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'91 744 Fuel Level Sending Unit 700 1991

So, I just got out the fuel sending assembly out of a recently acquired '91 744.
The previous owner had a "reputable" garage install a new regina fuel pump. The fuel guage worked before the pump was replaced.

The car ran no problem, but the fuel guage was at empty and the red light was driving me nuts. I had to fix it.

Well, whoever did the job didn't bother pulling the harness through the rubber grommet, they just cut all the wires about 6" from the sending unit. Now that would be ok, but when the put the unit back in, they wired the white/grey & brown wires FROM the sending unit together, and somehow then tied into the same wires on the harness side. Needless to say it was a mess, and they used WIRE NUTS to splice the stuff together, and then sloppily wrapped the entire mess up with duct tape and then over that, electrical tape. At least they got the fuel pump and ground wired to the correct harness wires. Of course they neglected to address the big crack in the pump wire about an inch from the top of the outside of the sending unit....left it totally exposed and only half of the wire strands were still connected.

To my dismay I troubleshot it down to the sending cylinder itself....oh, and the morons didn't solder wire to the two terminals, they clamped a butt connector to it with wire clamped on the other end.

I pulled the canister apart to find that the little criss-crossed contacts had slipped and were only touching one rod, and the windings on the top of one rod were coming loose to boot.

I took them out, re-wrapped the windings superglued with a glue that petrol doesn't break down. Had to re-bend those little crossed contact setup...which took quite a while to get just right so they rode upon the rods with solid contact and didn't get jammed up. Put the canister, float, rods back in to test the movement of the float.

Aha, the float jams part way....took back out, discovered I had slightly bent both rods when disassembling it the previous time, so I had to very gingerly roll the rods to find the humps and tweak them straight.

Got the assembly back together, float moves freely, contacts looked good when I put the float in....ohmmeter tests from top to bottom.

Test in car just hooked up to harness leads to top of terminals = success!!!!!!!!!

It's strange how slowly the guage reacts to movement of the float, but I guess that's due to the balast resistors that are used to smooth out the needle on the guage....I remember bypassing those resistors for the temp guage on my '86 240 to get more accurate readings and no more shorts.

Now I've got to put the assembly back together (correctly this time), install it and hope it still works......

Just my 2 cents worth, and despite the royal pain in the posterior, well worth saving the ton of money to have to buy an entirely new assembly.






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New '91 744 Fuel Level Sending Unit [700][1991]
posted by  145Guy  on Mon Jan 18 05:31 CST 2010 >


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