97 4.0 OHV No-Start. Tried everything. Any advice????

[97SportinMn]

Hi everyone, this is my first post. I joined hoping to tap the wisdom of this site.

Here's my dilemma.

I recently bought a very nice black 97 Sport, OHV & manual trans., and only 92k miles. I bought it not-running, from a guy who only said it quit on him and he can't figure out why. He just spent $1800 on front-end rebuild and complete brakes on it and wasn't spending anymore money on it. I paid him $400 cash, couldn't walk away from the challenge!!!!

Heres what I've done so-far.

>Fuel pressure at Schrader 40 psi with key on, pressure holds there when I turn key off.

>No spark. No switching signal at the coil from the pcm. Coil has power as it should. Absolutely NO attempt to fire when cranked, even when I squirt some gas into the throttle body. Coil tested good with VOM. I used a inline spark tester to confirm no-spark.

>My Snap-On scanner shows the TPS responds as it should, and with the right voltage. It also shows RPM's when cranked, so the CKP is good. I replaced the CMP only because its a p.i.t.a. to test behind the engine, and it's the original (and only $25)

>No codes set in memory.

>A noid in a injector plug shows injectors cycling when cranked, confirming the CKP is good.

>Compression test was concerning. All cylinders were between 110-120 psi. This is a good spread, but it's too low for a 92k mile engine IMO. Is it possible that the timing chain jumped causing low, but even, compression? If the t chain did jumped, would the CKP and the CMP not being in sync cause the PCM to deny a switching signal to the coil? Which would account for no-spark. Again, the engine doesn't even hint at firing.

It sounds to me like a PCM issue, one way or the other, but would like your opinions.

All thoughts, ideas, advice or condolences welcome!!!

 

[Dono]

At the coil, can you find a wire that is the input pulse the coil of a certain cylinder and see if you can see that pulse? Im not even sure what you could use. A volt meter probably isn't fast enough.

Here's a link
http://wiki.answers.com/Q/How_do_you_check_ignition_coil_operation
You will need some kind of a wiring diagram to figure out which wire is for which cylinder. Im betting there is a common ground to the coil pack..................I just found excellent links on this forum with the same issue you are seeing.

http://www.explorerforum.com/forums/showthread.php?t=264205
http://www.explorerforum.com/forums/showthread.php?t=314961


If its all cylinders that dont have spark, I guess you can rule out wiring, unless the plug is out at the pcm. Im no expert here, just trying to think what you can try next, and hopefully giving you an idea of something to check.

 

[97SportinMn]

Hey thanks for the response.

Actually, Ford calls that "pulse" you suggested a switching signal. It switches from powering the primary side of the coil, to switching it to ground to fire the coil.

I tried all three of the wires, and all are dead.

It seems like a complex problem I'm having. One thing I thought of was to test for continuity between the PCM and the coil, as unlikely as that problem may be.

Those are interesting threads you sent me Dono. I went through them, but didn't come up with anything

 

[Dono]

Sorry I didn't strike a cord anywhere in my post.

Do you have any idea what colour wire would be a pulse wire to the coil off the pcm? I'm GUESSING that there is no pulse right at the PCM either. That would mean that something is either not telling the pcm its supposed to sent spark pulse, or that the PCM is truely malfunctioning.

 

[2000StreetRod]

waste spark system

Explorer utilizes a waste spark ignition system: two plugs fire simultaniously (one plug on compression stroke and the other on exhaust stroke). There are only three wires from the PCM to the ignition coil. Each wire is normally shorted to ground by the PCM allowing primary (12 volts) current to flow thru the ignition coil. When the PCM breaks the path to ground the electromagnetic field collapses in the coil primary winding inducing a high voltage in the secondary winding that fires the spark plug. The interruption of primary voltage is a very narrow pulse and difficult to detect with any type of meter. Check/clean the ground wire connection at the firewall next to the PCM main connection. Make sure the PCM connector pins are not pushed back and the connector is on tight.

 

[bstarz65]

This might be a stupid question ,but is the cel light on with koeo. I had this problem and it was a bad relay for the pcm.

 

[97SportinMn]

Hey guys!

bstarz, the cel is on with KOEO. So the PCM is getting power. It goes out when I crank the engine,which I think it's supposed to do. Good question, thanks!!

streetrod, I've checked the 3 wires coming from the PCM. I put a test light on positive post and probing each of them. The light should flash when the PCM switches them to ground while cranking the engine, but the light isn't flashing. So I don't think the PCM\ICM is doing it's job. I will check the PCM plug to make sure it's plugged in and the pins are not pushed back. thanks for the suggestions!!!

I'll let you know if I find anything.

I'm trying to my garage ready for another tough winter here in the great white north (MN)!! LOL

 

[koda2000]

not familiar with this year/engine, but does it use a crank or cam sensor? if so, a bad sensor could explain why you're not getting any spark because the PCM doesn't know when to trigger the coil...

Update: I checked RockAuto for this year/engine and they list both a crank and cam sensor.

 

[2000StreetRod]

test light

With one lead of a 12 volt test light connected to the positive battery terminal and the other lead connected to a back probed pin of the connected ignition coil connector the light should illuminate continuously due to the PCM grounding the path. When the PCM breaks the path to ground when cranking the starter the light might blink off but it will probably be so brief that it won't be noticeable.

You might try disconnecting the radio noise suppression capacitor. Sometimes they cause problems.

 

[budwich]

Of course, your vehicle has NO type of anti-theft system either factory or after market... right? How do you know?

 

[97SportinMn]

Budwich, I'm pretty sure that anti-theft started on Ex's in 98, at least that what the sites are saying and I dont have a chipped key. It also doesn't have an aftermarket either.

streetrod, I think you might be on to something. The flashing of the test light from + to - may be too fast for the light to respond. Too bad mine isn't a LED test light, that might be fast enough! ;0) So, if it's blinking but too fast to respond, any ideas? Coils good. Got fuel. No life at all. This takes me back to a jumped timing chain which would have it firing at the wrong time. what do you think?

It may be time to pull the front of the motor apart?

 

[97SportinMn]

Streetrod where is the radio interference capacitor? I'll unplug that and see if that does any good?

 

[budwich]

I guess I'll ask again... How do you know? You are saying you don't have a chipped key... BUT that's not what I asked. There are systems that DON'T use a chipped key to provide a form of theft protection. I do believe they were offered AND involve the RAP module. Anyways, that's my guess.

Other guesses is a faulty PCM ... Have you tried a different one?

Lastly, have you checked other things in the truck... window operation, ac controls, door locks, etc... as a hint of a broader problem.... maybe

 

[2000StreetRod]

radio capacitor location

Streetrod where is the radio interference capacitor? I'll unplug that and see if that does any good?

I'n not that familiar with the OHV but the radio capacitor lead connects to the primary power connector to the ignition coil. There should be a disconnect between the capacitor and the coil enabling easy capacitor replacement.

 

[97SportinMn]

And I'll answer again, Budwich. If you READ my original post, you would have understood that I just bought my Ex, and have NO history regarding it. So, to the best of my knowledge, I do NOT have a security system. I did not get a remote with it so I turned the ignition\off 5 times to check if I have keyless remote, and I don't (assuming it's working). When I turn the key on, I don't get a security light on the IP (assuming it's working). This is what I know, so this is all I could answer to your question.

Aside from the nasty tone, I appreciate the question. It gives me something more to look into. I never heard of a RAP module, and had seen no mention of it anywhere til you brought it up. You may be on to something. I see it's located in the left quarter panel area. Do all Exs have one or are they only on those with security systems? How about keyless and no security system?

I'll look into it and let you know what I find.

 

[97SportinMn]

Thanks Streetrod, I know exactly what part you're talking about, I didn't know what that did! I'm guessing, being a capacitor, when they fail they short to ground? I'll test it. thanks.

 

[budwich]

That's better... that's why I asked how do you know? Instead of quoting some stuff about options etc, you now have indicated that you have done some testing/checking to see if there is something related to the feature...great. good luck.

 

[ranger7ltr]

Look at the red arrow...

Streetrod where is the radio interference capacitor? I'll unplug that and see if that does any good?

The ignition capacitor is mounted on the coil pack in front of it...I think this picture shows it best...

 

[Robert Nick]

The Capacitor is used to Filter Noise from the Coil Pack. It prevents feedback into the Radio. Leave it unplugged.

 

[ranger7ltr]

Problem with a used vehicle...

And I'll answer again, Budwich. If you READ my original post, you would have understood that I just bought my Ex, and have NO history regarding it. So, to the best of my knowledge, I do NOT have a security system. I did not get a remote with it so I turned the ignition\off 5 times to check if I have keyless remote, and I don't (assuming it's working). When I turn the key on, I don't get a security light on the IP (assuming it's working). This is what I know, so this is all I could answer to your question.

Aside from the nasty tone, I appreciate the question. It gives me something more to look into. I never heard of a RAP module, and had seen no mention of it anywhere til you brought it up. You may be on to something. I see it's located in the left quarter panel area. Do all Exs have one or are they only on those with security systems? How about keyless and no security system?

I'll look into it and let you know what I find.

Is that you often do not know what the previous owner or owners have installed... I too did not know the history of my 99 Explorer Sport... I did know that on the throttle pedal bracket there was a mini toggle switch that seemed to do nothing...And I too got no kind of remote but when I dropped the under dash pan on the drivers side I found an Audiovox unit installed and it was apparently functional... When I removed it I lost the starter and the ignition...I had to find the wiring diagram for the unit and repair the wiring cut when that POS was installed...

It is amazing what people will install when they could have added the same items that the factory made available...Not saying this is the issue here but it is something else to look for...