1999 Grand Cherokee Lerado 4Lt Auto

[nallyrt]

Originally Posted by turbomart

A lot of mechanics say stuff like that , not just about Jeeps either, its just fear of the unknown.They know cruisers & patrols so they say go them.Cruiser & patrols have just as many (if not more) problems of thier own.
Gotta say, you havent attacked this problem from a logical progressive way, although we all do that sometimes, get convinced we know the problem & waste lots of time chasing phantoms.
First step is gather info, ie get codes using key on off three times trick.Then replicate fault if possible, then fault find when faults present, ie spark or fuel inj. pulses present (use noide light or diode).Fuel press. is easy to check & any half decent mech should be able to do it.
Electrical interference from phone towers is highly unlikely to cause fault while running, it will cause radio frequency remotes (all car type remotes) to play up, ie lock/unlock.

First of all my mech I spoke about is from what I worked out old school I guess being he is not into all the electronics cars have today,
As for attacking the problem from a logical perspective, well I guess I must not be logical.
And yes I am guilty as charged in chasing phantom. In relation to using the 3 by key cycling process, in the 1999 Cherokee this from personal experience and the Manual does not work.
Reading codes when the problem is repeated I have now done this three times while driving and while stationary with motor RPM at between 1800 and 2000 and also at idle rpm.
No codes come up with any of these tests.
So back to trial and error I guess. The fault as it stands. When motor is running runs fine until stall out, no codes, motor idles fine as it is suppose to no rough idle, when stalls no codes.
Fuel tank is coming out this weekend; pump is going to be changed out with new one. Oh I am also going to manufacture an inspection port hole to access the pump without having to remove the tank each time.
One last thing you said as quoted (use noide light or diode). I did research on Noid lights, found they are just led lights or similar used to check if power is reaching the injectors, never heard of these before.

OK it was me I did not complete the three key on of cycles correctly, so I was wrong WJ Cherokee's do! Do it, it comes up was one code, P0320 Crank position not sensed during last cranking

Am I right in thinking this comes up because the engine was not cranked over there by position not sensed during three key on of process?

[shyslider]

i have done the 3 key test also as my car is running rough, the dials move and the trip counts through to 9 but then nothing, how hard is it to remove the tank? i want to clean the pick up and also might aswell change the fuel filter/reg im on the hunt for a spare injector for a test if someone has 1

[nallyrt]

[QUOTE=vk2jdh;1141553]

Originally Posted by nallyrt

Last week it happened again this time it was worse, the fuel gauge went to empty from around half a tank reading,
QUOTE]

Did any other instruments fail at the same time? If only the fuel gauge I would be checking the wiring and earthing around the fuel pump and connector. Also I be getting a pressue /flow test done on the pump .

How's your battery/alternator output voltage and earthing? I'd also get that checked.

But first get the DTC (codes) out and see what they are telling you.

Earthing all checked from bumper to bumper, fuel gauge only once went to zero; all other tests resulted in no instrumentation faults. Battery New Alternator charging as per manual requirements, however it is also controlled by the computer. No Codes come up as faults. As for pressure and flow test no not as yet have been trying to get a system that dose both to no avail at this point. Will be doing this on the weekend provided I get the test equipment required, or will just change out pump, worst case scenario will have spare working pump. Note; as for flow, all lines have been checked to the best of my ability no crushed lines to or from the injectors and air flows through with no resistance when disconnected both ends. Fuel filter replaced already as well.

[nallyrt]

Originally Posted by shyslider

i have done the 3 key test also as my car is running rough, the dials move and the trip counts through to 9 but then nothing, how hard is it to remove the tank? i want to clean the pick up and also might aswell change the fuel filter/reg im on the hunt for a spare injector for a test if someone has 1

With my Cherokee I have an aftermarket tow bar system, so bumper needed to be removed, then tow bar, then disconnect fuel lines from filter and to tank and the electrical connection was a real pain, to work it out took ages, as did the push on connectors on the fuel filter/ regulator. Laying under the car it was difficult to reach the whole job is really a 2 man job by rights.

Wear safety glasses while under the car as dirt dose fall while working under there.

Once all the connectors were disconnected the rest was easy, Oh a side note, My Cherokee had an anti siphon system which is now no longer. Maybe I do this all wrong however this is the process I used. Others may tell you different, but it worked for me.
When removing the push on connectors from the fuel filter be careful not to bend the plastic lines as they may become damages and possible leak or restrict fuel flow. Re installing it was a breeze, however ensure all connectors are clean and apply a small amount of oil or grease to the tubes prior to inserting them back in. Also when removing the fuel pump Mark it and the tank first so its alignment will be the same. Get this wrong and your fuel level sender may not work correctly. Forgot to mention that if your system is working correctly, the fuel lines will be under pressure, to do this disconnect the fuel pump electrical connector first or remove the fuse for the fuel pump and start the motor this will release the pressure. Also make sure you have rags under the car with you as fuel will still be present in your fuel filter/ pressure unit, and most of all make sure you protect your eyes.

[turbomart]

The three key on -off trick is done with ign on but no start (engine not running).
You can do a instrament calibration by holding odo reset button down whilstturning ign to on (dont start).
All 96 on OBDII Jeeps work with 3 turn key trick.
Get instructions & codes from www.wjjeeps.com
Btw, not all faults will bring up code all the time, ie faulty crank angle sensor.

[purpleWJ]

dunno why people do all the difficult stuff before the ESSENTIAL basics

1 check the exhaust outlet and pull your plugs - they will tell you what the likely situation is - e.g. bad fuel pump or clogged lines etc causing fuel starvation will show excessive lean burning, rich mixture will show sooty, and a mixture of symptoms visible on the plugs wil tell you some plugs are working OK other not and gives a pointer to what may be needed next

2 work from what you have learned - the probs start AFTER MOTOR was RUNNING A SHORT WHILE and (unclear from what you say) but NO CEL shows - what that suggests is temp change affects something and its not CEL reportable- so look for loose elec connectors - re-seat them all - mainly those in engine bay and esp the main connector to the coils, and under vehicle look for clogged or dirt covered O2 sensors etc

3 could also be badly carboned head so think about engine foam treatment - the Chrysler stuff in a can is excellent and cheap

report your findings ................

[nallyrt]

Originally Posted by purpleWJ

dunno why people do all the difficult stuff before the ESSENTIAL basics

1 check the exhaust outlet and pull your plugs - they will tell you what the likely situation is - e.g. bad fuel pump or clogged lines etc causing fuel starvation will show excessive lean burning, rich mixture will show sooty, and a mixture of symptoms visible on the plugs wil tell you some plugs are working OK other not and gives a pointer to what may be needed next

2 work from what you have learned - the probs start AFTER MOTOR was RUNNING A SHORT WHILE and (unclear from what you say) but NO CEL shows - what that suggests is temp change affects something and its not CEL reportable- so look for loose elec connectors - re-seat them all - mainly those in engine bay and esp the main connector to the coils, and under vehicle look for clogged or dirt covered O2 sensors etc

3 could also be badly carboned head so think about engine foam treatment - the Chrysler stuff in a can is excellent and cheap

report your findings ................

Relating to doing the difficult stuff first, firstly I am not a mechanic I am just a person trying to save some service related expenses due to financial constraints at present. Being I own my own business and due to business has been slow, although things are picking up again slowly, anyway back to the car, Three key test only shows code P0320 crank position not known during last cranking.

Correct me if I am wrong but is this not due to not actually starting the car while doing the three key on test.

Secondly as for plugs all checked all ok no carbon or oil deposits and in excellent condition, even made sure the right plugs are installed. All connectors including earth points have been gone over at least three times in the last two weeks just to be sure and all connectors are in excellent condition, however I have not at this point replaced the Oxygen sensor since I have owned the car, Question How often should Oxygen sensors be replaced?

The engine foam treatment for badly carboned head you mentioned please explain what this is never heard of it before.

Regarding Exhaust I do believe it is no different than it has been since I got my Cherokee, always has been kind of black no different than other cars we own.

One thing I did notice though my coolant has just started weeping from between the thermostat temperature sender housing and the head, I will be looking into that next week, run out of time today. May need to replace the gasket and possible the housing, while apart will look at replacing the thermostat as well, temperature sender can be replaced anytime if it plays up. Also will be replacing the coolant as well need to look in the manual as to what type of coolant is recommended, any suggestions?