How to check to make sure timing on GMC Sonoma is right

pleasehelpme3pleasehelpme3 Member Posts: 3
edited February 2017 in GMC
I have a GMC Sonoma with a 4 cylinder. I was replacing the timing chain and when I went to put on the gears found the timing mark 180 degrees off.  I can't remember  when it turned but I know it didn't turn while it was off.  Just wanted to check to make sure I didn't screw anything up.  How do I check to make sure the timing is correct (the timing marks are now turned correct) I need to know that somehow the gears didn't turn and while they say they are right the Cam shaft isn't wrong.  Engine is out of truck and oil pan is off.  I am also a 16 so please dumb it down enough for me. Thanks. 

Answers

  • thecardoc3thecardoc3 Member Posts: 5,549
    edited February 2017
    The camshaft turns one time for two turns of the crankshaft. So with one crank rotation the gears are lined up, and then with the next the camshaft would be 180 degrees out.
  • smallinjecksmallinjeck Member Posts: 10
    Compression ought to be at least 100 psi, so if lower remove timing cover and ensure marks are properly stationed.
  • pleasehelpme3pleasehelpme3 Member Posts: 3
    I checked and the timing marks line up on exhaust stage and are 180 off on compression me my dad and my grandfather all don't know what is going on. I found several others with this problem online but no answers. Thanks for the help last time, but if you know anything please help.
  • thecardoc3thecardoc3 Member Posts: 5,549
    I think I understand what you are concerned about now. When you have the camshaft gear mark at "6 o-clock" and the crankshaft gear at "12 o-clock" which is where the timing mark pointers are, you are actually setting the timing by cylinder #4. The firing order is 1-3-4-2 so both cylinders #1 and #4 are at TDC (top dead center) at the same time. If you wanted to set the timing by cylinder #1, you would use "12 o-clock" for both the camshaft and the crankshaft and not the pointer on the chain guide.

    As I said earlier, the cam turns at one half of the speed of the crankshaft, so on one crank revolution the cam gear lines up with the mark, and on the next it is 180 out. The engine is easily set up either way.
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