1998 ford f150 4.2l 4x4

driving down the highway on a fairly warm day. Truck suddenly loses all power. my first concern is maybe fuel pump, or vapor lock, but as I cranked on the side of the road, I was concerned of hydrolock with the way the engine seems to buck back against the starter. hydrolock is ruled out upon further investigation. currently in a crank/no start condition. It seems as though the ignition timing may be advanced. it backfires intermittently through intake and exhaust. so symptoms lead me to believe at this point that the timing chain may have slipped a tooth. Though I'm not sure that is possible without some audible indication as to that being the case. also, for every forum and google search I do. i never hear of a timing chain that actually slipped on a ford 4.2. that being said, if would be just my luck for me to be the first one it ever happened to in the history of the ford 4.2, and that is my next logical assumption at this point? no trouble codes on obd2 (pulled battery may times before reader could be attached), and I believe the check engine light is burned out. It never comes on.
Ruled out so far:
Crank and cam sensors
coil pack
spark plugs and wires
fuel filter
fuel pump does cycle and gets returned pressure to rails after relief on schrader valve. not sure about individual injectors. there is fuel pressure, i have no reason to believe it's inadequate. or that lack of fuel is the problem
spark is there
AIR is everywhere!!!
BOOM im stumped!!

Where it gets more tricky:
Right as the truck died it started having another strange condition where the "beeper"/indicator for the key being in the ignition. would stay on while the key was not in the ignition. i would turn the headlights on (another action that triggers the beeper, but faster) then turn off the headlights. at which point it would silence for a minute or two. the beeper leads me to believe that there is a short in the system that (if I'm not mistaken) also controls the pcu of the truck. this could possibly have fried the pcu, and if i can find one at the junkyard, im hoping that may tell me something.
will update when pcu is replaced and timing chain is inspected. Any help or suggestions are greatly appreciated!!

 

A compression test might tell you something. A while back a member posted about a timing problem on a high mileage 4.2 engine. It had abnormally high compression. That problem was the keyway on the crank pulley had worn to the point the the pulley/harmonic balancer was not in the correct position.

 

Indeed, and I was mentioning that thread to a friend this morning that also hoped me to believe that could be a fix to my symptoms. certainly explains how it could be off time far enough to keep the truck from running, but nothing sounds amiss mechanically speaking.. May have even been you that had mentioned it in that thread even... now that you mention it. lol. That thread never ended up coming to a solution, at least one that was posted. i want to say dude ended up scrapping his truck. but his crank spline (keyway?) seemed in line as well, something i still need to rule out. so you say a compression test may tell me something. i agree, but my tools are very limited. i need to actually know how much, not just that there is compression right? YAY for new tools!! should i also inspect the keyway as i pull off the harmonic balancer? as far as i can tell, the gear looking thing that the crank sensor reads (assuming that is the "keyway") seems to be in good shape with no play in it, or the harmonic balancer. I will have to do that to inspect the timing chain at any rate. what should i be looking for?? are there alignment marks that should line up the keyway at TDC? hopefully that is a much easier solution than the alternative options i'm left with at this point. There was also another forum i came across that mentioned that the wiring harness that goes over the egr tube on the pass side over top of engine. likes to char and short. i am in the process of testing everything on this truck, but i dont think a short in this harness is the issue. its soft and malleable everywhere i can reach it. Thank you for your suggestion roadie, and thank you for any suggestions in the future. im going to look the process fofr pulling off the timing cover, it should say what to look for as far as aligning the balancer id think

 

http://www.autozone.com/repairinfo/r...00c152801e5250
as far as i can tell. removal of the timing chain is quite an extensive procedure. requiring a synchronizer tool for the cam sensor? My question is. if i rotate the motor to =TDC before i remove the timing cover, should the notches line up on inspection so that further tear down is not necessary and i can just line up the cam sensor synchro with my marks?

 

The thread I remember about the worn keyway ended with the truck being fixed and the cause discussed. The truck had been shipped to a carribbean island and was being worked on there.

 

ill look for that thread. this one is the one i found. http://www.truckforum.org/threads/19...t.28634/page-2
does me little fixing the problem (if that is the problem) if I don't know the cause. everything on the crankshaft seems to be in order. nothing amiss. i have already had water pump off to replace the cam sensor, and replaced crank sensor no apparent damage in that area. can you point me to the thread where it was resolved by chance?

 

This is one I found but not the one I remembered.
https://www.f150online.com/forums/v6...arely-run.html

and another
https://www.f150online.com/forums/v6...-no-power.html

Seems to be happening a lot.

And this is the one I remember.

https://www.f150online.com/forums/v6...nna-try-3.html

 

Not saying that the Key in the Harmonic balancer isn't the issue. Certainly can be.

May I offer a simpler option...I had a Fram air filter come apart on my truck and some of the filter media landed across the MAF sensor...my fix was simple clean the MAF sensor and install a new air filter, and no it wasn't a fram.

Pretty sure that the air filter is the same no matter the engine size on these

 

already cleaned maf sensor. have not replaced it, but is that a issue that can keep the truck from running at all? backfiring through the intake, not starting on starting ether. maf sensor looks fine, is there any way to test it?

 

so the keyway is definitely the problem. as i pulled off the serpentine belt to inspect the balancer, it spun around freely. i removed the bolt without even using a wrench, and the balancer slid off with ease. least i dont need to rent a puller.. so what next? is this fixable?

 

If the end of the crankshaft is not worn/damaged you just need a new balancer and key. If the crank is worn, the engine is toast or at least you will need a new crankshaft.

 

how long should the key spline be on the crankshaft? seems to only be about 1/4 inch long at best. it does not seem to be damaged, just seems to be short considering the keyway slot on the balancer goes all the way through, and is at least 1 1/2 inches long. im hoping the bolt just loosened itself, and it slid off the keyway. it seems weird to me that it would wear completely smooth on everything but the 1/4 inch of the driveshaft closest to the timing cover.