Fuel sending unit rebuild?

7259 Views 8 Replies 3 Participants Last post by itsacrazyasian, Jul 2, 2010

digitalbill

Discussion Starter · Jun 30, 2010

When I bought the truck, the fuel gauge was pegged on “empty” all the time.
After having the truck for about a month, the fuel pump crapped out on me and I put in a new one.
That one lasted about three weeks.
I pulled it out and discovered a crack in the top of it so I exchanged it for another one.
Sometime while doing all of this, I knocked off the yellow wire as shown in the picture.

I tested the sending unit with a multimeter and determined that it was not functioning properly although I have never used a multimeter before.
I put the wire back in place and put everything back together and now, instead of being pegged at “full” it was now being pegged at “empty”. Not a big deal right? At least the fuel gauge is getting a signal.
I guess when I put everything back together, I did not put the rubber gasket on correctly because I was getting spills when I would fill it up or hard braking so, I took it apart again and put in a new rubber gasket.
Now, my fuel gauge bounces around a bit between empty and ¼ full.
I figure maybe I knocked something around this last time I removed it or something but, I am stumped.
Thoughts?

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miesk5

· #2 · Jun 30, 2010

Yo Bill,
as for "Now, my fuel gauge bounces around a bit between empty and ¼ full"; is this while travelling down da road? if so, figure on at rest a gauge reading that doesn't move indicates an open circuit (blown fuse; corroded terminal) on the power (battery) side of the gauge OR a bad instrument cluster ground at C251 pin 9.
The terminals of C251 (& C250) are known to corrode & lose contact. Polish both the connector pins AND the film circuit pads with brown paper or a pink eraser. The larger version of C441(WPT454) was used until '93. The level sender can usually be disassembled & repaired by bending the wiper arm inside the plastic housing to apply slightly more force..."by Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/744437
See his diagram and read more.
Sender Range: 160 (full) - 16 (empty) Ohms

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digitalbill

Discussion Starter · #3 · Jun 30, 2010

miesk5 said:
Yo Bill,
as for "Now, my fuel gauge bounces around a bit between empty and ¼ full"; is this while travelling down da road? if so, figure on at rest a gauge reading that doesn't move indicates an open circuit (blown fuse; corroded terminal) on the power (battery) side of the gauge OR a bad instrument cluster ground at C251 pin 9.
The terminals of C251 (& C250) are known to corrode & lose contact. Polish both the connector pins AND the film circuit pads with brown paper or a pink eraser. The larger version of C441(WPT454) was used until '93. The level sender can usually be disassembled & repaired by bending the wiper arm inside the plastic housing to apply slightly more force..."by Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/744437
See his diagram and read more.
Sender Range: 160 (full) - 16 (empty) Ohms

It doesn't quite "bounce" as you described.
If I get in it right now and start it up, it might read dead empty.
If I just turn it off and fire it back up 30 seconds later, it might read at 1/4
I will read Steves page a bit more throughly and see what I can see.
That would friggen RULE to have a working gauge.

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miesk5

· #4 · Jun 30, 2010

yo Bill,
ok, but i think that symptom is what Steve describes as "gauge reading that doesn't move" so.. starting it may show diff readings but it doesn't peg to empty or full, etc.

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digitalbill

Discussion Starter · #5 · Jun 30, 2010

miesk5 said:
yo Bill,
ok, but i think that symptom is what Steve describes as "gauge reading that doesn't move" so.. starting it may show diff readings but it doesn't peg to empty or full, etc.

Thats correct.
The wife and kids will be out of town this weekend so I have a chance to mess with it.
I am not quite sure exactly WHAT "pins" Steve is talking about.
I would imagine that it is either in the back of the gauge cluster or in the back of my fuse block.

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itsacrazyasian

· #6 · Jul 1, 2010

hey if you need help this weekend you can run it down to my shop and we can check it out. I was chasing an intermittent gauge in my truck up until today. Might also run up to the yard to find a deck lid and taillights for another crown vic i just got and a few bits for my truck at the yard in west palm.

BTW i have a few spare fuel senders/hangers if you need any parts. I can usually bring the senders back to life though fairly easily.

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digitalbill

Discussion Starter · #7 · Jul 1, 2010

itsacrazyasian said:
hey if you need help this weekend you can run it down to my shop and we can check it out. I was chasing an intermittent gauge in my truck up until today. Might also run up to the yard to find a deck lid and taillights for another crown vic i just got and a few bits for my truck at the yard in west palm.

BTW i have a few spare fuel senders/hangers if you need any parts. I can usually bring the senders back to life though fairly easily.

(and this is why I love this site)
I will be happy to take you up on that offer.
I work in Boca so I can either go after work on Friday or, I can do it on Saturday or Sunday.
Your call really since I am a beggar at this point.
Need a hand at the U pull?

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miesk5

· #8 · Jul 1, 2010 (Edited)

MAJOR EDIT; I added a URL to the Post and test info for you Bill

yo,
Now that I am @ home today I re-read your original Qs and have a clearer mind.
Steve is looking at the instr cluster connector C251 , Pin 9 is a ground Black/white

But go back to the tank connector and check wiring and connector condition

I'd rather not open up instr cluster to do anything for now to save you more problems w/wiring in there.
This is a my 96's EVTM;
PINPOINT TEST A: FUEL LEVEL READS INACCURATELY
A1 VERIFY POWER AT LOAD SIDE OF FUSE PANEL
Key to RUN.
Using Rotunda 88 Digital Multimeter 105-00053 or equivalent, verify system voltage at the load side of fuse. verify system voltage at the feed side of the fuse.
This is Ford's way of sayin' .. check Fuse..lol

Now, I'll skip the instr cluster part and suggest you look at the tank connector for all other tests they describe;
http://www.thedieselstop.com/faq/9497faq/maint/stj/stjd1017.htm#pptd1001

So in Tank Connector C441;
Y/Wh is gauge power
Bk is gauge Ground

Go to
A10 CHECK FUEL TANK SENDING UNIT GROUND
Key off.
Measure the resistance of the BK wire at the fuel level sensor connector to ground at battery.
Is the resistance less than 1 ohm?
NO - SERVICE the BK wire from the fuel level sensor to ground.

Yes - Inspect fuel tank for distortion or damage.
Is the fuel tank damaged?

Next tests are on da float

Summary is;
"...With the sending unit float arm in the empty stop position, resistance should be 15 ohms (below E). With the sending unit float arm in the full stop position, resistance should be 160 ohms (above F). The fuel gauge should read empty at 22.5 ohms and full at 145 ohms..."

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itsacrazyasian

· #9 · Jul 2, 2010

digitalbill said:
(and this is why I love this site)
I will be happy to take you up on that offer.
I work in Boca so I can either go after work on Friday or, I can do it on Saturday or Sunday.
Your call really since I am a beggar at this point.
Need a hand at the U pull?

If you work in Boca, why dont you come by my shop afterwork? I'm on 441 just north of Yamato. You have a PM with my phone number.

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