I was out checking all my fuses the other day, and found that there is not a fuse in the socket that says "auxilary fuel tank selector". My truck runs fine on the front tank right now, but not off the rear tank. I'm really curious about what this fuse does.. and i dont wanna put one in there until i know what it's for... Any help is greatly appreciated.


Dave

 

It is for the Fuel tank selector motor, if you are a gas job you will not have one in 1990. They were used on Diesel in the 80's and 90's and on 460's from 1983 to 1987 with dual tanks.
I think you are talking about fuse #15.

Your fuel system:

 

When the rear tank is selected and you turn your key on, do you hear the fuel pump?

Adrianspeeder

 

adrianspeeder,
when i have it set on the rear tank, i do hear the fuel pump, just it sounds different then when its set on the front tank.. also the truck will technically run on the rear tank, just when you rev it up or put it in 1st and try to move, it just sort of dies down as soon as you start to give it gas.... i've been told that the rear in-tank pump is gone, but im still not quite sure..

i actually have this story of how i had to call a friend for help when my truck "ran out of gas". i'd been running on the front tank(this was before i had ever tried running the truck off the rear tank), and i was coming home from a friends house and the truck started sputtering and i noticed i was right on "E".. luckily i was able to coast into a little turn-around spot... so i'm setting there for a minute, and i realize that i've never tried to use the rear tank before, so i flip the switch, and turn the key to "on" and the gas guage goes all the way up to "F". At this point i think im the luckiest man on earth :o , so i start the truck up and it starts and idles perfectly.. as soon as i put it into 1st and start to move, the truck just instantly dies way down and wont move.. so im sittin there for a minute thinkin of what the heck i should do, and just for the hell of it i shift into reverse and try movin' and it goes perfectly normal in reverse. at this point i'm seriously confused and frustrated, so i call up one of my friends and have them take me to a gas station to get some gas for my front tank and i drive home just fine on the front tank.

sorry for the long story, but i was just in a story tellin' mood tonight for some reason

-Dave

 

I think you have a bad rear pump.

 

So you dont think that the rear in tank pump is the problem? because thats what a lot of people have told me that they think it is. one more thing.. a few days after that night when i ran out of gas, i was sittin in my driveway and i tried using the rear tank just to see if it would actually move this time, and it started up and idled fine like it did before, and this time i was able to drive about a 2/10ths of a mile down the road from my house and then it started to lose all power. i pull off the road and put it in nuetral and sat there and revved it up for a few seconds and it sounded normal when i would rev it up, and as soon as i start to move again, it loses all its power.. so i switch to the front tank and drive home. hopefully you guys can help me figure this thing out, cause i basically have no idea whats wrong with it..

-Dave

 

It sounds like the rear pump is bad.

 

I must need some sleep, because I don't follow what your saying...

Adrianspeeder

 

To Adrianspeeder:
He was just asking about what a fuse place in his Fuse Box was for and I though that I answered his question. You made a small comment, nothing wrong with that. Then he comes back acting like he never seen my response and only wanted information from you so I was going to bow out of the thread and let you handle his questions. Then he came back and it sounded like he was trying asking me a question so I gave him a wrong explanation and a wrong thread to go read.
I must have been sleeping also as I was under the impression that his truck was a 1989. Every thing I said did not apply except about the fuse.
Sorry.

You do a good job with the questions over here and I only come over once in awhile, keep up the good work and I will go back over to the other forum.

 

To david_aaron236:

Sorry about yesterday, I was helping three different people with 1989 trucks and 1989 was on the brain. Somehow after your initial question I was thinking you had a 1989. I see now you have a 1990 and more than likely you do have a bad pump in the rear tank.

I changed the diagram above for your 1990 also.
You do not have the Fuel Selector Valve I was talking about in 1990.

 

No worries mate! I just got confused with the 89 to 90 mixup. Hang around over here and keep helpin me out!

Adrianspeeder

 

Hey subford, thanks for your help. I was pretty confused when you started talkin about a '89 and all that other stuff... but at least now we got everything sorted out, eh? so how much do time and money do you guys think that replacing the rear fuel pump will take? if its not to hard of a job i wanna get it fixed pretty quick, cause not having both tanks work is kind of a pain in the ...butt.
Also thank you very much adrianspeeder as well!

-Dave

 

If the tank is empty, it is a pretty simple job to drop. I did a 33 gallon bronco tank 3/4 full and that wasn't fun at all...

Some claim it is actually easier to pull the bed to do the tank work if you have enough helpers.

Adrianspeeder