If there was a mechanical failure under the valve cover which caused something to erupt out of the cover your mechanic should easily be able to look in the hole with an inspection mirror or borescope to see what broke. It appears to me the fire started outside the engine.
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So here is a question: would it be possible for (1) fire starts outside the engine (2) burns hole in valve cover (3) ignites and through fire consumes the oil inside (4) thereby decreasing oil pressure to the extent that (5) it throws a rod?
And one more thing - if the engine threw a rod and punctured the valve cover, thus causing the fire - I should expect to see a dent on the underside of the hood opposite the valve cover because what projectile exited the engine would most likely have traveled at a high velocity another five inches and struck the hood -
The connecting rods are in the lower part of the engine, they generally damage the block and oil pan when there is a failure.
I doubt the engine threw a rod, it stalled because the wiring harness was burning and shorted out basic inputs and outputs of the PCM.
The fire didnât consume the engine oil, did you check the engine oil level and find it to be low?
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to add to this- i would think that you would have noticed the fire well before the engine stopped because of lack of oil- if the on fire oil were to be the cause for a thrown rod.
The engine never stopped entirely. It was bucking and coughing, but even after I pulled over to shoulder and shut it down, I started it up a minute or two later just to move it further off the road. It was coughing pretty hard, and I shut it down again probably 30 seconds after I started it - the time it took me to shift into drive and move it a few feet over. The sound reminded me of the noise my lawnmower makes when it is near empty and then an uphill push starves the engine for fuel.
As for oil - I pulled the dipstick two nights ago and it is at the âaddâ line - not below it, not above it, right at âadd.â And, there is oil spattered in the front passenger wheel-well and on corresponding frame and parts nearby.
Appreciate all the input here -thanks
Likewise, if the fire started on the engine and burned a hole in the valve cover, it should be quite obvious that it was a hole melted in the cover. So just look at the hole.
No, I donât see that happening. Thereâs nowhere near enough oxygen in the crankcase to sustain combustion of the oil in there, even if it somehow ignite in the first place.
The connecting rods are in the lower part of the engine and arenât really related to whatâs inside the valve cover.
With a hole in the valve cover, oil will get squirted out that hole as the engine runs. Thatâs what the valve cover is for, to keep the oil lubing that areaâs rapidly moving parts inside the engine. Maybe the oil loss you experienced is partly b/c of that. Posters here have reported a problem that they lost most of their engine oil b/c the oil cap located on the valve cover was accidentally left off after somebody added oil. They started the engine and drove off, and soon thereafter the oil light came on and when they popped the hood, oil was all over the engine. On some of those threads so much oil was lost out the oil cap hole the engine was damaged. But it seems unlikely OPâs engine was damaged by low oil, as âat the add markâ on the dipstick is still plenty enough to adequately lube and cool the engine.
https://www.youtube.com/channel/UCtAGzm9e_liY7ko1PBhzTHA had an episode on Jeep Liberty having rough operation
he found a rocker to fall off for no apparent reason, he explained it by âmaybe the owner went close or over red line?â, but would not be able to tell it is 100% accurate diagnosis
after putting rocker back, engine worked just fine
now, if we imagine that rocker was the factor in OPâs vehicle, potentially it might have created a neat hole in the valve cover, the rest of events cascaded ?
valve cover removed and mechanic reports major engine failure - rocker, valve, spring - broke off punched a hole in the valve cover which released oil which caught fire - mopar 3.7
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Looks like you were less lucky than the guy I mentioned, in his case rocker simply fell off, but the rest of mechanics was not damaged/
From what Iâve heard, 3.7 was not very reliable engine (to say the least), especially of older production 
Thanks for the update.
More updates . . . NHTSA features 20+ instances of either engine fires (âunexplainedâ) or rocker arm or similar issues to my vehicle in the 2006-2012 Liberty - did not check 2002-2005 or other models (Nitro, Ram) that used the 3.7 engine. FCA sent a third-party engineer to examine the vehicle (I opened a ticket there), which I thought was interesting b/c the vehicle is out of warranty. Though as one person said, if I could find records of 3.7 valve/rocker failures and fires, chances are Jeep is aware of the commonality of the issue, too . . . will keep you posted . . . in the interim, my gift to myself this December is a re-manufactured engine and install kit.
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well, hopefully FCA will own the issue and you will get some of your gift costs offset
UPDATE: FCA letter . . . ânot a manufacturing defect, youâre on your own . . .â (but maybe a design defect . . . ?). Remanufactured engine in, but 30 miles later threw an engine light - misfire on cylinder 5 - spark plugs are new; injector coil, fuel injector, compression all test OK . . . mechanic said this wonât be simple since it started shaking after the new engine was installed
Misfires are usually diagnosed by swapping parts between cylinders, seeing if the misfire goes to the other cylinder or not. If you are certain the coil, injector, and cylinder compression are ok, other ideas might be
- the injector isnât being pulsed the same as the others
- the ignition system isnât firing the spark plug the same (voltage, time, etc) as the others
Since the engine was shaking as soon as the newly installed engine was first started, common sense says the first step is to make sure the spark plugs are connected to the ignition system in the correct order. Very easy mistake to make, just as easy to fix. After that a o-scope analysis of the ignition system, then the same for the injector pulse circuit. Good idea to make sure the fuel pressure checks out too, on a rebuilt engine install like that. The fact that it didnât run well right off the bat may prove to be a good thing. My guess is this is something minor.
A Christmas miracle - the light did not go on this morning, stayed off throughout the day.
maybe the engine software had to go through a learning mode with the new engine install, and now it has learned the correct engine operating parameters.
Well, after a week of the CEL going on and off every couple of days, I rolled the vehicle back in - 467 miles on the new engine - when they raised the vehicle for the 500 mile oil change, they law bulging hoses and leaking coolant - then to the CEL - swapped parts between cylinders, injector was firing properly, ran a CO test and found a bad cylinder head gasket in the cylinder that was coding misfire - hence the bulging hoses and leaking coolant and misfiring - now playing phone tag with the engine reman company from which I also purchased the no-fault warranty - and they seem to be in no hurry to call back -