Hey Scotty. So I am trying to figure this one out and its leaving many people scratching their heads, including me. Where I work we have some LPG forklifts. One of which is 2013 Hyundai 15LC-7A, its a 4 cylinder with dual overhead cams and has just about 8600 hours on it. About a month and a half ago, I was operating it for about two hours. After I was done, I shut it off, parked it and walked away. The afternoon shift came in about two hours later and one of them tried to start it. It just cranks and the engine will not startup. I checked the spark plugs and put new ones in as they were never changed. But by the sound of it turning over, I knew it wasn’t the plugs. So I checked the compression. All 4 cylinder have absolutely 0 compression. I looked into each cylinder to see if the pistons are moving and they are. I decided to take off the valve cover to inspect the timing belt and it is intact. Cams spin and the valves are opening and closing. So my question is how can this engine loose all compression after just sitting for two hours? It ran completely fine before I shut it off and had no abnormal noises. Oil and coolant were full, clean air filter with no obstruction to the intake. I’m very confused as how this happened and what went wrong. Any insight is much appreciated. Thank you!
Sounds like a valve timing issue.
With the valve cover off, if you rotate the engine until both intake and exhaust valves are closed on one cylinder, and you do a leak down test/procedure on that cylinder, does it hold pressure?
That was my next step to investigate the timing. I was going to pull the timing cover and see if the timing is off. But that involves pulling the counterweight and removing various components obstructing the cover. Your procedure is much less troublesome. Thank you, I will share my findings when I can get to it.