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Access to D117A fuel sensors

Posted: Sat Oct 05, 2019 11:42 am
by Stoxsie
I have a problem with the readout on my fuel gauge on G-AXAT a Jodel 117A. I plan to check the sensor outputs and the gauge before blaming them, but think they are most likely to be the issue. Does anyone have an easy solution to accessing both front and rear tank sensors? My thought is to replace them with capacitance based sensors because I understand the new float based ones are almost impossible to fit with the tanks in situ. I realise this is probably a common problem and pilots ‘live with it’ by using a dipstick and fuel management. My instincts are screaming that fuel is pretty important and reasonably accurate gauges fairly crucial.

Re: Access to D117A fuel sensors

Posted: Sat Oct 05, 2019 4:37 pm
by Brian Hope
Hi Robert, if it's the same as my D117 was then I'm afraid you won't get either sender unit out without removing the tanks, or at least dropping them down from their normal location. The senders are both at the top of the tank, so the front one is up against the front coaming, and the rear up against the underside of the parcel shelf. There is a slight chance that somebody in the past has put an access panel in the parcel shelf but they didn't have one from new.
Both tanks are held up by a pair of metal straps, the front attach nuts being on the engine side of the firewall (they come out at an angle and have an angled spacer against the firewall). Disconnect the battery before you start. Before releasing them you have to clear anything from under the tank, wiring, throttle/carb heat/mixture/fuel valve rod etc.
Drain the tank and remove the fuel pipe from the bottom. To fully remove the tank you need to remove the passenger side control stick, easily done.
The rear is similar but easier. Drain it, remove the fuel pipe, disconnect the filler neck hose and undo the strap fixings. The tank will come out through the large inspection panel just behind the trailing edge - the one you squeezed your torso through to gain access.
While you're at it, replace the small length of rubber hose between the pipe and the tank banjo fitting (if it has one), it goes hard with age and may well have been in there for an age.
If you are going to use capacitance probes you will need a gauge that will work with them. Modern digital stuff often works with either, older gauges don't. I can't see how they are any easier to fit than the float type to be honest, you still have to have access to the hole.
It sounds harder than it is but it doesn't take too long to do if you work logically and have somebody to remove the front tank strap nuts while you stop it from dropping to the cockpit floor.
If you need more info please don't PM me, give me a call or drop me an email, details in mag.
Good luck.