This morning in the recent Fuel Gauge thread, I accidentally deleted it while trying to edit out a duplicate post.
But, Bully Bob was able to re-establish this thread!!! Thanks to BOB!
here are some tests;
Testing; "...the little resistive strip in them gets bad and causes erratic readings. Also, while you are at replacing it, check out the connector to make sure the ground is good back to the battery. Do a resistance check from the black lead to the battery (-) post. If is is more than a couple of ohms, run a new ground lead to it..."
Source: by Seabronc (Rosie, Fred W) at Ford Bronco Zone Forums
Testing in an 78-86; "...Ground the Y/Wh wire at the fuel tank, turn the key to RUN, and observe the gauge. If it pegs FULL, the sender is bad inside the tank. If it stays at EMPTY, it's an electrical fault, probably in the cluster, or its connector..."
Source: by Steve83 (Steve, That dirty old truck) at Ford Bronco Zone Forums
Testing in an 78-86; "There is a yellow wire with a white tracer coming off the fuel pump to the gauge. The easiest way to ck the gauge and wiring is to disconnect the y/w wire and ground the wire on the dash side of the wire. If you can slide your hand up on top of the tank and disconnect the pump and ground out the y/w wire turn the key on and watch the gauge if the gauge goes up the sender in the tank is bad, if youre going to replace the sender you may as well put a pump in it..."
Testing; "...floats either way; There is a brass float attached to the sending unit, and eventually they can develop a pin hole leak.."
Source: by Dave's Bronc 90
Testing; Fuel Level Sender, "...disconnect the plug & jump the terminals, it should peg the gauge at full..."
Source: by Billz4x4z at Ford Bronco Zone Forums
Testing in 87-88 Bronco & F Series; When the fuel gauge needle is below the 1/2 to 1/4 tank range the needle will swing all the way above the full mark on the fuel gauge; An erratic fuel gauge needle when the fuel tank is 1/2 to 1/4 full may be caused by excessive wear of the resistive film on the fuel pump sender assembly. The wear occurs during transporting of the vehicles via rail or truck over long distances. The fuel gauge will indicate correctly from a full tank to about 1/2 or 1/4 tank of fuel. When the fuel gauge needle is below the 1/2 to 1/4 tank range the needle will swing all the way above the full mark on the fuel gauge. To correct this, install a new fuel pump sender assembly. Refer to the appropriate 1988 Car/Light Truck Shop Manual, Section 24 for detailed service information. Refer to the following fuel pump sender application chart for the correct service part number. in Fuel Gauge Erratic TSB 88-18-03 87-88 Bronco & F Series 4.9L/5.0L (all PN E9VY-9275-A) & many others; Miesk5 Note, Steve83 wrote, Pre-'87 fuel level senders are TOTALLY different from '87-up. Not only do they work over a different range; they work in the opposite direction
Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net
Testing & Connector Pin-Outs in 92-96 Bronco; Sender Range: Full = 160 Ohms; Empty = 16 Ohms; "... gauge that pegs past full indicates an open circuit (broken wire; unplugged connector; corroded terminal; burned sender) on the Y/W wire. gauge that pegs past empty indicates a short to ground (pinched to the frame, body, or dash supports) on the Y/W wire, OR a sunk float. gauge anywhere in between that doesn't move indicates an open circuit (blown fuse; corroded terminal) on the power (battery) side of the gauge OR a bad instrument cluster ground at C251 pin 9. The terminals of C251 (& C250) are known to corrode & lose contact. Polish both the connector pins AND the film circuit pads with brown paper or a pink eraser. The larger version of C441(WPT454) was used until 93. The level sender can usually be disassembled & repaired by bending the wiper arm inside the plastic housing to apply slightly more force..."
Source: by Steve83 (Steve, That dirty old truck) at
http://www.supermotors.net/registry/media/744437
******* READ AND SEE MORE *****
===
Tech Tip Guide, General; "...Many times, the Ford fuel pump hanger/sender assemblies are frequently found with extensive corrosion on the cover and on the metal tubes. Over time, the terminals can loosen and cause intermittent loss of continuity. Erratic reading of the fuel sender level is one of the other problems that could occur..."
Source: by spectrapremium.com