fuel sending unit question

[Chrispbrown36]

My truck has dual tanks on it but the passenger side tank is not working. The previous owner said he knows the sending unit needs to be replaced. I was thinking I might go ahead and pull it out now and change the unit when I have a chance. I have never dealt with dual tanks or even a sending unit in general, so I am wondering if dropping the tank will cause any problems with the working tank? Any tips on dropping the tank or what else I might need to replace while at it?

[tucsonjwt]

If you search this forum you will find a lot of information on changing sending units and fuel gauge repair. Most feel that grounding is the primary issue.

I replaced my sending units by moving a couple of concrete blocks under the tank and shimming up with 2x and 1x wood pieces until they were snug. Then I disconnected the filler neck (and ground strap, if you have one), the rubber fuel lines, and electrical plug at the sending unit, and the ground wire. Then I removed the 8 bolts holding the fuel tank brackets to the frame rail. Then I removed the wood and blocks one by one until the tank was on the ground. I replaced the sending units and hooked up all of the lines and reinstalled the brackets.

Some say you can remove the bed and leave the tank in place. The problem is you can round out the square mounting holes in the bed and have a bigger problem to deal with. Bed bolts usually don't come out easily or in one piece if they are rusty, so you might need new bolts/nuts.

Of course, make sure that your tank is empty prior to starting.

I used Spectra brand sending units and the fuel gauge bounces. The original Delco units won't do that, but they cost about $150 per unit vs. about $40 for Spectra. The Spectra units will give an accurate reading when the gauge needle settles down, but when you accelerate/decelerate/stop/turn the gauge will bounce.

You may be able to reach up on top of the frame rail and feel the ground wire from the sending unit . There is a hex bolt and star washer which can be removed with an end wrench by feel, then you can clean it off and the mating surface on the frame rail. This might help, and is a good maintenance procedure anyway. I think the driver's side ground wire might be on the side of the frame rail. If you feel around the sending unit you can determine where the ground wire goes.

I would say that the sending unit replacement is a doable task for most anyone who has a little patience. Figure on spending the better part of a day working on it. You will get very dirty. Use safety goggles - lots of crud will come loose with that fuel tank. Use PB Blaster on the bracket bolts.

If you have rusty fuel tank brackets/straps you should also replace them. Check Ebay for good used brackets - don't buy aftermarket Chinese new brackets - they require loose nuts and bolts for installation rather than single bolts with captive nuts on OEM brackets, and cost about twice as much as refurbished used brackets.

[Chrispbrown36]

I tried the search and found plenty on sending units but didn't see any that mentioned whether you could drop one tank and still drive it. The bouncing needle....I wonder if that has to do with the quality of the float or maybe even the shape? If I remember correctly the Spectra units had a flat float vs most of the others that had round ones....I wonder if this might have something to do with that.
Until the ground dries out some I won't be sliding under the truck...except for emergencies which hopefully I have none. Thanks for the tips I will definitely keep this in mind when I do get a chance to drop the tank.

[hatzie]

IMHO it's an SOB to pull the tank out to just service the sender.
The bed can be pulled off and set on sawhorses by 2-4 guys or you can slide it back onto some timbers till the sender is accessible.

[tucsonjwt]

You can use just one tank and disconnect/plug hoses to the other tank. I would do something to the fuel inlet on the tank not used so somebody doesn't fill it by mistake. In my opinion, it is worth the trouble to try to get both tanks working, since these trucks are gas hogs and having extra fuel allows for longer trips between fill ups. I think getting both tanks operational is not a big issue. Even if you have to replace a rusty tank they are only about $100.

[Chrispbrown36]

Oh I am definitely going to get the other tank going. As far as someone filling up the missing tank....I am the only one that drives the truck and there are no full service stations around here so no issue there unless I lose my mind. The fuel gauge isn't accurate on the working tank so I think a new sending unit for it is in order, but I want to get the other one working first.

[Titomars]

Originally Posted by hatzie

IMHO it's an SOB to pull the tank out to just service the sender.
The bed can be pulled off and set on sawhorses by 2-4 guys or you can slide it back onto some timbers till the sender is accessible.

The 16 gal tanks used on SWB trucks position the sender under the cab so bed removal is not an option. The only way is drop the tanks on the short squares.

[hatzie]

Originally Posted by Titomars

The 16 gal tanks used on SWB trucks position the sender under the cab so bed removal is not an option. The only way is drop the tanks on the short squares.

Well that's painful. I feel sorry for all you guys with the shorties.

[tucsonjwt]

Removing the tank really isn't very difficult - just very dirty. Even if you have never done it before, it should not take more than 45 minutes to an hour.

If you remove the filler neck and ground strap, disconnect the ground wire from the sending unit, then remove the 8 bolts on the brackets - you can then drop the rear of the tank far enough to reach up and disconnect the rubber fuel hoses and the electrical plug on the sending unit. It is tight but a pair of vise grips for factory clamps or a nut driver or screw driver for aftermarket clamps is all you need. You won't have to disconnect the big rubber filler hose and vent hose if you use the method. The whole works comes out with the tank - filler hoses, filler neck, bracket with straps, etc. Then you can work on the sending unit with it up on a table somewhere.

Check your brackets for rust (use a flashlight to check between the bracket and the tank on the bottom side) before your begin. Remove the plastic rock shield first - you don't really need to put it back, and I would not use it if I was in the rust belt. If you get the tank out and find that you need new brackets your truck will be out of service for a while longer.

[hatzie]

I do highly reccomend using bolt on "fuel injection" clamps or even spring clamps instead of the smaller Ideal type worm drive clamps for smaller rubber lines like fuel lines. The larger Ideal type clamps work great on radiator hoses and such but the design doesn't seem to scale well.

Bolt Fuel Injection clamp.

Spring Fuel Injection clamp.