Hello all, I just purchased a 2001 Grand Cherokee Limited V8 4X4 as a project. It doesn't start. I ran a compression test and all cylinders averaged around 120-145 except for the last one, I got a big fat ZERO, but I think that happened cause my battery isn't that new and might have been very low by the time I did the last cylinder. Funny thing is that when I turn the key it sounds like sewing machine kinda, high pitch sound. Didn't sound normal to me. All electrical works fine, windows, door locks, sunroof. Any ideas???

 

It's an early 4.7, you may have some internal engine damage. Those engines are known for dropping valves.

 

Turns out it might just be a stripped out spark plug. Doesn't idle very well and then dies but if I rev it, it runs smooth. Buying a Heli-Coil today and re threading it, let's see what happens!!!!

 

My guess is either a thrown lifter or dropped valve seat.

Max