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Old 08-23-2011, 10:28 AM   #1
Traderssd
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'91 Bronco Fuel Gauge Issues

Hi,

We're the new and proud owners of a very nice '91 XLT. It's a great rig with only 51K original miles on it! Been tinkering with it to fix some of the "little" things that happen to any 20 year old vehicle. One that has me stumped is the fuel gauge that doesn't work. I've read a lot of the posts that people have put up on the web about this problem but I'm probably more confused now than I was in the beginning.

My mechanic, who partialy diagnosed the issue, said that the problem is NOT in the tank sender and most likely in the gauge. He said they made a few tests and grounded the sender wire from the tank to the gauge, which should have made the gauge swing one way or the other which it did not. On his suggestion, I replaced the gauge (module, not the whole instrument cluster) and it still doesn't work. The symptoms are, when the key is on, the gauge goes to past empty and never moves from that spot as long as the ignition is on. When the key is off, the gauge goes into a "floating" position.

I then checked the ohm reading on the sender wire (yellow/white) which shows about 10-11 ohms. To me and from what I've read about these issues, it seems like the sender but my mechanic still says NO.

Can any one help me? Does anyone have any thoughts on this? I'd sure appreciate any advice anyone might have.

Thanks in advance!

Sincerely,
Stuart D
Portland Oregon
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Old 08-23-2011, 10:55 AM   #2
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yo Stuart,

The R reading looks ok for Empty reading; we are in the ball park on that even though we have slightly diff ohms posted by many here and inother sites; such as:

16 Ohms Empty; 160 Ohms Full; "... 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. 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 SuperMotors.net


Testing in a 90; from 90 EVTM; "... 22.5 Ohms Empty & 145 Ohms Full; there is a fuse that goes to all of the guages. Again in a 90 it is is position 18, 15 amps. Checking all of the fuses is a snap with a test light. Just touch each side of the fuse, if you have power on one side, you will have power on the other side if the fuse is good. Just check them all..."
Source: by BroncoJoe19 (Joe) at FSB

Floats are avail!;
Float Part Number; LMC 30292; "...LMC sells the float too. I just bought 2 from gaudin ford for 9 each plus shipping because I wanted to make sure I got the right ones ($32 total shipped 2 houirs after I ordered them). I had the fuel gauge pegs past E blues. Both trucks had gaslogged floats(as opposed to waterlogged). The floats look just like the ones in my 75 trucks..."
Source: by wood4d at FSB

Float Part Number; Motorcraft COAZ-9202-B
Source: by Chris340 at FSB


Repair; "...As much of an improvement as the FDM system was over the previous EFI pump system, it's still subject to failures, mostly related to fuel varnish building up on its internal surfaces. When it builds up in the level sender, it causes the gauge to peg FULL, as any open circuit would (high resistance). If diagnosis shows the fault to be inside the tank, the sender can sometimes be cleaned & returned to service for a fraction of the cost of a new sender. In either case, a new O-ring is required between the pump mounting plate & the tank. Instructions for removing the FDM can be found in this '90-96 Fuel Pump System
album's captions..." READ MORE by Clicking Next
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net

Fuel Level Sender & Gauge Wiring for '92-96 Broncos ('87-96 F-series & Bronco similar)
IF THE IMAGE IS TOO SMALL, click it.

Sender Range: 160 (full) - 16 (empty) Ohms
A gauge that pegs past full indicates an open circuit (broken wire; unplugged connector; corroded terminal; burned sender) on the Y/W wire.
A 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.
A 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 (open). 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.
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Old 08-23-2011, 11:55 AM   #3
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Hi and thanks for the response but I'm still confused .............I guess my question is, if the yellow wire is disconnected and then shorted to ground, wouldn't the gauge move one way or the other and if it did, eliminate the possibility of a bad sender unit???
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Old 08-23-2011, 12:14 PM   #4
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Just drop the tank and replace the float...if you had a short it would read full all the time. You can buy just a float, or replace the whole fuel pump/sending unit assembly for peace of mind, but it's your choice.
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Old 08-23-2011, 12:20 PM   #5
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Your description sounds just like a cracked metal float to me. :)

BTDT swapped it out with a foam float, just took some careful
rod bending and an old sending unit I'd found on the ground at
a friend's place. ;)

Try this:
Pull the connector off the fuel tank and see if it goes past full.

If it does that, it isn't a pinched wire or the gauge. If that's the
case, do yourself a big favor and from here on... do your own
mechanic-ing. ;) No one-mechanic can know more than 1000
guys that are into the exact rig you got.

Alvin in AZ
ps- Cool find BTW! :) ...mine had 125k on it. :)
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Old 08-23-2011, 12:25 PM   #6
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Quote:
Originally Posted by rcracerx View Post
Just drop the tank and replace the float...
x2 right after the "pulled connection" test to see the gauge read full.

Quote:
if you {have an open circuit} it would read full all the time.
x2 (now ;)

If you got a -short to ground- it'll ready empty.

-------------------------
{edit:}

Yes it can be confusing.

Ford changed to the Chevy system on different vehicles in different
years, the older Ford fuel gauge used the "gauge voltage regulator"
like the rest of the gauges, so when reading about them from other
sources than the shop manual for your vehicle and year it might not
be "right".

The difference between the two systems can be seen in where the
needle rests when the key is off.

"stays kinda where it was last" -is the Chevy system.
"goes to empty" -is the older Ford system.

------------------

I've read where the blame for all these cracked-brass-floats is being
caused by too much un-even spring-wire pressure on the float. So
when replacing the float loosen that loop up a little.

-------------------

Butthead in AZ
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Old 08-23-2011, 01:40 PM   #7
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Thanks for all the tips guys...........I'll try disconnecting the yellow/white wire first and see what happens. If it goes to full............the sender is coming out! Now, would you guys recommend dropping the tank or cutting an access hole from inside cargo area on top of the tank and doing it that way? Also, what do I do about the fuel lines and the o-ring? I read the fuel lines are difficult to take off and where do I get the o-ring?
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Old 08-23-2011, 03:56 PM   #8
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Quote:
Originally Posted by Traderssd View Post
I'll try disconnecting the yellow/white wire first and see what happens.
If it goes to full............the sender is coming out!
<-----Fill out your stuff. Where you at?

Just pull the plug off the tank. ...you're prob'ly going to be anyway. ;)

That's one connection you'll have got done with and there's three more
to drop the tank.

I used a small floor jack with 15" of lift. Weird but never needed anything
like that to drop a tank before or put it back in but that skid plate made it
too much trouble for me, so I used a floor jack. Only thing I've ever used
it for and it was given to me more than 10 years ago.

Quote:
Now, would you guys recommend dropping the tank or cutting an access
hole from inside cargo area on top of the tank and doing it that way? Also,
what do I do about the fuel lines and the o-ring? I read the fuel lines are
difficult to take off and where do I get the o-ring?
Off hand I'll say... You need to drop the tank to cut the hole.

If others tell you how to cut the hole with the tank in place then that'd be
worth while! :)

Auto parts stores sell the o-rings and new lock rings in the "Help" section.

If your lock ring is in real nice shape and can be cleaned up good, a 4"id x
1/8" (4+1/4" od) o-ring from the hardware store will actually fit better
than the Dorman o-ring IME.

Alvin in AZ
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Old 08-23-2011, 04:08 PM   #9
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Don't cut an ugly hole, do it right and drop the tank. Don't be lazy, it's just 8 bolts holding it in via the skid plate. It took me less than an hour dropping my old tank, and replacing with a new tank with new everything. It's not hard at all, just be careful not to rupture a fuel line as they are brittle with age and you'll be fine.
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Old 08-23-2011, 04:23 PM   #10
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Quote:
Originally Posted by rcracerx View Post
...be careful not to {break the tank vent} as they are brittle {and weak as hell}
x2 ;)

The hose from the rear end of the tank vent (if yours has even got the rear hose)
is hooked to the frame and just a slight tug will snap that sorry sucker right off. :/
BTDT ...even after knowing about it and being careful ...they are that friggin' weak.

I plugged a short piece of 3/8" fuel hose and used it to cap that rear vent off one
time and that worked good. Those things are expensive it's a Ford only part.

The (pre-'86?) single-port vent is solid nylon and tough as anything tho. :)

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Old 08-23-2011, 05:17 PM   #11
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Everything in there is brittle, I accidentally snapped the fuel line when I had everything buttoned up and gave it a light tug to make sure it was seated and it snapped right at the plug. Just get a fuel line slice kit and you're good to go.
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Old 08-23-2011, 06:14 PM   #12
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Quote:
Originally Posted by rcracerx View Post
Everything in there is brittle, I accidentally snapped the fuel line when I had
everything buttoned up and gave it a light tug to make sure it was seated
and it snapped right at the plug. Just get a fuel line slice kit and you're good
to go.
Wow I guess I've been lucky then, I've messed with the nylon lines a-lot and
never even kinked one, let alone break one. :)

How did you shove the kit's hose barb into the nylon hose? :)
Was how water enough to do the trick?

I've cut quite a few and sliced them and had to use hot oil to get the nylon
line hot enough and the barb was like 300F too and I figure that's where the
real heat-softening-effect was coming from since the hot oil didn't work so
good going directly to a plastic fitting.

My next go-around with nylon fuel line is going to be easy since I got the
K-Tool that's made to shove the fittings in cold, the way the factory did it.

http://www.ktoolinternational.com/KT...x?pt=KTI-75305

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Old 08-23-2011, 07:19 PM   #13
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Quote:
Originally Posted by rcracerx View Post
Don't cut an ugly hole, do it right and drop the tank. Don't be lazy, it's just 8 bolts holding it in via the skid plate. It took me less than an hour dropping my old tank, and replacing with a new tank with new everything. It's not hard at all, just be careful not to rupture a fuel line as they are brittle with age and you'll be fine.
That sounded really good to me, until my 2nd float quit after 1 year or so. This was the 4th and last time to drop the tank.

Unlike the conventional, I drilled a 6" hole in my floor last weekend. It looks ok and is covered by the cardboard (now plywood) sheet, juke and carpet. I stil need to get a donor floor piece to make the panel.

Point is, I was really against cutting a hole in the floor, but after this last time, I decided I was tired of spending even an hour when I could spend 15minutes and accomplish the same thing. Looks like Ford is gonna have a history of problems with their floats.
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Last edited by j. r. Nice; 08-23-2011 at 08:11 PM.
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Old 08-23-2011, 08:04 PM   #14
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Thanks..........So how do I remove the pressure fuel lines from the tank? I've heard they are a real nightmare and to get them back on requires the use of the tool mentioned above. Do I need to invest in this tool? Is it worth it for a once in a while use? I'm wondering if investing in the tool and taking the chance of damaging the fuel lines and related parts is worth it or might it be more cost effective for me to supply a shop with the sender/pump and let them have all the rest of the fun/problems?

Thoughts anyone??

Thanks!


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Old 08-23-2011, 08:23 PM   #15
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Do it yourself. It's not highly technical. Doesnt require a lot of costly tools and on a scale of 1-10 is probably about a 2 in difficulty. BUT, it's is much easier to do with an empty tank.

1) go get a 2 gallon gas can and fill.
2) drive till it sputters (running out of gas).
3) put enough in it to get home.

EDIT: use the emergency fuel shut off on the firewall to shut off the pump. While the engine is running.....take a pointed probe/pick and lift (push up) the red plunger, wait for engine to shut off.
4) disconnect the fuel filler neck.
5) If you can reach them, disconnect the supply and return lines
(for that I think you need the disconnect tool, my 89 uses a different system that I think they quit using in 90.
6) drop the skid plate (8 nuts/bolts).
7)Drop the tank. It's light with only 1-2 gallons in it.
8)If you couldn't do step 5, lower the tank on a jack until you can release them.
......dont forget the vent tube in the front and to disconnect the rear tube from the frame in the back.
9) Using a brass punch, remove the locking ring holding the pump/sender in place.
10) Remove the pump/sender unit and service.

Reverse
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Last edited by j. r. Nice; 08-23-2011 at 08:35 PM. Reason: release fuel pressure!!!
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Old 08-23-2011, 08:32 PM   #16
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Oh, tool is cheap and available about anywhere automotive tools are sold. Depending on mfg......$6-$12
Not a nightmare. Removing a 1999 Escort VSS is a nightmare. Simply take the tool, encircle the fuel line, near the bell shaped flange, push in on the line and them push in on the tool, (slight turning/twisting) until the line releases..

Oh yeah.......see my edit on directions above!!!!!
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Old 08-23-2011, 08:41 PM   #17
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Its not too bad, you just need the proper tool.

Something like this......


http://www.summitracing.com/parts/WMR-W83114/

You just have to close the tool around the spring fitting and shove the lip between the spring and the jacket. The first time you successfully do it you will have it down. It make take a few trys to get the hang of it though. Just be careful, all those lines are brittle and could break on ya. I would also suggest, as JR alluded to, While your in there and have the tank dropped, go ahead and cut yourself an access hole in the bed.

Here is the procedure on exactly where and how to cut it.
http://www.supermotors.net/registry/2742/33276

Just follow the sequence of pictures from Steve83's supermotors site. It walks you right thru it.
Do not attempt this with the tank still in the truck.
[IMG][/IMG]

You can get a patch panel at the bone yard, I think even a f-150 bed will suffice, but don't quote me on that.

[IMG][/IMG]


[IMG][/IMG]

Its not ugly when done right. Paint it to match if ya want. Its covered up with carpet anyway so it doesn't matter
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Old 08-23-2011, 08:43 PM   #18
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Old 08-24-2011, 09:11 AM   #19
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yo,
For a nrw patch panel (& left-over WILL BE USED in the Bronco someday for rusted out sections);

Patch Panel, 48in. x 16in. for 80-96 Bronco & F Series; $35.00 as of June 2011
Source: by Jeff's Bronco Graveyard @ http://broncograveyard.com/bronco/i-...n-x-16in-.html
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Old 08-24-2011, 12:33 PM   #20
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I prefer to pull the fuel line clip rather than use the tool Jowens showed,
YMMV?



See how that Dorman aftermarket part doesn't have the little wing on it?
That's how the original Ford clip looks after the little wing is missing off the
left fork. Just break or pull or cut it off and then work the clip out of place
with a little screwdriver, save it and reuse it if it doesn't look out of shape.

The thicker ones (usually white) are for the 5/16" fittings and the thinner
ones (usually black) are for the 3/8" fittings.

The tool Jowans posted is for sure needed on the engine's fuel rail "banjo"
type metal-fuel-fittings tho and also work on the fuel tank fittings, I just
prefer to pull the clip is all. :) Also the one-way-valves on duel-tanked
pickups will need a tool like Jowans posted.

I bought this set on sale from Autozone after the scissor-type failed me...
OEM 25182 Six-Piece Aluminum Disconnect Set

...they worked even better after my modification too! ;)

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