Chrysler Repair/97 3.5 Won't start
QUESTION: Hi Roland. Going back to the Intrepid that wouldn't start some days after the timing belt was changed, recall that there was no spark on 1/4 and then after some days of testing, no spark on another pair, and then no compression on the left side of the engine. All I could figure was something wrong with the timing, though somehow only affecting one side of the engine. That's where we left off.
The mechanic has finally looked at it just called to say that it's the valve lifters that are at fault. Now I don't know what to think about that. All the lifters on one side would be affected? I guess I don't know enough about how they work to say. He asked if I had added anything to the oil, which I hadn't. I thought I'd see what your thoughts were. He's apparently looking at it now and will call back in a few hours.
ANSWER: Hi Mike,
The valve lifters are pressurized to be stiff (not squishy) via the oil pressure that is pumped to them along the rocker shaft. If the oil passageway from the block to the head to the shaft becomes plugged up then the lifters will loose their pressure and there will be increased gap between the cam shaft lobes and the lifters. This definitely would cause valve lifter noise (clacking sounds from all the lifters on the affected side, did you notice that?). It would certainly result in the valves opening much less (possibly not at all) and thus the compression would drop way down.
If indeed the lifters are spongy then the camshaft would need to be removed and an inspection as to why no oil pressure on that side existed. The oil passageway to the right side rocker shaft comes from the cylinder head at the third rocker shaft support which can be inspected after removing the shaft.
What about the spark issue? Did you ever get spark on all 3 pairs of plugs?
Thanks for the rating and nomination.
---------- FOLLOW-UP ----------
QUESTION: Hi Roland. I'm familiar with a moderate clacking sound, as the other side of the engine (1-3-5) has been that way for years. (Previous owner suggested worn rocker arms, I recall, and gave me a new shaft/arm assembly but I've never installed it.) Now I haven't heard any similar noise from the side that has no compression now.
And of course, I don't know what this would have to do with the original problem of no spark. It had no spark on two pairs when I gave up testing it. A coincidence of problems? I don't see how the computer would know that the valves are not working so that it could discontinue the spark--assuming it's even designed to do that--but maybe it does indirectly?
My conjecture about the spark issue was that the cam and crank sensors were out of synch due to a timing belt mal-alignment such that the spark would not be 'driven' to 4 of the 6 cylinders. I am at a loss to suggest anything further so would have to leave it to the mechnanic to first determine why the compression is so low on the right bank. The tappet noise, if present, might not be noticeable at cranking rpm as compared to the noise when the engine is running.