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Need some help 5.3 no start

mark84k5 said:
View attachment 520063Must have chain to start!!!!! Go figure
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So you should have felt something different when cranking, if the is not turning it sounds different. I am trying to think what else could have shown signs without opening the covers.
If you had checked for spark it wouldn't have any since the distributor is driven by the cam gear
 
Blue85 said:
I think you need the crank sensor for spark and fuel, but cam sensor only affects fuel timing, like it should start with a bad cam sensor. I don't have proof of this, so some one can correct me. If it's sparking, you probably have a crank signal. For fuel, a stethoscope on an injector should tell you what it's doing.

To test your code reader, you could unplug a sensor to see if the code shows up. You should be able to run with a bad MAP sensor, as it's usually secondary, but a MAF that's wrong can screw everything up. Another free test is to leave either the MAF or the MAP unplugged and see if it's any different.
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If he had checked for spark like you suggested
 
Fortunately, the LS Vortec is non-interference.

I wonder if the running issues you experienced earlier were from having jumped timing.
 
A loose chain will still turn the cam after it slipped.
Most engines will still run with a bad cam sensor. Not well, but at least run.
 
1st post talked about random misfires. I'm just theorizing that either a) wrong/sloppy valve timing causes misfire/running issues or b) The ECU sees a mismatch between the crank and cam position and logs that as misfires.
 
when cranking it sounded normal. I have been working a lot of hours and haven’t had time the last couple of days to work on it. Sunday I had off, put on a ton of layers and got to work cleaning all grounds. That did nothing. I went back and rechecked everything I checked before and still found nothing except this time I had no spark, weird cause I thought I did before. Back probed coils for power and ground and everything was fine. I thought I’ll throw some other coils I have sitting around on. After pulling the old ones off I thought, I pull the valve cover and crack it just to make sure rockers were moving. Had my neighbor crank the key and that was when I found out how much work I had to do. Non of the rockers were moving so I knew right away. Pulled the from of the motor apart and all the bolts from the oil pan. Picking up parts today and will try to get a little work done everyday while I have sun light till I get it done. I just hope I didn’t bend a valve.
 
Blue85 said:
1st post talked about random misfires. I'm just theorizing that either a) wrong/sloppy valve timing causes misfire/running issues or b) The ECU sees a mismatch between the crank and cam position and logs that as misfires.
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The random misfires were from clogged cats. This truck has been running me through the wringer. T-case also got a hole in it a month ago. I rebuilt the tcase and then pulled the cats. IMG_7111.jpegThe random misfires started intermittently then got worse. I’m not a mechanic so it was kinda hard to diagnose.
 
mark84k5 said:
I thought it is an interference motor!
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It looks like the internet is split on this topic. I guess I don't know for sure. I do see stories posted both ways - some slapping a new chain in and running - others with bent valves. When the chain lets go you can fire maybe one cylinder, but it's hard to believe you wouldn't get at least a whole revolution from inertia.
 
Blue85 said:
It looks like the internet is split on this topic. I guess I don't know for sure. I do see stories posted both ways - some slapping a new chain in and running - others with bent valves. When the chain lets go you can fire maybe one cylinder, but it's hard to believe you wouldn't get at least a whole revolution from inertia.
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I figured I’ll get all back together and then I’ll know when I start it. Unless anyone has a trick to tell if you have a bent valve prior to doing the timing chain.
 
You can do a leakdown test, but you probably have to have the valve covers off to know when the valves are closed. If something is really bad, a visual + wiggle inspection up top might catch it. If the cam does a full revolution with some valves never closing, that's bad news. If it is an interference engine, there will be some point you have to rotate the crank to keep moving the cam.
 
if a valve head is bent that valve will not seat all the way. So there will a difference in stem height. It might be a lot or very little. would probably need to remove all rockers and lay a flat edge across the stems and see if any are low.
 
mark84k5 said:
I will info dump first to get any helping hands up to speed. In the last couple months I have had a tone of issues related to random misfires dealing with plugged cats. So in that time I have put a new mad,map, 4- o2 sensors, pulled cats out. New plugs wires, cam and crank position sensors, and fuel pressure regulator. The other day on the way to family’s house on Xmas it died on me. Had to get a tow. Just died while doing 50, threw it in neutral and coasted to a safe spot. It cranks and has fuel pressure and spark. It will not start. What should I do?
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Got like 90% back together. No bent push rods and one valve a 1/16” lower than the other 8 on the passenger side bank. I moved it up and down and it seemed ok but that’s not really a legitimate test. I went ahead and put the new chain and oil pump oring. Everything I took off got new gaskets. I have a few little things to wrap up tomorrow. One of my neighbors came over and started talking to me when I was putting all the accessories on and I didn’t realize till the end I didn’t put the harmonic balancer bolt in, my fault not his I should have payed attention. Still needs oil and the rest of the oil pan bolts. Another hour or so tomorrow after work and I’ll give you guys the new weather it’s good or bad.
 
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