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Another fuel gauge issue...

V

VAcherokee

NAXJA Forum User
Location
Madison Heights
Howdy,

My 98 has had some issues recently...

I ran out of fuel with 1/4 tank left and no low fuel light. Pinpointing it down to a fault fuel level float. Since my pump would bleed down, I replaced it with what my local parts house had in stock, airtex complete assembly. After the installation, the jeep gauge went right back to where it was @ 1/4 fuel BUT, the low level light was ON. I cycled the key a few times and the gauge pegged EMPTY. I put in 5gal and the gauge went back to 1/4 (seems to favor this reading). Primed the pump and she fired up. After filling it up it went above FULL. 80 miles later, it's still above FULL.

History on the jeep: 245,000 miles, the gauge cluster does stop working from time to time but always resets after pushing on it & I have oxygen sensor heater circuit failure codes for both sensors.

I'm hoping I don't need to condemn the new pump and since the gauge WAS initially stuck at 1/4 and is stuck at FULL now that this might be a grounding issue?

Any help our pointers would be MUCH APPRECIATED.

(Disclaimer, I'm new here, my post is as through as I could get it and yes, I did a search but with limited internet, I felt posting would be easiest :) )
 
The pump itself is not going to change the fuel gauge reading.

Did you install a fuel pump OR a fuel pump module? Fuel pump module is a complete assembly with the sending unit and fuel pump plus plumbing.
 
Bump? Anyone? I was able to fix the check engine light for oxygen sensors... Chafed black wire to rear oxygen sensor.

Fuel gauge goes passed FULL when I fuel it. Old pump was stuck at 1/4, no warning light and it ran out of gas. New airtex fuel pump/module/sensing unit assembly. I've run the self test on the cluster and everything works!

I drove around 100 miles and went to fuel it up. took 7gal and the gauge showed 1 notch before the F.

Figured I'd ask again as I'm sure either someone else has had and fixed this issue OR will have this problem and can use the info.

Thanks!

98 Cherokee Sport 4dr, 4x4.
 
The fix is to get rid of that Aitex fuel pump module and replace it with a Bosch module or a Carter module.

If you are talking about a Black wire in the body harness, that's the ground circuit for both upstream and downstream O2S heaters.

If you are talking about a Black wire belonging to the O2S, that should connect to the O2S Signal wire to the PCM.

Unchafe the wire and check the O2S Heaters fuse in the PDC (pic).

It's always a good idea to make sure the grounds at ground point G101 near the ignition coil) are free from corrosion and are secure (pic). The pic will tell you why.

PDC:

1997-1999XJPDCannotated.jpg


G101:

G101.jpg
 
Thank you for the pictures! As for the grounds, I replaced the coil recently and cleaned / inspected the four grounds. I pulled my old pump assembly from the trash, I'll plug it back in and see what the gauge does with a full sweep of the float armature. I really hope it's not the dang pump assembly, again!

As for the oxygen sensors, it was the body harness black wire that was completely broken and the green body harness wire was exposed and touching the tcase... I reset the computer asks 15 miles later, still no codes.
 
Sidewinder CC said:
The fix is to get rid of that Aitex fuel pump module and replace it with a Bosch module or a Carter module.
Click to expand...

x2! the airtex pumps are known to be junk when it comes to the jeeps for some reason. they're just cheaply made pieces of crap. Put a carter in there. you can get one at NAPA (all NAPA's fuel pumps that have a part number starting with a "P" are made by carter), Rockauto.com also has good prices on the carter brand pumps.
 
GrimmJeeper said:
x2! the airtex pumps are known to be junk when it comes to the jeeps for some reason. they're just cheaply made pieces of crap. Put a carter in there. you can get one at NAPA (all NAPA's fuel pumps that have a part number starting with a "P" are made by carter), Rockauto.com also has good prices on the carter brand pumps.
Click to expand...

Chrysler actually had a recall on Airtex pumps at one time. Probably pumps installed at the stealerships.
 
Good afternoon!

I just took the OE fuel pump out and tested it against the airtex. I know my tank is full with only 10mi driven on it...

*AIRTEX INSTALLED: Beyond F On the gauge.
*FACTORY MODULE OUT OF TANK: Even float is in the E position, instrument gauge reads 1/4 full, no low light. When I put it at 1/2 level, gauge went a bit beyond 1/2. When float was put to FULL, gauge goes passed FULL just like the airtex... I also noticed if I cycled the key on and off with the OE module float at E, the gauge would vary from 1/8 - 1/4 fuel level again without a warning light.

I'm thinking it has to do with a grounding wire from pump to IC or Ecu or IC CLUSTER gauge is bad?

Thanks!
 
Did you say you did the instrument cluster actuator test? Like this:

(1) Begin the test with the ignition switch in the Off position.

(2) Depress the trip odometer reset button.

(3) While holding the trip odometer reset button depressed, turn the ignition switch to the On position, but do not start the engine.

(4) Release the trip odometer reset button.

(5) The gauges should cycle through their ranges, stopping at intermediate readings, going up and going down, at two second intervals. The indicator lamps should cycle on and off.

(6) The instrument cluster will automatically exit the self-diagnostic mode and return to normal operation at the completion of the test, if the ignition switch is turned to the Off position during the test, or if a vehicle speed message indicating that the vehicle is moving is received from the PCM on the CCD data bus during the test.

If there is a malfunction in the instrument cluster gauges it will show
up during this test.

~~~~~~~

The PCM puts the low level advisory light on (based on the voltage signal
from the fuel level sensor). It should come on when the
fuel level gets to approximately 15% of the fuel tank capacity.

There is no seperate grounding wire from the fuel level sensor to the PCM.


 
Correct. I ran the IC test, it passed. I remember when I installed the new AIRTEX pump, the fuel gauge was at E with the light on... I'm so lost. If there isn't a separate ground from pump to cluster, what else would cause the cluster to read beyond F? I verified the gauge does go to E when the pump assembly is disconnected from the body harness... I'm stumped! :repair:
 
VAcherokee said:
Correct. I ran the IC test, it passed. I remember when I installed the new AIRTEX pump, the fuel gauge was at E with the light on... I'm so lost. If there isn't a separate ground from pump to cluster, what else would cause the cluster to read beyond F? I verified the gauge does go to E when the pump assembly is disconnected from the body harness... I'm stumped! :repair:
Click to expand...

I take it that your fuel quantity indication worked properly before you changed the fuel pump...correct?
 
VAcherokee said:
No sir, gauge never worked as designed. I ran out of gas with the gauge at 1/4, no warning light.
Click to expand...

Ouch.

Looks like we are beating up on the poor Airtex pump module for no reason.

If the instrument cluster actuator test shows the fuel quantity gauge works okay and your old fuel sending unit shows that the problem still exists from BA (Before Airtex), then we have to ASSume there's a wiring problem between the sending unit and the PCM. You'll have to do some testing.

Couple of questions:

1. There are three connectors close by each other at the tranny dipstick tube. One for the transmission range sensor (NSS), one for the tranny ISS/OSS and solenoids, and one called C107. One of the fuel level sensor wires, Sensor Return/Ground, goes through C107. Were any of these connectors distrubed in the past, or is there evidence that they are oil soaked, or otherwise contaminated? Are they secure?

2. Both sensor wires go up through the cargo bay floor and travel forward on the left side of the body through a harness loom to under the dash. Was there any work done on the cargo bay floor that would have disturbed these wires? Were any mods or repairs done along the way that would have drilled into the harness, or pinched the wires, along the left side of the Jeep?

3. The two sensor wires that go under the left side of the dash go to connector C100, which is located on the far left side of the dash. Did you replace the HVAC Unit in the past where wiring under the dash was disturbed?

4. The two fuel level sensor wires leave C100 and go into the engine bay on its way to the PCM. The Sensor Return/Ground wire goes through two splices in the harness along the firewall, one before C107 and one after C107. Were any repairs done to the wire harnesses along the firewall?

5. Was the PCM ever replaced?
 
Fricken awesome info right there brotha! I just bought a cluster at the pick n save yard. Worst case, I have a spare. Lol I'll update after I check the connectors. Honestly, I've had this jeep a few weeks. Been a project in the works. So far, I'm glad to have another one!
 
Figuring I'll hit all the connectors with dielectric grease, I'll plug in the new IC and if it works, I'll pull it apart, clean it and restore the needles to neon orange (thanks to my teenage daughter) Here's hoping to a long life of accurate fuel levels!

On a side note, the cluster I got at the junk yard has a RECERTIFICATION decal on it dating back to 2003. I'm assuming that's a good thing?
 
Fuel gauge is still incorrect with the new cluster... I was able to clean up and paint the needles on the junk yard cluster, looks GREAT and my Cherokee list 135,000 Mike's with the new cluster!

Of I go with the plugs mentioned above.
 
VAcherokee said:
Fuel gauge is still incorrect with the new cluster... I was able to clean up and paint the needles on the junk yard cluster, looks GREAT and my Cherokee list 135,000 Mike's with the new cluster!

Of I go with the plugs mentioned above.
Click to expand...

Why did you replace the Instrument Cluster? I thought you said you did the Actuator Test and the fuel gauige worked okay.
 
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