aeopav

My son's 93 Cerokee Sport quit on him last week. After getting it home we did a compression check. 30-35 PSI on all 6 cylinders cold. If you crank it over, there is no hint of it starting but once you let off the starter, the engine will rotate backwards a few turns before stopping completely. There is good spark and good fuel pressure. It all led me to believe the engine skipped time somehow. Pulled the timing cover and, indeed the chain was extremely loose. What really concerned me though was what I found by looking at the timing marks on the gears. With the #1 cylinder at TDC, compression stroke, the cam gear was 180 deg. out! Or so I thought. Could this be possible? I bought a new timing set and now the only way to get the engine timed is to set the cam gear just as I found it the first time. 180 deg. off of what the manual states. Anyone seen this before?

Thanks,

Mark

Throttle Jockey

i have not heard of this. as i'm sure you know the cam turns one revolution to two crank revolutions. are you sure you are on tdc compression stroke?

aeopav

I'm almost certain I have it right. I have used my finger to determine that there is compression, then kept turning until the piston is at TDC. I have the valve cover off so I can see the valves moving also. I'm seeing the intake valve through the spark plug hole too. After the intake opens/closes, the next upstroke of the piston is compression.

mud909

I just got a freshly rebuilt engine from flightline. When I got #1 to tdc, no fire. I tripple checked. I pulled everything off front half of engine. and checked sprockets. 180 out! with #6 at tdc marks are on. Never tried turning dist. 180. Fresh engine should be right, wrong!!!!!!!!!!!! I will put it back together right now and see if I can do this. This would make #6 first in timing sequence. I don't want to pull the cam and turn it around

mud909

The backwards cam means nothing. It is perfectly symmetrical The timing was exactly 30 deg retarded. What retards the timing exactly 30 deg? You guessed it, knock sensor. Manually advanced the distributor 30 deg. Ran perfectly.