2.5 will turn over but not start (lack of spark)

[Lxatattoo]

My 97 Wrangler 2.5L stopped working on me a couple of weeks ago. I thought it was the fuel pump so I changed it out. Afterwards I did a fuel pressure test. It was hard to start but I was able to get it going after a while. I ran seafoam through the engine to clean the injectors and did a hot soak. After it sat for a while, it was hard to get the jeep running started. Again after a few more attempts I was able to get it running and drove around for a few minutes to clean the system.

When I got home. I killed it, then started it right back up. I decided to let it sit for several minutes and came back out to start it, but was not able to get it going.

I did a little research and thought it could be the ignition coil, so I just changed that out but it did not start. I checked the spark plug, but I am not getting a spark now. I swapped out the automatic shutdown relay with the A/C relay to try that as well.

I am thinking it could be the ECM, but I am not sure what to check before going down that route. I am a novice and have basic tools.

I appreciated your collective experience and any advice. Thanks

 

[Chris]

My 97 Wrangler 2.5L stopped working on me a couple of weeks ago. I thought it was the fuel pump so I changed it out. Afterwards I did a fuel pressure test. It was hard to start but I was able to get it going after a while. I ran seafoam through the engine to clean the injectors and did a hot soak. After it sat for a while, it was hard to get the jeep running started. Again after a few more attempts I was able to get it running and drove around for a few minutes to clean the system.

When I got home. I killed it, then started it right back up. I decided to let it sit for several minutes and came back out to start it, but was not able to get it going.

I did a little research and thought it could be the ignition coil, so I just changed that out but it did not start. I checked the spark plug, but I am not getting a spark now. I swapped out the automatic shutdown relay with the A/C relay to try that as well.

I am thinking it could be the ECM, but I am not sure what to check before going down that route. I am a novice and have basic tools.

I appreciated your collective experience and any advice. Thanks

Since you’ve already replaced the fuel pump and ignition coil, and you're not getting any spark, here are a few steps you can take next:

Check the Crankshaft Position Sensor (CPS): This could be a culprit if the engine turns over but doesn’t start. If the CPS is faulty, it won't send a signal to the ECM, and you won’t get spark. Testing it with a multimeter can help you determine if it’s functioning properly.

Inspect the Wiring and Connections: Make sure all wiring and connectors related to the ignition system are secure and free of corrosion. A loose or damaged wire can easily lead to a lack of spark.

Test the ECM: While it’s less common, the engine control unit (ECM) can fail. Make sure there are no blown fuses related to the ignition. If you can find a local auto parts store that offers diagnostic services, they might be able to check the ECM for you. If you need help testing the ECM I'd highly suggest sending it to @Wranglerfix who is the resident PCM / ECM repair guy around here.

Verify Ground Connections: Ensure that the ground connections for the ignition system are solid. A poor ground can disrupt the spark signal.

Look at the Distributor: Check the cap and rotor for any signs of wear or damage.

If you can get your hands on a scan tool, it might also be helpful to read any stored trouble codes that could give more insight into the problem.

 

[Lxatattoo]

I checked my wires but did not see any damage. I checked the fuses I. The dash and found 17, 18, 19, 20, & 12 had no power going to them with the key turned on. The fuses are good but no power to thos specific fuses. Every other fues seems to be getting the power it needs. Does this give you any further indication of what could be going on with my TJ?

 

[macleanflood]

Do you get RPM on the dash gauge when cranking?

-Mac

 

[Lxatattoo]

If you mean does my rpm gauge move while cranking. The answer is no. My fuel gauge usually doesn’t move until it gets cranked up either, but some times it does move while I have the ignition on, but not usualy the case.

So today I went to turn it over to see if my RPM gauge moved while cranking and it coughed. So I tried a couple more times and she fired up. Note it was about 75 degrees today. I’m not sure if that had anything to do with it.

 

[macleanflood]

No RPM on tach when cranking is your crankshaft position sensor (or the wiring, etc).

-Mac

 

[Lxatattoo]

I changed out the crankshaft position sensor and after a few tries the old girl did start. I let her warm up a bit, then shut it off. I tried to start it again after sitting for no more than 5 minutes and it would not start. FYI my tach works, but to my knowledge has never shown RPM while I am cranking it over, even after I changed the sensor.

When I had it running I checked the fuse block behind the glove box and the left side and half the bottom row still does not have power to it.

I had the negative disconnected for several day prior to changing CPS, I saw someone say that is how you "reset" them. I reconnected it immediately after installing new CPS and starting it up.

 

[macleanflood]

I think you need to start investigating wiring issues. Continuity checks and ohm. But I'd probably just start pulling the harness and physically inspecting it.

-Mac

 

[Lxatattoo]

FYI, I got the problem resolved. It was the computer. I looked at all my wiring and changed out the ignition coil and crank position sensor and the fuel pump (was going out already). But first crank with a new computer and she popped off. Thanks for your assistance.

 

[macleanflood]

Where did you source the PCM?

-Mac