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Calibrating Fuel Gauge

Reading a couple of stories about fueling up prompted me to share my recent experience calibrating the gauge in our 1997 U295. When we got the coach, a full tank would send the gauge needle well above F. On one of our early trips we allowed the gauge to go down to about 1/4 and filled up. It only required 75 gallons. Another time, the gauge was on F when I chose to fill tanks before checking the weight of the coach on a Cat scale. Even though the gauge was on F, the tank held an additional 30 gallons. The needle moved well above the F mark. I decided to adjust the gauge.

BTW, I always level the coach before adding fuel and almost always fill from the curb side. I quit filling when the fuel reaches the nozzle and causes it to shut off.

On our coach there are two VERY sensitive adjustment screws on the fuel gauge sender. The sender is near the fill tube on the curb side. I filled the tank and used the "full" adjustment to set the gauge to read F. Our coach gets about 7 mpg and the specifications indicate that the tank holds 140 gallons of fuel. Using those numbers, we took a rest stop when we had driven about 490 miles since filling with fuel. I adjusted the "empty" adjustment screw to set the gauge to read 1/2. At the next fill up, I had to adjust the "full" screw a bit to get the needle to settle on F.

We have filled and run down to 1/2 a couple of times. The gauge shows very close to full after a fill up and very near to 1/2 at around 490 miles. Those adjustments have proven sufficiently close for us. They are much more accurate than were the readings before the adjustment. I have some confidence in the gauge as an indicator of our fuel level. We prefer to operate in the top half of the tank.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Calibrating Fuel Gauge

Reply #1 –
Quote
On our coach there are two VERY sensitive adjustment screws on the fuel gauge sender. The sender is near the fill tube on the curb side.

If it is a Centroid Programmable Fuel sender there are some additional instructions at
http://www.beamalarm.com/Documents/Centroid_fuel_sender_calibration.html
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: Calibrating Fuel Gauge

Reply #2 –
 JD,
The Centroid sender potentiometers just might be the weak point in the old sender design.  As many of us have found out, when they start to bother, they often won't stay stable, particularly after readjustment.
Be aware that there is a new direct plug in replacement Centroid sender that is digital and programmable, that should resolve the instability.  I bought mine directly from FOT last winter.

For more info (Installation, Calibration, Pictures), take a look at Album:

http://www.foreforums.com/index.php?action=media;sa=album;in=175
and look at thread:

http://www.foreforums.com/index.php?topic=10197.msg46947#msg46947
And Barry also has the Centroid installation and calibration procedure and pictures on his site at:
http://www.beamalarm.com/Documents/Centroid_fuel_sender_calibration.html

Hopefully yours will stay reliable, but if it doesn't, thought I'd mention the above so that you are aware.

Neal
The selected media item is not currently available.
Neal (& Brenda) Pillsbury
'02 U320 SPEC, 4200, DGFE, Build #5984
'04 Gold Wing
'07 Featherlite 24'
'14 Jeep Grand Cherokee Summit
MC #14494
Exeter, NH & LaBelle FL
Quality makes the Heart Soar long after Price is Forgotten

Re: Calibrating Fuel Gauge

Reply #3 –
Having a well calibrated fuel gauge is a very good thing indeed.  I find the only way to verify it is when using the VMSpc readout.  Have found the VMSpc is extremely accurate over many fills and many gallons of fuel.
It does not take into account, fuel used by either the generator or the Aqua Hot.  That is why knowing your fuel gauge is important.
FWIW
Dave

Re: Calibrating Fuel Gauge

Reply #4 –
When I purchased my 95 U320 in April, the fuel gauge was absolutely useless.
I removed the 3 screws holding the connectors on the sender, cleaned all contact surfaces with plastic scrubber and reinstalled.
After adjustment, the fuel guage seems to be quite accurate. I only have a few fill ups to judge from.

I wonder if the erratic behavior mentioned in a previous post in this thread was caused by dirty contacts, rather than bad potentiometers. Any comments!
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Calibrating Fuel Gauge

Reply #5 –
Wyatt,
I've had both problems. 
The first time, I took the wiring off both the sender and the dash gauge, cleaned, used dielectric grease and that fixed the problem for several years.
The second time, repeating all of the above had no effect and tank level would read full one evening and 1/2 full the next morning.  Just plain erratic behavior that would "come and go".
Then I calibrated the (old style) analog sender IAW the Centroid instructions.  It would only stay reliable for short periods of time.  FOT recommended changing sender, which totally cured the problem for several years after.
Then, last fall the second (still the old style analog) sender started acting up, again.  Cleaned connections at both ends again.  No improvement.  Recalibrated the sender and this time I put a dab of red Locktite on the Potentiometer adjustment screw head.  It seems to still be holding 10 months later, but I have had a couple of erratic readings. Once, it read 1/2 full for several hundred miles, starting on a nearly full tank.  Then, at about 1/2 tank, it started working again. 
While I was at FOT last winter, I inquired about known behavior problems.  FOT Parts offered to sell me an old style analog replacement (never mentioning that there is a replacement digital/programmable Centroid).  Before I left NAC, I discovered at MOT (asking about known problems again) that Centroid now makes a replacement digital/programmable sender that Centroid says resolves the problem.   
I have not installed this digital replacement yet...............just carrying an onboard spare is sometimes the easiest way to cure a problem!
Anyway, that's my saga, AND I'm sticking with it!
At times like this, I lust after the electronic Cummins and the VMSpc luxuries..............but then I regain my composure and go on enjoying the 8.3 mechanical simplicities. KISS, KISS (I have to keep reminding myself to Keep It Simple, Stupid)
Thanks,
Neal
The selected media item is not currently available.
Neal (& Brenda) Pillsbury
'02 U320 SPEC, 4200, DGFE, Build #5984
'04 Gold Wing
'07 Featherlite 24'
'14 Jeep Grand Cherokee Summit
MC #14494
Exeter, NH & LaBelle FL
Quality makes the Heart Soar long after Price is Forgotten

Re: Calibrating Fuel Gauge

Reply #6 –
Thanks Neal for the clarification.
You did everything I would have thought of doing, so trying to fix the old sender would be fruitless.
I will order a new style digital sender and carry as a spare also.
 
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Calibrating Fuel Gauge

Reply #7 –
On a 99 u320 40ft 450hp where is the sending unit located on the tank. Checked both ends no luck, I guess a stick is standard equipment, I fell for the old match trick 3 times, figured out that is not a good method. Suspect maybe in the aquahot area.  Would  temp sensitive tape (on tank) work for verifying difference in temp of fuel and air above, thus fuel level for backup purposes?thanks jc
JC
1999 U320

Re: Calibrating Fuel Gauge

Reply #8 –
Oh Yes, the ole match trick is more illuminating when used for checking the Gasoline tank  :o
Just hold the match up close to the filer neck when you strike it. :o :o
Dave

Re: Calibrating Fuel Gauge

Reply #9 –
Quote from: Dave M –
Oh Yes, the ole match trick is more illuminating when used for checking the Gasoline tank  :o
Just hold the match up close to the filer neck when you strike it. :o :o
Dave
If you can get it past the fumes quick enough, your okay!
1994 U225
build #4514

Fuel Guage

Reply #10 –
I have been having an issue with my fuel gauge.  When I fill the coach the gauge only will go just past half full.  It will stay there and then will gradually move back towards Qtr full.  I always refuel at this point.  Is it the gauge or the sender or both?  Tks DAn Stansel
99 U270 36 ft.
Dan & Shirley Stansel
2002 U295 4020 AGDS Build#6054
Towing Buick Enclave & M &  G Braking
Emerald Bay, Lake Palestine, Texas
MC# 16650

Re: Fuel Guage

Reply #11 –
Check Calibrating Fuel Gauge
I explain my experience and actions that I took.

Calibrating the sender worked for me. There were one or more posts that indicated I probably didn't calibrate the sender correctly, but I have been satisfied with the results.

As always DISCLAIMER ==> Your results may vary <== DISCLAIMER
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Fuel Guage

Reply #12 –
Tks that gave me a lot of info.  Maybe I can figure it out from here.  DAN STANSEL U270 36 99
Dan & Shirley Stansel
2002 U295 4020 AGDS Build#6054
Towing Buick Enclave & M &  G Braking
Emerald Bay, Lake Palestine, Texas
MC# 16650

Re: Calibrating Fuel Gauge

Reply #13 –
Quote from: Dan J. Stansel –
I have been having an issue with my fuel gauge.  When I fill the coach the gauge only will go just past half full.  It will stay there and then will gradually move back towards Qtr full.  I always refuel at this point.  Is it the gauge or the sender or both?  Tks DAn Stansel
99 U270 36 ft.

I just replaced my fuel sender.
I would fill up and it would show 100% but a few minutes of driving & it drops to about 80%.
Centroid told me the diodes give out in the older ones.
The new ones are already calibrated so you just put it in the tank.
No adjustment needed.
You must know exactly how long the rod is in the tank when ordering.
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: Calibrating Fuel Gauge

Reply #14 –
Quote
I just replaced my fuel sender.

Barry,
May I ask how you removed the fiberglass panel covering the fuel tank in order to replace the fuel sender????

Thanks,
Brad

2000 U320 4000

Re: Calibrating Fuel Gauge

Reply #15 –
Quote from: Brad –
Quote
I just replaced my fuel sender.

Barry,
May I ask how you removed the fiberglass panel covering the fuel tank in order to replace the fuel sender????

Thanks,

I cut a hole in the cover for access to the fuel sender & then used a piece of like material with 2 sided tape to conceal it.
To take the cover off you need to disassemble to many pieces for my liking including the strip on the bottom of the door  ???
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"