sitting on the highway...

[RonD]

Engine won't die like that if it's 1 tooth off, lose power with lower compression but not die.
More than 1 tooth off and the valves starting hitting the pistons, and it would still run, I know that for a fact, unfortunately, lol, friend used the wrong timing mark on his motor, started right up but had a heck of a lot of lifter tap........wasn't the lifters tapping

Now the chain could have broke, that would kill the engine and at speed probably bend the open valves over pretty good(or bad), so they are no longer in the way of the pistons, cam shaft is no longer turning..
That would make the starter turn the engine over faster since there would be pretty much 0 compression on all cylinders.


Hopefully it's just a bad wire.

 

[kunar]

2.9's aren't interference engines. I had one lose a timing set one time, no damage done. If the harmonic balancer bolt is loose, it will wear on the indexing tab on the crank sprocket until it eventually shears. At that point, the engine cranks, but the cam isn't moving. Given the proper circumstances, the 4.0 will do the same exact thing. Believe me, I know.

Sent from my HTCEVOV4G using Tapatalk 4 Beta

 

[dispatchrobb]

It's not a timing chain issue. Engine was just completely rebuilt last year. When I said "freely" I meant it turns over just sounding different, make your truck not have a spark and turn it over, it sounds like that.

Right now I have 12V to the coil with key on, but there is no switching when I check that side. replaced the TFI module on distributor and still nothing. Wires that needed checked look good to me.

The only code I've ever pulled is the code 15 Failure in ECA. How do I know if the computer is shot? All check engine lights come on when I turn the key on but no spark. The other issue is when it did run, there were times when it just sounded a tic off. No one would notice normally, but since I drove it everyday I am used to what it sounds like and feels. Rarely the check engine light would come on while driving and it would run just a tic off, sometimes, or it would be on and there was no change. Sometimes no light and it still started running a bit off. but still no other codes but 15. Sometimes there would be no light and running fine, I'd stop somewhere for a few minutes, and when I started it up, about 10 seconds later the light would come on, it'd run a bit off, but then I'd start driving and it would go off and be fine. no rhyme or reason as to why it would do this. Then this last day I was on the highway, no signs of anything, no loud bangs or noises, it just shut off and that's that.

A few months ago the engine light was on all the time, it ran a little off all the time. I replaced the computer, then it ran totally fine, up until now. If it is the computer, how do I know that I'm not doing something to destroy the computer? It just seemed like a slow progression till it didn't run anymore. It does seem like I'm getting a higher than normal voltage when it's running. Would slightly higher voltage slowly kill the computer? I sort of think there's something wrong with my alternator, because the voltage varies slightly while running. Would the voltage going up and down a volt or two eventually kill the computer?

 

[adsm08]

The voltage can and will vary with the engine running based on what the computer wants it to do, and this can be affected by everything from battery charging to the cigarette lighter in the dash. A volt or two fluctuation will not damage the computer in any way shape or form. Taking a PowerProbe and hitting the + button while hooked into the PCM power line will kill it, and a bad voltage rectifier letting AC bleed through can damage it over time, but normal 1 or 2 volt flux won't.

The other thing is that a bad computer won't cause a no spark condition. You can take the computer out completely and still get spark (I've done it). The engine computer on the 2.9 only controls timing, the TFI is in charge of firing the coil.

No switching on the green/yellow wire at the coil means that the TFI is not seeing the engine spin, which means the computer probably isn't seeing it either, so I bet you have no fuel injector pulse in addition to your no spark.

Since you say the TFI is new, the next best suspect is the pickup in the distributor. They are kind of a pain to replace because the dis must be removed and completely disassembled to get it out. While not as common as a bad TFI they do sit in the back and cook and can be prone to heat related failures.

If it is more than 5 years old and you have suffered repeated TFI failures it is generally recommended to replace the pickup and the ignition coil because either of those parts being worn can place an undue load on the TFI and kill it.

 

[dispatchrobb]

Coil is also new. Since I've owned it for a few years I have never experienced a TFI failure.

Is the pickup the same as the Hall Effect thing? I was reading the test procedure and not sure I understand how to test this. Is there a way to know for sure that the pickup is bad?

 

[adsm08]

The pickup is the same as the hall effect sensor.

I am not 100% sure how to test it. I know it will generate an A/C signal with the engine spinning, but it is a 3-post sensor and I don't know which pins need tested.

 

[RonD]

Bottom of this page has OHM readings to test for.
http://www.therangerstation.com/tech_library/TFI_Diagnostic.html

Hall effect sensors can fail, but they are not the most likely failure on a TFI system.


As always check the basics, the dumb ones, is there really gas in the tank, is the distributor shaft turning.
While it's always a good feeling to track down that "elusive problem" while doing so we often forget to check the basics.

 

[dispatchrobb]

Ok, I checked the easy stuff, power is to the computer, the wire from dist to coil is good, gas is certainly in the tank. I took the cap off and wouldn't you know it, the dist does not turn! I can't turn it by hand, but it does not turn while engine cranks.

Now what do I do?

 

[Andy D]

I would be looking for exploded diagrams of the dizzy drive. . I don't know a thing about the particulars ,so that is where I would begin. The Jeep 360 V8 used a Ford distributor that was gear driven off the cam. When gears were replaced they were a matched set. If not , wear was excessive . Does my 4.0 use a similar design? I dunno, it isn't broken . Please post a follow up

 

[dispatchrobb]

Ok, took the distributor out and the gears are all perfect, no chips, or stripped or anything of the sort. Holding the gear and trying to spin the top it does not appear to be broken at all. Have not been able to see into the hole to see if that gear spins or not, it started raining. Gonna look today to see what's up. Is there a key or pin in the cam that can strip on the gear? This engine was rebuilt a year ago. Does not bang or clank or make any weird noises when it's turned over. Is the gear on this cam part of the cam or bolted on? Just trying to figure out what's up with this thing.

 

[shane96ranger]

The cam gear is part of the cam. Does the gear on the distributor have any play at all? Does the shaft have any play?

Posting whilst sitting upon the throne.

 

[dispatchrobb]

Dist shaft has no play, I can hold the gear and hold the top and there is no play or anything. the pin in the gear looks just fine, I can see through the hole of the pin. I looked down the engine and gears look fine. I have a sneaky suspicion that when the engine went back together that the other end gear was not torqued right and got loose and spun that end. Is the other end gear a woodruff key, or a pin out of the cam or some other bump out type pin? This is probably why it sounds different when it's turned over, it's probably not turning anything on top.

 

[dispatchrobb]

UPDATE-

Ok, so I finally got around to it and have the timing cover off, and the crank is what is spinning in the gear. No gears turn, just the crank. Starter turns and I watch the end of the crank just spin and nothing else. I guess that's clear enough lol.

So how does that gear attach to the crank? Woodruff key? I don't see anything else on there. Is this thing going to have to come completely apart?

 

[shane96ranger]

Yes, it has a key. You will probably need a puller as well.

Sent from my Quad Core Acer A210

 

[RonD]

Yes, woodruff key is what holds the timing gear in time with the crankshaft.

You should be able to remove the sheared off key from the slot in the crank, and the gear.

My concern is why it sheared, have you pulled the valve covers and looked at the push rods, rockers and valves?