Fuel Sending Unit / Sensor Testing

CoastalWinnebago · January 28, 2016, 03:12 PM

Long story but I tore my tank out and I am coating the inside, but I want to insure my Fuel Sensor is working before I re-install.

Here are the details: Usually a float/sensor and sending unit are all one component. In my tank there is a separate tube/inlet for the fuel to be drawn. There is also separate sensor/float system in a larger hole. It looks to have been replace at some time by the PO. In addition, there was a new fuel gauge installed in the instrument panel.

With the fuel sensor/float out of the tank and not attached to anything, is it possible to test this unit with a multimeter to insure it is functioning properly before I re-install? Any idea how I would perform such a test?

(I will provide a detailed write up of my tank rust, and subsequent refinishing of the tank in a different post)

SLEETH · January 28, 2016, 03:52 PM

hi yes with a ohm meter = digital or analog black= ground red is wire to sending term=usually brass
there are different ohms (resistances)= cant remember= but im sure some one will chime in

Rickf1985 · January 28, 2016, 04:03 PM

You could also hold the sensor and run jumpers to the power wire from the gauge which is usually but not always brown and the other to ground, the frame. Now have someone watch the gauge with the key in the "on" position while you move the float up and down. The gauge should follow what you are doing in the back.

SLEETH · January 28, 2016, 04:14 PM

just a ps: be very careful not short out the wires with this live test=damage can be done both to the sender & the gauge unit

CoastalWinnebago · January 28, 2016, 04:14 PM

So it seems this youtube provides a good outline on how to do said testing.

Does anyone have any idea what the resistance values should be in ohms for full and empty?

https://www.youtube.com/watch?v=hHzeOOzQKR8

SLEETH · January 28, 2016, 04:17 PM

each manufacture ie ford dodge chev had diff values =gettin old cant remember = just google it = the tank & the sending unit is dodge from that erea

Bnova · January 28, 2016, 07:02 PM

The resistance value is probably not terribly important to know, as long as when connected to an ohmmeter there is resistance value at one extreme position (ei full or empty), and also resistance at the other extreme position.

One reading will be high and the other extreme would low, relatively speaking. I would also look for a smooth change in resistance indication on the ohmmeter as you move the arm through it's range of motion and check to see that there are no drop outs.

DaveVA78Chieftain · January 31, 2016, 08:29 PM

Stock Dodge ohm value for gas gauge is 10 ohms (full) to 73 ohms (empty).

However, comma, you said the PO replaced things so who knows what you have now.

Rickf1985 · February 01, 2016, 10:39 AM

Quote from: DaveVA78Chieftain on January 31, 2016, 08:29 PM
Stock Dodge ohm value for gas gauge is 10 ohms (full) to 73 ohms (empty).

However, comma, you said the PO replaced things so who knows what you have now.

Aha! Dave is using Dragon software isn't he?

No wonder he is so fast on the keys, he isn't using them. :)rotflmao

No worries, due to my arthritis I also got it and I am just learning how to use it. Haven't started yet though.

CoastalWinnebago · February 01, 2016, 11:38 AM

Tested the unit before I replaced it. I was reading .002 ohm at empty, and around 100 at full. I rewired the ground line and we will see what happens when I get the tank back in place.

I will update later.

Getting this tank back in has been extremely challenging.

DaveVA78Chieftain · February 02, 2016, 10:08 PM

QuoteAha! Dave is using Dragon software isn't he? No wonder he is so fast on the keys, he isn't using them.

:)rotflmao
Nah. Tried that many years ago however I cannot be stealthy with it.

Bnova · February 03, 2016, 08:21 AM

Quote from: CoastalWinnebago on February 01, 2016, 11:38 AM
Tested the unit before I replaced it. I was reading .002 ohm at empty, and around 100 at full. I rewired the ground line and we will see what happens when I get the tank back in place.

I will update later.

That should work, as long as the gauge and wires are good.

Getting this tank back in has been extremely challenging.