I'm experiencing worrying inaccuracy on our MXT7-180's Fuel Gauges. Although I know they are never super-accurate, they seem to have got much worse in recent months, over-reading to the extent of showing FULL when known to be around a quarter full, or similar. I'm sure they can be better than that, and I've rarely seen that level of inaccuracy.
Some helpful folk have suggested the following:
--to check that there is a good connection to the Sender,
--Check that Sender is well earthed (this may involve removing it)
-Check wire connections to the gauge.

Anybody here have any other suggestions before I send a list to our engineer?
Thanks in advance...[/b]

Dorian,
The old sending units are long in the tooth, inaccurate readings are the norm, leaks are common and frankly there comes a point where enough is enough. I reached that point last year.
Probably not what you want to hear but if you upgrade to digital sending units 99% of the problems disappear. CRIES fuel senders have the option to use your existing analog gauges or you can go all in and get a digital display and see your fuel down to the tenth of a gallon. They're not cheap, but WAAYYY cheaper than an inadvertent fuel starvation event. The peace of mind is amazing. I have a JPI-830 that shows fuel flow and between the two of them I'm very satisfied.
Short of that, I'd say double check the grounds on the sending units themselves (both on the sender and where each grounds to the wing) then also double check the back of your gauges where the wiring connects, sometimes the nuts holding the wire onto the back of the gauge comes loose.
Hope this helps. Good luck!

James

Air Parts of Lock Haven does a good job of overhauling OEM senders but if gauges are going full swing might be a broken shorted wire. Don't remember which goes which way. CRIES senders are very accurate but when used with JPI units they jump around a little. Not much dampening.

Forget the gauges, put in a JPI 450. Much more accurate.

A couple of you mentioned CRIES senders. Is that actually CiES fuel senders?

I have a new set of CiES senders waiting to be installed. I recently had a situation where I would have sworn I had enough fuel in the tank but clearly not. Luckily I had plenty in the other tank to get down safely. I will never neglect or short change my fuel level system again.

A fuel totalizer such as the JPI 450 is worth its weight in gold in my opinion. I have a JPI EDM 800 engine analyzer that includes a fuel flow sensor and fuel totalizer. I seldom fly with less than full main tanks so having more accurate analog gauges would be nice but not essential. I plan for 38 gallons in the two main tanks when full and enter that in my EDM 800 after startup. The EDM 800 is wired to my Garmin GTN 650 GPS and tells the GTN 650 how much fuel I have at startup. The GTN 650 tells the EDM 800 how long to my next flight plan leg and the EDM 800 continuously calculates if I have enough fuel to get there. It will warn me if I don't in case strong headwinds make the leg longer.

I guess the best of both worlds would be to have digital senders that accurately communicate the amount of fuel in each tank to the fuel totalizer and a fuel flow sensor that tells the fuel totalizer how much fuel has been used and the current fuel burn rate.

I have a JPI 900 and it’s fuel totalizer is great. But it can account for lost fuel due to so many possibilities including theft which I have dealt with. The flight I spoke of before should have been fine based on fuel remaining from the JPI. But had someone “borrowed” fuel or a drain failed and I didn’t know about it or even had I left a fuel cap off accidentally then it could have been a totally different flight. Luckily I have big tires, long Tavel suspension and I was over a small ranch surrounded by the big city so I could have easily landed without incident. Knowing what’s in the tanks from the cockpit is in my opinion more valuable than taking off the fuel cap to check during pre-flight or even using a dipstick. Though preflight fuel check is still massively important except for the difficulty of using a dip stick on a Maule tank.

I am most certainly fuel sensitive and was before the above incident, but I’m very pro fuel gauge accuracy. I hate it when my buddies say “well the FAA say it only needs to be accurate when it’s empty”. That’s an ignorant comment in my view even as a joke. Without reasonably accurate fuel level readings you loose the ability to make so many good decisions. Including things like running an anticipated down wind tank as low as possible to aid in heavy cross wind landings and much more.

I don’t discriminate between old resistance senders or digital senders. They all work if taken care of and all work well. But given the opportunity to use a digital sender with my digital gauge is an awesome option.

Rebuild or replace, just make sure it all works well and is accurate at more than just empty.

Just my 2¢

I remember a story about a guy who flew low over some stills in the Tennessee mountains and unexpectedly ran out of fuel landing at his home airport. He couldn't figure out how he could have burned so much fuel. One of the old timers at his airport asked how high he had flown and suggested that he take a look at the underside of the wings on his low-wing airplane. Sure enough, there was a bullet hole in the bottom of the wing but not the top. One of the still operators fired a handgun at his airplane and the slug had enough energy to penetrate the bottom of the wing but not the top. The pilot couldn't see the fuel leaking from the underside of the wing in flight. Accurate fuel gauges would help catch something like this.

One type of fuel leak that I've experienced in my Maule is from a fuel cap when the gasket gets worn out. Full tanks in a bank will cause fuel to spray out from under the cap. You can usually see it coming off the trailing edge of the low wing.

Yes, Bullets. That a good reason as well. I can use that when I explain the $900 I spent to my wife on my new senders.