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throwinwrenches 11-02-2013 06:15 PM

82 cj8 fuel sending unit rebuild.
I know ... why bother they are not expensive to replace but as the deep rooted desire in me to try and fix , rebuild or remake a part for the cost of time rather than those precious green pieces of paper that so easily pass thru our fingers.
I thought I would share my morning adventure into my fuel tank. I can't seem to get pics to seperate between each caption so I will write the story with photos following.
I hope some other members can relate to my endeavor and hopefully teach some of the new comers to the wrench turning or in this case diagnosis and repair.
I started by double checking just to make sure it was the sending unit at fault.
1. disconnect ground from sending unit using a ohm meter set on the auto scale probe black lead terminal and touched chassis with other lead -good
to battery negative - good.
2. disconnect pink lead from sending unit and guage ohm ,meter on each end ... no good. disconnect 4 lead plug above e-brake pedal ( black connector with pink wire, black wire and i think white and grey. ohm meter on pink wire and at sending unit - no good. reconnect and disconnect pink wire connector inside left rear wheel well wire harness under bed- good . pinch connector alittle for better connection when plugged back in and recheck from pink wire at guage and sending unit- good . turn key .... **** still empty. ooops hook ground back up turn key .... **** still empty.
key on, check red power wire on back of guage - good ( volt meter not test light ) yup 12.65 volts .test light will still light bright with less than 12 volts giving a false sense that there is enoughe voltage . not sure what minimum voltage is for guage to work propely but im assuming it shouldnt be less than 11.0 v before it would effect reading of guage.
okay ... remove plywood that is covering whole in my perfectly good rusted thru bed to remove sending unit ( i did do this first to access wires to sending unit ) found 2 problems, 1 float half full of gas, copper sweep finger not connected to float arm.
1. remove float arm tension spring with small needle nose pliers.
2. bend three tabs up on housing and remove plate making sure to catch little spring and fiber washer located inside that will fall out and bounce to some magical wonderland to never be seen again.
3. clean float arm and sweep finger with sand paper . also gave a light scuff to contact piont of sweep finger
4. light coat of flux on both pieces for soldier to siphon into joint.
5. use paper clamp to hold sweep finger to float arm, i used a small needle nose pliers to form sweep finger around float arm first then clamp.
6. heat underside of assembly. (this part took a little time untill heat transferd thru to sweep finger) once hot enought to melt soldier i kept pushing it untill it siphoned smoothely . if it just balls up for you it's not hot enough yet.
7. let cool then used jewlers file to smooth out .then cut a small piece of shrink tube to make a clamping collar( just in case )
8. starting at float end slide small spring on float arm all the way up to sweep finger. if shrink tube collar is too long spring will not slide all the way around bend. next slide fiber washer on float arm followed by sending unit plate ( the one the three little tabs were holding down).
that part done i now repaired the float which i failed to take photos of.
using a drill bit the size of a needle (very very small) i made a hole in center of float end (plastic is thickest there) and shook it till all gas was out.
i then heated a small flat tip screw driver with a micro torch and gently melted hole shut . then submerged in bucket of water and gave a couple very gentle squeezes to make sure there were no more holes. if so a new float was in order. i'm assuming the fuel just wicked into the float to get there over a long period of time, no gas seeped out any where before i drilled the hole .
reattach float to float arm.
make sure to clean pocket for sending unit and lightly coat o-ring with lube. i use a light film of white grease . a dry o-ring does not seal it needs lubricated to seal properly.
reinstall in tank, tighten lock screw or ring wichever you have.
make sure while sending unit is apart to check windings . if they are broken then obviously this wont work .check for a black line where sweep finger runs across windings this can be cleaned with a pencil ereaser gently rubbing with the windings not across them that can change there placement and effect resistance reading for guage or even break them if rubbed too hard.
ok well apperantly there is a security token missing and it wont let me upload the pics just yet. i'll get them up as soon as possible.

throwinwrenches 11-02-2013 09:56 PM

well if you havent noticed i figured out the photo issue. i hope this helps

ScroungerLee 11-03-2013 07:19 AM

Thanks for that, it is well documented. I too like to stubbornly repair something like that instead of replacing it. I do wonder about the float though, could gas really get in through the plastic given enough time?

throwinwrenches 11-03-2013 08:38 AM

Well i would not think so but that is the only explanation i can think of. I must have shook that thing and rolled it around did everything i could think of but nothing came out . even the slightest of imperfection would have left the fuel wick out showing me where it got in, but nothing . it was completely dry.

John Strenk 11-04-2013 03:30 AM

603 Attachment(s)
A brass float would be nice.

Good work.

The time now is 09:19 AM.

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