Ford Repair: 97 ford f150, engine cranks, ford trucks

Question
Hi,

I have a 97 Ford f150.  We were on a trip and the truck started to lose power especially going uphill, we were pulling a trailer but it was barely moving. finally the truck just stopped working.  we had it towed and a diagnostic run that told us that cylinders 6 and 8 didn't have compression.  I was told by a few people that sometimes the rocker arms come off in ford trucks, so I took the valve covers off and the rocker arms were fine. when I try to turn over the truck it makes kind of a grinding noise rather than the normal noise that an engine makes when it is trying to turn over do you have any idea what this might be?

Thanks,

Kyle

Answer
Hello Kyle, my best guess is possibly a timing chain or chain guide issue. I'm guessing the engine jumped time, which will cause valves to be open so when the engine cranks over you will not see compression. Some engine tear down will be needed to verify concern. Front timing cover removal is where I'd start first if you are wanting to try to repair. Hope this helps! Thanks for the email.