Fuel gauge stopped working, failing at full.
I removed the fuel pumps/fuel level sender Christmas Tree and disassembled the fuel level sensor unit. (See the schematic representation) I opened the three metal tabs, cleaned Lhe brush. and put more tension in the brush arm. The resistor is mounted in the inner edge of the metal housing. I have drawn the resistor and the brush on the schematics provided. This is just because l forgot to shoot the pictures when I had the unit open. I was just too much in a hurry to see if this was going to work and I closed the housing too soon. I ran a dry test with the Christmas tree out of the tank. the pumps disconnected, key on. & no engine start obviously. As I moved the float up and down, the gauge went up and down. What a relief. The computer could also be broken, in which case this would not work.
  1. Removal of the pump assembly was as described by Scott Fabre. First a bit up 90° counterclockwise, then forward. backward, rotation. etc. Eventually. the whole enchilada comes out. Don‘t abuse the Float.
  2. Not much dirt observed on the socks.
  3. Not much debris observed at the bottom of the tank. I cleaned anyway with the tank half full. A towel grabs most of the orangey residue at the bottom of the tank. I also cleaned the white plastic open container that houses the float. I would swear this container is open at the bottom to allow it to empty out.
  4. Did not need to replace the lid gasket although I bought a new one just in case.
  5. Did not touch the pumps. Just unplugged them for the dry test. They seem to be OK. I plan to get me a couple of new ones ASAP and will replace them in a year or so. I don't believe these are expensive enough to do much testing and after ll years they probably should be replaced. Same applies to the socks. Unfortunately. the Chevy dealer is telling me that they don‘t sell them as a separate item. I thought they did. I will look in the aftermarket as everyone else.
    The whole sender unit by GM is valued at $l200+ . What a rip-off for something so flimsy.
  6. The fuel level sensor probably will require a new resistor soon. I don't know where to find one. It would probably have to be installed using a rivet. The brush is not the strongest thing either. To replace the whole sensor unit might even be better. This may require some welding.
  7. When testing the flloat after fixing it, being outside the tank but connected I observed full tank condition with the float at maximum deflection, but tho low tank condition was with two bars left on the gauge. At this point the Reserve light comes on. This seems to be normal I hear. I am not sure. In reality, these meters are not linear at all.
  8. Putting the unit in was not easy either. However, you have a better view of what's going on. It took two attempts.
  9. Almost no gas was spilled out when taking out the pumps. I spilled some out when cleaning the interior. WARNING: Do this away from all flames in an open space.

Most important conclusion: I don't agree with what it has been said on the ZR-1 Net recently regarding one of the pumps running dry under low fuel condition. If you look at the configuration of the Christmas tree and how the bottom of the pumps will align with the bottom of the tank after assembly, you will find out that both pumps bottoms (socks) rest almost at the same level and parallel to the bottom of the tank. So, the running dry situation may happen only under extreme conditions when you are literally out of gas. However, the pumps may overheat under these conditions. I would say, don't drive hard with less than a 1/4 tank left, just in case.

The whole thing did not take more than two hours. The hardest thing for me was to figure out how to do the electrical disconnect. You are supposed to disconnect the plug hanging from the rear wall of the car. I tried to disconnect the yellow plug on the tank lid. Big mistake. Luckily enough I did not damage it. This is one of the evident things that l saw originally and then I forgot about it.
Thanks to all of you that provided me with so much information. I studied it for almost three weeks before I did it.
I am providing some photos. You will see in all photos the pump’s connectors are disconnected.
  • If any of the plastic (Snapper) hose clamps are protruding outward; positioning the protrusion inward makes the sender unit easier to install and remove.
  • When installing the sender; temporarily using a couple of the right size aluminum standoffs will properly align the sender such that the screw O-rings will not be damaged.
  • If your tank is one of those annoying 18 gallon units (due to the filler neck being too long), while the unit is out, you can nibble a slot up to about 1.25 "from the bottom.


Author: Juan Sepulveda (ZR-Juan)
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