Just bought my 1990 4.0L (inline 6) cherokee. The jeep cranks but hardly starts.

It has a new air filter (which makes me think air isn't a problem). There was fuel in the fuel bar (made me think fuel wasn't a problem). I figure the problem was electrical.

I replaced the distributor cap and rotor. Also replaced the spark plugs and spark plug wires. After doing that the jeep ran better but still started hard. Im talking 2-4 tries while it turns over for 5-10 seconds before starting.

I just tried to replace the fuel filter and the O2 sensor and haven't been able to start the jeep since. I made sure the fuel filter was facing the right direction. even put the old sensor back on thinking it would help. It didn't.

I need help figuring out the problem. The only thing left i can think to do is check the fuel injectors. Anyone have any suggestions??

 

Wow, you sure are throwing a lot of money at it without knowing what is wrong. Its never bad to replace tune up parts though, but stop guessing!

First suggestion I would give you, is start diagnosing the problem, and stop throwing parts at it, hoping you eventually solve the issue.

Check your fuel pressure. A bad fuel pressure regulator or leaky injector will not keep pressure when the engine isn't running, so it could several attempts at starting it to build the pressure back up.

Check for spark. You want a strong snappy blue spark at your plugs. anything less and it could easily cause a no start condition. If you're not getting a spark, or not getting a strong enough spark, start working your way back. Check the condition and resistance at your coil.

Besides fuel and spark, you need compression. I wouldn't worry about checking that yet. Start with fuel delivery and ignition system. Figure out where the problem is, and then you can start trying to figure WHY the problem exists and repair or replace parts at that point.

 

I haven't had a chance to check the actual PSI on the fuel rod; however hen i hit the release valve on the side of the fuel rod fuel sprays out vigorously. Do you think that i need to still test the fuel pressure?

Do you think that the CPS could be the issue? Im not sure the last time that was replaced.

 

Think it through... I understand you don't have immediate access to a fuel pressure gauge. But, you say its is coming out with decent force when you hit the valve. Without the gauge, you can't bee 100% sure, but if its all you can do, then don't stress about it yet.

A bad CPS will cause a no start condition, but don't jump to conclusions. Next check for a strong spark. Pull the plug, leave it attached to the wire, and ground it to the engine while you have someone crank the motor. Look for that strong blue snappy spark. If its any other color, then you've narrowed down the problem. If its missing entirely, you've narrowed down the problem.

 

Just tested to see if i have power going to my spark plugs. I don't have any spark what so ever in any of the plugs I've tested. I then tested power going into my distributor. I took the wire that provides power to the distributor cap and tested it. Nothing. Next thing in line, the ignition coil. Pulled that out and tested it with an ohmmeter and it tested fine.

Also got a fuel pressure test kit. When the engine is cranking there is 38.9 psi in the fuel rod.

What do you think? Out relay?

 

No spark 9 times outta 10 cps cures it. As for long cranking thats how Renix Jeeps start . Repeated attemps just add to your issue.

 

Good tips here......

https://www.cherokeeforum.com/f2/cru...x-tips-153663/

 

Great job on diagnosing the problem. As Freegdr said, with this diagnosis, it generally leans towards a bad CPS. BUT... before you go spend money for a replacement, check all the connections and trace the wires to make sure there are no break or wear spots. If everything looks good with the wiring, then I think the next step is tackling the CPS. You can test the resistance in it, but that is not always conclusive as to whether its functioning or not.

If you do decide its bad, then stick with a genuine Mopar sensor, or at least an Echlin from Napa. Don't waste your money on a "lifetime" warranty sensor from the other places. Many of those are failed right out of the box and can have you chasing your tail looking for other causes of your problem, because in your head, you're thinking, "Well its a new CPS, so that can't be the issue... let me start tearing other things apart."

 

That's exactly where I'm at right now. Hoping it's not the sensor, but I'm going to test it anyway.

 

Thanks for all the help thus far but i still don't have a solution. Most of my wires looked good; however i didn't cut open all the bundles and follow each individual wire. I went to AutoZone and got the durlast sensor and installed it. The jeep didn't start.

Do you really think that i got a bum sensor?

Sad to say, Im about ready to tow this thing to a mechanic and have him diagnose it for me. I just need to get this thing going...

 

From what I've been reading, the problem could be the ignition inside the steering column. Can that be the source of the problem?

What do you guys think?

 

Click on the link below in my signature and learn how to test a CPS. Tip 7.