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Fuel Sending Unit Possible sure fix by Joseph Upson
Started on: 07-20-2013 02:35 PM
Replies: 3 (415 views)
Last post by: Joseph Upson on 08-05-2013 06:15 PM
Joseph Upson
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Report this Post07-20-2013 02:35 PM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
I tried the fuel sender fix posted here but did not get satisfactory results, the gauge was accurate at full and empty but all over the place in between and I suspect it is partly the result of using sand paper which probably caused micro particles to lodge between the windings and cause continuity points where they shouldn’t be. For others intending to try restoring the OE parts, I suggest a fine metal polish to remove the varnish. The dull appearance of the surface of the centrally located contact plate looks harmless until you touch the surface with multimeter leads and note there is no change in the reading until you clean the surface.

I found the universal sender below on ebay for $22 shipped and thought I’d see if it could be of any use and to my surprise so far it is amazingly adaptable. Not sure when I’ll actually get it in the car with the new pump but so far it looks promising. This is a backup sender the mock up is being performed on.

Universal adjustable GM sender 6-24” 0-90 ohm



Disassembled.



Next to the fuel rail seated on retainer.




Wiper arms side by side, the donor arm needs to have the axis and set bore drilled out, along with an opposing set hole drilled in, and the little arm on the side will need to be ground a little narrower or off






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Joseph Upson
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Report this Post07-20-2013 02:39 PM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post

Joseph Upson

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Member since Jan 2002
These pictures provide an idea of how far inward the resistance board will need to be positioned, however, I now realize that instead of adapting the new wiper to the unit, trimming the old wiper to slightly longer than the new and chamfering the edge may be all that is necessary along with securing the board to get it to work properly.

Otherwise my initial intent was to apply a little solder to join the two at a non flexible point and apply a little JB weld as added security. The multimeter measured as low as 0 ohms but since the board is not secured in place yet it moved a little to show 1.9. It also appears the original adjustment ability will be maintained.

I’ll post an update on the results when I get it installed.









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Joseph Upson
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Report this Post07-20-2013 02:49 PM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
On second thought, it maybe that the wear on the original wiper is resulting in more of the windings being contacted at once due to flattening and therefore reducing the resolution so perhaps crimping it a little to restore a smaller contact area on the wiper may prevent the erratic needle in the midrange of the gauge which is where the greatest amount of wear is on the original wiper as can be seen on close examination.

As for securing the board in this application, it's probably best to use flexible RTV sealant as a preliminary and once assembled and confirmed to be setup just right apply the permanent fix.
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Report this Post08-05-2013 06:15 PM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
It works!, took me a little extra time because I tampered with the float angle by bending it downward a little to make it sit a little lower after I lowered the pump pickup inlet as far as it would go in the tank. I forgot I didn't do a perfect job of centering the new wiper which when combined with the little adjustment caused an overshoot at half a tank causing a reading of ~3/4 of a tank at about 6gal.

Be sure to adapt the new wiper, modifying the original did not work well during tests before installing it in the tank.

I also ignored the fact that there was a little more resistance (binding) to the float movement than normal mainly at empty and thought it wouldn't be a problem. It was and required hitting a few bumps in the road to free it from the empty range after adding fuel not to mention it was sticking at "E" instead going a little below it as I had initially adjusted it to do which had I not been watching the trip odometer would have caused me to run out of fuel. Of course I fixed all of that after having to drop the tank again. Now true empty sits just below "E" to encourage me to fill up at empty when there's at least 2gal in the tank.

The tank is empty at about 1/2 a gal and the needle rests below "E" with 1.5 gal and on "E" with about 2.5 gal in the tank

If you decide to attempt this modification, take your time and perfection is an attribute. Keep that in mind and it should work out fine.

I soldered the two wipers together although it wouldn't be a bad idea to remove the portion of the old wiper that isn't needed if you have a backup float just in case you make a mistake.


The two dimple bars on the back side of the wiper mount are what caused the binding, I had to remove them to allow additional space for the increased stack height with the additional wiper.


Here are some pictures of it assembled on the rail.





The DW200 pump is very, very quiet.

In regards to the OE wiper board resistance, it is not important to get a 0 ohms reading at empty as the gauge will read empty at probably as much as 8-10 ohms, another reason is that the closer to 0 ohms the sending unit is the hotter that variable resistance board gets as indicated by the hot spot on the one I took out plus the worn out extras I have. It appears that is why GM switched to a higher resistance range on the later sending units as the heat is what was causing them to fail or malfunction. The board I took out appeared to have melted some of the solder I applied to the 0 ohm end in an effort to get it to read 0 ohms so it got pretty hot.

Hope this helps someone.
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