My 1996 4.0 Cherokee would not start this morning. It has run perfectly for the last 18 years (104,000 mi) so a problem of some sort should be expected eventually. Perhaps someone could help me diagnose the problem.

1. The starter motor cranks the engine over forcefully and the battery is near new so I don’t think that is the problem.

2. I cannot hear the fuel pump spin for a second or two with the key in the on position. Normally I can hear the pump.

3. I have no fuel pressure at the rail (I used a fuel pressure gauge to test this). Also when I depress the Schrader valve no fuel comes out.

4. I switched the ASD relay and the fuel pump relay - still no start or fuel at the rail.

5. I tried to pull the codes . I don’t have a code reader but the computer will blink out the codes on the dash “check engine” light. I could not get this thing to display any codes. Next I tried unplugging the Crank PS to see if it would display any codes. It did. The only code in there is code 42 which is a fuel system problem. However, that code has been in there for some time and I was too lazy to disconnect the battery to erase the code. (Several months ago I pulled the fuel pump relay so I could crank the engine without the thing starting. I was checking the battery and starter motor. It checked out OK).

6. I put an Ohmmeter on the CPS pigtail but was not able to get a reading on the meter. I don’t know why not.

7. It won’t start in either Park or neutral - the back up lights work fine.

8. I don't believe I have spark at the plugs (difficult to test by myself).

My question is this - will a bad CPS cause the fuel pump to not work??? Am I facing a fuel pump replacement ,or a CPS replacement, relay replacement, or some other problem???

Any help is greatly appreciated.

 

Sorry to hear your down so maybe I can help recently on my 95 cherokee 4.0 with 101k I could start it but however it run until warmed up and then shutoff with no hesitation. Anyways to help make sure it's not your fuel pump have some turn the key to the on position while your listening thru the filler tube with the cap off you shd hear it for about 1-3 seconds. If you can hear it then that's good next check spark in a similar fashion but pull a plug or have a spare good one and place into the wire an hold near a ground so you can see a small blue spark. If you have spark but still no fuel pressure at the rail could possibly the fuel filter clogged. However if your getting both spark and what seems to be the fuel pump kicking in check the crankshaft postion sensor (that was my issue) it is a know thing to go but it's also expensive. Do those things first to double check

 

Try spraying some starting fluid and see if it starts. If it does your fuel pump may have given out.

 

Good advice, save that he has no pressure at the rail, filter is a possibility but not so much spark. Computer looks for Cps signal for 3 seconds before it cuts the pump off, that's why when cranking, it gets the signal and therefore you get spark + fuel. My vote is on pump

 

I agree, the pump. You should hear it run to pressurize the rail before even turning the key to start. The CPS only comes into play after it fires.

 

Thanks to all for your comments and suggestions.

I guess the thing I don’t understand is why I have neither spark nor fuel flow.

If the CPS is faulty then the fuel pump should still prime for 2 or 3 seconds when I place the ignition key in the “run” position. It does not.

If it’s a bad fuel pump then I should still have spark at the plugs. I don’t.

Maybe I’m looking in the wrong places.

 

Of course you have a point, but the CPS will not keep it from priming. I'm not so familiar with a 96, but I think it's fuel pump relay is like the one below. Jumping power to socket 87 should make the pump run, I think.

 

I want to take this opportunity to close the loop on this issue. The problem turned out to be the Crank Position Sensor. Replaced it and now the thing runs perfectly again.

Special thanks to all of you for your input. Maybe others can learn from my experience.

 

Could someone with a 96 unplug their CPS and see if that stops the pump from coming on for a few seconds with the ign. on?

Glad you solved it!

 

Unplugged the CPS....
Fuel pump still primed. Cranked for about 3 sec. No Spark (visually verified). I think injectors were working cuz when I plugged CPS back in to start, there was a strong smell of unburned gas in the exhaust.
Hope that helps.

 

Thanks for clarifying that Harky. On an 87-90 Renix Jeep, the injectors shouldn't fire without the CPS. I've got plenty to learn about the later though!

 

I see some info on starting issues and I don't have answer, only have added question.
2001 Cherokee Sport. Sometimes when I go to start jeep it fires immediately and runs (starter gear grinds as it starts so quickly), sometimes it turns over several times and starts I consider normally OR if neither it does not start. Sometimes sounds like starter begins to turn then stops so I release key and turn to start again or I have to put gas pedal to floor and turn key to start. Once it starts does not seem to be any problem runs fine.
I have a ignition switch that I'm betting needs to be replaced. Few times put key in and turned and nothing. Removed key, reinstalled and started. I'm having crankshaft position switch changed within week. Wondering if that is cause of the erratic starting. New plugs in last 3,000 miles

 

Sheez. Well first your 01 is none of my business. "hydro lock" is what happens if there is fluid in a cylinder, doesn't compress, so the piston (engine), stops.

On my Jeep, holding it floorboarded is what you do when it's flooded. (cuts injector pulse and gives max air)

A really leaky injector might be dumping a bunch of fuel in one of your Cyl's. (sort of a long shot).

Here's a pic of a test for that.... OR, right then when it stops, stop, pull the plugs and see if one is wet....Just a thought....

 

Thanks for pic. Question: when do I pull injectors and how do I test?
Pull injectors and let them sit on "card board" over night and look for fuel dripped on board near an injector?
Now, never pulled an injector on this so what is the secret to getting them out. Oh if I pull them out I need to replace "O" rings?