Bench Testing Fuel Sending Unit (1 Viewer)

[Green Bean]

I'm trying to bench test a new OEM fuel sending unit PN 83320-3520. From what I've read, it should test 110 ohms empty and 3 ohms full. Using a digital multimeter, I'm getting around 24 ohms at various positions through the arch. I guess it is possible that I got a defective unit but it is much more likely that I'm probably doing it wrong. Is there some secret to taking ohm readings on these things.
Thanks.

 

[Skreddy]

I’ve never ohmed the Toyota one before (have done others) but I usually hook it up not installed in tank, run a jumper ground wire to a good ground, then run it through its cycle and watch the gauge. Bend the arm a little to get it where I’d like and boom, done. I have never had a 40 gauge give me a good full and empty reading so I err to the empty side. Meaning, I want the gauge to show empty slightly before bottoming out so I know when driving, if that thing says empty it’s not a lie. In my current 40, this means it sits on full a little longer and once it gets to half it starts dropping pretty quick.

 

[fjwagon]

You are correct, should have minimum ohms in the full position as mentioned. And youthe ohm readings should increase in linear fashion on different positions on the way to the empty position. Clean the contacts with a little wire brush. I sometimes use a Simpson 260 analog meter if the digital meter is not reading it as you move it. But I don't think you measuring the ohms that way. You may need a better meter. I say that in a good way.

 

[Green Bean]

Okay. I've tried testing with both digital and analog multimeters with the same results. The sender maxes out at about 30 ohms. When I emailed the vendor this is the response I received: "We've gone through this question with 2 other customers in the past. These fuel senders are all made exactly this way by Toyota. This is the spec these are made to today." Any suggestions on getting a functional sender?
Thanks.

 

[sggoat]

Did this a while back on my 77--OEM sender

 

[ERNRAM]

Did this a while back on my 77--OEM sender

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You must be an engineer

 

[ToyotaMatt]

 

[Engineer8000]

83320-35020? This sender works much like the oil pressure sender. It cannot be tested with an ohmmeter.

 

[Green Bean]

83320-35020? This sender works much like the oil pressure sender. It cannot be tested with an ohmmeter.

Engineer: Can you please explain "It cannot be tested with an ohmmeter." I thought
that is exactly how we are supposed to test resistance. Please educate this dummy.
Thank you.

 

[Engineer8000]

This sender works like the oil pressure sender. It has a bimetal points type regulator it it. The float moves the contacts closer together and farther apart as fuel level changes, causing the amount of current to the fuel gauge to vary. If you want to test, just hook up to the sender wire in the truck before installing and raise/lower the float while watching the gauge. The mounting provides the ground so you will also need a jumper from the sender mounting flange to ground on your truck. Here you can see the cam moves the diaphragm on the sender.

The later style senders are potentiometers, resistance wire wound on a form with a wiper contact that is moved by the float. These can be tested with an ohmmeter. I would use a Simpson analog meter to test as they have more "ass" to push through surface corrosion, plus easier to see bad spots as the wiper moves across the winding.

 

[Green Bean]

FYI: I ended up using an after-market fuel sending unit. (Actron SP0F000013 Bosch Fuel Level Sender ). This one has a range of 240 - 33 ohms which is fine because I'm pairing it with a Dakota Digital instrument cluster and this is one of the preset choices. There are probably better choices for anyone going this route. The Bosch sender had to be cut down in order to fit and the flange holes had to be drilled out a bit. Currently, the gauge reads 99% full on a close to full tank, so that is good. The test will be if it gives accurate readings heading towards empty. As @Engineer8000 pointed out the 83320-35020 would not pair well with the DD because it has a bimetal points type regulator it it, rather than a linear resistance. The later style sender might have been a good choice if the tanks are the same.