NAXJA Forums -::- North American XJ Association  

Go Back   NAXJA Forums -::- North American XJ Association > NAXJA Unibody Jeep Technical Forums > Jeep Cherokee XJ (1984 - 2001) > OEM Tech Discussion
HOME Member FAQ Sponsor Info Rules Bylaws E-Mail

OEM Tech Discussion Forum for OEM (Original Equipment) or stock XJs and MJs.

Reply
 
Thread Tools Display Modes
  #1  
Old May 8th, 2017, 07:56
tjmotter tjmotter is offline
NAXJA Forum User
 
Join Date: Sep 2011
Location: Houston
Posts: 333
'90 XJ Fuel Gauge acting up

Looking for insights on where to look for an issue with a '90 XJ 4.0L.

Symptoms:
- when full, the fuel gauge seems to act normally
- at 3/4 of a tank, the gauge shows full
- at 1/2 tank the gauge shows a little less than full
- at 1/4 tank the gauge still shows a little less than full but will randomly peg the needle almost to the bottom of the gauge, back off and then do it again

Not the best way for me to recognize I need to fill up ;-).

This is a new issue. The gauge has worked perfectly up to now. This vehicle is very lightly used (maybe 500 miles per year) and can go months without starting. I keep it on a battery tender and locked up safely in a garage so there is no exposure to the elements.

Not sure where to start on this one. My initial thought was to remove the gauge cluster and clean all the contacts but when I first bought this XJ, it was very tough to start and I found that the short rubber hose that connects the fuel pump to the outlet in the tank had come loose causing a fuel pressure issue. I am probably over thinking this since the XJ runs like a dream but am wondering if this problem has re-occurred causing a high pressure flow of gas to hit the sending unit when the tank is low.

Pulling the pump is my last resort. Hoping y'all can give me some ideas on other areas to check.

thx
Reply With Quote
  #2  
Old May 8th, 2017, 08:19
RCP Phx RCP Phx is offline
NAXJA Forum User
 
Join Date: Mar 2003
Location: Phoenix,Az
Posts: 10,572
Re: '90 XJ Fuel Gauge acting up

Sounds like the typical old sending unit !!
Reply With Quote
  #3  
Old May 8th, 2017, 08:43
Green Mesa XJ's Avatar
Green Mesa XJ Green Mesa XJ is online now
NAXJA Forum User
 
Join Date: Aug 2004
Location: Pensacola, FL
Posts: 1,050
'90 XJ Fuel Gauge acting up

The especially early xj senders could be a bit random. I'm not sure anything is actually wrong.

The plugs to back of the cluster can tarnish, an eraser can help renew them.
I've never had this fix work because my 85's sending unit was the problem, found a 86 unit NOS and then had to redo the plug to match the new sender which led to other wiring troubles.

If it's suddenly wonky maybe there is tarnish on one end, sender or cluster. My experience is the wires going to the cluster are usually ok, body harness from under the passenger seat to the plug near the fuse box are usually ok.
Oh, I think there is a ground that affects the sender in the body panel behind the spare tire.
After 30 years mine didn't look bad at all. But others have had problems with it.

Thing is even with a lot of NOS parts and new (used ) dash harness , best I can get it the fuel gauge is still twitchy, which is a lot better than it was when I first got it. For example it would randomly twitch just sitting at idle. Almost like it was the jeeps pulse.

New sender is a lot better but as the tank sloshes it can jump around more than any other car I've owned.


Sent from my iPhone using Tapatalk
Reply With Quote
  #4  
Old May 8th, 2017, 10:03
Hypoid's Avatar
Hypoid Hypoid is offline
NAXJA Member
 
Join Date: Jul 2006
Location: Golden, CO
Posts: 6,999
Re: '90 XJ Fuel Gauge acting up

Drive it over some washboard roads with the tank less than half full and see what happens.
__________________
The Lost Boys' motto: We don't know where we are going, but we'll be there for awhile...
Reply With Quote
  #5  
Old May 8th, 2017, 22:45
clydefrog's Avatar
clydefrog clydefrog is offline
NAXJA Member
 
Join Date: Aug 2015
Location: Northern California
Posts: 388
Re: '90 XJ Fuel Gauge acting up

Dump some cleaner in the tank with a full tank of quality fuel and see if that helps. My '87 had probs with the gauge cluster (corrosion or rather lose of contact with the contact board/sheet). From what your explaining though I bet your sending unit is tarnishing.
__________________
'87 with over 300k miles, and a CA legal LS swap.
Expedition built: http://www.naxja.org/forum/showthread.php?t=1129315

When you want to be someone you drive a lifted JK, when you already know who you are you drive an old XJ.
Reply With Quote
  #6  
Old May 8th, 2017, 23:17
blu3fan's Avatar
blu3fan blu3fan is offline
NAXJA Forum User
 
Join Date: Apr 2009
Location: california
Posts: 198
Re: '90 XJ Fuel Gauge acting up

My sending unit is trashed.
but I am a lucky one. it works enough that its not worth replacing yet... the replacements get expensive. I think like $200.
1/2 tank is full to 1/4
anything less than half a tank is less than 1/4
and the fuel light. means 2 more gallons.




I am still looking for one better than mine.
but I would suggest a junkyard run.
they always seem to be gone by the time I get there tho.
wonder why... $$$$

Last edited by blu3fan; May 8th, 2017 at 23:21.
Reply With Quote
  #7  
Old May 9th, 2017, 08:34
8Mud's Avatar
8Mud 8Mud is offline
NAXJA Forum User
 
Join Date: Sep 2003
Location: Central Germany
Posts: 8,367
Re: '90 XJ Fuel Gauge acting up

If it is constantly reading higher than the tank level at the gauge, I'd start at the instrument cluster contact strip and try to clean the connectors front to back. Then check the ground at the pump. Cleaning that contact strip is a TSB.

The higher the resistance the higher the fuel gauge reads on Renix (and even some YJ's).

Should read 88 ohms full tank, 0 ohms empty tank. If you check it at the pump and make sure your ground is good, it should tell you if it is in the connectors or the sending unit.

I forget the exact count but around 4-5 connectors between the cluster and fuel pump module and a couple in the ground circuit. Note: if you ever have occasion to try and troubleshoot that circuit the wire colors change in the middle and then change back again at the end. Which gave me fits the first time I tried it.
Reply With Quote
  #8  
Old May 11th, 2017, 12:03
tjmotter tjmotter is offline
NAXJA Forum User
 
Join Date: Sep 2011
Location: Houston
Posts: 333
Re: '90 XJ Fuel Gauge acting up

Quote:
Originally Posted by 8Mud View Post
If it is constantly reading higher than the tank level at the gauge, I'd start at the instrument cluster contact strip and try to clean the connectors front to back. Then check the ground at the pump. Cleaning that contact strip is a TSB.

The higher the resistance the higher the fuel gauge reads on Renix (and even some YJ's).

Should read 88 ohms full tank, 0 ohms empty tank. If you check it at the pump and make sure your ground is good, it should tell you if it is in the connectors or the sending unit.

I forget the exact count but around 4-5 connectors between the cluster and fuel pump module and a couple in the ground circuit. Note: if you ever have occasion to try and troubleshoot that circuit the wire colors change in the middle and then change back again at the end. Which gave me fits the first time I tried it.
AWESOME! thanks!! I will measure it on Monday when I get back to the XJ. Your note and the one below on the possibility of tarnish build up have me thinking. The tank is currently full so I will look for 88ohms but when it starts acting up again, I will put the meter back on it. I only use the XJ occasionally and then only for short trips. A tank of gas can last me 6-8 months. It is possible (even likely) that sitting for so long could have caused a tarnish build up on the sending unit wires causing it to give bad readings. It is also possible that when it got below 1/4 tank (which is where I would estimate it was when I filled it last week), it hits a spot where the tarnish had coated the sensor wire to the point that it gave readings much higher than 88 ohms which would explain the gas gauge pegging.

I think I will also throw a bottle of Seafoam in the tank to see if it clears it up.

I should add that I completely rebuilt the XJ a couple of years ago. At that time I stripped it to bare metal, fixed a couple of rust spots and repainted it. I know that I checked the chassis ground at that time so I am sure it is still good.

thanks again!
Todd
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
temp gauge acting crazy rockreadyyj OEM Tech Discussion 10 October 5th, 2008 16:50
bad fuel gauge alek21 Modified Tech Discussion 1 June 12th, 2008 08:59
fuel gauge and pump acting up? MoparManiac OEM Tech Discussion 3 September 30th, 2006 13:48
Fuel gauge '91+ XJ Mar Wanted: Private Party Only 0 October 28th, 2003 14:21
Temp Gauge acting screwy RedJeepXJ OEM Tech Discussion 7 October 2nd, 2003 18:28


All times are GMT -7. The time now is 18:45.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
NAXJA and NAXJA logo's Copyright NAXJA. All content/images Copyright NAXJA 1999-2014