GM Service Manual Online
For 1990-2009 cars only

This procedure checks for proper camshaft gear timing without removing the front cover of the engine.

Important: The following test will not be accurate with the rocker arms on the heads. The valve spring pressure causes the hydraulic lifters to bleed down. This will not give true lobe lift readings. The crankshaft must be rotated in a clockwise direction so that the timing chain slack does not effect the position of the maximum lobe lift.

  1. Remove all the glow plugs.
  2. Remove the valve cover and the rocker arms for cylinder number 1.
  3. Mount a dial indicator on the exhaust pushrod in order to read the camshaft exhaust lobe lift.
  4. Slowly rotate the crankshaft clockwise until the dial indicator shows maximum exhaust lobe lift.
  5. Place a chalk mark on the torsional damper (harmonic balancer) next to the timing tab.
  6. Reposition the dial indicator over the intake pushrod.
  7. Slowly rotate the crankshaft clockwise until maximum lobe lift is obtained.
  8. Place a second chalk mark on the torsional damper next to the timing tab.
  9. Measure the distance from each of the chalk marks to the factory timing groove in the torsional damper. If the camshaft gear is properly positioned to the crankshaft gear, the distance of each chalk mark to the factory gear timing groove (TFC) will roughly be the same. If the gears are out position by one tooth or more, the distance from the chalk marks to the (TDC) mark will differ by roughly 50.8 mm (2 in) or more.