How do you tell if timing chain jumped?

[turbotroy]

Hey All, I was doing a compression test on a newly acquired tb and all of a sudden my gauge reads zero, after testing four cylinders. My first thoughts were that the rental gauge took a dump, especially since it still read zero on previously tested cylinders. The next thought that occurred to me was did the timing chain just jump? I know I'm showing my age, but us old timers use to have distributors on cars that would tell you pretty fast if one jumped. Is there a quick way of telling without removing the valve covers to see what the valves are doing at TDC? Thanks, Cheers, and Happy Thanksgiving!

 

[Nick Micale]

I do not see how it would be possible for a chain jump a tooth, and especially on a recent built engine?

Put your finger on the spark plug hole when turning the engine and you will quickly find out if you have 0 compression or not.

 

[turbotroy]

Hey Nick, how are you? The engine wasn't recently rebuilt, and if I had 7 foot long arms and 2 elbows I would do that. Working by myself without a remote starter. Back to my question, is there an easy way to see if the timing chain jumped without pulling valve covers?

 

[RmvBfrFlght]

Maybe see if the cam sensor is still timed correctly?

RemoveBeforeFlight

 

[87geeinn]

You answered your own question. Faulty or loose fittings on the gauge. Check the o-ring on the end of the gauge hose that seats inside the spark plug hole. This should be lubed often as it will bind in the spark plug hole and tear it up if you tighten it down dry. Also check to make sure if any adapter fitting is used on the gauge that it is not loose. Pressure release valve/button binding up?

As Nick stated above, just bump the motor over and if you feel puffs of air coming out, you should be good.

 

[jasjamz]

You can make a starter bump tool from some alligator clips, wire, and a momentary switch.

 

[earlbrown]

stuff a piece of paper towel in the spark plug holes then spin the engine over.

 

[turbotroy]

Thanks for the replies, Guys. I was out for Thanksgiving but will keep y'all updated. Earl, I like the one about a paper towel! Will try that tomorrow.

 

[MeanBuicks]

I do not see how it would be possible for a chain jump a tooth, and especially on a recent built engine?

Happened to me many years ago on a cam sprocket that had shed 90% of its Nylon. I started the car and it idled for about five seconds and unceremoniously shut off. In attempting to restart it the starter was laboring to turn the engine over (as the valves were contacting the pistons.)