After shutting off the engine in a parking lot, the engine would not restart. Towed it back to my house. Discovered that the #5 plug wire was melted from contact with EGV plumbing. I could start the engine with the wire loose but not connected so I surmised that the wire had an internal short and replaced it. After replacement the engine won't start. Pulled #5 plug again and held it against the intake manifold -> no spark. Put a screw driver in the wire cap and held it near the manifold -> no spark. I can smell gas on the plugs. I have replaced the coil pack. The 25A coil fuse checks OK. There's nothing in the after-market manual I have that describes how to check the four input wires to the coil pack. Can anyone help me out here? I'm going to head to town for a spark checker.

 

Welcome to FTE.

Do you have a CEL lit????
If so, have the computer scanned for trouble codes & post ALL the trouble code numbers found, as they can provide good trouble shooting clues.

We have a "Waste Spark" system, in which there are only 3 coils in the coilpack for all six cylinders, so plugs 1/5, 2/6, 3/4 are paired to fire together, such that for instance, when #5 gets a spark on it's compression stroke, #1 is getting spark on it's exhaust stroke, ect, ect, so be sure to check the #1 plug wire to make sure it's ok & not shorted out, as that would kill the spark for the #5 plug wire too.

Same for the other cylinders also.

So if all the plug wires check out ok, make sure the coilpack has 12 volts B+ to it on the R/Lg wire, so that it's hot all the time at KOER.

So check to see if you have B+ to the coilpacks electrical connector @ KOER on the R/Lg wire & if not, check the coilpacks electrical connector & wiring.

Did you have the new coil pack bench checked at the store before you left with it???? Just because it's new doesn't automatically make it good!!!!

If you come to suspect the new coilpack & know that the old one is likely good, since finding the shorted #5 plug wire, then put the old coil pack back in & try it again.

If your sure the coilpack is ok & if the other plugs aren't getting spark, but you have B+ to the coilpack, the computer supplies a ground switch to fire the correct coil in the coilpack & that ground is triggered & timed by the crank sensor.

So, check the crank sensor, it's wiring all the way back to the computers electrical connector on the fire wall & the sensors crack shaft reluctor, for missing, or damaged teeth, it should have one tooth missing, as thats the timing mark, but not more than the one. The teeth shouldn't have any metallic debris on them either.

A whole bunch of thoughts for pondering.
Let us know what you find.

 

My brother-in-law came over with a friend of his who is a certified mechanic and scanned the computer. We got no codes, which he said was equal to "OK". But, we couldn't find anything else so I replaced the computer. Still no joy.

The crank sensor is all that's left. So, is it a crank sensor or the sensor that's where the distributor used to be? There's got to be a signal from somewhere to tell the coil to fire, is that the crank sensor? Is there a way to test it?

 

OK, lets think about this some more & get positive trouble shooting results, BEFORE you throw any more parts at the problem!!!!

I'm not real clear on some of the things you've posted.

Recap:

The vehicle wouldn't restart in the parking lot, so you towed it home.

You found #5 plug wire shorted & replaced it, but no spark.

But the vehicle would start with the #5 wire removed!!!??? Is this true, the vehicle would/will start with the #5 plug wire removed????

So you tested the #5 plug wire to ground, but no spark, you checked the coilpack fuse as ok, but still no spark.

So you replaced the coilpack & still no spark.

So you had a friend scan the computer for trouble codes & found none.

So you replaced the computer & still no spark!!!!

Again, at KOER, does the coilpack have 12 volts B+ to it on the R/Lg wire????

Did you have the old coilpack bench tested before you replaced it, or the new one bench checked before you left the store with it?????

Right now we don't know the status of either coil pack.
I know it's logical that the new coilpack is ok, but "Murpheys Law" doesn't subscribe to logic!!!! lol

So now you want to replace the crank sensor because it's the only remaining ignition system component????

If you decide to pull it, why not check it, or have it bench tested, before buying a new one????
Do you have a DVM & know how to use it????
If so, you might get an idea if it's ok before removing it.
But if it's bad, the computer will be unhappy & you should have a trouble code for it.

So right now I don't know if we should suspect it, as we seem to have some unknowns remaining.

Right now I'm not sure your old coilpack or computer were/are bad!!!!

So check the coil packs electrcal connector for 12 Volts B+ at KOER & have the coilpacks bench tested.
If that checks out then check, or have the crank sensor bench checked before buying a new one.

Let us know what you find.

 

Recap in sequence:

Car dies, tow it home.

I went down the list in my Haynes manual and after eliminating all the possibilities was left with 'broken timing belt'.

I had the fan and shroud and alternator off to replace the timing chain when my neighbor convinced me they almost never fail.

We discovered the burnt wire on #5, I pulled the #5 wire and it would start. In fact, it would start with the plug out. I put the alternator and shroud and fan back on but then the engine would not start. I replaced the plug wire. We checked the spark and there was none on any cylinder.

I verified that there was 12v to the coll pack and so I replaced the old one. Still no spark.

My brother-in-law brought his computer reader over and there were no codes at all. Looking at the schematic, it shows that the computer supplies ground to get a spark. Not being able to find any other problem I replaced the computer with a salvage unit. It could be bad itself.

Along the way I got a suggestion to check for voltage on the throttle position sensor connector and found 5v which I believe is the correct value.

This afternoon I took the crank sensor off and found metal bits over the sensor and I cleaned it up and reinstalled it, but still no spark.

I do have a DVM and I know how to use it. I'm guessing the crank sensor should have a low resistance, it looks like it's just a coil that pulses every time a tooth goes by until the missing tooth. Open would be bad. Does a parts store or a dealer have a better way to test it? Dynamically?

I will take the new coil pack into town tomorrow and have it tested. The original one is back on the engine. I'll take the crank sensor off and take it, too. I live way out in the boonies so I have to plan these things around commuting to work and it's usually dark when I get home.

Thanks for the help.

 

OK good feedback.

Your neighbor is right, the timing chain rarely fails.

When it started after removing the shorted #5 plug wire & plug, that sorta said that the coilpack & computer were working at that point, so right now I suspect that the old coilpack & computer were/maybe are, still ok.

OK good, you checked & have B+ at the coilpack at KOER, so we know that the ignition switch & wiring to the coilpack is likely ok, so can forget about that one.

Ford doesn't have a resistance value for the coilpack primary, but it should be less than 5 ohms. The secondary resistance should fall between 13K & 15K ohms.

Be sure to check out the "3.0L Tech Info" link Rockledge has compiled, it's in the "read first" "Tech Info" thread atop this forums thread listing page, scroll down toward the bottom of the page to find it. Lots of good Vulcan 3.0L & flex fuel 3.0L info there.

Most autoparts stores around me can do a dynamic operational output voltage bench test, on the coilpack & CKP sensor & that is better than just a continuity test imo, as the continuity test will only indicate an outright open circuit, or poor connection high resistance type failure.

Without a scope it's difficult to do a meaningful CKP test with your meter, but you should get a pulsing output when back probed with the engine cranking over. I can't remember what the values are, but a forum search should turn it up.

Anyway sometimes the operational bench test will catch other failure modes.

Seeing as how the failure occured during a "heat soak", it might be worthwhile to take a hair dryer along to heat the coil pack & CKP sensor up during the bench test.

Call around & ask if any parts stores can also test the computer.

Good find on the CKP sensor metal shavings & good idea to clean them off.
Also check the crankcase reluctor vanes for debris & clean it up good if any is found.

Right now with the info you've provided, the crank sensor belongs high on your suspect list imo, so be sure to have it tested & check it's electrical connector contacts & wiring closely.

Let us know what you find.

 

Something happened between here:

"We discovered the burnt wire on #5, I pulled the #5 wire and it would start. In fact, it would start with the plug out."

And here:

" I put the alternator and shroud and fan back on but then the engine would not start. I replaced the plug wire. We checked the spark and there was none on any cylinder."
...
I would check that the coil pack is grounded properly, with ALL the screws reinstalled. I would check all the wires that got moved around between the two 'actions' listed above.
Murphy was an optimist, but the odds of all that stuff failing in such a short time frame are miniscule to tiny. All the parts are the same except a plug wire. That is, if you told the whole story about replacing just one wire. If you replaced more than one, were they installed one-at-a-time to insure they are correctly installed?
There is something funny here, in that if you re-connected the #5 wire, it wouldn't start. As noted, the waste spark system fires both plugs, one on compression stroke and one on an exhaust stroke. Connecting #5 *should* make no difference unless the #5 plug is shorted or fouled, and in that case, it would prevent it's pair from firing also. Two plugs not firing could make it difficult to get the engine running.
Does the engine crank over without trying to start, or does it shake and wiggle like it is about to start?
Pull the #5 plug and check it out.
tom

 

I believe the CKP sensors output is a kinda sawtooth, about +/- 5 volts, so you could try reading it on your DVM A/C scale & see if it's
outputting a trigger signal to the computer.

But if it's not working, seems to me you should have the computer complaining about it & setting a trouble code & you say no codes have been detected!!!!???? Kind of a contradiction!!!!

Will be interesting to hear what you discover the problem is.

 

It was the crank sensor. As soon as I compared the old one to the new one I knew. The old one was about a 1/4" shorter from wear and the new one is magnetic where the old one is not. It was apparently good enough to satisfy the computer status check circuits but not enough to fire the spark. Also, it was marginal enough so that it gave up its last gasp when we were checking plug wires but had nothing left when the engine was all back together. I was under the impression that the engine would run rough, but would run without it. Not so.

 

OK, good find fix & feedback & to hear you are on the road again!!!!

 

New theory. The toothed wheel behind the crankshaft pulley was reinstalled slightly off-center during timing chain false start. During the testing for the spark plug wire it wore down the crankshaft sensor. It has worn down the new part again.

 

Hmmm, that could be expensive. Maybe you'd better buy a new truck.

OTOH, how did it get off center? I am truly baffled, as I thought they were installed on the crankshaft directly. I have been wrong before.
tom

 

I have finally figured the whole thing out and I offer this conclusion to help the next poor guy. It wasn't a burned spark plug wire, the original problem was that the circular plate with the teeth that drives the crankshaft position sensor was broken. It is not one piece and it broke at the spokes. it then was free to rattle around some and this gouges and heats the sensor to the point that it stops functioning. Now all I have to do is find/make a suitable puller to get the vibration damper off.