Topic: gas leak in tank / possible tank removal?
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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...just noticed that I've developed what appears to be a slow leak from the base of the sending unit on my tank ('74)...and as luck would have it the tank is full. Anyway, does this require removing the tank to remove the sending unit or can it be done without? Can I somehow seal the outside without removing it??
If removal is neccessary, any suggestions...this is a new one on me. Thanks....
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It isn't hard, but you likely will have to drop the tank. I did this on my 76 recently and I think yours is virtually the same except you won't have the bladder inside the tank. I ran my car until the tank was empty (if this isn't feasible for you, siphon it out and run until empty to get rid of the remainder). It is too heavy to mess with if there is significant fuel in it.
Get the car up high on jack stands and remove the spare tire and cover. This will expose the bottom of the tank where you can access the strap bolts (two of them). Once you undo the strap bolts and pull the straps out of the way, you can manhandle the tank out. You will want to disconnect the items at the top where the filler assembly is, but this is much easier once you drop the tank a little. The hoses can be disconnected easier that way also. It is possible you will have to disconnect exhaust components (mufflers), but I was able to wiggle the tank out without much trouble (just loosened the rear hangers and wedge apart some).
Once out, you will have to decide on a new tank or a recondition and then check out the sender and pickup tube, screen etc. Mine just needed a good cleaning (the bladder was great) and some minor repairs on the sender unit. Be sure to use a fuel compatible RTV compound when replacing the sender unit. Also, I found it helpful to calibrate the full and empty positions on the sender unit prior to reassembly. You can bend the float arm slightly to make sure the gage reads the way it should when actually full and empty.
A Haynes shop manual will be very helpful if you get one (available on line everywhere). Of course, disconnect the battery and make sure you take all precautions to avoid sparks when working around the tank (can't be too careful).
Hope this helps.
My 76
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
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Luckily, the '74 tank does not have to come out to remove the fuel sending unit. Unlike the '75-up cars, everything is installed from the bottom.
Drain the tank first, either by driving, or siphoning.
Remove the spare tire, carrier(tub), and the top piece that bolts to the frame.
Once the tank is empty, you can remove the sending unit. Take the two wire connections off, then the two fuel lines. Be sure to have a large pan to catch the fuel that will still be in the tank. The sender unit is removed by turning the lock ring. A small hammer, and a screwdriver can be used to turn the ring, but a brass drift punch is best, to keep from having any sparks ruin your day.
Once the lock-ring is loose, the sender will come out. You'll need to twist/turn it a bit to get it all out, as the float can be a little tricky to worm out.
Clean the surface of the tank where the o-ring goes, as well as the surface of the sender unit. Get a new oring, and use a small amount of wheel bearing grease to hold it in place. Now would be a good time to replace the "sock" filter on the end of the sender unit, too...
Reassemble in reverse, making sure the lock-ring is fully seated. Put a couple of gallons of fuel in, and check for leaks. That should take care of the leak if the o-ring is the source.
Drain the tank first, either by driving, or siphoning.
Remove the spare tire, carrier(tub), and the top piece that bolts to the frame.
Once the tank is empty, you can remove the sending unit. Take the two wire connections off, then the two fuel lines. Be sure to have a large pan to catch the fuel that will still be in the tank. The sender unit is removed by turning the lock ring. A small hammer, and a screwdriver can be used to turn the ring, but a brass drift punch is best, to keep from having any sparks ruin your day.
Once the lock-ring is loose, the sender will come out. You'll need to twist/turn it a bit to get it all out, as the float can be a little tricky to worm out.
Clean the surface of the tank where the o-ring goes, as well as the surface of the sender unit. Get a new oring, and use a small amount of wheel bearing grease to hold it in place. Now would be a good time to replace the "sock" filter on the end of the sender unit, too...
Reassemble in reverse, making sure the lock-ring is fully seated. Put a couple of gallons of fuel in, and check for leaks. That should take care of the leak if the o-ring is the source.
Joel Adams
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in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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