Fuel Gauge stuck on full

[DeniseRV]

On our 2002 Fleetwood Southwind 32VS, F53 chassis, the fuel gauge always shows full, except when engine is turned off. With engine off, needle goes to empty. RV runs/operates fine otherwise. This just started happening after using the RV for 2 1/2 years (purchased it in 2016). Looking at the chassis doc, there do not appear to be any fuses associated with the gauge. We found no loose wires under the dash but cannot access the area directly under the gauge. Any advice on how to fix this or ideas on where to start troubleshooting? I did see an online post that we should check the sender wires. Would those be on the fuel tank? I'm guessing we would have to crawl under the rear section and try to find the wires somewhere on the fuel tank? Does anyone have pictures/diagrams that would help? I am not a mechanic at all, so apologies for any dumb questions... also this is my first post since joining rv.net. Thanks in advance for any help fellow members can provide.

[Gdetrailer]

enblethen wrote:
DFord: that is if his needle is pegged and not just full. If pegged, then yes, it could be open circuit. If just showing full, then odds it is a stuck float assembly.

YEP, IF "pegged" (IE, WAY ABOVE FULL) then an "open" circuit or broken wire would be more likely the fault.

IF needle is NOT "pegged" and simply is at or near the NORMAL full tank position the OP is used to then it is MORE likely the SENDER FLOAT STICKING.

The OP HAS NOTHING TO LOSE BY TAPPING ON THE TANK AS I MENTIONED BEFORE TEARING INTO WIRING HARNESS!

In fact, with that age it is BEST to minimize disturbing the harness and connectors as much as possible.

I have experienced the sender float hangups multiple times on a 2003 Ford, comes with age and buildup on the float assy over time, often gets worse when the vehicle SITS for LONG PERIODS OF TIME LIKE A MOTOR HOME DOES.

[enblethen]

DFord: that is if his needle is pegged and not just full. If pegged, then yes, it could be open circuit. If just showing full, then odds it is a stuck float assembly.

[DFord]

wa8yxm wrote:
By the way I forgot to tell you how to test if the issue is internal or external to the tank.

Disconnect gauge lead from tank connection. if the gauge now reads EMPTY it's in the tank (Sender stuck float) and may be expensive

Still reads full trace the wire back and find the fault. 10 cents worth of electrical tape or if close enough to the end heat shrink tubing .

And again I repeat - if the gauge shows full, the signal from the sensor is not getting back to the tank. The wires are cut in some fashion.

If you have no sensor, the gauge will show FULL!

[SidecarFlip]

If nothing else, use your tripmeter to ascertain mileage and fill when needed.

[wa8yxm]

By the way I forgot to tell you how to test if the issue is internal or external to the tank.

Disconnect gauge lead from tank connection. if the gauge now reads EMPTY it's in the tank (Sender stuck float) and may be expensive

Still reads full trace the wire back and find the fault. 10 cents worth of electrical tape or if close enough to the end heat shrink tubing .

[DFord]

PaulJ2 wrote:

wa8yxm wrote:
Stuck float or short on the gage line.. For the most common gage those are the only options. There is one other gage style but the fact that it moves to zero when you turn off suggests you don't have that one (it does not move when turned off).

X2 short to ground gauge reads full, an open on the wire gauge reads empty.

Read my post above!!!!!
Unless Ford reversed what it did in 2000, high resistance (over 160 ohms like an open circuit) drives the gauge to FULL. Shorting the wires together (20 ohms or less like a short) will show on the gauge as an EMPTY tank!

[enblethen]

There is normally a connector near the fuel tank. Locate it and separate tosee if gauge changes.

[PaulJ2]

wa8yxm wrote:
Stuck float or short on the gage line.. For the most common gage those are the only options. There is one other gage style but the fact that it moves to zero when you turn off suggests you don't have that one (it does not move when turned off).

X2 short to ground gauge reads full, an open on the wire gauge reads empty.

[wa8yxm]

Stuck float or short on the gage line.. For the most common gage those are the only options. There is one other gage style but the fact that it moves to zero when you turn off suggests you don't have that one (it does not move when turned off).

[Dick_B]

When I had my old VW bug which did not have a fuel gauge I would just keep track of the miles from the last fill up and I never ran out of fuel. Of course, it helps to know what your mileage rate is. Mine is between 8 and 10 mpg depending on whether we are driving into the wind or with the wind.

[DFord]

Referring back to a post I made in Sept 2001 wrote:
The fuel sending unit is a variable resistor controlled by the action of a float arm. When the fuel level is low, resistance in the unit is low (Empty = 17 ± 2 ohms). When the fuel level is high, the resistance is high (156 ± 4 ohms).

Wire number 1203 (BK/LB) is connected through connector C441 (Left rear of vehicle) and C1046 (Inside left frame rail, near 4WABS module) to G204 Ground (Lower left corner of support [fire] wall. Wire 29 (YE/WH) is the signal going through connector C441 (Left rear of vehicle), C1046 (Inside left frame rail, near 4WABS module), C141 (Lower left corner or dash) and C205 (Left of steering column, behind I/P) to the Instrument Cluster.

At the time, I had a 2001 Residency. The gas gauge quit working soon after I bought it. I had to by pass the wires to the sending unit when I figured out there was no connectivity between the dash and the tank.

After I dropped the tank and check the ohm readings on the sending unit, put it back in and raised the tank back up, the engine wouldn't run because the fuel pump wasn't pumping. I dropped the tank again and pulled out the pump. I found the Siamese 1/4 inch spade connector on the pump had lost its tension and burned up the connector. I cut the connector off the end of the wire and replaced it with individual 1/4 inch spade connectors. I put another 40,000 miles on it and the fuel pump was never an issue again.

Back to the sending unit. I traced the wires along the frame rail. There was a connector close to the tank. When I shorted it nothing happened. The gauge should have gone to empty but it stayed on full. I found another connector alongside the emergency brake. When I shorted the wires there, the tank went to empty. I knew then the wires lacked connectivity between that connector and one near the tank. I bypassed that wire and the gauge worked great afterwards. I never replaced the sending unit or the fuel pump during the 16 years I owned it.

When the gas line to the generator started sucking air later on I wasn't going to drop the tank again. I had a pass-through compartment above the gas tank so I cut a hole though it to expose the tank and sending unit/fuel pump flange where the generator gas line comes out. It was a tight squeeze to get at but it was a lot easier than dropping the tank again.

I saved these notes - they pertain to the wiring diagram I had for my 2000 vintage F53 chassis and helped me locate the wires to the tank:
Wire number 1203 (BK/LB) is connected through connector C441 (Left rear of vehicle) and C1046 (Inside left frame rail, near 4WABS module) to G204 Ground (Lower left corner of support [fire] wall. Wire 29 (YE/WH) is the signal going through connector C441 (Left rear of vehicle), C1046 (Inside left frame rail, near 4WABS module), C141 (Lower left corner or dash) and C205 (Left of steering column, behind I/P) to the Instrument Cluster.

[Gdetrailer]

Yep, can be pricey for fuel pump and sender IF you can find one, Motor Homes tend to make this even more of a challenge since tanks are often much different than say the pickup version..

However, many stepvans use the same chassis as motor homes so, perhaps you might be able to find a stepvan sender and fuel pump that will work..

A good source for stepvan parts is MILL SUPPLY INC

HERE is a link to their Stepvan fuel tanks, pumps and senders..

[enblethen]

Just went through similar issue with fuel gauge.
Gdetraier option two may knock the float loose from what every is holding it.
In my case it would stick at about 1/2 tank. The float rides on a open resistor to change fuel level.
Hitting it did not work! after draining nearly all the fuel, I was able to see movement in the fuel gauge.
I decided to fix it correctly. Took to my heavy repair facility. Resistor was rubbed to the extent it snagged the arm. Tried to get exact replacement. Parts houses said this is the one, wrong my tank is 15 inches deep, replacement is 12 inches.
Had the shop modify the complete assembly that came out of tank. New float mechanism, and most important a new fuel pump.
Tank your heart medicine as in my case expensive! Trace over $1000.

[MEXICOWANDERER]

If the rig has more than 60K miles on it, replace the fuel pump as well if the tank must be dropped. A floor transmission jack works best.