What sensor would tell ECM to not allow spark?

[Lee's Automotive]

usually smp alright i assume that woyldnt keep it from running that bad. i mean yeah mc>smp but they aint the worst either lol but lee got more experience than i

Nah bro you know alot more I'm just trying to rule out a partially defective sensor I've had good fuses test and look good and be bad same goes for relays

 

[Postal_Dave]

The Relays are good. I checked them with voltage to make sure they opened. The CKP I bought is a motorcraft one. I just used that link to show you what a CKP looks like for my Explorer. I have purchased motorcraft for all the parts I've replaced, if they were available.

Tomorrow I'm going to check the ODB II for both computers I have and see if I get the same results for the RPMs. I'll post the results and see if there is a difference.

 

[Lee's Automotive]

The Relays are good. I checked them with voltage to make sure they opened. The CKP I bought is a motorcraft one. I just used that link to show you what a CKP looks like for my Explorer. I have purchased motorcraft for all the parts I've replaced, if they were available.

Tomorrow I'm going to check the ODB II for both computers I have and see if I get the same results for the RPMs. I'll post the results and see if there is a difference.

OK might be worth it find someone with a decent scanner that can communicate with each computer and module or get forscan

 

[Fix4Dirt]

Nah bro you know alot more I'm just trying to rule out a partially defective sensor I've had good fuses test and look good and be bad same goes for relays

weve been through this discussion LOL you know way more/have/do more than I LOL true could be defective though i havent had an issue with the smp parts i have, granted none of them are "critical" so to speak

 

[Lee's Automotive]

@Postal_Dave Everything at this point is pointing to a bad ecm and i found another thread where the op replaced the ecm and it solved the issue

Won't start, no spark

I'm buying a 99 Explorer 4.0 OHV from a family member. It cranks, but doesn't start and he's fed up with it, so he's giving it to me. I already helped him do some diagnostics but I still haven't figured it out. Here's what we found so far: I put a fuel pressure tester on it and there's 65 psi...

www.explorerforum.com

 

[Josh P]

Only 1 forum member reported having two bad ecm units but his issue was slightly different that he was chasing ghost codes for problems that really didn't exist. From everything I've read, if all the sensors test good it ends up being a ground issue or a bad wiring connector somewhere.

 

[Lee's Automotive]

Only 1 forum member reported having two bad ecm units but his issue was slightly different that he was chasing ghost codes for problems that really didn't exist. From everything I've read, if all the sensors test good it ends up being a ground issue or a bad wiring connector somewhere.

I'm honestly thinking that ecm is bad or there's a ground issue almost like there's a ground when starter is shut off

 

[Josh P]

The chances of the junk yard ecm suffering the exact same issue as the 1st one are very slim. I believe Dave stated he could see 190 RPM when cranking the motor. That means there is weak spark, not enough to fire the motor.

 

[Lee's Automotive]

The chances of the junk yard ecm suffering the exact same issue as the 1st one are very slim. I believe Dave stated he could see 190 RPM when cranking the motor. That means there is weak spark, not enough to fire the motor.

Oh, ok could it be a weak coil? I mean it's not making much sense

 

[Josh P]

Oh, ok could it be a weak coil? I mean it's not making much sense

None of this makes sense, everything checks out and it doesn't work. He stated coils tested good. If a circuit is shorted out or a bad ground, the ecm doesn't work properly. We initially thought it was the ecm after all the tests, it made no difference swapping it so the problem is much deeper.

 

[Mbrooks420]

Stupid thought. Have you tried cranking it with no accessory belt?

 

[Postal_Dave]

Today I swapped out the computers to see if there was a difference that the ODB II tool would show. They both produce the same results on the Scan Tool. And once again, I tried starting it with Live Data on and looking at the RPMs. They got to around 190 RPMs and then the reading went to 0. I then double checked the voltage coming from the CKP and it seemed fine. I checked the grounds on the harness and the case grounds and they are fine.

Something is telling the computer to ignore the signal from the Crankshaft Position Sensor. The first three times it happened as soon as the Explorer hit operating temp. Now it doesn't run at all. It's not in the computer but it may be something that effects the computer. The computer has good voltage and a good ground. The CKP produces good voltage and seems to have good wires.

Thanks guys for you input. If you think of anything else, let me know.

Mbrooks: No I haven't tried that.

 

[Lee's Automotive]

Today I swapped out the computers to see if there was a difference that the ODB II tool would show. They both produce the same results on the Scan Tool. And once again, I tried starting it with Live Data on and looking at the RPMs. They got to around 190 RPMs and then the reading went to 0. I then double checked the voltage coming from the CKP and it seemed fine. I checked the grounds on the harness and the case grounds and they are fine.

Something is telling the computer to ignore the signal from the Crankshaft Position Sensor. The first three times it happened as soon as the Explorer hit operating temp. Now it doesn't run at all. It's not in the computer but it may be something that effects the computer. The computer has good voltage and a good ground. The CKP produces good voltage and seems to have good wires.

Thanks guys for you input. If you think of anything else, let me know.

Mbrooks: No I haven't tried that.

Ok so we have ruled out computers so at this time im thinking wiring or weak coils but what makes no sense is you are seeing rpms almost like its trying to fire but the spark is to weak to actually fire the engine

 

[Lee's Automotive]

From what i understand fuel pressure should be 40+psi on the OHV engine but that still don't explain the spark issue

 

[Lee's Automotive]

Have you checked the EEC relay and EEC fuse?

 

[Lee's Automotive]

Camshaft sensor might be an issue too because it could tell the ecm/pcm not to deliver spark

 

[Lee's Automotive]

@Postal_Dave I found this thread here maybe this will help some 1999 FORD EXPLORER 4.0 NO SPARK
I will try my best to help you fix this issue I'm also researching as much as I can and I'm also trying to get the full-service manual for your 96

 

[Turdle]

Stupid question time.

Coolant level in radiator? Check radiator, not reservoir.

Oil level good? Is oil pressure switch closing when cranking?

Is oil pressure signal getting to PCM?

Check to see if cam sensor inside rotor is moving.

 

[Turdle]

Also. Aldives thread was solved with replacement of ckp sensor and harness.


Same issue. Seems the harness would work for testing but flake out during actual use.

Weird starting problem

 

[Mbrooks420]

Camshaft sensor might be an issue too because it could tell the ecm/pcm not to deliver spark

These will run just fine without the CPS. It’s not needed to spark, or fire the injectors.