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My wing tank fuel senders are not working on my 108-1. Does anyone know of a suitable replacement or do I have to buy them new from Univair. Thks.

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Posted : 05/03/2016 2:25 pm
resto108
Estimable Member

Earl Allen. I think he advertises on Barnstormers. Seems odd both would be bad.

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Posted : 05/03/2016 3:42 pm
maxchord
Estimable Member

Earl Allen: ekallen@theskybeam.com

Al CordenN97555 - Sid1946 108

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Posted : 05/03/2016 10:10 pm
lawheelock
Honorable Member

I agree. Both should not fail, so there are many other things to check. The wires. The switch. The gauge.
Some cautions. Very early 108-0 had a different sending unit that is not compatible with the tank or the gauge.
Later 108-0 through 108-3 all used the same sender. The new Univair senders are not compatible with the original gauge unit.

I have often found inop fuel gauging system to be caused by someone failing to attach the ground strap from the fuselage to the wing. There is a stud on the fuselage and one on the wing for a ground braid or strap. It is accessed under the top of the wing root fairing.

You can probably get either the sender or the gauge repaired by Keystone in Lock Haven, PA.

Larry Wheelock, A&P/IAStinson 108 N584LW 180 LycTexas in Winter; Indiana in Summer

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Posted : 06/03/2016 6:24 am
tim
 tim
Eminent Member

I had a similar problem with mine. It seemed both senders went out. I started fiddling with the nut that holds the switch in the pannel and the needle stared to dance around. I took the nut off and emery clothed the surface on the panel underneath the nut and reassembled it and haven't had any problems since.

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Posted : 09/03/2016 4:02 am

Thanks everyone for your replies. One sender worked to some degree. It registered half on the gauge when the tank was full. We put an ohm meter on yesterday, and the one that registers half tested ok. Hooked it up out of the tank and I got full range, full to empty on the gauge so now I have to bend the wire the float is on to give me that correct reading. I either have to send the units to Lockhaven or look for an aftermarket sender that will work in the correct ohm range. I was given Air Parts of Lockhaven as people who rebuild sending units and will check out Keystone. Is there an aftermarket fuel sender that will work? Thank you..Ian

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Posted : 13/03/2016 11:07 pm
lawheelock
Honorable Member

Univair's new fuel senders fit the tanks, but are not compatible with the original gauge. They also sell a new gauge that is compatible with their new senders.
I have found that the older Tri-pacers used the same gauge unit and most likely the same tank sender, but the float and arm would probably have to be modified to work in the Stinson tanks which most likely are of a different depth than the Piper ones.

Larry Wheelock, A&P/IAStinson 108 N584LW 180 LycTexas in Winter; Indiana in Summer

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Posted : 15/03/2016 5:10 am
markwdavis
Trusted Member Registered

I also need to deal with a faulty sender unit on the right tank. It registers full when less than 1/2 full so I think I need to bend the float wire so the float is higher than its present position. Is there a way to do this without guess work of a bend then gas in the tank, then drain and remove to bend a little more. etc etc. I intend to do all this with tail up in level position. Any suggestions?

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Posted : 18/03/2016 2:38 am
lawheelock
Honorable Member

Davism,

Ask yourself, "how would the float arm have gotten bent wrong? I think you will have to figure out for yourself how to do it without emptying filling emptying. Make some measurements with reference to a flat surface to see where the float would be at empty indication and where it would be at full indication. Measure depth of tank at about where the float will be and go from there.
In another life, I was an engineer in a Ford plant where we were manufacturing fuel senders that were very much like the ones that are in the Stinson. We made up a jig to fit the wire in and automatically positioned the shaft on the sender to the correct resistance for the float wire setting and then spot welded the wire to the shaft. I wrote a computer program that read the resistance and had a stepper motor to position the shaft. One of the first small computer programed production line. It used a HP "electronic calculator" programmed in basic before Macs or PCs or TRS 80s came along. Totally archaic now. That was in 1979.

A lot of Stinsons used a cork as the float and were coated with a varnish to keep them from absorbing fuel. Maybe it floats too high. At Ford, we used mineral spirits to simulate gasoline to check out floats, but they were brass or copper.

So, I can't really tell you how to do it, but I think you can come up with a way.

Larry Wheelock, A&P/IAStinson 108 N584LW 180 LycTexas in Winter; Indiana in Summer

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Posted : 18/03/2016 5:08 am
orange4sky
Trusted Member

Resurrecting this thread as I'm just going over my senders. I found a part number under the flange on my sender in my 108-0: 9275. Did a search and came up with a Ford sender unit with the same screw pattern. Combining this with Larry's story, I'll bet Stinson bought these from Ford. There's no way Stinson would have made their own and the part number match, screw hole match makes it very unlikely that it's a coincidence.

I found a Ford truck restoration parts seller that has them for $39.95.

Anyone know what the original senders' OHM range is? I don't trust my old ones. They are all over the place.

Gas Tank Sending Unit 1939 - 55
99A-9275
Can be used either 6V or 12V systems
Easily Adjustable Length Brass Float
Includes Float, Gasket, and Screws
Improved solid state electrical design
Includes installation instructions
Use on 1935-55 vehicles with original dash gauges only

OHMS Reading:
88-94 Empty
14-18 Full

http://dennis-carpenter.com/fuel-tank-sending-unit/p/99a-9275/

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Posted : 17/08/2018 5:38 am
tim
 tim
Eminent Member

I don't know off hand but I'm willing to bet the ohms range is the same.

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Posted : 21/08/2018 3:12 am

I agree with your assumption. Older Cherokees have a VW interior door handle, even with the VW logo and part number.

Hard to turn down a new sending unit with the correct P/N

Awesome find

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Posted : 21/08/2018 4:23 pm
hohanshelt
Eminent Member

The stock fuel senders read 30 ohms when full. They go down to near zero when empty. Michell sells a 30 ohm fuel gauge that can be used with these senders. I installed two gauges to eliminate the switch when I restored my -1.

Bob H

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Posted : 05/10/2018 7:35 pm
orange4sky
Trusted Member

When you say "these senders" are you referring to the original Stinson senders?

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Posted : 14/02/2019 7:07 pm

I am late to this discussion, but for what it's worth, Keystone Instruments in Lock Haven, PA can rebuild our fuel senders and fuel gages. They literally make them like new again.  Actually, better than new.

My freshly restored 108-3 has gages and senders they reworked and they work perfectly. The unrestored gages in my 108-2 bounce around and vibrate when fuel sloshes or when you switch the tank selector switch for the gage. I asked Keystone if my nervous gages were an indication of deeper problems they said no, that there is a small fluid damper in the needle pivot mechanism and that the liquid goes away after a while, letting the needle jump around and vibrate but it works just fine in spite of that. He also mentioned that they now use a modern damping fluid of some type that lasts a lot longer so their reworked gages should remain steady much longer than the OEM gages. I can't complain about a 71 year old gage that still works ok, just vibrates and jumps a bit. However the rock steady gages in my 108-3 are surely nice!

Keystone says that they can do their best work if you send them the sender(s) and gage(s) both at the same time. Then they can rework them and calibrate them as a matched set to assure the best performance. However, they can rework just a gage or just a sender and set it up for standard behavior which will make it just as good as a brand new one off the shelf, it just won't be part of a matched set that works even better.

Bob and Pat and the two Stinsons

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Posted : 28/10/2019 3:00 am
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