank switch, fuel is still being pulled from the rear tank, and somehow the gauge no longer works. I don't think this is too likely, as it would mean I'd basically have two different problems: fuel supply not changing, and something wrong with the circuitry involving the gauge.
3. There is gas in the front tank, there is just some problem with the sender/wiring for this tank. This is the way I am leaning.
So, first, if anyone has seen this exact problem, I'd appreciate knowing how you fixed it. I'd also appreciate any advice regarding the best possible way to go about troubleshooting and narrowing this down. My thought at this point is to just flip to the front and run until it quits, then switch back to the rear tank. Based on how long it runs, and how much fuel remains in the rear tank, I should be able to make a reasonable conclusion as to what's going on. My only concern here relates to what I mentioned before - do I risk fouling up a filter or pump by running that tank dry? The last thing I want to do is create a more serious problem when trying to diagnose something that is really no more than an annoyance.
When I bought the truck, it was using the rear tank, which was full. After 200 or so miles, it was down to a bit under 1/4 tank, at which point I decided to fill up. I asked the attendant (no self serve in OR!) to fill the rear and put $5 in the front. When the pump kicked off on the rear tank, she put the hose back on the rack. I asked her about the front tank, and she said she had done that one first. My Rear tank shows full, but the front tank is still below E. I have switched to the front tank and driven for a short period (a couple of miles), but am afraid to leave it there for any extended period of time. Is there any danger in sucking sediment up into the filter / pump if I run it dry?
I took a total of 16.5 gallons of gas. I believe it was roughly $1.60/ gallon, so about 3 gal were pumped into the front, with the remaining 13.5 pumped into the rear.
From what I have gathered, I can have one of three things going on:
1. The gas from the front tank was pumped into the back tank immediately. I don't think this is too likely as the vehicle was off during the fueling. Also, I think my rear tank is 19 gal (?) and I had roughly 1/4 tank (5 gal). So, this tank probably had ~14 gal of capacity, which is consistent with what I figured was pumped into the rear.
2. Even though I flip the tank switch, fuel is still being pulled from the rear tank, and somehow the gauge no longer works. I don't think this is too likely, as it would mean I'd basically have two different problems: fuel supply not changing, and something wrong with the circuitry involving the gauge.
3. There is gas in the front tank, there is just some problem with the sender/wiring for this tank. This is the way I am leaning.
So, first, if anyone has seen this exact problem, I'd appreciate knowing how you fixed it. I'd also appreciate any advice regarding the best possible way to go about troubleshooting and narrowing this down. My thought at this point is to just flip to the front and run until it quits, then switch back to the rear tank. Based on how long it runs, and how much fuel remains in the rear tank, I should be able to make a reasonable conclusion as to what's going on. My only concern here relates to what I mentioned before - do I risk fouling up a filter or pump by running that tank dry? The last thing I want to do is create a more serious problem when trying to diagnose something that is really no more than an annoyance.
#2
12-17-2003, 05:54 PM
Posting Guru
Sending unit is most likely your problem, I have the same problem with my front tank, although unlike you, my sending unit worked for a long time. It's an annoyence not knowing how much gas you have in one tank, but I mostly just use my rear tank.. Since replacing the sending unit is not a fun task. It's a very common problem though.
You don't risk very much by running the tank dry, I've done it several times, and the worst that can really happen is that you'll have to replace your fuel filter which is a very easy task. Doing it often wouldn't be a good practice though.
You don't risk very much by running the tank dry, I've done it several times, and the worst that can really happen is that you'll have to replace your fuel filter which is a very easy task. Doing it often wouldn't be a good practice though.
#4
12-18-2003, 06:21 PM
#5
07-14-2015, 07:10 AM
#6
07-14-2015, 08:25 AM
This thread seems to be for a 1989 and older truck and you have a 1994 so this thread does not apply to your truck as you have a different fuel system.
I am guessing that the front tank is filling from the rear tank also.
So the the valves in the front FDM are bad and the pump may be bad also or the switch on the dash for the pump.
In your truck the sending unit is for the gauge only.
In the 1989 an older trucks the sending unit was the whole hanger with the gauge resister spot welded to the hanger and the you had to bend items on the hanger to get the pump off of the hanger.
The 1989 and older sending unit:
Your FDM in the tank (1990 and newer):
/
I am guessing that the front tank is filling from the rear tank also.
So the the valves in the front FDM are bad and the pump may be bad also or the switch on the dash for the pump.
In your truck the sending unit is for the gauge only.
In the 1989 an older trucks the sending unit was the whole hanger with the gauge resister spot welded to the hanger and the you had to bend items on the hanger to get the pump off of the hanger.
The 1989 and older sending unit:
Your FDM in the tank (1990 and newer):
/
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