I’m looking at a hard start/rough running 5.7 and I suspect the cam timing is off.

It will only start once a day - after that it won’t start again until it’s had several hours to cool - and when it does start it’s running very rough with a hard misfire on #5, and it won’t stay running for more than about a minute, with or without throttle input. #5 has zero compression.

During cranking - either with the key or jumping the starter relay - it has uneven cranking speed, meaning there’s a clear difference in how it sounds, with acceleration and deceleration of the crank.

The customer stated they self-installed a cam and lifters before this problem, so I want to verify the timing without removing the timing cover.

With no external timing marks the only idea I had was to set #1 to TDC and look at the position of the tone rings for the cam and crank by pulling the sensors - but I’m not able to verify what the position of the tone rings is supposed to be.

Any ideas/methods that work? Thanks.

 

Update:

What I ended up doing is pulling the left valve cover and one plug out of each cylinder, then rotating the engine by the crank pulley bolt. The valves appear to be correctly timed (comparing valves opening/closing to piston travel) however the intake valves on #5 and #7 are bent and not closing all the way.

Compression testing on the remaining cylinders ranged from 0 to 190.

I suspect the customer installed a cam with too much lift, they possibly installed it 180* out, or the timing chain jumped on initial startup.

Waiting to hear how they want to proceed.

 

That's not gonna be inexpensive......

 

Definitely not. I got some more details shortly after posting that.

Turns out the engine was initially running well after the cam and lifters. The customer let it idle up to temperature to make sure the coolant was full, then did some short range driving with it. All was well, They were in the middle of about a 20 mile drive when, just after coming to a stoplight, it died without warning and wouldn’t start after that.

Knowing that now, I suspect there was a failure with the cam actuator that possibly also caused the chain to jump, but I’m waiting to hear for sure if they want us to proceed with removing the timing cover.

 

If he has ya go in there, be sure and post pics.

 

Well, unfortunately I probably won’t have an answer to this.

We’ve been overwhelmed with the workload pretty much all of 2021 and are almost always struggling to keep up, and I had 2 engine swaps and a cylinder head repair, as well as minor repairs and diagnosis as needed (and a week of vacation), lined up before I could get to this jeep. Unfortunately the owner grew tired of waiting (understandable) and picked it up to take it elsewhere - I was going to get started on it before the end of this week, too.

Occasionally I’ll hear follow up in these situations, so if I ever hear what caused it, I’ll update.

 

Update:

I don’t know where the customer ended up taking the jeep, but the necessary mechanical repairs were done. I don’t have the details on what repairs were done, but knowing it had bent valves, I’m sure, at the very least, the heads were pulled and repaired/replaced.

Apparently it’s still running rough and has multiple driveability problems, so I’m guessing the root cause of the problem was never discovered and the engine has mechanical damage yet again. But that’s just my SWAG (Scientific Wild A** Guess).