Won't Start!!! No Spark!!!

[steveo94]

Hello!!!!

My 97 Explorer 4.0 push rod won't start. There is no spark. The coil and crank shaft position sensor test good as did the cam shaft sensor. I put new relays in, the rest of the fuses were good. The intertia switch is not engaged. There was no ground signal from the PCM to the coil. PCM relay has blown multiple times in the past. The engine turns over and you can hear the fuel pump engaging when trying to start it. No diagnostic codes were returned when I pluged in the OBDII. It ran fine, but then just didn't start.

Any help would be appreciated!

Thanks so much!!!!

 

[MustangP51]

Is the THEFT light blinking?

 

[budwich]

does your "check engine" light come on during your start sequence???? What do you mean "the pcm relay has blown in the past"???? the contacts?, the coil of the relay???

 

[steveo94]

The check engine light comes on with the key in the on position. When I'm turning it over it turns off.

I don't have have sercurity system on the car, so no theft light.

Thanks for the quick reply!

 

[steveo94]

Oh, and I don't know how the relay failed. When I replaced the relay, it started right up. When I popped open the relay the coil looked fine. I'm not sure what was wrong with the relay itself though.

Something else....The scan tool was not getting an RPM signal on a cranking engine.

 

[budwich]

well, a couple things.... the PCM relay has to operate... if it doesn't, no "good things" can happen. don't know what the scan tool "sees" if the PCM isn't powered "properly"... but if its indications are "correct", then it is quite likely that your aren't getting a signal from the crankshaft sensor which is used for "spark timing generation" and I think "RPM" stuff.

The check light should come on for a period as it "initializes"... once that is successful (ie. powering), it then goes off (ie. during the actually "crank").... so that to me is good. As for the relay, a meter can be used to measure coils and contacts to see what actually died.

Lastly, check your crankshaft sensor wiring as there have been posts about the wiring/ connector not "completing". I think this is where your problem lies.

 

[steveo94]

If the PCM is not getting a signal from the crankshaft sensor, would there be a diagonistic code?

I checked the PCM with a meter and it is getting power. The coil is getting power as well.

Thanks for the reply!!

 

[steveo94]

The crankshaft wiring is good from sensor to PCM. Any other suggestions?

Thanks so much!!!!

 

[witchdoctor]

Check out this thread:

http://www.explorerforum.com/forums/showthread.php?t=85965

Just because the Crankshaft Position Sensor wiring tests good to the PCM and you have power at the coil doesn't mean the coil is good or that the CKP is good. You have to check the wiring at the coil with the ignition turned on...see step 4 of the thread.

It took me months to finally diagnose the problem.

 

[newmab]

Check out this thread:

http://www.explorerforum.com/forums/showthread.php?t=85965

Just because the Crankshaft Position Sensor wiring tests good to the PCM and you have power at the coil doesn't mean the coil is good or that the CKP is good. You have to check the wiring at the coil with the ignition turned on...see step 4 of the thread.

It took me months to finally diagnose the problem.

Great tip!!
I had a no spark condition. Just after driving the thing a few hours before. So I went to check the CKP and forgot to turn the key off. As soon as I pulled the retainer from the plug the fuel pump cycled (why I'm not for sure). After turning the key off I checked the connection, added some dielectric and fired it up.

BN