Troubleshooting and replacing a fuel sending unit in a GM A-Body.

In this video I show how to determine if the fuel sending unit in my 1972 Buick Gran Sport is bad or if the gauge or wiring is the problem. My step by step process will help you determine the cause.
#fueltank #abody #sendingunit #buick455
To see more videos on the Buick restoration project, check out this playlist.
• Buick Restoration
Follow the progress of this Buick and get some behind the scenes content on Instagram @72GS455
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[@steve911b]

Hi. Thank you for posting this video. My 1969 Impala was showing full on the indicator all the time. I followed your instructions and was able to diagnose and fix the problem. It turns out that my sending unit was working but the signal wire connector pin was grounding out because of the old rubber insulating grommet. I was able to change the rubber grommet using rubber that I had lying around and replaced the old sending unit back into the tank. The fuel indicator is now working properly. 😊 Thank you so much for posting this video once again. 😊

[@JackofAllTrades1]

Awesome @steve911b that's great to hear.

[@deanfawbush9071]

Man that was a great help I think I saw my problem with my vintage car watching your video thanks, very informative and to the point video not a lot of hype, very understandable for a Lehman like me, thanks again bro !!

[@JackofAllTrades1]

I have lots of plans for this classic.... fuel sending unit is also doing great from this replacement.

[@donh8563]

Nice video. Helped me diagnose my sender issue. Thanks

[@JackofAllTrades1]

That's great Don, glad I could help.

[@TTABBQ]

Thank you so much!! I have a 72 skylark. Same problem.

[@JackofAllTrades1]

Nice! I'm glad I was able to help.

[@caitlins.3012]

Thanks for this!

[@JackofAllTrades1]

Glad I could be of help.

[@gregalot200]

I can smell the gas from here! mine only lasted a few years after replacing the whole tank assembly, right now it shows full like yours, must be from cheap aftermarket parts.

[@JackofAllTrades1]

Don't jinx me! Lord knows this sending unit was probably made in China....could go any day.

[@givemetheoutdoors1590]

Thanks. I need to do this on my 72 buick lesabre 😮

[@JackofAllTrades1]

Good luck! Get as much fuel out as you can because it's awakaward enough with it empty.

[@PNW_Car_Mods]

Cars were so much simpler back then and on that same token so much more of a pain in the ass to work on lol.

[@JackofAllTrades1]

50 years of dirt and rust but ver basic technology....sounds like a wash compared to new, more complicated but clean. 😂

[@PNW_Car_Mods]

@@JackofAllTrades1 It's weird seeing such a radical scenery change in your background hahaha

[@JackofAllTrades1]

@@PNW_Car_Mods yea, everything is still green here.... like 80 today as well.

[@PNW_Car_Mods]

@@JackofAllTrades1 :( I really need to become one of them snowbird types. I haven't seen the sun in months.

[@JackofAllTrades1]

@@PNW_Car_Mods well, in NH the sun would come out but barely be over the horizon... I felt like I was in Alaska

[@billwall3913]

cool man thanks

[@JackofAllTrades1]

Thank you!

[@tankerman4916]

Great vid. Very informative, My 67 Bonneville the gauge stays at 1/2 tank . Does this mean the sending unit is bad or the gauge? This will be one of many winter projects on my classic. Thanks Butch

[@JackofAllTrades1]

It could be the guage, the sending unit or the wire between the two. If you have easy access to the wire harness connection between the two you could easily run this test I show to let you know which one it is. If it's the sending unit then it could just be getting hung up in the tank or it could be going bad or the connections could just be dirty. Good luck!

[@medhams]

Can you please post the link for the fuel sending unit. I need to get one for my 73 Buick century. The gas gauge don't work and there's no fuel being sent to the fuel pump in my Buick. Thanks

[@JackofAllTrades1]

Here is the one I used. Spectra Classic Fuel Tank Sending... www.amazon.com/dp/B000C7QMJO?ref=ppx_pop_mob_ap_share Can you disconnect the fuel line at the pump end and get any fuel there? Have you tried shooting a little compressed air from the pump end, through the line that runs under the car and into the tank? You might have a clogged sock but won't really know it until you go through all the work of dropping the tank. Good luck.

[@trig5010]

I just replaced my gas sending unit. Gauge bairly moved. Is there an amount of gas I should add to test it ? ( Trying to minimize gas since I'm selling the truck.)

[@JackofAllTrades1]

I think the standard is 2 gallons is "empty" that way if you run it to empty you have some wiggle room. Was your tank already empty or close? That sending unit is a reostat so the higher the resistance the more full the tank appears to be. Grounding out the leads should make it go full.

[@trig5010]

@@JackofAllTrades1 I put like 6-7 gallons in and the gauge only moved a little. I'll add more. If it doesn't move more, I'll pump it out and drop tank to reach the sending unit.

[@JackofAllTrades1]

@@trig5010 to me that seems strange. If you can safely pump it out then def put more in there and see. Sorry I can't be more help.

[@einstein3509]

I have a 71 Chevelle I pulled the fuel tank and replaced the sending/float unit because the gauge would stick on fuel. I noticed that the stop tabs for fuel and empty were bent off to the side. When I pushed the float all the way up past the fuel tab it would stick there. So when I installed the new sending unit I did not bend the tabs. Now when the tank is full the gauge read between 3/4 and 1/2. Once the fuel gets down between 3/4 and 1/2 then the gauge works. Any ideas on what’s wrong?

[@JackofAllTrades1]

Hey Einstein, could you tell if the wiring harness back there going down to the fuel tank was original? This is the one that passes through the trunk. I ask because these sending units are reostadts so they measure resistance. If the wires are heavier guage than factory original OR are possibly grounded on some sharp metal, then they will display more resistance which will effect the amount of fuel displayed. Some other ideas would be possibly using the wrong sending unit for the car. When you say "tabs" I am imagining the small pins on the fuel guage for full tank and empty where the needle rests when at its maxes, is that correct? Theoretically the needle could and would go way past those pins if allowed. Makes me wonder if it has in the past (since they are bent) and now the calibration is off. Another idea would be the float on the sending unit is getting hung up on something... possibly the sock or something in the tank like a baffle if it's the wrong unit and too long.

[@einstein3509]

@@JackofAllTrades1 Don’t know for sure if the wire is original but I’m guessing it probably is. When I received the new sending unit it looked the same as the one I took out. The tabs I’m talking about are the tabs one the sending unit that stop the float arm at empty and full. They were bent off to the side on the one that I took out of the tank. On The new unit the tabs were not bent out of the way

[@JackofAllTrades1]

@@einstein3509 it's good that you compared the two parts before using the new one... you never know what you are really going to get these days. Testing out your situation is a beast because of having to empty and drop the tank but I'm willing to bet if you pulled that unit back out and hooked the sending unit up to the harness (this time not in the tank) and manually moved it to full... then your guage will only read 3/4 full like you are seeing. Our cars should be near identical with these parts as GM reused a lot of stuff between their car families. I didn't have to make any changes to mine but I do not recall there being any tabs on the sending unit to manipulate. It almost sounds like you have the ability to adjust yours for variances....like a universal sending unit. Let's put it this way if you bent that upper tab on the new unit, what's the worst that could happen? That float is only going to go as high as the fuel line. Worth a shot.

[@einstein3509]

@@JackofAllTrades1 With the sending unit tabs bent off to the side the float arm would go way past where the stop was and stick there and at some point and time would drop and start reading. The problem was you never knew when it was going to drop and start reading. The gauge in the car would work when the float arm unstuck. I did clean ground with sandpaper and put a dab off dialectical grease between the frame and the ground tightened it up and coated the whole thing with liquid electrical tape to keep it clean. Based on what you just told me I’m wondering if the dialectical grease is creating a problem?

[@JackofAllTrades1]

@@einstein3509 ok, I have an idea now then... the more I think on this. Sounds like the previous owner bent those tabs as sort of a bandaid solution to fix a problem they couldn't actually locate. Did you get the gauge to go full by grounding out the wires like I showed in my video? If you can get it to go full with the wires at the unit itself then the problem exists at the sending unit. If you can't, then it lies withing the guage or the harness. Now that you've got it greased up... try grounding it out. You don't have to fully drop the tank to test this out... you may just be able to loosen the long bolts on the straps enough to get access.

[@frednicholson]

For viewers - don't put weight on that filler neck as shown in the video - you can break the seal and then you will obviously have a gas leak upon reinstall.

[@JackofAllTrades1]

I had no idea there was a seal. It looked like one piece to me. Thanks

[@cj5035]

Where did you end up buying the sending unit from?

[@JackofAllTrades1]

Rockauto.

[@4everDCOOL1]

How long did this take

[@JackofAllTrades1]

A couple hours. The hardest part was getting the rusty bolts off carefully. If I did it again I would immediately cut the strap bolts off and just replace them with stainless hardware... would shave 30 min off the project.

[@brettslater872]

I replaced my sending unit a couple years ago. Patton Glade (pglade) on v8buick reproduces the pads and they're top notch quality.

[@JackofAllTrades1]

Thanks for that info Brett.