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chaseincats

Replacing Fuel Sending Unit Float

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Hi guys,

My gas gauge has never been accurate past the 1/3 emptyish mark.  When the tank has 8 gallons remaining, it will always read as empty (I've tested this by going to the pump the second it reads empty multiple times and I always end up putting in about 8 gallons.

Recently my gauge hasn't been reading full when I top the tank off - it will read maybe around 15 gallons in the tank instead of 18.  I have taken the fuel sending unit out a few times for cleaning and everything inside on the coil/arm (both plug ends too) look great.  I pulled the dash gas gauge and everything in there looks pristine as well.  The real nail in the coffin is when I have the sending unit out and bend the arm up and down to the half and 1/3 mark, it will read that on the gauge so that leads me to believe it's the 40 year old hard-as-a-rock float.

 

TL;DR: My question is, is there a way to replace the float?  A new fuel sending unit from zstore is almost $200 so I'd prefer to steer clear of that if possible.

 

Any ideas?

chase

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What do you mean "bend the arm" for testing.  Do you mean simply move the arm up and down?  My gauge responds similarly as it reads empty with just less than half tank remaining.  To me, it will be an easy fix by actually bending the float arm down so the gauge thinks there is more fuel in the tank.

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21 minutes ago, David F said:

What do you mean "bend the arm" for testing.  Do you mean simply move the arm up and down?  My gauge responds similarly as it reads empty with just less than half tank remaining.  To me, it will be an easy fix by actually bending the float arm down so the gauge thinks there is more fuel in the tank.

Sorry, yes I meant moving the arm up and down while watching the fuel gauge.

I'd prefer not to alter anything with the gauge.  Is it really that tough to find something to replace the float with?

 

EDIT: Also, the problem only develops when the tank is less than half full.  Up to that point it is correct I believe.

Edited by chaseincats

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Why bend the float arm to compensate for inaccurate readings.  If you look 

closely at the float arm pivot point, you will see a small set screw.  This set screw,

when loosened, would allow you to change the sweep of the float arm in relation

to the pickup contacts thus changing the tank fuel level readings.

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On 12/9/2019 at 2:00 PM, AZ-240z said:

Why bend the float arm to compensate for inaccurate readings.  If you look 

closely at the float arm pivot point, you will see a small set screw.  This set screw,

when loosened, would allow you to change the sweep of the float arm in relation

to the pickup contacts thus changing the tank fuel level readings.

I'd really not like to change any of the calibration.  Are replacement floats (or substitutes) not available?  I was thinking about replacing the float with some Styrofoam but I'm guessing the gas will eat that up, right?

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Styrofoam will last about 10 seconds in gasoline and then you will have a little blob of Napalm...

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1 minute ago, Patcon said:

Styrofoam will last about 10 seconds in gasoline and then you will have a little blob of Napalm...

Ya exactly haha.  Do they sell the floats anywhere or do you know what they are made of?

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So as soon as I bought the float (but haven't installed yet), the possible real problem reared its head.  My gas gauge needle now bounces around and sometimes the gauge will just plain die - the needle will fall as fast as if I shut the car off then pop right back up a few seconds later.

I've checked the gauge & fuel sending unit connectors before but don't remember seeing any corrosion at all.  Is the ground for the gauge/sending unit hidden somewhere else in the car or is there something else you guys recommend I check?

 

Here's a brief video of the needle slightly bouncing around: https://www.youtube.com/watch?v=6MJjEKJtesk&feature=youtu.be

 

Any ideas?

-chase

Edited by chaseincats

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Anyone?

Also - on the sender unit, is the wiper arm supposed to contact the the wound wire or just hover above it?

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6 hours ago, chaseincats said:

Also - on the sender unit, is the wiper arm supposed to contact the the wound wire or just hover above it?

I can't help you with your bouncing needle except to say make sure all electrical connections between the sender and gauge are clean. Also, the wiper arm should touch the wound wire, the wire is one continuous strand from end to end so as the wiper moves up and down so does the resistance and that is what move the needle.

Hmmmm, check to see if there is anything stuck on the wire that might be preventing contact with the wiper at one point.

 

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11 minutes ago, grannyknot said:

I can't help you with your bouncing needle except to say make sure all electrical connections between the sender and gauge are clean. Also, the wiper arm should touch the wound wire, the wire is one continuous strand from end to end so as the wiper moves up and down so does the resistance and that is what move the needle.

Hmmmm, check to see if there is anything stuck on the wire that might be preventing contact with the wiper at one point.

 

Gotcha.

I remember that my wiper arm also has a red liquid between the wiper arm contact (the part of the wiper arm that touches the metal wire winding) and the wire winding.  I always assumed that was some sort of lubricant - should that be there or should I wipe it off?

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I have a few old 240 senders, I could send you one and you could use it's float. I'd splice the metal rod close to the float, don't try to "remove" the float per sey. I'll see if the 240/280 floats are the same size. 

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8 hours ago, chaseincats said:

Gotcha.

I remember that my wiper arm also has a red liquid between the wiper arm contact (the part of the wiper arm that touches the metal wire winding) and the wire winding.  I always assumed that was some sort of lubricant - should that be there or should I wipe it off?

Lubricant is okay although the gas will wash it off pretty quickly, I just thought that if the needle was jumping around that there might be something on the wire that momentarily broke the contact.

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36 minutes ago, grannyknot said:

Lubricant is okay although the gas will wash it off pretty quickly, I just thought that if the needle was jumping around that there might be something on the wire that momentarily broke the contact.

Gotcha.  I'll wipe off the red stuff and bend the wiper arm so its touching the coil and not hovering above it - then see if that fixes the accuracy issue.

@zKars I'll take the sender out and pop it in a bucket to test the float - I may take you up on that offer depending on what happens - thanks so much for offering

Edited by chaseincats

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58 minutes ago, chaseincats said:

and bend the wiper arm so its touching the coil and not hovering above it

Wait, the wiper has not been touching the wound wire?  If that's the case then there's the answer to your problem, no wonder the needle is all over the place.

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I've been chasing electrical in my 77' for the last three month's .  A floating/misreading fuel gauge was one of those problems. I know I checked and cleaned the connections and wiring from the gauge to the sender at least three or four times.  Today, just by chance, I noticed that yellow/green mate lock connector to the fuel sender was slightly receded in the connector housing not making a full contact with the male pin when they were pushed together. I've repaired that and will double check it again tomorrow if I can get my car out.  So, when you inspect the connections, look really close.?

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48 minutes ago, grannyknot said:

Wait, the wiper has not been touching the wound wire?  If that's the case then there's the answer to your problem, no wonder the needle is all over the place.

I believe its not firmly pressed up against it.  When I get back in town I'll pop it out and report back

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Update: so there wasn't any red stuff on wiper arm (not sure where I came up with that) but the wiper arm wasn't 100% pressed up against it.  I heavily bent the arm so that it makes good contact with the coil wire now but that didn't seem to be it.

I grounded out the connector to the gauge to see if it would peg as a full which would confirm the wiring and gauge were working and they are, which is good.

I started jiggling stuff on the sender unit and the gauge started dying then coming back to life so it was an electrical connection issue between the harness and unit coil.  What it ended up being (we think) was the rivet connector between the yellow power wire (from the harness) and the wire for the coil/wiper arm on the sender unit.  I could spin the rivet inside the housing meaning there was a poor contact between the yellow power wire and the sender unit's coil wire.

We put some solder on there to bridge the rivet with the wire's connector and it may have done the trick.

If it still isnt working properly, then we're out of ideas - will update you guys later on.

 

EDIT: I forgot to mention, I tested the float in a bucket of water and it worked with no problems

Edited by chaseincats
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