Question about GMC K3500

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Replaced sender unit in driver side tank with 0-95 ohm. Still only reads a little over 1/4 tank when full. What is causing this ???

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An inhibited float would cause this condition.. or a bent control arm on the sending unit...

Posted on Sep 28, 2010

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Trouble shootfuel guage94 jeep cherokee


gauge stuck high or low or"??????????????
how to ?
with no tools or with ?
got meter? or nothing.?
is tank full now, empty?
knowing that we can check the sender.
using an OHM meter, dmm set to resistance
unplug sender and check its ohms to ground.
infinity reading is bad sender
btw at 63ohms the sensor is at, cause the low fuel lamp to glow.
page 8e-6 in the factory manuals shows doing all this.
its in every jeep book in print. XJ jeep.
8e-23 shows.
empty tank is 105 ohms
1/2 full is 33 ohms
and full is 5 ohms.

first is fuse good to cluster, do all other guages work?
then unplug C203, below near tank
see that wire,DB, (dark-blue)
measure it to with ohm meter, must read 5 to 105 ohms
if not and is why too too high .
unplug C307, and measure black to VT, (violet?)
100 to 5 homes if ok now, the ground wire there is rusty.
if not ok, the sensor is toasted.
if all this check ok.
then at c203, DB wire ground that wire,
and gauge must go to fULL key on,
if not . the DB wire is bad, or custer guage, bad,
if this test fails we do this same grounding test
at the actual gauge. if fails, gauge is bad.



26337223-lfvi2b44iwkqit5d2rqve4gf-5-0.jpg

Nov 02, 2016 | 1994 Jeep Cherokee

1 Answer

Tank empty, gauge reads 1/4, tank full, gauge reads full, tank 1/4 full, gauge reads 1/2. Engine off, gauge reads below empty. Any ideas will be welcome.


The values differ in all types of cars. Older cars peg out at 90 ohms. Newer cars range between 0 and about 400 ohms. Dis-connect the connector at the sender. Ground the sender wire and the gage should read empty. un ground and it should read full. They use a ceramic resistor in the tank that usually go bad.

Jan 09, 2015 | Cars & Trucks

1 Answer

How to fix fuel guage


ZJ
what does it do now? stuck high, low. ,read off a bit. ? or what?
the tests are easy.
covered in the FSM 100% ( in a bad way)
see that here in chapter,called, "instrument panel"
chapter 8E.
page 5
as you can see the gauge is digital (CCD)
and the PCM (engine controller) sends fuel data to the gage via
the CDD data bus.
so the sender , may be telling the PCM wrong information.
I'd start there.
if your read page 5 it tells you the PCM sends, Empty stop data
to the gauge when the sender messes up.? DID YOURS?
does your low fuel warning lamp still work?
if not, that is clue 2 that the sender is BAD. if dead lamp.

that means sender bad, or wires TO it are bad, as in all cases, electrical..
In a real Jeep dealer, they use the DRB tool and read the sender
data directly and in 1 second, ahhh, it reads wrong.
then find the cause.
but us poor, sand crabs, we dont have DRB scanners.
we are not blessed.

but we are not helpless, not yet.
see the last chapter "wiring", see the fuel page. #
8w=20-3 (pdf 69)
see the sender
see the 2 wires,
see the colors. bingo.
what i do is, inplug the PCM (battery neg lug, disconneted)
the measure the resistance of the 2 wires.
DB-LG and BR-YL
PCM C2 -A4 and C1-c26

the sender is JUST a crude Rheostat (a wire wound var. resistor)
0 ohms (near is full) 100 (near is empty)]
if it reads infinity the line is bad. wires, connector all the way to the sender.

old data on older jeeps 86
73 ohms Empty 23 ohms 1/2 tank 10 ohms Full

1998
With float in up position, resistance should be 20 ohms. With float in down position, resistance should be 220 ohm
i dont have spec. on all years.
but it dont matter.
its near zero full
and near 100 to 200 empty
and infinity dead, they all wear out and go open circuit some day.
or the connector rusts 100:1 . over bad sender.
corrosion is no rare thing on cars.

1997 TJ
20 ohms - full
220 ohms - empty.

im scanning the internet finding others data.


96 GC

The same wires can be tested on the pump side to measure the resistance of the sending unit. A low resistance of 20-30 ohms would indicate a full tank and an empty tank should be around 260-300 ohms. If the sending unit resistance tests higher or open circuit the sending unit is bad.

Apr 28, 2014 | 1996 Jeep Grand Cherokee

1 Answer

GAS GAUGE STUCK ON FULL


well its not connected>? or you forgot to ground the ground wire?
if you had a DMM meter , this would be easy,
you can measure the sensor ohms, at any time with tank in car.
and id have never put back any tank with out checking it first.
not me, pulling tanks is no fun.
and empty tank the gauge sender is at max ohms, (lever down)
so is about 100 ohms and 10 ohms full (ball park) RTM
read the FSM read alldata.com
heck the FSM has a flow chart for these tests. amazing huh?
i dont use it, i use my meter and ohms law.
ill now look online at alldata.
the only think complex is which of 2 systems it is,
in the late 90s most cars changed. to indirect way.
ok , i looked, your car is direct way, (cave man)
its just 2 parts, a gauge and a sender. (sure wires)
the sender is grounded at G751
if the dash temp guage works , then the fuse is not blown , fuse 1.

the tests are cave man simple , all FSM show this.

1: unplug the Yellow/Blue sender wire, at any point
from front (gauge) to sender, any place, there are many.(4 junctions)
now, on the upstream side, key on, and ground this pin for 1min
max, if guage moves pull the ground. (i use $#194 lamp for tests )
i connect my lamp to ground and the other side to the guage,wire.
then key on and see guage move. bingo gauge is 100% good.
cave man easy. (

now the sender.
i measure the ohm.
DMM on 200 ohm scale if manual meter.
i connect black meter to body ground (shiny steel not plastic)
i connect red lead to down stream wire above..Yellow/Blue
it must read 100 ohms empty
not 0 ohms.
not infinity.
if read infinity? the wire is cut, or gound it open or the sender is bad.
if reads 0, the wire is grounded to the body or the the sender is bad (shorted)
do not take my facts on ohms as verbatim,
read the FSM and get the facts.

but i think your tank sender wire is shorted to ground.
some gauges work backwards, and my poor online version
dont cover this. well.
unplug the sensor does guage go full or empty?
most go empty, but not all.
use the lamp to test the gage, get to swing both ways
with lamp to ground and with lamp and wire disconnected.
cheers.

















Dec 02, 2013 | 1997 Acura CL

1 Answer

I have a 1992 Mercury Grand Marquis Ls with a fuel gauge that does not work (gauge may be reversed)??? help please.


The fuel level indicating system is a magnetic type system, which consists of the sending unit located in the fuel tank, an anti-slosh module located on the back of the instrument cluster, and a fuel gauge located in the instrument cluster. The sending unit changes resistance according to the level of fuel in the fuel tank, which varies the current flow through the gauge.The pointer position varies proportionately to the current flow. In this system, the sending unit resistance is low (22 ohms) when the fuel level is low and high( 145 ohms) when the fuel level is high. The pointer of the magnetic gauge remains in position when the ignition is turned to the Off position. On some models, an anti-slosh module is used to dampen out fluctuating fuel signals from the sender. Some vehicles are equipped with a low fuel warning indicator. The anti-slosh module will also actuate the low fuel indicator when the fuel level in the tank reaches 1/16 to 1/8 full.


Do your other gauges/warning indicators work properly with the ignition on? If not, check for power at the fuse panel/fuses.

If they do then partially remove your cluster with connector still installed and check for voltage at cluster connector and gauge. Check continuity of cluster and gauge for ground.

Sometimes the anti-slosh module (if installed) goes bad in the Grand Marquis but not likely.

Sender troubleshooting:
  1. Perform test with resistors as follows:
    1. Disconnect wiring connector at sender unit, then connect resistor between gauge lead and a suitable ground.
    2. Turn ignition switch to On position.
    3. With 145 ohm resistor, the gauge pointer should contact the Full mark.
    4. With 22 ohm resistor, the gauge pointer should contact the Empty mark.
  1. Perform test with fuel sender of known quality as follows:
    1. Turn ignition to Off position.
    2. Disconnect wiring connector from sender and connect it to test sender.
    3. Move float rod away from fuel filter against Full stop position. Wait approximately 30 seconds, then turn ignition switch to On position. The gauge should read on or above the Full mark.
    4. Move float rod toward fuel filter against Empty stop position. Turn ignition switch to Off position. Wait approximately 30 seconds, then turn ignition switch to On position. The gauge should read on or below the Empty mark. If gauge works properly replace sender, which involves dropping fuel tank.

Mar 23, 2013 | 1992 Mercury Grand Marquis

1 Answer

Ford ranger 1988 gas gauge dont work


the fuel sender and the gauge needs to be checked. the wires run along the driver side frame rail. inside of the wire loom, look for a yellow wire w/ a red or grey stripe. test it with a ohm meter. the resistance reads between 240 ohms(empty) to 70 ohms(full). if you test and find reading betweeen 240 & 70 ohms, safe to say that that sender in the tank is fine. if you ground that wire directly to the chaasis, the gauge should max out to full. Good luck.

Feb 10, 2011 | Ford Ranger Cars & Trucks

1 Answer

Fuel gauge stays at 3/4, after fill up


fuel gauges work using a variable resistor. Typically, when the fuel level is low, the fuel level sender is working at a high resistance. When the tank is full, the sender is working with a low resistance. Anything that increases the resistance in the circuitry will lead to a false low reading. Dirty or corroded wire terminals in the fuel sender circuit would raise the resistance. If you can remove the fuel sender unit from the tank, you can use an ohm meter to check its resistance. When the float is low, you should see a resistance of around 100 ohms. When the float is up (tank full) you should see a low resistance of about 2-5 ohms.

Jan 29, 2011 | Subaru Outback Cars & Trucks

2 Answers

Fuel gauge not working all the time.


This is a normal concern.
The instrument cluster uses 4 different operating modes to calculate the fuel level:
Anti-slosh (default mode)
Key OFF fueling
Key ON fueling
Recovery
After a fuel fill up, the time for the fuel gauge to move from empty (E) to full (F) ranges from 2 seconds to 55 minutes depending on which operating mode the fuel gauge is in.
The default fuel gauge mode is called the anti-slosh mode. To prevent fuel gauge changes from fuel slosh (gauge instability due to changes in fuel sender readings caused by fuel moving around in the tank), the fuel gauge takes approximately 55 minutes to go from empty (E) to full (F).
The key OFF fueling mode (2 seconds to read empty [E] to full [F]) requires 3 conditions be met:
The key must be in the OFF position throughout the entire refueling of the vehicle.
At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
The instrument cluster must receive a valid key ON fuel sender reading within 1 second of the key being put into the RUN position. The key ON sample readings are considered valid if the fuel sender reading is between 15 ohms ± 2 ohms and 160 ohms ± 4 ohms.
If these conditions are not met, the fuel gauge stays in the anti-slosh mode, which results in a slow to read full (F) event.
The key ON fueling mode (approximately 90 seconds to read empty [E] to full [F]) requires 3 conditions be met:
The transmission is in PARK (P).
The key is in the RUN position.
At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
In key ON fueling mode, a 30-second timer activates after the transmission is put into the PARK (P) position (automatic transmissions). When the 30-second time has elapsed and at least 15% of the vehicle's fuel capacity has been added, the fuel gauge response time is 90 seconds to read from empty (E) to full (F). When the transmission is shifted out of PARK (P), the fuel gauge strategy reverts to the anti-slosh mode. The key on refueling mode prevents slow to read full events from happening if the customer refuels the vehicle with the key in the RUN position.
Recovery mode is incorporated into the instrument cluster strategy to recover from a missing fuel level input during a refueling event. Missing fuel level inputs result from intermittent opens in the fuel sender or its circuits. Recovery mode (empty [E] to full [F] approximately 20 minutes) is initiated when the following 2 conditions are met:
The instrument cluster is in the anti-slosh (default) mode.
The actual fuel level in the tank is greater than what is being displayed by the fuel gauge

Feb 18, 2009 | 1983 Mercury Grand Marquis

1 Answer

1989 Saab 900 low level fuel light


You don;t say whether the fuel gauge is reading accurately, or whether it's always on empty. If the gauge is always showing empty, it's most likely a problem with the sending unit in the fuel tank. Check the resistance across the two terminals of the sending unit.

On a C900, the fuel sender level unit is separate from the fuel pump and located on the right side top of the tank, accessible by removing the trunk floor lift up panel (the pump is located on the left side top of the tank.
Possible problems are: electrical line off or broken, float not working (it's fairly delicate); or gauge not working.

Test the resistance of the sending unit with the lines disconnected, the resistance should be 2.6 to 3.8 ohms full tank, 63.3 to 67.5 ohms empty tank; and test for voltage across the top of the sender unit, if no voltage, that's likely the problem!

If the gauge is otherwise reading accurately (showing 'full' for a full tank, etc) then the problem is likely a gauge malfunction and can be simply replaced.

Good luck!

Saabreur

Jul 10, 2008 | 1989 Saab 900 4 Door

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