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fuel sending unit??


New Member
June 27, 2008
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Year, Model & Trim Level
1991 xlt
Well my gas gauge started acting up lately on my trip to visit my parents. The gauge was working fine until about half way there the gauge dropped to empty, then when I got there and shut the truck off it worked again.

Now the gauge only goes up to a 1/4 tank of gas when the truck is off and when i turn the truck on it drops right down to empty and stays there until I turn the truck off.

I'm suspecting its the sending unit but just wanted to make sure before I spend the money on one.

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yeah sounds like the sending unit...if it's a 91 and a never had a new pump/sending unit ( all same unit in the tank) it's most likelly about time to replace it .dropping the tank is not as hard as it sounds ...one of the best things about dropping your tank is that now you can clean out the decades of crap in there ! just buy a quality fuel pump and not a cheapo unit like i did the first time.bought a cheaper unit and installed it and it failed and had to do it over again ( not fun to do it twice) .make sure before you begin to drain as much fuel out as possible to drop the tank and if you can try to find something for the tank to rest on when you drop it ...i used a carpet piece we had to put under the tank just incase it falls down onto the ground and not hard concrete.

Ok thanks for the info. When I drop the tank what should I clean it out with?

ahh well ,what i did after getting the tank out onto the ground and cleaning it was to get a a clean rag and make sure you get all of the remaining gas out and once gas was gone i stuck my arm in as far as i could and wiped down the inside really good(working from the top to bottom) then i took a water hose and washed out the tank really good(outside and inside of the tank) .the only material i had left was a small ring of stuff around where the pump resides in the tank (pickup tube).even washing it out did not get this stuff so i had to get a copper penny and scratch it off (very small amount of stuff left) so i gota a vac and cleaned the rest out.

also since you got your tank out i wipped mine down with armor-all (kinda stupid i know )but on the tank there are bumber strips glued to it and they looked like the could use some re-juvinating so to speak.plus when i dropped my tank/skid plate i found many rocks that had worked their way between the skid plate and tank....not good to have a knife next to a 19 gal plastic fuel cell ...you know ......

ps>>> when i jacked my truck up to do this i used some rail road tie pices ( 2ft long) and put those under the rear wheels to get the proper amount of height to remove the tank out .jacking up the truck and useing jack stands alone did not give me the right height ..plus once the rear was on the railroad ties i could let the jack down and take it out( felt much safer under there with all the pulling and no fear of the truck falling on me as well) ...more than enough room to work under there ( after you take out the spare) to work .left frame rail is where the connector to the fuel pump may be a little hard to get it out enough to unplug it because it has a small keeper that holds it on the rail .i had to rip mine off the rail but no big deal just poped it back in was i was all done).also good time to replace that 8$ fuel filter to to make sure it's all good .

hope this helps :salute:

Just to add a thought. If the tank has never been dropped before, make sure you have plenty of liquid wrench, wd-40, pb blaster, whatever you like handy. It took me 3 days at 10 hrs a day to unbolt 3 of the bolts holding the tank and skid plate. Also a good idea in getting some new tank straps, mine (a '91 living in NY since the beginning) were toast.

You will also need a fuel line disconnect tool.

Do a search for fuel pump access panel. You cut a hole in the sheetmetal above the fuel tank and you can change the pump that way, no need to drop the tank. I haven't tried this yet, but from reading the post, sounds like it works from others have replied with.

easier yes , but dropping the tank may sound like a pita but it's really not .i can do mine in about 30 min if i have all of my tools in front of me and the truck is already lifted ( maybe a hours worth of work to get it out if your slow and another hour to get it back in ) but dropping the tank i think is more a productive use of your effort imho .first of all you dont have to cut a hole /remove carpet/cleaning out all the metal shaveings your going to create not to mention that if you dont get the blade depth just right you could quite possibly punture the tank ( oh what fun that would be.... new tank = $ 500 or more est) .
dropping imho is the best and safest way, plus you can clean it out really well to .either way you do it just remember to mark the postion of the fuel lines (pump side..metal lines from the pump) on the tank so that when you go to install the new pump your lines comeing from the engine will meet up at the proper angle when you re-connect everything .:salute:

I'll have to agree with pugsy.. I did the do it your self access panel and it was probably the best thing i ever did.. mines a 98..but the articles actually on a 91-94. Took a piece of stainless plate i had laying around a few selftapping screws, sily-cone.. and voila. an access panel i can use time and time again.. All i had to do was remove a seat, cut a hole. I did this last weekend..total time from start to finish 1 1/2 hrs.

Here's the link to the access panel:


As I said, I haven't done this yet - thinking about cutting out the access panel this summer (even though nothing is wrong) so that when/if I get fuel pump trouble or a leak on top of the tank mid-winter, I don't have to send sparks flying with fumes around that area in a confined garage.

To anyone that's done this - any tips for a sucussful cutout that is safe and easy to patch back up?