Fuel Gauge Sending Unit Troubleshoot; Fuel Flow and Tank Corrosion Issues

Discussion in 'Interior/Electronics' started by DAW, Jun 6, 2012.

  1. DAW

    DAW Member

    Joined:
    Aug 18, 2011
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    Location:
    Seattle
    Truck:
    75 Hilux Chinook
    Mini Mo-Ho is a '75 Hilux Chinook 20R 4 speed. I'm sorting out a bad fuel system. The fuel supply was a trickle and the fuel gauge always indicated empty. I noticed a damp oily spot on the bottom of the fuel tank, although it held gas OK and didn't smell like gas in or around the truck.

    I siphoned the gas rather than drain it, so that I would stir it up less and be able to see the fuel as I partitioned it into clear containers. I stopped siphoning as I got down to the last 1/2 gal or so. The premium fuel looked good and I used in another vehicle and for mowers, etc. Once I pulled the tank and removed the pick-up assy, I sloshed this residual gas around and dumped it out with rust particlulate in suspension.

    I had no continuity across the sender potentiometer/rheostat, regardless of the position of the lever. Confirming what the ohmeter said, I spotted the complete fracture of the solder joint (right about in the center of the photo: http://i205.photobucket.com/albums/bb237/DAW_cars/december0001107.jpg). I repaired the solder joint. I also treated the rheostat windings/lever contact with this: http://i205.photobucket.com/albums/bb237/DAW_cars/december000118.jpg. The corrosion at the upper frame of the pick-up I cleaned up with a brass brush, then touched it lightly with rust convertor spray.

    The in-tank pre-pump was inoperable and the impeller turned stiffly due to corrosion. I replaced it with AIRTEX AIR E8188:p from Rock Auto (it was about $37 IIRC [I also got a clutch master kit and slave cylinder for cheap with the same order because shipping didn't increase and those are good to have in the glovebox]). You have to trim out the original rubber seal/mounting piece a bit because the new pump has a slightly larger diameter input (which is likely an improvement for flow); it's easy. Installed pre-pump: http://i205.photobucket.com/albums/bb237/DAW_cars/december0001111.jpg. The cleaned strainer was reused.

    Light was showing through two pinholes in the tank floor and there were a half-dozen BB sized holes in the roof of the tank, adjacent to the pick-up opening, from corrosion of water vapor condensing to droplets and promoting rust there. I used Dawn detergent and water to flush the tank of residual gas. I the put some M.E.K. (careful! or use acetone) to slosh around and pour out, then dry overnight (the tank pick-up assy and hoses were off for all of this and I left the tank outside and blew it out intermittantly with air). Once dry, I put an 8" length of chain in there while I shook it around. I got the rust particulate out with a magnet to get rid of the pile of particles, then Shop-Vac. I could force my hand and wrist into the opening for the pick-up and use a brass brush in there on the roof where the worst corrosion was.

    Next stage is to treat with Metal-Prep, re-rinse and dehydrate again, then JB-Weld shut the holes, then seal the tank with two-part epoxy (Caswell from Bonneville Cycles/EBay).

    I'll update with any surprises on reassembly, but otherwise; that's it.
    DAW
     
  2. DAW

    DAW Member

    Joined:
    Aug 18, 2011
    Messages:
    28
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    Location:
    Seattle
    Truck:
    75 Hilux Chinook
    This should be in Maintenance/Repair; not Interior/Electronics.

    a little help mods?
     

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