Timing chain slip?

[jklanier]

so, is it possible, for the jeep to be running fine then just jump timing?

I was driving along, and i felt some hesitation accelerating out of the corners. Pulled over, jeep died, and hasnt started since.

Threw codes p1391 (intermittent loss of cam/ crank sensor signal), and p0300 (multiple misfire). Replaced cam (new MOPAR) and crank sensors (Junkyard MOPAR){backorder from dealer}. Still cranking but not starting/running.

I 100% have fuel and spark.
It isnt throwing ANY codes but it also isnt running, soooo.....
It kinda souds like a timing issue, but i dont understand how it could just be fine one second then be off the next.

help!

 

[J33Pfan]

so, is it possible, for the jeep to be running fine then just jump timing?

I was driving along, and i felt some hesitation accelerating out of the corners. Pulled over, jeep died, and hasnt started since.

Threw codes p1391 (intermittent loss of cam/ crank sensor signal), and p0300 (multiple misfire). Replaced cam (new MOPAR) and crank sensors (Junkyard MOPAR){backorder from dealer}. Still cranking but not starting/running.

I 100% have fuel and spark.
It isnt throwing ANY codes but it also isnt running, soooo.....
It kinda souds like a timing issue, but i dont understand how it could just be fine one second then be off the next.

help!

try a compression check ASAP -maybe first four cylinders

 

[jklanier]

pulled the valve covers
everything looks perfect. timing chains are tight
timing appears to be correct, v6 marks on cam sprockets at 12 oclock but the notch on the harmonic balancer is a little off of the TDC mark

also i have compression, because i spun it over a couple revolutions by the crank and it has plenty of resistance, valve train is fine also

 

[JeepinJarhead03]

when it wont crank youd need a scope to see 100% which sensor is causing the problem - best bet is to pull the battery for a few, and let the sensors try to re-identify their sync and double check your wires for melts and such as well

without the sync between the sensors the engine cant properly determine between an intake and exhaust cycle or when to trigger fuel - so without that sync it basically is out of timing, electrically rather than mechanically.

The likelihood of both sensors taking a dump at the same time is pretty low - so its worth a try putting the original crank sensor back in instead of the junkyard sensor and resetting the battery and trying that as well

so either you got a bad new cam sensor, and/or a bad junk yard sensor, a melted wire, bad old info on where TDC is
without a scope youre legally blind , but its good youve verified physical spark existence and that the injectors are triggering. just unfortunately the cms and cks have to cooperate for the noise to make happening

****
As for it jumping timing, according to your description of how it was running prior to it stopping cranking all together - progressively getting more sluggish and then not cranking up doesn't really match with a instantaneous jump of timing. - does match up with sensor failing and or wiring melting though.

 

[jklanier]

i pulled the battery for probably a half hour or so and played with the sensors back and fourth, buuuutttt, decided to pop the valve covers so i clould check and somehow with both the 'V6' marks at 12 oclock, the notch on the harmonic balancer is about an inch to the right of TDC.

hooray....

so im pulling the timing cover today to see whats going on
the only thing i can think of is a timing chain tensioner went out?

 

[jklanier]

also, i tried some generic sensors first and when that didnt work i started looking for damaged wires, havent seen any yet but ill look some more bfore i pull the harmonic balancer and the timing cover, as they are a giant PITA.

 

[tjkj2002]

also, i tried some generic sensors first and when that didnt work i started looking for damaged wires, havent seen any yet but ill look some more bfore i pull the harmonic balancer and the timing cover, as they are a giant PITA.

I did both heads on a '02 KJ a few weeks ago,pulling the valve covers takes twice the time as pulling that front timing cover(literally a 15min job).

Another issue could be you broke a keyway on the crank allowing the pulley and/or sprockets to move on the crank.

 

[jklanier]

ok, so the issue for me is that while i can find the tool to remover the balancer, its a lot harder to find the tool to re-install the balancer, plus having just done a head gasket, the timing cover got sealed with RTV soooo thatll be fun too

im just whining i know, out to the jeep i go....

 

[Logan Savage]

I have reassembled 2 - 3.7's in the last year & I haven't needed any special tool to install the damper pulley . On both engines the pulley slid in far enough to start the bolt .

 

[jklanier]

Yea, I wish, I got the valve covers off, and the notch on the crank is about an inch to the right of tdc when the v6 marks are at 12 o'clock

Also my balancr was a bear to get off and back on when I did the head gasket a couple months ago.

The AutoZone tool isn't.long enough so I have to go rent a long reach puller tomorrow.