How to Test A Fuel Sender Unit

[55 Fargo]

Hi all, how does one test a 2 wire fuel sending unit on the bench. I have mine in front of me at the computer, ohm meter in hand, but there is no measured continuity, when I test this unit.Any ideas.............Thanx Fred

[Plymouthy Adams]

Fred..if you cannot see between 28 and 32 ohms between the terminal I and terminal 2..then the wire is probably broken and the sender shot..if you are trying to read either to ground...odds are the ground is open..very very common..disassembly of the unit if this is the case and and run an aux braided wire similar to the wire in your distributor..will ensure good ground the float arm itself is the wiper on the resistor...it should read the total ohms of the resistor ..put the one lead on the float arm..other lead to terminal 1...if it reads say 8 ohms to that terminal the other 24 ohms will be read on the other terminal with float arm in same position...

[55 Fargo]

Hi Tim, and anyone else who may have an idea on this. When I touch the 2 terminals on the sender with the ohm meter, there is no reading whatsoever.

The unit is probably shot, or I don't what I am doing in testing it.

Can I use an aftermarket sender for the replacement, the only thing is this, the aftermarket sender is a single wire type, will or can this work when it was originally a 2 wire set-up.

The other thing with my new tank and the OEM sender is this, the swing on the float is in the wrong direction, what gives, there seems to be no luck on this new tank.

If I was to go with an aftermarket sender, does that mean I will need and aftermarket gauge also...............Thanx Fred

[Plymouthy Adams]

you pretty much locked into the two wire sending unit for the guage you hve..it is designed to pull in opposite directions at the same time..the built in regulator and slow reacting circuit make them rock steady..if you wish you can check with about any boat/marine facality and get a 12 volt sended..should be same pattern bolt in..single wire but you will need to remote mount a guage...

[55 Fargo]

Okay, if I cannot get the 2 wire setup to work, can use the single wire and remote gauge. I can buy a single wire 73-10 sender from Yogi's in Iowa, what gauge or what kind of gauge would I need, could I mounthe gauge in the trunk, is this a good idea, I did not think this would get this complicated.

If I can get another 2 wire sender, would that be the best idea................Fred

[Young Ed]

Fred the 2 wire units are available new. I bought one from Roberts for my pickup. Never have gotten it installed either. Primitive pickups don't have an access for the sender-you have to drop the tank to swap it

[BobT-47P15]

The two wire senders are available from Atwater Kent company, I believe listed with other sources on this forum. The cost i think was like 50 or 60 bucks. If the float is hitting the side of the tank, you can probably turn the sender - but then the holes will likely not line up. Would have to make some new holes in the collar of the float. I would guess the ones in the tank are

threaded.

The needle on your meter should move (or the digital numbers change) when you move the arm of the float from one side to the other....because of the

changing resistance. It appears someone actually took the top off my old

float to work on it.....have to drill out the rivets or whatever holds it on.

[Young Ed]

I've heard of that float arm problem before. I guess the deal is with some of them the rivets are installed in the screw holes. I don't see why you couldn't drill them out and not worry about reviteting it. The 5 screws would hold it all together when installed anyways.

[Young Ed]

Bob we took mine apart and Dad fixed the insides. I can't recall if we left it 2 pieces like I just mentioned or if we riveted it back together somehow.

[Alexander]

In many cases you can fix the sending unit. There is a rheostat (Nichrome wire winding) inside the sending unit. In some cases this winding develops an electrical break from the traveling contact. Open the sending unit and see if you can reattach the break by either soldering it or twisting the 2 ends together from the back side.

In my case I twisted the 2 broken ends together on the back side of the rheostat where the contact does NOT travel. Still work greats except for the small dead spot at 3/4 full (where the attachment was made). Any reading befor 3/4 or after show 100% correctly.

You can close back the sending unit with a few small nut and blots

Hope that helps

[JohnS48plm]

After I repaired my sender I reassembled it with steel pop rivets. Install the pop rivets and then use the stem that breaks off to drive the ball out of the back side of the rivet. Then flatten the back side with a punch. It worked well for me. JohnS

[55 Fargo]

So far I cannot get any reading from this sender, whether I test it with an ohm meter, or I put power to it and agauge from my parts car, zero reading in every test.

Will try and find another sendeer and go from there, not sure I can fix the one I have or not............Fred

[55 Fargo]

Opened up the sender, the little wire on the contact board were all ripped up, not just broken in one piece, every strand was torn. Will buy a another 2 wire sender or go with a single wire sender and remote gas gauge, what the H the car isn't totally original anyway.......Fred

[Plymouthy Adams]

this is basically what I expected you would find when you were not able to get a reading between 1 and 2 on the sender..

[Norm's Coupe]

this is basically what I expected you would find when you were not able to get a reading between 1 and 2 on the sender..

Tim, I'll agree you should be able to get an ohms reading off the sender if it's working. However, when I was having trouble with mine, I could not get a reading on my old sender when I tried testing it. However, the old sender is still in the car, along with the old gage and both are working after replacing the wires between the two. For what it's worth, I still can't get an ohms reading off the sender. So.......checking for an ohms reading doesn't always tell the whole story. Don't get an ohms reading off my new sender either, but if I power it up and hook up a gage to it on the bench, it works too.

[Plymouthy Adams]

Norm..if the wire is good you WILL have a reading between 1 and 2 in or out of the car...and will average between 28 and 30 ohms so your meter nees be sensitive enough to read this..which is a good R1 scale..but when reading between 1 and ground and 2 and ground which goes through the wiper to the ball of the unit and further grounded by that base to the tank and from tank to chassis ground..lots of places for erronous reading in that path...but 1 to 2..is a must and guaranteed if wire is intact..but yuou must hace good contact at terminal 1 and 2...