Topazwoods

1990
Jeep Cherokee
Laredo
4.0L
Straight 6

My XJ has been giving me problems from the start; hell, it's a year older than me.

In short, it's not starting, battery is good and it the starter is engaging. It started yesterday fine and did not miss a beat. It might be the fuel pump, but I'l have to go listen to it again. I tried resetting the NSS without any luck. I need to get it started for two reasons: first to get to work when I can, and second to sell it for a more reliable car.

I wish I could keep it, but it seems like this is going to be the last straw. I'm open to any ideas to get it started, or I'm accepting offers to buy. I'll have an update on the fuel pump soon. Post any questions you have about it, I'll be watching this thread all day.

Update:
It sounds like the fuel pump is working, but I'll check it again while I'm testing the distributor.
There are 4 recently new spark plugs and I think it would start even if the two old ones were bad.
Alternator appears to be fine, and my battery is new and charged.

I'm running out of ideas. All the electrical inside appears to be working, the battery is good and has a complete circuit, and I am pretty sure that I can hear the fuel pump.

XJGrason

spark plugs firing? checked your alternator? you probably have just wondering.

Topazwoods

I think I can hear the fuel pump working. There are 4 recently new spark plugs in and I still think it would turn even if one, or both, of the two old plugs are not sparking.

The battery is still good so I can assume that my alternator is working. Also, it should still start from the battery even if the alternator was bad, shouldn't it?

I'm going to check the distributor soon. I'm running out of ideas for what it is.

RTorrez1

If you think you have a fuel problem You need to verify! You need to verify it with a mechanical fuel pressure gauge at the fuel rail.
BTW, Why would you only put 4 new spark plug and not all six. Not trying to be a smart a$$. But half A$$ thing will end up catch up to you down the line and if that is what you have been doing it just may have caught up now. Like I said not trying to be a smart a$$ just say what will happen when you do that.
Anyways verify the fuel pressure and get back with the results. Also Check if you have a good blue spark from the plugs. White and orange spark will not do for our Jeeps.

Topazwoods

At the time I was replacing the spark plugs I wasn't able to move the radiator hose and wiring harness that was in the way of the two that have not been replaced. I just haven't gotten to it since.

I got no spark from the distributor which causes me to believe the problem lies with that, or is around there; especially since it wouldn't even jump start.

I haven't been able to get a fuel pressure gauge yet.

So the distributor didn't spark when I tested it. I hope it's just the cap. Does this sound like it would be the issue?

Lowrange2

I'm confused. Perhaps I read it wrong.

Is it cranking at all? Just no start?

You keep mentioning the battery and alternator and jumping it off?

You mentioned the NSS. Have you tried starting it in neutral?

Topazwoods

It's cranking but no combustion. The battery is good and jump starting it did not work either. The alternator isn't the problem because we tried to jump it.

I did the reset for the NSS and tried starting it in neutral. Turned over but didn't start.

Just got a new distributor cap and it still didn't start. I pulled the distributor out and now I'm trying to decide what to do with it, and if I should get a new one, or not.

Can a distributor even fail? If it's not the distributor than I'm coming to a real loss of ideas on what it could be.

Lowrange2

Test this:



"The most likely cause of it cranks and cranks but won't start up is the Crankshaft Position Sensor (CPS) located on the transmission bell housing. Often this part is also referred to as the CranKshaft Position Sensor (CKP) CPS/CKP failure is very common. The CPS/CKP can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason.

Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when engine gets hot, but works again when it cools back down.


Symptoms-
- Starter cranks and cranks but engine won't start up
- Fuel gauge and voltage gauges may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump should run and prime for 3-5 seconds.

If the CPS/CKP is failed sometimes the OBD-II code reader cannot make a connection to the computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed.


Diagnostic steps to confirm the CPS is the cause of your no-start:

You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now displays correctly, replace the CPS.

Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables and replace as needed. Do the same for the grounding wires from the battery and engine to the Cherokee's frame/body. Jeeps do not tolerate low voltage or poor grounds and the ECM/ECU will behave oddly until you remedy this.

CPS Testing


Crankshaft Position Sensor Connector (CPS/CKP)




TESTING PROCEDURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.


The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector may be on the passenger side, near or on top of the Transfer case, not as shown in the diagram below. Simply follow the wire from the sensor to the connector. "

Topazwoods

I can't find the sensor on top near the manifold or on the bell housing. I've disconnected the 3 pronged connectors that I can find and tried to reset the ECU locally. It didn't work and still just cranks until the battery completely discharges.

Way too cold to keep working on it. I'll have to get back to it tomorrow. It really sounds like it's the CPS, but I won't be sure until I find the censor.f

Any other ideas?

The Rooster

make sure all your Grounds are good... just because they look good does not mean they are good... also take the time to click on the link in my sig... you will learn a lot about your Renix Jeep and trouble shooting..... and your Jeep being old has nothing to do with it not working it has to do with the person who owns it... or previous owners...
btw change the last to spark plugs please....

Topazwoods

I do know that the previous owner messed up a lot of things, including the wiring harness inside the cabin and possibly the outside. I've been fixing issues like this for a long time and it's really not surprising.

My engine is probably in the best condition since I got it several years ago and have been fixing it up ever since.

Yeah, I will get to the spark plugs tomorrow. Also, thanks for the link to the other thread.

The Rooster

np We are here to help.. Renix Jeeps run great just takes some time to get it right again