• Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!

Fuel buffer sensor Cat 966f

pedrocar

Well-Known Member
Joined
Jan 25, 2016
Messages
110
Location
australia
Occupation
grader operator
Hi How do i go about checking a fuel buffer sensor on a 966F loader
S/N 8BG02280 fuel guage generally shows low fuel and flashes ,thought it maybe the sender then discovered
this buffer when i removed the tank to replace steer cyl seals
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
28,984
Location
G..G..G..Granville.........!! Fetch your cloth.
Pedro, There's an explanation on Pages 4 & 5 of how the buffer converts a DC voltage from a resistive sender into a PWM signal that the electronics can read.
If you can measure the DC voltage being produced by the level sender while you fill the tank, it ought to change as the tank fills. The only issue is that the buffer supplies power to the sender, so you have to do the test with the buffer connected to the sender and the key switch on.

upload_2019-1-24_9-54-52.png
 

Attachments

  • Fuel Level Sensor & Buffer.pdf
    248.3 KB · Views: 10

pedrocar

Well-Known Member
Joined
Jan 25, 2016
Messages
110
Location
australia
Occupation
grader operator
Hi Nige is there a way to check the sender unit once the tank is back in pos the sender cant be removed without removing the tank . I earthed out the sender wire some time ago and the guage went up to full level does this indicate maybe senders at fault
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
28,984
Location
G..G..G..Granville.........!! Fetch your cloth.
Hi Nige is there a way to check the sender unit once the tank is back in pos the sender cant be removed without removing the tank . I earthed out the sender wire some time ago and the gauge went up to full level does this indicate maybe senders at fault
You can check the sender function with a digital multimeter. With the tank low on fuel disconnect the sender at connector marked FF above. Measure the resistance. Fill the tank with fuel and observe the resistance to see if it changes as the tank fills. There are two possibilities - 0 to 90 ohms or 33 to 240 ohms. Unfortunately I can't find any information to identify which one you have. Either way the resistance should change as the tank fills. See explanation below regarding how the sender works, and consider the possibility that you might have a seized rod/float assembly inside the tank. The rod/float, etc, are all part of the sender assembly.

upload_2019-1-25_7-41-52.png

The depth of fuel in the tank determines the position the float (2) will travel up or down the spiral rod (3), rotating the rod as it moves. The sender (4) is attached to the top of the assembly and magnetically coupled to the rotating rod. The output resistance of the sender changes as the rod rotates.
 
Last edited:

pedrocar

Well-Known Member
Joined
Jan 25, 2016
Messages
110
Location
australia
Occupation
grader operator
Ive had the sender out has a float of sorts attached to two guide wires all seems free so by moving the float up and down the tube with a multimeter attached i should get a variable reading
 

kshansen

Senior Member
Joined
Mar 11, 2012
Messages
11,129
Location
Central New York, USA
Occupation
Retired Mechanic in Stone Quarry
I'm thinking this one is like the one Nige posted above. That float sliding up and down the "guide wires" should be rotating a twisted rod that looks like a dipstick. The turning of the twisted rod rotates the contact that slides around the resistance wire up at the top.

So to answer your question, yes if you hook a multi-meter across the screw terminal and the mounting flange or connect across the two wires in the plug connector and slide the float up and down the "Ohms" scale on meter should vary in relation to the position of the float.
 

pedrocar

Well-Known Member
Joined
Jan 25, 2016
Messages
110
Location
australia
Occupation
grader operator
Hi put a multi-meter on the unit ohms went up and down all over the place as the float moved up and down .
Removed the plate on the bottom and one of the guide wires has broken from the top its not servicable
reckon its R/S
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
28,984
Location
G..G..G..Granville.........!! Fetch your cloth.
I dunno about everyone else but I got the impression from your post #5 above that you'd already had the sensor out of the tank and it was physically OK, which is why you were asking questions regarding the functioning of the buffer. Now you say that after inspection the sensor's bust - I'm confused.
 

pedrocar

Well-Known Member
Joined
Jan 25, 2016
Messages
110
Location
australia
Occupation
grader operator
When i removed the sender all looked ok testing with the mm was all over the place i removed the base plate one of the guide wires had come off broken from in the top of the tube wich is not acceptable. Sealed unit
May be tilting the sender checking the resistance may have broken the wire but in no way was it roughly done .i asked about the buffer as i only found it when i removed the fuel tank never seen one before the fuel guage never worked only flashed i did the old test and earthed out the sender the guage went strait to full only knowing of a resister type sender .
 
Last edited:

pedrocar

Well-Known Member
Joined
Jan 25, 2016
Messages
110
Location
australia
Occupation
grader operator
After a pile of repairs steer cyl reseal hyd hoses , new brake hoses ,sand blast ,paint and a new sender unit fuel tank back on
fuel guage works a treat
 
Top