fuel sending units
 

I was told that if I replace my fuel (6)sending units on
my 336 it will solve my unreliable fuel quantity readings.
I understand that cleaning terminals on guages and cleaning
sending units is a temporary fix at best.
How much should I pay for the (6) sending units and does
this sound like a good investment. Anyone have any thoughts.

Thanks for your time guys,
John

fuel guages
 

John

These fuel guages are a pain. These are pennycap capacitive type probes and since there are no moving parts (only capacitance that changes). Replacing the probes will not fix the problem IMO.

Suggest cleaning the contacts and checking resistance of wires. The control unit is up under the headliner and check the wires going in and out. The output of this unit changes the current to the guage on the instrument panel. There were a couple of versions.

I would consider going the EI route as I think these guages are certified for the 336/7.

The best alternative is to use a Shadin Fuel flow instrument then you know EXACTLY how much fuel you have remaining.

I personally do not trust the guages, and they do work most of the time....

Wiring and connectors are most of the problems....

bob

Re: fuel guages
 

Connectors: A source of trouble than joins two other sources of trouble.

Fuel sending units
 

John:
I don't think those are pennycap sending units. I believe they are like my 1967 337, the old resistor type and there is no good solution to those old gages and sending units. The safe answer is ALWAYS KEEP TRACK OF YOUR FUEL USAGE. There are good fuel gage systems out there if you want to invest the money. sorry I can't be more help!!!!!!!!!!!!!!
Fred N358

On my 77 normal aspirated...
 

...337 G, I feel my guages are some what accurate. I check them frequently with my Shadin. I don't normally fill the tanks however periodically I do top them off. The last time 50 hours between top offs and the Shadin was within .5 gallons per hour. In other words I had not toped it off for 50 hours, when I did, the fuel on board was 40 gals. I added 84 gals. to top it off, that came out to 124 gals. telling me that I had an additional 26 gals. on board. In 50 hours of flying and fuel added to 80 gals. or so as needed during the 50 hour period, could that 26 gals. be fuel that is returned to the tanks which comes out to approx. .25 gals. per hour per engine? Guy, old72driver....

I have the Shadin unit, and I love it. It is always close in agreement with the fuel I put in (I always top off the tanks). However, be careful using a fuel totalizer in place of the gages. The totalizer only keeps track of the fuel used by the engine. If you are losing fuel through some other means (a broken fuel line, a loose cap, or a leak) the totalizer won't indicate that. I know this from experience when I had a leak in the diaphragm of a fuel pump in a Seneca. I was crop dusting the local countryside with fuel. Fortunately I noticed the dropping level of the gage in time to land with plenty of fuel aboard.

Mark

72 and earlier 337s have resistance type mechanical fuel senders. 73 and later are capacitance.

Kevin

fuel guages
 

OOPS
guess the earlier guages are different. sorry for the misleading information.

BTW when I am down in the islands I take a roll of XMAS tape (colorful) and tape the fuel doors, oil doors to make sure no one has tampered with the fuel when leaving the AC unattended. I will then make sure the FUEL ON BOARD is correct if the tape has been altered or removed.

You can calibrate the shadin to fairly easily. Mine is within 5% accuracy and always indicates less than actual.

bob

Fuel sending unit
 

Where can I get sending units, new or recon.[list]
At i have a 1964 A model

I think Mark's point is spot on - and important. I have a Shadin, have found it to be extremely accurate, and depend on it, along with a time flown/estimated fuel used plot. BUT, as he rightly points out, if you're leaking fuel somewhere the Shadin isn't going to show it. I rely on the Shadin, but also maintain at least my main fuel gauges as a cross check.

Joe

For sending units try

Air Parts of Lock Haven

or

Preferred Air parts may also have them

Do you have the part number?

1426013-2 for aux
2ea 1426012-1 and 2ea 1426011-1 this is the part #

This is parts search from Controller

see attached photos

Yingling - Cessna Parts Direct - http://www.cessnadirect.com/7740-00438.html
1426012-1 is now part #7740-00438

fuel sending units
 

John.
If you're still looking fuel sending units, I bought two Aux sending units for $50 each. New surplus! These are wrapped in original wrapping and are in original boxes. This guy ONLY has the Aux! BUT at $50 each it will help in the overall costs. Just check E-Bay under "Skymaster".
BILLS