Fuel Tank Float Gauges

[Gary0747]

My original fuel tank gauges read fairly accurate when not in motion but bounce around quite a bit while flying. Is there a way to dampen the gauge needle movement?   Do the EI or JPI electronic displays do any dampening?   I hate to have to purchase 4 new float senders. 

[0TreeLemur]

We put the JPI900 in our '67C earlier this year.   The old float gauges were retained.  The fuel level readings are stable and within 1 gallon compared to the in-tank dial gauges.  It seems that the JPI does include some averaging circuitry.   The indicated fuel levels vary a bit when you power up the JPI but after a while they are really constant.   That is what makes me think that they probably do some averaging in the JPI.

Fred

Edited November 23, 2018 by Fred_2O
clarity

[Gary0747]

Did your readings bounce around in the air on the original meters?

 

[Marauder]

Did your readings bounce around in the air on the original meters?

 

 

My original factory gauges were solid and didn’t bounce. Same for the JPI 900 with the original senders. Although I would periodically get a “fuel mismatch” error message on the JPI. This indicated that the report fuel quantity for that tank didn’t match what the system thought should have been in the tank.

 

This mismatch came up as I was burning the tanks down to install the CiES senders. The correct quantity should have read 6 gallons. Not 21.

 

 

 

Sent from my iPhone using Tapatalk Pro

[0TreeLemur]

8 hours ago, Gary0747 said:

Did your readings bounce around in the air on the original meters?

 

Before we changed to the JPI the fuel needles did bounce a lot when the fuel was sloshing in the tanks due to turbulence.   When the floats were steady, the readings were steady.  I think you nailed it they needed some damping.  The JPI does that.

BTW, installing any contemporary engine monitor is pretty straightforward.  If you install one that can be primary like the JPI900, you can get rid of a bunch of steam gauges, plus get the oil and fuel lines out of your cockpit.   We removed: tach, MP/FP, carb temp, and the entire six-gauge cluster containing L/R Fuel, CHT, Oil Temp, Oil Press, and Amps, because they are all primary on the JPI.   Now all that info is located in one display, including 4 CHT and 4 EGTs.  I highly recommend it.  It is probably the best bank for the buck you can install in your Mooney.  I seldom get the "fuel mismatch error" described by @Marauder

[Gary0747]

I bet the bounce maybe caused by a worn resistor or dirty resistor wiper.  Has anybody ever had theirs cleaned and repaired?  It looks like around 2 AMUs for new ones. 

[Andy95W]

4 hours ago, Gary0747 said:

I bet the bounce maybe caused by a worn resistor or dirty resistor wiper.  Has anybody ever had theirs cleaned and repaired?  It looks like around 2 AMUs for new ones. 

AirParts will overhaul them for a lot less.

http://www.airpartsoflockhaven.com/air-parts-services

[gsxrpilot]

7 hours ago, Gary0747 said:

I bet the bounce maybe caused by a worn resistor or dirty resistor wiper.  Has anybody ever had theirs cleaned and repaired?  It looks like around 2 AMUs for new ones. 

I think the CiES senders are about half that cost. Buy those and be done with this once and for all.

[0TreeLemur]

Some CB's overhaul them for a lot less...   An AC/Delco 0-30 Ohm sender from a 1934-1946 GM pickup truck with a lengthened float lever is what Mooney used in the original M20 smaller (<=26 gal.) tanks. 

[Gary0747]

Paul:

That would be my first choice reading all the favorable comments.  I think CEIS originally had a price of $250 but their website now shows the price at $495 each.  I assume it still requires 4 senders?

[gsxrpilot]

16 minutes ago, Gary0747 said:

Paul:

That would be my first choice reading all the favorable comments.  I think CEIS originally had a price of $250 but their website now shows the price at $495 each.  I assume it still requires 4 senders?

Yes, you still need the four senders. But I'd check the price with them. When I bought, I think it was something like $1150 for the set of four. It was a package deal.

[M016576]

17 hours ago, gsxrpilot said:

Yes, you still need the four senders. But I'd check the price with them. When I bought, I think it was something like $1150 for the set of four. It was a package deal.

“Deal”. <sigh>... 50 dollar capacitive sensors (at least for high end auto applications) sold for 450 bucks.  

Aviation parts.... ugh.  These certification costs are just crushing the CB in me

[Gary0747]

I just got a quote from Scott. $1740. Seems to have gone up pretty dramatically.

[kortopates]

48 minutes ago, Gary0747 said:

I just got a quote from Scott. $1740. Seems to have gone up pretty dramatically.

They were never $250, I was a early adopter while the STC was still pending. I recall more like $400 each which is a great price considering airparts of lockhaven charges something around $350-$395 to overhaul them. So I think your $1740 price suggest a $35 markup as best as I can tell.

Edited November 30, 2018 by kortopates

[ArtVandelay]

They were never $250, I was a early adopter while the STC was still pending. I recall more like $400 each which is a great price considering airparts of lockhaven charges something around $350-$395 to overhaul them. So I think your $1740 price suggest a $35 markup as best as I can tell.

Actually overhaul is $185 and new is $395. In my case both inboard sensors were bad, which makes sense since they are always submerged where outboard sensors are not. Don’t forget to add labor, so $2000 for 4 new sensors.

[Gary0747]

Studying all the old posts on the senders. Apparently a couple of posters got the resistive senders to work with the JPI 900?  Although another person concluded they would not work and switched but had to send his unit back to JPI for reconfiguration?  The CEIS senders apparently allow 1 gal or less accuracy. What kind of accuracy are people seeing with the original resistive senders?  

 

Edited November 30, 2018 by Gary0747

[Aspen2013]

I replaced all the steam gauges with the primary JPI EDM 900. Awesome way to go. I purchased the fuel option which included a new fuel flow transducer.  I found after they calibrated the JPI the fuel level sensors do not read accurately.. This next year we may have them overhauled. Kind of pricey.  I am not sure if it will be worth it. This is a problem of mixing very old technology with new. The fuel flow is very accurate and the fuel remaining readout is very accurate maybe within a gallon. I purchased new wing sight gauges and those things are very accurate as well surprising enough.. So I will look out at the wing and verify against the fuel level indicators on JPI but one tank is at least 7 gallons off and the other 5 gallons. The fuel remaining readout is what I mostly use. When this is paired with a Garmin product it uses a waypoint and tells you how much fuel to that point is required.

[Steve W]

37 minutes ago, Gary0747 said:

Studying all the old posts on the senders. Apparently a couple of posters got the resistive senders to work with the JPI 900?  Although another person concluded they would not work and switched but had to send his unit back to JPI for reconfiguration?  The CEIS senders apparently allow 1 gal or less accuracy. What kind of accuracy are people seeing with the original resistive senders?  

 

I can't yet say how accurate my resistive senders are on the EDM 900. They're not fully calibrated as the plane isn't sitting level and doesn't yet have an engine, but I did a bit of magic with the old gauges to get them accurate enough for a ferry flight. Since they're typically(with 32 gallon tanks) calibrated every 8 gallons(0,8,16,24,32) I'd expect the worst case to be 4 gallons off assuming your senders work properly to begin with, mine are from 1994 and haven't given me trouble with the old analog gauges so we'll see.

It's fairly easy to display the raw data that's used for the calibration so the pilot could get that data each time before adding fuel and keep a log, and then after enough samples work with an A&P to check/update the JPI calibration table again. Or if the data doesn't make any sense when graphed, then investigate other issues.

[carusoam]

Use some logic while going through the process...

1) The JPI can be configured to work with either the resistance or frequency based fuel senders...

2) The frequency method has the best accuracy possible...

3) The combination of resistance and JPI is better than resistance and an analog gauge...

4) To have the JPI swap between resistance and frequency, it needs to be sent back to JPI...

5) I believe the senders can be wired for either frequency or resistance without needing to send back or reprogram...

For a more in depth source of info for Cies fuel level equipment... ask @fuellevel he is pretty familiar....

Best regards,

-a-

[fuellevel]

So in the interest of education and sharing what we know.    We extensively tested resistive senders alongside ours when we were going through development and certification.  Actually the performance of the float,  led us back to using this device to find the fuel surface as it isn't easy to mess that up.    Yes you can pull the senders and ultrasonically clean them  and they will perform better for a while.   Or you can get the resistance wire rewound, but there are issues .   Trouble is that most new senders are printed ink resistance grids and they simply wear out.   Avgas is an especially good solvent and what is designed for autogas is not exactly compatible with avgas, in regards to printed ink composition. 

Here is the critical issue and - Mooneys will perform better in this regard due to sender placement.   Unlike the heavy equipment the senders are normally applied to  - fuel movement in aircraft is particularly aggressive  due to the length of the tank  this motion takes the float out of plane with the normal arc movement.   Pretty good if the motion is up and down with the rising of fuel in the tank  - bad if it is fore and aft  like on on climb, descend and taxi.   Always filling to full mitigates this effect as the floats can't move. 

This motion tends to wear the pivot on a resistance sender -  Resistance senders rely on a precise contact pressure on the grid to minimize wear of the grid or wire and provide a good electrical connection.   The longer the arm on the float - the greater the issue.    I doubt that this issue is addressed in a rebuilt sender - I have a few that have  been donated 

Basically clean repair or replace the printed grid or wire test and return.   Uniform contact pressure is the key to accurate readings   -  anything less or more causes issues.

The float sender reads fuel by slowly, very slowly dropping to be in contact with the fuel surface  - too much friction will hold the sender suspended in air  until vibration brings it back into contact with the fuel surface  (corrosion and corruption assist or in better words don't assist here).   To little friction allows free motion with interrupts in contact with the grid (the windshield wiper fuel gauge).   Aircraft have quite a bit of vibration so the floats will get shaken down eventually. 

Electronic instruments are susceptible to this loss of signal - far greater than the analog gauge they replace   -  we have lots of AOG requests on new installs of JPI, EI, And Garmin systems as what the owner thought were working fuel senders now become exposed.

So with how we measure and how we build - this above is taken into account  - we actually have a relatively free pivot connection however side to side motion does not affect accuracy or interrupt output    - only loss of power to the sender  

Why do we know this is good - well we have 26,000 senders in the field  - On Cirrus Aircraft now getting to be 8 yrs old we have zero in service replacements  - our MTBF is now over 80,000 hrs   - the senders are  airframe life rated.   There is no discernible wear and if wear occurs it does not affect accuracy or output 

Why are they relatively expensive - well unlike components in the cockpit  these devices live in a far harsher environment.   They are relatively complex circuit devices.     The FAA Certification guys considers these items  to be "CRITICAL" to flight   So the environmental testing we are subject to would quickly ruin your new radio or GPS.  This forces us to use higher graded components throughout.   And to achieve longevity we have some pretty complex and detailed coating requirements on the billet machined parts we use.     In a relative sense - we should be three to four times more expensive vs an analog sender.   Because of our non-contact measurement nature we meet a new FAA/EASA fuel and lightning safety requirement and we have a lot of OEM business around the world.   Quantity and consistent production allows us to offer competitive pricing.   The flexible nature of our sender allows for the unique customization we can do without charging substantially more   -  For example in the mix this week are senders for a Ford Tri motor, Grumman Mallard and a PBY Catalina   how's that for obscure.  We are dedicated to making fuel indication for all aircraft  - airworthy.

No other complex component on the aircraft is warranted for the life of the purchaser   -   I like to think that says it all