fuel sender

[Trev]

Anyone got a rusted tank with a good fuel sender they want to sell me?
Doesn't matter what kind of tank (sedan, wagon), I have some spare parts here to make it work.
Thanks, Trev.

[Devilrod]

Did you get a sender in the tank you took from me awhile back? If not I think I may still have one here.

[Trev]

Yes, they are both stuffed (broken wires in the sender).
If you could have a look that would be great, thanks.

[rosco]

If you get stuck Trev - Rares do a change-over.... but they are quite expensive and outshop to a specialist...... 'nuf said.

frats,
Rosco

[Trev]

I saw those Rosco, thanks.

[Devilrod]

I"ll have a look. Can the wires be replaced easy enough?

Forgot to ask was this part of Saturday's problem?

[rosco]

Not that I want to deprive business from a company who support us.... but...

If you do get one re-conditioned - you'll find that all they change is the potentiometer (pretty cheap from an electronics supplier) and do a bit of scrubbing up and coating the original metal bits...
The cork gets a coat of black something - and what's left of the mount gets dipped.....

There's only one connection which comes from the unit - which goes to your gauge.
There's a POT (called a potentiometer or rheostat) - a wire wound spiral of resistance wire with a metal wiper - which is mechanically connected to the float arm....

When the float goes up, the wiper arm moves either up or down (can't remember which) along the wire-wound resistance wire and changes the resistance.....

Whatever the readout is goes to the gauge the differential between a high wound and low wound coil with 12v +ve on the supply side causes the gauge needle to deflect....

I should have measured the resistance with both the arm lowered and raised - before fitting my re-conditioned one and purchased a POT which would give the needed readings..... at one end, it would be zero resistance (i.e. closed circuit... ummmmm direct contact to body earth through the mount of the unit) - the question to be answered is how much resistance is shown for the gauge needle to show either full or empty (can't remember) where the maximum amount of resistance indicated empty/full.

POT's come in many different scales - the wire-wound ones are the most expensive - but last the longest... the carbon ones are much cheaper - and last accordingly......

It's an "earth" connection - so there's no power down the line to the tank...... that line is looking for earth to tell the two coils how much to deflect the needle.

If you wanted to, you could probably just replace the POT - if you pull the old one apart... there's a pretty good chance it would have a marking on it stating the resistance... in OHMS..... something like 10K and a little "omega" sign..... that tells us it's a 10 thousand ohm resistance POT.
There may also be a letter (A B C D) at the end of the value which designates what scale the POT works on.... I believe A is linear - which is what we want....
Something is nagging me that B is exponential - and used for volume devices/audio.... long time since I played with this sort of stuff....

I'm firmly of the opinion that the only things which break in the sender unit are.....
The float falls apart (cork - how hard is that to replace?).
The resistance wiper corrodes... new POT - wire wound if you can find one - but a carbon one will do for yonks.
The wire-wound resistance winding breaks one of the loops... new POT
Gunk/crud/corrosion gets between the wiper and board... might get away with cleaning it out and making it shiny again.
The actual housing loses contact with the tank - scrub up and a new cork gasket.... make sure one of the screws is making good electrical contact with both the tank and the unit housing and one end of the POT has good contact to the housing.

That'll probably more than do anything you ever wanted to know about the fuel sending unit....

Oh - and be "wery careful"..... drop anything into the tank whilst you have that hole uncovered and you're in for a long battle looking for it......

You might just remember one post I threw up about the dreaded "Bogong Moth".... for a chuckle, you might like to chase it up......... I got the remnants of the critter some six months and one nationals down the road...... all that was left was the fuselage.... the rest had been eaten away by whatever our fuel suppliers add to the mix...... I was very concerned that my nationals trip to Tenterfield would be plundered through this blasted moth blocking the exit line from the tank.......

frats,
Rosco

[Blacky]

Scotty did a pretty thorough "how to "on reconditioning your sender unit - I used it to sort out the one on my ute
A search ought to bring it up , from memory we made it a sticky. By the sounds of it though, Trevs existing one needs a new resistor and they are not available

[Trev]

Ok, both of the wire wound strips inside the sender have broken wires, 1 has a broken strip too.
That's the only part I need to replace.
I have followed Scotty's how to, thanks Blacky.
DR, a part of Saturdays problem was the gague wasn't working and hadn't been for quite some time.
But having used a full tank of fuel in 160 km threw a spanner in the works.
I filled up about 60 km from home and when I pulled the sender out the tank the next day it was still chockers full, so it used sweet FA in 60 km ( weird) .
I have since pulled down my carby, checked the float level, reset the mixtures, went over the timing and everything seems to be running as it did before ( perfect, it never missed a beat).
I usually get at least 300 out of my usual Friday night trip to Johns R&C ( including my parts collecting run around), and still have plenty in the tank, so I'm stuffed if I know what happened!

[fj_225]

got a couple here trev u can check out

[Trev]

got a couple here trev u can check out

Thanks Shane, I plan on going to the Picnic on Sunday so I'll call in if thats OK?

[fj_225]

no probs trev