can't figure it out

[DemonWithin99]

Brother's car has trouble starting, mech replaced the crank sensor, but not the cam sensor. (I wondered if that might be the issue). the compression tested a little low on the first try, but until they find out for sure that it is/or isn't the timing chain we're trying to eliminate all the simple stuff first. he said it wasn't throwing any codes, but don't think he really has enough knowledge about the LS. really trying to avoid tearing apart the motor for fear the cost in labor. shit's killing me.

I'd rather do it all in my garage, but can't.

[Batman]

Crank sensor test is a PITA to get it to throw a code, cam should be straight forward. But to get the crank sensor to throw the code you have to crank the engine for 30-45 seconds, not a good plan if the timing chain is in question. Have you tried turning the engine by hand to see if anything binds?

[84ta406]

Both sensors should be tested with a labscope or with a Tech 2 IMO. If it was the chain wouldnt the results be really screwed up since the valves wouldnt open/close at all?

Could you take the plugs out and turn the motor by hand and see if all the rockers are moving as well? Was the compression test low on all or just one cyl?

[Slowhawk]

OMG, pretty simple.
Pull valve cover,turn motor over by hand, valve move =timing chain OK. 1/2hr to test.

Next -check fuel pressure
Next - check spark / injector voltage

[84ta406]

Yay I was kinda right! lol

[DemonWithin99]

thanks I'll give it a check