Fuel gauge reading

[82chevdiesel]

Im having a problem with my fuel gauge, just recently after a fill up the gauge will read way past full. The gauge works and will move throughout the range but it just reads very far off the scale past full after a fill up.

[wyattglock]

Its very possible that the sending unit is on the way out. I just had one do the same thing on my truck.

[78 Big10 454]

Mine has done that since factory new. 34 years later, no problems.

[WarBeard]

That's the good way for you gauge to be off. It's when it says you have a 1/4 tank left and your stuck on the side of the road is when it sucks

[bowtiemanchevyman]

if you want to make it read right. you can alwas move the needle, run the tank dry the fill it half way then move the needle to the half point thats what i did on my when i replace the sending units.

[Rich84]

Originally Posted by bowtiemanchevyman

if you want to make it read right. you can alwas move the needle, run the tank dry the fill it half way then move the needle to the half point thats what i did on my when i replace the sending units.

Well, I guess that explains way changing my sending unit did nothing to correct the same issue with my gas gauge..Once it gets to a half tank look out it drops real fast..

[tucsonjwt]

It is possible that you have a defective gauge. If so, $50 fix at Classic Parts.

[Rich84]

I had three different gauges in mine..did the same thing on all of them.

[tucsonjwt]

Interesting - I have had 3 squares and they all went about 1/4" past the full mark when full, but that seems consistent with all vehicles I have owned. I have read somewhere that those automotive engineers design the gauges to stay at the full reading for an abnormally long time and read empty prematurely. This gives the drive the illusion that they are getting a very full tank when they fill up and discourages them from running out of fuel by prematurely showing an empty tank. I have found this to be true in vehicles I have owned.

[Rich84]

They think we are idiots...

[motornut]

my fuel gauge used to bounce when driving
since adding more grounds (behind cluster) <---I'd check that
and changing from idiot lights to tach/gauges
not a prob

I had a switch on my tank,in high school
it grounded the sending unit ,reading empty tank
nobody bum a drive home with the tank empty ...
if the sender wire is lifted (open) it will read over full
other wise it worked as normal

when i change a tank i bend up the arm of the float
so the gauge reads full ,when full
doing this leaves 1/4 tank ( about ) below E
that way the line won't freeze up as easy
and for those times,your "almost there"

and i've heard of soggy floats...

[AGearHead4Life]

Mine read like that with the original '84 cluster. Just last week i put a 90 burban cluster in for the digital speedo and now it seems to read full correctly. But I did notice that when I added 5 gallons to an emptied the 16 gal tank the guage read half full..? I guess I'll just learn and adapt to what it wants to do.

[gramps77]

Originally Posted by motornut

my fuel gauge used to bounce when driving
since adding more grounds (behind cluster) <---I'd check that
and changing from idiot lights to tach/gauges
not a prob

...

adding more grounds? How did you do that? Ive got a very bouncy gauge and the lens and dash is out right now with the exception fo the gauges to its time to fix the bouncy gauge if I can

[motornut]

they all go to one ground
it's about a foot from the plug

[motornut]

Originally Posted by AGearHead4Life

Mine read like that with the original '84 cluster. Just last week i put a 90 burban cluster in for the digital speedo and now it seems to read full correctly. But I did notice that when I added 5 gallons to an emptied the 16 gal tank the guage read half full..? I guess I'll just learn and adapt to what it wants to do.

seen it mentioned the ohms reading changed on the gauges.....
might be the prob

[tucsonjwt]

My bouncy gauge was caused by changing to aftermarket (Spectra Brand) fuel sending units. Previous AC Delco sending units did not do that. However Spectra Gauges were about $45 each and Delco gauges were about $145 each - so I will bounce along with the cheap gauges since the do read correctly when the vehicle is stopped for a while.

[motornut]

Originally Posted by tucsonjwt

My bouncy gauge was caused by changing to aftermarket (Spectra Brand) fuel sending units. Previous AC Delco sending units did not do that. However Spectra Gauges were about $45 each and Delco gauges were about $145 each - so I will bounce along with the cheap gauges since the do read correctly when the vehicle is stopped for a while.

My 78 did the same
After seeing spectra on the tank I didn't look any further
And was pleasantly surprised when it stopped bouncing
Just mentioning my 79 needs anew one and I'm ordering GM one based on problems others have said
And my parts guy said he's never heard of it
Thinks I'm nuts wanting a GM one $$
Thought mentioning it maybe it would help someone else
Posted via Mobile Device

[motornut]

before
http://youtu.be/7lqXLgFScHw
but actually i did change the gauge....going idiot to gauges or big to small
but thats all i changed

[grs]

Not sure how many gallons my 87 holds, but my gauge goes past full. When it shows about empty it takes 14 gallons to fill it up. I will just fill it up at one forth a tank from now on. The more gas in the tank the better. It will help keep the fuel pump cool. Do this on your new cars to.

[Tucson38]

Originally Posted by tucsonjwt

Interesting - I have had 3 squares and they all went about 1/4" past the full mark when full, but that seems consistent with all vehicles I have owned. I have read somewhere that those automotive engineers design the gauges to stay at the full reading for an abnormally long time and read empty prematurely. This gives the drive the illusion that they are getting a very full tank when they fill up and discourages them from running out of fuel by prematurely showing an empty tank. I have found this to be true in vehicles I have owned.

Yeah, I've noticed that too. When my 20 gallon tank is at the half full mark it will take 14 gallons to fill it up. Runs forever on the first half tank then it drops like a paralyzed falcon between half and one quarter.

[AGearHead4Life]

Originally Posted by Tucson38

Yeah, I've noticed that too. Runs forever on the first half tank then it drops like a paralyzed falcon between half and one quarter.

Yep, mine does that also.
Posted via Mobile Device

[made2drag]

my 78 blazer has a fuel gas that also has a bouncing needle. you can tap on the glass and sometimes it reads right for a minute then bounces again. it fluxuates from full to 1/4 sometimes while driving too. the speedometer and the rest of them seem fine though

[82chevdiesel]

Well I checked my grounds today and cleaned them up but still the same issue. And btw Im not talking about the gauge reading a little past full Im talking about reading at the 3 o'clock position. So whats the verdict here? New sending unit or new gauge?

[AGearHead4Life]

Originally Posted by 82chevdiesel

Well I checked my grounds today and cleaned them up but still the same issue. And btw Im not talking about the gauge reading a little past full Im talking about reading at the 3 o'clock position. So whats the verdict here? New sending unit or new gauge?

Isn't there a ground on top of the tank where you install the sending unit?

My guess would be that ground, the gauge or the sending unit. Knowing what ohm the sending unit should read would help to trouble shoot this. Anybody have this spec? Without this information, you could temporarily swap another gauge cluster to eliminate the gauge from the list.

Odds seem to be in favor of it being the sending unit. If determined its the sending unit, you may even be able to clean it up or adjust it. LMC is probably a dependable source for a new sending unit.

[hatzie]

Originally Posted by motornut

seen it mentioned the ohms reading changed on the gauges.....
might be the prob

Not in my experience with square body fuel gauges. I have tested fuel gauges out of 89, 85, 79, & 77 clusters that have nearly identical (within 1-3 ohms) responses to my General Radio 1432M decade resistance box settings.

GM senders were weighted to read full longer just after the 1973 OPEC oil embargo. I read this in one of my mid 70's Chevrolet Service News magazines.