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66-96 Ford Broncos - Early & Full Size
Jgrden

Gas Gauge Reads "FULL"

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My '85 Bronco has hd a rough past. It was bought to rebuild and after looking into replacing rusted parts it seems as though it has seen more  water, more than a rain, and than I had thought. .  than normal. 

So here is the question; Why does the gas gauge read FULL, always?  Does this look like a instrument issue or a gas tank gauge event?

 

I hav e looked for a library of issues but cvannot find any. 

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It sounds to me like you have a poor connection in the wire from the tank sender to the dash.   There is a plug near the tank.    That would be the first place I would look.

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Sounds like a short (to ground) of the wire to the dash gage.

Pull the elect. plug from the tank & see if gage drops to "E"   If so, the gage is good.

 

The float could be stuck full up.

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Yikes. I went under the Bronco to look for the plug. It must be located on top of the tank. My fat hand cannot get to it. Never mind, this is my issue and your information is appreciated. I may cut a hole in the truck bed to access the gauge. But that is extreme. 

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Not really.., many folks have done the same thing.., putting in a "trap-door" for sending unit/pump access.

It could be tricky as you wouldn't want to hit the tank.

 

If you could find just the wire via color code., couldn't you cut it to test, then splice it..?

 

Which-ever.., good luck & let us know the results.

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Access to pump thru bed floor.

 

https://www.youtube.com/watch?v=N2aEAeUNVLU

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OMG....Bob !... I can't believe you'd agree about this kind of solution ! ..for sure it's SMART&CHEAP but we are talikn' about our loved Broncos ...not some Chevy "trush" to destroy ...! lol, obviously i'm jokin ..., but my tip for J. is to wait for "Time&Money" makin' a proper job when possible in the future (  www.youtube.com/whatch?v=v_p251h8sLM )  . At the moment 1 gallon tank inside the truck for emergency is enough . All i wanna say to J. (with some less money' problems than me..) he is going to fix some "actual" problems...but it doesen't means his truck becames brand new after that... . How about to take this "occasion" for clean everythin' n check many others components about fuel' line mayby close to die..? Its an OLD truck in the end.. the more you'll be able to "change" (as new parts) n "control/clean/fix" as "overall".. the less problems you'll get in the future ...for happy/safety travels n money saved.. . (just my 2 cents) Good Luck J. ! :)>-..Lets have a beer all together now ...! lol

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Hi Mark..,

How's everything over there in the "Big Boot" ...??

Oh yah, I'd have to give it some serious thought B/4 I'd cut through.

Luckly, my pump is on the engine.. :D/

Many shops take the bed loose &/or tilt the bed to get to the pump on PU trucks.

 

When GM was thinking of re-introducing the El-Camino.., they were going to have a

flip-up bed floor.

 

The guy in the video, wasn't real concerned about looks.  It would be easy to do a neat job

& make it look factory.

In his case.., he should have pulled the tank, as he already replaced the pump TWICE..!

Meaning he likely has some crud in the tank that's damaging the pumps.

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:) hi Bob ! ...yeah exactly..., even for him was better do the job one only time n correctly (cleanin' the tank n all the rest ispected..) . I don't like to see Jgrden in the same unfunny situation one day..plus..with his truck cutted like a pie for nothin' ...lol he don't have any "important" problem now  , but it's a "zone" he have to take care for sure soon in the future.. as ispection n maintenance.  About "the Big Boot"...we are just tryn' to survive in this moment..lol.....it's been a long economy' recession. (end O/T).   Have a nice day my friends !  :)>-

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Picjy picky picky, I want a gauge that will not leave me along the highway with the possibility of needing to get to Urgent care. My issues may seem trivial to you, sir, but they are important to me.  [-X

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Hello J. , believe me it wasn't my intencion to "minimize" about anythin' ... , personally i was just assuming it was better for ya to remove n clean the tank directly , check / adjust all the organs inaccessible in that area (as ur gauge) AT ONE TIME n without cuts for your truck . Your only "annoyance" actually ( but i could be wrong ) it's about not knowing how much gas you have in the tank ..n i don't think it's somethin' "difficult" to menage (waitng for the repair..in the way i told ya ) That's all i was tryn' to say..,  always with the utmost respect for you n your choises.. :)>-

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Ya  J..,

I didn't see anything in Marks comments that weren't helpful. 

Sometimes it's hard to express things over a keyboard & things can be misunderstood.

 

Anyhoooo..,  do let us know what you decide & how it turns out.

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Maybe my skin is  little too thin.   :closedeyes:  I enjoy this forum and everyone that contributes to it. It has saved me money, time and allot of general assistance in restoring a rig that needs allot of attention.  Carry on,  cheers. 

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P.S.:  There is a possibility that the tank is full of gas. I need to run it to see.. heh, heh, heh.  Go ahead,call me what you want. 

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Mine fluctuates greatly....from where I think the fuel level is to way past full...sound like a bad sending unit?

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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

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yo, more;

The gas gauge being stuck on full indicates a ground somewhere in the circuit. The quickest way to determine if it's the sending unit or the wiring is to disconnect the electrical plug at the tank. If the needle goes back to empty (as it should), your sending unit is bad. If it stays on full, the wire is pinched and shorted to ground somewhere between the instrument panel and the fuel tank. Trace it out visually to find the pinch point and then repair it. my JP

 

floats either way; There is a brass float attached to the sending unit, and eventually they can develop a pin hole leak and cause erratic readings

Testing; "...If the guage reads normally for some of its range, but reads full or bounces between full and the real value, the most likely cause is a worn level sender. The fuel level sender is a variable resistor located in the gas tank. A wiper attached to the float rides across the resistor, causing a change in the resistance seen by the dashboard guage. A high resistance (or open circuit) reads as "Full" on Ford gas guages. Over time, the wiper may wear through the resistor, causing dead spots which read as full. The only fix for this problem is to replace the sender. by Matt K at off-road.com via web.archive.org

 

 

DIY Test in 78-86;

Full = 10 Ohms

Half Tank = 25 Ohms

Empty = 50 Ohms

 

Sender Float & Resistor Assy. pic & Test in 90-96; "...The level sender merely screws to the side of the FDM & its wire plugs onto the tank plate. Before reinstalling the FDM, I removed the EEC PWR relay (which also kills the FP relay), turned the key to RUN, & checked both the old & new senders through the full range of motion. The old was definitely bad, & the new definitely good..." Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net

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Wonderful information. I now have a plan. Thank you.  :-B

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How about when your gas gauge used the half-full mark as the new "full mark?" Sounds like a float problem but wondered if anyone has that issue.

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