4.0 problem

I have a 96 Jeep Cherokee with a 4.0L. Friday I filled it up and got it washed in the touchless car wash. I drove home and parked it. Plugged the heater block in for the night. Saturday I tried to start it and it just turns over and will not start. The battery is not weak. It ran fine when I parked it. There is no fuel at the injectors. I replaced the Fuel pump and fuel filter. It ran just fine. Drove it to work with no problems. Went to start it up after work and it was doing the same thing as before. I can't hear the fuel pump turn on. Is there a box that controls the fuel pump? I replaced the little relay in the black box on the right side of the engine compartment. I also bought a scanner the other day and it said that there was a misfire at every cylinder. I replaced the coil just in case. There was no fuel at the rail again. I replaced the fuel pump again and it fire right up. I then cleared the codes. 2 days later I drove it to a friends. When I went to leave I turned the key and it acted the same way. I pumped the gas and it fired up. I checked for codes and there were none. It drove home good. This morning I went to start it and it started right up. Someone told me that maybe the cam position sensor is going bad. Any advice or anyone had an issue like this.

Thanks in advance

If the CPS (or CPS connectors or wiring) is acting up, you get no fuel or spark. The way I test for spark is to pull the number 2 or 3 spark plug cable and use an old spark plug, held firmly to a clean ground and have somebody turn the motor over. A pair of insulated pliers can save a hair raising experience. I also open up the plug to around 0.060, so I can check and see if I have a good strong spark and see the spark color well. Crisp blue spark is good, pale yellow and some spark splash usually means weak spark.
The CPS acting up can be an intermittent thing.
You spoke of pumping the gas and getting a start, this may be a symptom or may just be that the CPS decided to work at that moment.
Next time it fails to start, try holding about 1/8-1/4 steady pedal, if the IAC is stuck closed this gives you enough air for a start. The IAC acts up for various reason, often it is sticky from gunk, sometimes a weak battery, low voltage or a crispy ADS relay can affect the function.
The PCM closes the fuel pump relay for a second or two, when the key is turned initially to run or start, but the relay won't stay closed and supply steady fuel unless the PCM gets a pulse signal (CPS) from the motor turning over or running.
Low fuel pressure is also a possibility, but less likely since you have a new pump. Though there have been many instances of newer (replacement) pumps failing. The rubber fuel hoses from the pump are also a known trouble spot, they deteriorate, shed chunks and eventually leak/bypass fuel back into the tank. If your old pump hose was shedding rubber, it likely ended up in the filter (if there) or in the lines someplace, it may be worth a look see if all else fails, just to make sure your new filter isn't plugged up.
Also have a look at your rear O2 sensor, the harness has a habit of being damaged, if the harness shorts, this can suck down voltage your CPS needs to function properly, as can a problem in the sync sensor and other sensor shorts.
What codes did you clear?

Ok this probably isn't related to your particular problem but I'm going to tell you about it anyway just so you have one more place to check. Ok so my engine temp sensor went bad on my 97 and wouldn't read over 100 and would do it occasionally but not all the time. Then it got to the point where it did it all the time. When this started happening I would have to almost everytime give it some gas in order to start otherwise it would just keep turning and no start. I replaced the temp sensor on the thermostat housing fixed my temp gauge problem and the starting problem. So watch your engine temp gauge and make sure its reading. I am sure you would have noticed it though. Anyway hope that helps at all.

I was getting codes for misfires, every cylinder. That is why I changed the coil and have not gotten these codes back.

Have you checked your spark plug cables? I've never replaced a coil, but have replaced numerous cables sets. Find a really dark place, run your motor and check for spark arch. If you have an ohm meter check the resistance in the cables.
I spend a lot of time in mud holes, partial high voltage grounds, engine misses and similar problems are a way of life for me.
If you have a timing light you can use it to test for spark loss, the coil wire will barely light the timing light, putting the timing light on every cable and shinning it on a dark spot will let you see weak pulse and misses.
Corrosion in the cable ends, especially at the distributor cap is fairly common.
I replace at least two distributor caps for every set of plugs. Plugs seem to last forever in the 4.0, distributor caps don't.
Often a weak coil is because of dirty connectors.
Distributors aren't water proof, sometimes the moisture in the distributor can manifest when the motor is hot from evaporation or cold from condensation.
Having said all that, I'm still thinking you have a CPS problem. Either a short between the B and C pins, low resistance between the A and B pins or possible a low signal voltage to the CPS which can be from various reasons.

HigherElevation - just make sure you are checking your CRANK position sensor, not your cam position sensor....i'm pretty sure that's what 8mud and ILLXJ are referring to.

Where is the crank sensor located? I know that the cam position sensor is located on the bell housing of the transmission.

Thanks

higherelevation said:

Where is the crank sensor located? I know that the cam position sensor is located on the bell housing of the transmission.

Thanks

Click to expand...

The one on the bellhousing is the crank sensor. I think the cam sensor is inside the distributor, under the rotor (that's where it is on RENIX, anyhow. I'm fairly sure it didn't move in later years.)

I was getting a check engine light when the misfires happened. I haven't had any lately.

I drove it to work today. Ran good. After work I tried to start it and the same problem is there. No fuel at the rail and it just turns over. I checked for codes and there are none.

higherelevation said:

I drove it to work today. Ran good. After work I tried to start it and the same problem is there. No fuel at the rail and it just turns over. I checked for codes and there are none.

Click to expand...

When you turned the key did you get a CEL? JIM.

Crank sensor is on top of the bellhousing, drivers side as mentioned by an earlier post. IMHO, the crank sensor is the single most common sensor failure on the XJ.

The cam sensor is located in the distributor. They don't fail as often as the crank sensor but yea, they can go bad. A bad (or intermittent) cam sensor can absolutely create a no start condition. The cam sensor sends a signal to the computer that controls fuel injection as well as some other things.

Good luck and post back what you find if it comes back!

Sounds like you have an intermittent electrical problem with the wiring or relay in the fuel pump circuit on yours. Get a wiring layout and locate the fuel pump relay, make sure you replaced the correct relay. See if the starter switch has seperate contacts for the fuel pump, I think it does, if so the ignitiion switch may be failing on those contacts.

Did they still use a fuel pump ballast resistor in 96?

Ecomike said:

Did they still use a fuel pump ballast resistor in 96?

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No. JIM.

I sent it to the shop and they told me that the fuel pump is bad. It is seized. He tapped it and it started working again. I bought Bosch which is supposed to be good. He suggested the entire assembly be replaced incase the harness is bad. Anyone have thoughts on this?

Thanks

The shop can't get a whole assy. It was just a fuel pump. The assy is back ordered nation wide and they said it would take 2-3 months to get. I am going to clean my tank out and try a different brand of fuel pump. I tried to pump the gas a little and then hold it 1/8 down when it happened last time and it nothing happened. I checked the maintainance records the lady gave me when I bought it. The crank sensor was replaced in May 07 and the the distributor cap, wire , and plugs were changed at this time also. The check engine light came on when I turned on the ignition and then went out when I was having the problems.

All info is appreciated

Thanks

Ben824 said:

Ok this probably isn't related to your particular problem but I'm going to tell you about it anyway just so you have one more place to check. Ok so my engine temp sensor went bad on my 97 and wouldn't read over 100 and would do it occasionally but not all the time. Then it got to the point where it did it all the time. When this started happening I would have to almost everytime give it some gas in order to start otherwise it would just keep turning and no start. I replaced the temp sensor on the thermostat housing fixed my temp gauge problem and the starting problem. So watch your engine temp gauge and make sure its reading. I am sure you would have noticed it though. Anyway hope that helps at all.

Click to expand...

The temperature guage does work.

What are the chances I have had two bad fuel pumps. The guy at the parts store said it is because they have been run outside of the tank and with no fluid they are burning up. Could this be true?

higherelevation said:

What are the chances I have had two bad fuel pumps. The guy at the parts store said it is because they have been run outside of the tank and with no fluid they are burning up. Could this be true?

Click to expand...

It's possible. The higher-pressure fuel pumps used in fuel injection systems are submerged to keep them cool - but they should still have no trouble running in open air for short intervals (that's how I test them, and I've not burned one out yet. Also, what do you do when you're running low fuel? You usually need a quarter-tank or better to fully submerge the thing...)