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2005 Jeep Liberty will only start with three spark plugs

Hello - I have a 2005 Jeep Liberty with about 129K. The car overheated and resulted in changing the head gasket and piston rings. Now the car will not start with all six spark plugs installed. It will only start and run for a short period time with three spark plugs on the driver side installed. Any help is highly appreciated. Thanks

I think that a good independent mechanic should take a look at your Jeep. Something was done wrong or something was not checked on your engine. Sometimes when an engine overheats…it becomes toast and repairing it is almost impossible.

Both head gaskets were replaced? New rings on all 6 cylinders? Were the heads taken to a machine shop? Were the valves worked on, any replaced?

My guess is one bank is down due to low compression. Perhaps the rings were installed wrong, the head and/or valves have an issue, or perhaps scared cylinder walls.

Without much more info it’s a bunch of guesses.

Did you do this work yourself and did you have a book to refer to.

I hope you did not rely solely on U-Tube videos to follow.

I recently helped a young man with an engine that he rebuilt himself, with only U-tube as a guide.
He missed so many important steps in the rebuild that I don’t even want to be involved with starting this thing. He checked no clearances with the new bearings with “plasticgage”, did not keep rod caps with the same rod, oiled all bolts before torquing, and even thought that the distributor cap firing order was 12345678 around the cap.

Even having rebuilt at least 40 engines in my life, I still get the proper info first. Why go to all that trouble and forget a step. Even a Haynes manual for $25 at least gives you all the steps and the spec’s you need.

If you removed the timing chain, you could have one bank of cylinders off with the valve timing and just got lucky with the other bank.

If the compression rings were not spaced properly on the pistons you would not have compression enough to fire those that were not spaced properly.

Firing order from the cap to the plugs could be wrong.
Or the distributor could be installed wrong.

If the timing chain was removed and not aligned properly when reinstalled, there could be bent valves on that bad bank already. I would recheck the timing marks for the chain and if that’s ok, I’d pull all the plugs and do a dry and wet compression test.

If you don’t have a book, buy one and go over the chapter on rebuilding the engine. You may find it was a simple mistake.


I tend to agree with Yosemite’s line of thinking about a camshaft being out of time on one head and possibly valve damage if that is the case.

Timing problem of some sort for sure. Clearly, the two cylinder banks are “fighting” each other when all spark plugs are installed. Are you absolutely positive you have the wiring to the ignition coils correct (nothing switched)?

You don’t mention anything about replacing the catalytic converter.

If the engine was overheated, the cat was probably damaged. And if that happened it may be causing excessive back-pressure. Removing the three plugs may be relieving some of that back pressure.

Try removing the Y-pipe from the exhaust manifolds and then see if the engine will run.


My first guess is what @Yosemite mentioned,

Firing order from the cap to the plugs could be wrong

If the spark plugs aren’t connected to the right places on the distributor, the car will usually run better if the miss-connected plugs are just not connected at all. And if you only have three plugs connected, the engine will probably run better on 3 cylinders if the other 3 plugs are completely removed so no force is required to compress the mixture in those cylinders.

This engine has coil-over-plug ignition. No distributor.

There’s a distributor function though. It’s just done electronically with the cop ignition. It’s still necessary to correctly configure the wiring for the coils and plugs, right?



You can hook the coils up however you like and the ignition system figures it out ?



I got it right? My guess was correct? Cool.

Generally, the wiring harnesses for C-O-P are such that it would be difficult to mis-wire them to the wrong cylinders. However, since the top of the motor was taken apart, I wonder if the harness was somehow reinstalled in a way to make such mis-wiring possible, such as reversing the cylinder banks. Kind of grasping at straws here, though.

Thanks for the great explanation @NYBo … yes, with the top end of the motor taken apart, a wiring harness or similar wiring connection problem should definitely on the list of suspects.

I have a 2005 Jeep Liberty that I just installed another engine in . It would be very difficult to mix up the wires to the coils .

How are the other ends of the wires connected? Not at the coils, but at the ignition module or ECM. Is there a connector there that could be connected backwards?

I think the one of the camshafts is mistimed. Distributor cap talk is always fun, in other news President Nixon has resigned…

Who’s talking distributor caps? This is the space age @Nevada_545 … besides @Tester says above you can hook up the coils any way you like and the engine computer sorts it out. :wink: