2.5 issues... timing ?

[Greg-100]

 Bought a 98 TJ with a 2.5 engine, 295K on it with 4 hibernating squirrels in it.

Seller sold as a possible timing chain issue as he had did a compression check with 30 psi in all 4 cylinders and no increase when a few squirts of oil is put on top of the rings.

I confirmed the compression test.

Holds compression well .... very little leak down.

I have checked the alignment of the timing marks, they are aligned.

Chain is stretched beyond the 1/2 deflection and the teeth are sharp on the sprockets.

Looks like someone replaced the chain tensioner in the past, not a lot of wear on it.

Question: Is there any other issue that would cause low compression over all 4 cylinders other than cam/crank timing on a 2.5 engine?

I am not wanting to throw a lot of money at the engine as it will be cheaper to buy a used motor and swap it into the TJ.

Greg

[foghorn]

Bent rods? any marks in the piston heads? guessing the po threw the chain and is maybe playing dumb now?

[Greg-100]

Shone a light into the spark plug hole on each cylinder, nothing that looks ontoward.

The part that has got me baffled is all four cylinders have the same low compression.

Moved the chain one tooth on the cam sprocket with no change in compression.

Waiting for a timing chain set that will be in tomorrow.... may try moving the chain the other direction to see if that brings up the compression while I am waiting.

Thinking the timing between the crank and the cam is so far out that not enough fuel / air mixture is getting into the cylinders to make high compression?

Greg

[foghorn]

Im talkin valves here, marks on top of the cylinders? cant see another changing comp. id pull the head myself.

[Greg-100]

Still thinking timing.... the all cylinders are holding pressure... how be it low.

Have a timing set coming tormorrow.

But again I don't have the answer.

Greg

[Greg-100]

Nice new timing chain/gears set did not change anything....

Foghorn you are right!

Now thinking all the push rods are bent, so that gives the low compression on all four cylinders.

Will pull the valve cover and see if the push rods are bent.

Greg

[Greg-100]

Push rods are straight.

I guess I am looking for another engine.

Still not sure why the low compression, but will tear it apart to find out.

Greg

[Greg-100]

Put air to number 1 cylinder with the rocker arms off the valves.

Holds air without any leakage.... now thinking camshaft is wore out.

Will pull the engine and see if it is worth rebuilding.

Greg

[afb]

Chances are the valves are leaking. The 2.5l only have a single angle valve grind on them and the valve springs were weak.  I just had a buddy that was going through the same problem and he stripped the motor down and re-ringed it but still had the problem. I convinced him to get the head done and now the problem is gone. f your interested get a hold of "the machinist" on here. He charges little and you get a 3 angle valve job with new guides.

[Greg-100]

AFB,

Have the motor stripped ready to come out. (engine has been worked on, lots of new bolts and no fighting to get bolts to rotate)

Been working away from home this week, so ready to go back to working on the jeep today.

Talked to mechanic, his opinion is for me to make sure I am TDC on number one as he says no way all four cylinders could be 30 psi at the same time.

He says I have four chances to be wrong.

Not thinking valves (just yet) as when I put shop air to the cylinders I have no air noises from the engine, but I have be wrong on everything so far. (have ordered a blow by kit, so I can see if there is a leak down)

On the plus side, I made a extension with air brake line for the compression tester, now I can put the gauge under the windshield wiper and watch it as I crank the engine.

This is my first run at valve timing.

Greg

[Vinman]

Is it possible you and the PO have the timing marks out 180 degrees?
When the mark on the crank is at the top, is the cam mark top or bottom? Try rotating the cam 180 degrees and see what happens.

[Greg-100]

Vinman,

Have be messing with the timing issue from all angles, I even put the camshaft one 180 out to see if I got a change in compression.

Had a friend come over and help confirm TDC and timing marks.

We pulled the jeep across the shop watching the number one intake and exhaust valves open and close, used and arrow to confirm the piston movement.

When we do the compression test ( with two different testers) it holds compression, how be it low.

Have the timing marks set by the book.

Will do the leak down on it this week. (still got to be in town during store hours to pick the kit up)

Starting to think someone put in a cam with a bad grind or wrong lifters.

Again thanks for the ideas.

Greg

[Greg-100]

Knucklehead.....

I did not take the valve out of the bottom of the compression tester when I converted it to put compressed air into the cylinder.

So when I put shop air to it pressured up without allowing air into the cylinder then slowly leaked down to 30 psi.

When I put compressed air to the cylinder (both rocker arms loosened) the intake valve lets air rush by loudly.

So AFB called it a 100%.

Kncklehead Greg