Questions and Answers
Quad 4 Timing Chain
Q. I replaced the blown head gasket on a 1990, vin D, Oldsmobile quad-four engine following the information from both a Chilton and a Haynes manual. When I tried to start engine, nothing, it is like there is no compression in the cylinders. I rechecked the timing, (setting of each cam and TDC of number one piston).
This engine has some strange characteristics in regards to the timing, no spark plug wires as such, firing of each cylinder, etc. What have I missed? All wiring connections checked okay, all bolts are where they are suppose to be. Still engine will not start. I would appreciate any help you may be able to give me.
A. There is a special and distinct procedure to follow when setting up the timing chain. The procedure is as follows:
CAUTION: Failure to follow this procedure could result in severe engine damage.Install or connect:
- Clean the threaded hole in the camshaft with a M10 x 1.23 tap.
- Clean old sealant off of the bolt with a wire brush.
- Use Adhesive / Sealant Compound GM P/N 12345493 or equivalent on camshaft sprocket bolt.
- J 36008 or equivalent through hole(s) in camshaft sprocket(s) into hole(s) in timing chain housing (this positions the camshaft(s) for correct timing).
- Intake camshaft sprocket retaining bolt and washer, tighten to 70 Nm (52 lbs. ft.) while holding the sprocket with J 36013 or equivalent (if removed). If the camshaft(s) are out of position and must be rotated more than 1/8 turn in order to install the alignment dowel pin(s):
- The crankshaft must be rotated 90 clockwise off of TDC in order to give the valves adequate clearance to open.
- Once the camshaft(s) are in position and the dowel(s) installed, rotate the crankshaft counter clockwise back to top dead center.
CAUTION: Do not rotate the crankshaft clockwise to TDC, valve or piston damage could occur.
- Timing chain over exhaust camshaft sprocket around idler sprocket and around crankshaft sprocket.
- Set camshaft sprockets at timed position and install timing chain.
- Remove the alignment dowel pin from the intake camshaft. Using J 39379 or equivalent, rotate the intake camshaft sprocket counter clockwise enough to slide the timing chain over the intake camshaft sprocket. Release the camshaft sprocket wrench J 39579 or equivalent.
The length of chain between the two camshaft sprockets will tighten. If properly timed the intake cam alignment dowel pin should slide in easily. If the dowel pin does not fully index, the camshaft(s) are not timed correctly and the procedure must be repeated.
- Leave the alignment dowel pin(s) installed.
- Raise the vehicle.
- With slack removed from chain between intake cam sprocket and crankshaft sprocket, the timing marks on the crankshaft and the cylinder block should be aligned. If the marks are not aligned, move the chain one tooth forward or rearward, remove slack and recheck marks.
- Reload timing chain tensioner assembly to its "zero" position as follows:
- Form a keeper from a piece of heavy gage wire.
- Apply slight force on tensioner blade to compress plunger.
- Insert a small screwdriver into the reset access hole, and pry the rachet pawl away from the ratchet teeth while forcing the plunger completely in the hole.
- Install the keeper between the access hole and the blade.
- With slack removed from chain between intake cam sprocket and crankshaft sprocket, the timing marks on the crankshaft and the cylinder block should be aligned. If the marks are not aligned, move the chain one tooth forward or rearward, remove slack and recheck marks.
- Tensioner assembly (56) to chain housing.
- Recheck plunger assembly installation, it is correctly installed when the long end (56B) is toward the crankshaft.
- Timing chain tensioner bolts (74) and tighten to 10 Nm (89 lbs. in.).
- Lower the vehicle enough to reach and remove the alignment dowel pin(s).
- Rotate the crankshaft clockwise (normal rotation) two full rotations. Align crankshaft timing mark with mark on cylinder block and reinstall alignment dowel pin(s). Alignment dowel pin(s) will slide in easily if engine is timed correctly.
CAUTION: If the engine is not correctly timed, severe engine damage could occur.
- Timing chain guides.
- Engine front cover and tighten to 12 Nm (106 lbs. in.)
- Start the engine.
- Inspect for oil leaks
If you don't follow the procedure outlined here, you can do engine damage that will result in the "no compression" condition. A quick compression test will confirm or deny this possibility.
Timing Chain Timed Position
Additional Information provided courtesy of ALLDATA
