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Fuel Tank Sending Unit (5 hole style sending unit)
Fits 46-66 CJ-2A, 3A, 3B, M38, M38A1

Part # 640694

New Fuel Tank Sending Unit

Comes complete with mounting gasket. Float sits inside tank to give accurate reading to gauge. For 6 or 12 volt systems. Proper arm length guaranteed for a sure reading.

This sending unit is attached to the top of the fuel tank with five screws (B0305).

Helpful Guides and Illustrations:
Fuel Tank Exploded View

46-49 CJ-2A
49-53 CJ-3A
53-56 CJ-3B (with individual gagues)
50-52 M38 (12 volt)
52-66 M38A1 (12 volt)

Part # Price





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I ordered this unit to replace a broken sender. The ohms on this unit are 3 - 130, which does not work with the gauge that is in my 47 -CJ2A. suggestions?

Willys Jeep Parts Tech:
The sending unit has the correct reading and will work for both 6 or 12 volt since sending units work on resistance. You need to check your gauge in the dash to confirm its 6 or 12 volts. That matters. Also check your ground wire on the gauge. Thanks!

This arm seems short for the M38a1, will it actually reach to the bottom of the deep portion of the tank? The 24v design is much longer, but I need 12v.

Willys Jeep Parts Tech:
Give us a call and ask for Mike M - he can help you with your question.

Does the orientation of the float make a difference? Should it swing side to side, or back to front?

Willys Jeep Parts Tech:
Should not matter. Typically the holes only line up one way.

I change the 24 volt electrical system in my 1955 M38A1 to a 12 volt system. Do I also need to change the sending unit in the gas tank to a 12 volt sending unit?

Willys Jeep Parts Tech:
You would have to change the sending unit out.

My fuel gauge reads full no matter how much fuel is in it or what position the float is in, is this a wiring, sending unit, or gauge problem?

Willys Jeep Parts Tech:
You need to test your sending unit with a ohms reader. and then make sure your gauges is the proper voltage. Also check your wiring and ground.

Can i just buy the white float? Mine has a crack in it where the wire wraps around... Thanks!

Willys Jeep Parts Tech:

What sealer do you recommend on the cork gasket? Thank you

Willys Jeep Parts Tech:
We typically due not use a sealer there so it doesn't get into the fuel. If you tighten properly it should not leak.

Can you clarify the Ohm readings for this unit at empty and full? There are two previous answers to this below, and the answers you provided are different.

Willys Jeep Parts Tech:
8-1/2 - 10-1/2" FULL 70-80 EMPTY

I just purchased the 5 hole sending unit for my CJ2A. What wire size will I need to go from the sending unit to the gauge?

Willys Jeep Parts Tech:
We typically use a 12 gauge.

Does the sending unit include the 5 Mounting screws? If not, what size screw will fit?

Willys Jeep Parts Tech:
B0305 is the part number for the hardware.

Do you have a spec sheet on this sender? I'm troubleshooting my fuel's always reading empty (even when full tank of gas) and need to know the ohms it should read at bottom (empty) and up (full). I think full should read 0 ohms, but what sould the empty reading be?

Willys Jeep Parts Tech:
8-1/2 - 10-1/2" FULL 70-80 EMPTY

What is the outside diameter measurement of this fuel sending unit I need to replace mine that is mounted to a rectangle fuel tank on my m38

Willys Jeep Parts Tech:
Please email the exact measurement on it you are looking for and we can help out.

Will this work for a 54 willys aero? 6 volt Negative ground

Willys Jeep Parts Tech:
As long as it will fit into your tank properly and you have a matching ohms reading gauge it should.

mike, i received this fuel sender and unpacked it. it is being installed in an m38a1 fuel tank, do i need to bend the arm to extend the reach because the m38a1 tank is deeper or leave it as is? thanks

Willys Jeep Parts Tech:
This is the closest one you can get for the M38A1 in 12 volt. Because the A1 is unique in that it has a extra well for fuel unlike the CJ-2A, 3A, 3B, ect you will know if your gauge is reading empty you have that extra well capacity.

Is this sending unite including the screws for mounting

Willys Jeep Parts Tech:
B0305 is the part number for the screw kit.

Do I need to ground the sending unit? My 53 M38A1 is 12 volt and always registers full even when tank is half full.

Willys Jeep Parts Tech:
Yes, this sending unit for 6 or 12 volt system needs to be grounded. Thanks

What gauge wire is used for this sending unit? Thanks

Willys Jeep Parts Tech:
16 gauge.

The fuel tank in my M38A1 looks like it has been replaced. It doesn’t have a hole for a sending unit. Can I drill a hole and add a sending unit and if so what size hole and what sending unit?

Willys Jeep Parts Tech:
I guess you'll have to drill the hole if you don't have one because how else are you going to read the amount of fuel in the tank. Just make sure you don't let any small pieces of metal fall into the tank. Once that happens, the fuel will push it along the fuel lines and into the fuel pump and carburetor. Thanks

What is the proper resistance range of this float assembly? I took my inoperable one apart to check the winding and I'm only reading 0 to 35 ohms (empty to full). Even a low resistance float usually reads around 0 to 90 ohms. I doubt this is a 33-240 ohm high resistance unit but I need to know so I can use it with the proper aftermarket gauge.

Willys Jeep Parts Tech:
7-9 Full and 130-140 Empty

I have a 6 screw holes unit down on the tank. Do you have available a 12 volt sending unit?

Willys Jeep Parts Tech:
This works on both 6 and 12 volt systems. It works on resistance. You just need to make sure your gauge in the dash is 12 volt.

I have a new gauge and new sending unit both purchased through you and my gauge reads 1/2 full when empty. It seems as though the sender is backwards and should have 1.5 Ohms when empty and 48 ish ohms when full but this one is backwards.

Willys Jeep Parts Tech:
Please double check the wiring and ensure you have a good ground. They are also adjustable on the tabs that bottom out the arm on the sender. Please call us toll free too and we can help. If you 12 volt you also need to make sure your gauge is 12 volt too.

Will this fuel tank sending work work in fuel tank of an M170? I know that the tanks are completely different. The M170 that I am working on has been converted to 12v.

Willys Jeep Parts Tech:
It may. As long as you have five screw holes that hold the sending unit down on the tank. The arm length can be modified. Thanks!

CJ2A new fuel gauge and sending unit-12V system. Needle on fuel gauge is erratic, mostly reads full but bounces around a bit depending on engine speed which makes me think the voltage getting to the gauge may be too high..I have a ground to frame from the sending unit as well as ground to frame on the back of the gauge via the ground post. I've tried a ground to frame from the sending unit as well as having the ground on the back of the gauge connected to the frame-any other thoughts-should there be an instrument voltage regulator or are these gauges designed to run on a full 12 volts? I've checked my alternator, the voltage is as it should be..

Willys Jeep Parts Tech:
Make sure you are grounding back to the battery. Call us toll free and we can help out too.

I have a CJ-3A and the origenal sending unit has 6 holes do you have one that would fit that?

Willys Jeep Parts Tech:
If your a CJ-3A you should be a 5 hole sending unit so most likely you have an unoriginal tank out of an early CJ-5. I would go with part number: 914850 which is a 6 hole.

My 53 M38A1 has 6 screws this has 5 how will it bolt up?

Willys Jeep parts Tech:
The M38A1 should only have a 5 screw sending unit installed. Please email photos of your tank to something is unoriginal on the vehicle.

My 1950 restored willys jeepster fuel gauge reads one half only when gas tank is full. Car is 6 volt system. Have a vintage wood boat whose gas gauge does the same thing and it is six volts also. What' the explanation?

Willys Tech:
You may need to adjust your fuel tank sending unit and check it with a ohm's reader.

My M38 tank is 7 7/8 or so deep. In a reply to another question, you said for an M38A1 they might have to lengthen the arm. Is this arm sized for a 13 gallon tank and does it reach down 7 7/8 inches?

Willys Tech:
800201 is the sending unit you want to use for the M38

I have a 53 m38a1 converted to 12 volt . I have a new tank and just ordered the 640694 fuel sending unit and need to replace 24 v fuel gauge in panel for 12 volt.Which 12 v gauge will fit in panel and how should it be wired to fuel unit in tank. Also, do you know if arm should be extended on fuel unit (bent down) to read accurately in tank?

Willys Tech:
640763-12V would be the dash gauge you need to use.

Will this work to hold the two lever boot down on a CJ 3B?

Willys Tech:
B0817 will work perfectly for the retaining ring for the transfercase.

My restoration project is a 1952 M38. It was converted to 12 volt a long time ago. I have been told that this sending unit will work with the M38 fuel tank. Will the arm have to be lengthened and, if so, how long should it be? Thanks, Don

Willys Tech:
Yes this will be the correct one for you. You can lengthen the arm if you like for that tank but really it will read empty and you will still have some fuel left with is good.

where does the wire hook on that sends the fuel level to fuel gauge on a 1946 willyz cj2a

Willys Tech:
It goes from the sending unit in the tank to the 's' post on the back of the gauge.

my question is I installes anew sending unit and a new guage on my cj3a fuel system, but whene Iturn the power on the guage goes way past full.I PUT WIRE from the sending unit to the frame and I still have the same problem. can you help with this problem.

Willys Tech:
Sounds like a ground issue. Check your ground as well as the wiring in back of the guage to confirm it is not arching.

Is this sending unit a replacement to be installed in a 53 M38A1 that's been converted to 12V? If not can you suggest another part number? -Thanks

Willys Tech:
Yes this will match up. On the M38A1 you may need to lengthen the arm if you want it to read accurate.

just bought '47 cj-2a with this fuel sending unit(item #640694) the the piece that screws into the top of the unit is missing, do I need to replace the whole unit or is that top piece available? Also, is the float cork?

Willys Tech:
Sounds like you need a new float. This will do the trick.

does this unit come with new float cant see one in the pic

Willys Tech:
Yes that is correct.

do the sending units and gauges have to match (ohms) or will they fit any gauge? reason i'm asking because i need both.

Willys Tech:
Yes, they should be a match. Please call us toll free. We can help. All our gauges and units match.
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