114,000 miles. bought for 4400 9 months ago. changed out cooing system, plugs. just lost compression cylinder 2 and low compression cylinder 3, all others are fine. told by mechanic timing chain skipped---i am skeptical. where to begin to fix? Please give some advice! i am a pretty good wrench, so be technical if need be.

 

if the timing chain had skipped(which is NOT by any accounts a common issue on these trucks) i would expect all the cylinders, or at least all the cylinders on that bank to have no compression, not one on each bank.

how low is cylinder 3?, try putting a capfull of oil in the cylinder and see if that brings it up to spec or increases the number any.

if you are set on the timing chain being replaced http://www.mediafire.com/?2cg2hgim2zz download the service manual and follow the directions, check rockauto.com for the kit.

 

+1 Sharps

If the timing chain skipped then you would have low compression in multiple cylinders not just 1 or 2. There is a trick you can do to help diagnose the issue. Do a compression test on all cylinders and write them down. Then while the spark plugs are out pour about 2-3 cap full of clean unused oil down through the spark plug hole directly into the cylinder. Now do the compression test on that cylinder and continue 1 by 1 and write down the new numbers. Do not try to pour oil down each one and take all readings like your in a hurry. Just take your time and do each cylinder (well at least the ones under 120 psi.

If you notice a substantial gain in compression then it is bad cylinder rings and you need the motor rebuilt. If you DON'T notice much difference at all then it is a head/head gasket/timing issue.

 

Cylinder 3 is @ 120. 2 is not registering. Thinking a valve problem? I agree the timing chain thing does not sound right as all cylinders would fail.

 

What was the first reading on #3 cylinder before and after the use of oil in the cylinder?

And I take it the putting oil into #2 right didn't change the compression numbers right?


Lastly, and I have to ask, these cylinders are next to each other in the middle of the engine on the drivers side right?

 

not if he is using the correct cylinder numbers, 3 is on the drivers side 2nd from the front, 2 is on the passenger side very front.

 

That is the reason for my question.

If it is in fact #3 and #5 or lets say #2 and #4 then it's a bad head gasket. Also there is the question of the before and after compression test (with and without oil) and that tells us more.

http://arrc.epnet.com/autoapp/9355JE.../93023g01L.gif

 

Remember, the 4.7 is an interference fit engine. If any of the timing chains skipped chances are good that a piston hit a valve & either broke/bent the valve, broke a valve seat, or broke a piston. That would explain a zero compression reading on one cylinder and a low one on a different (non adjoining) one. Pull your valve covers and rotate the engine to TDC, checking it with a piece of wire in the #1 plug hole to verify top of stroke. Take a look at your cam sprocket marks & they should be vertical & matching. Regardless of all of the other gear marks & plated links used to time the cams, if #1 is at TDC AND the timing pointer is at zero, BOTH cam marks should be at 12 o'clock. If they aren't, then at least one of the chains jumped & you need to do a teardown. By looking at the various plated links you'll be able to figure out which chain it was.


Bob

 

appreciate all of the remarks! compression did not change with oil in cylinder. leaking out valve or head gasket. we did have overheating problems with this vehicle and this may have contributed to the problem. #2 and #3 are on opposite sides of the motor and are NOT across from one another. head gasket is a big job, and i am not sure if i am THAT good of a wrench. I will begin the laborious task as I cannot afford to buy a new car right now! I will keep all informed as I go. I do have the Haynes manual to help also, but any tips/tricks on disassembly would be a godsend!

 

First and FOR MOST!

You must ensure that the motor is turned to #1 cylinder at Top Dead Center (TDC). You do this by removing the #1 spark plug and turning the motor over until the TDC mark on the crankshaft is in line with the mark on the block. Then stick a wire or small screw driver down the #1 spark plug hole and verify the piston it all the way up at the top, if it is at the bottom then turn the engine over by 1 revolution and it should now be at the top.

Then you can start the tear down. https://dodgeforum.com/forum/1st-gen...d-removal.html