Mercury F8AZ-6256-AA Sprocket - Camshaft

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Disconnect the negative battery cable from the battery and position the number one piston several degrees before TDC on the compression stroke. Remove the right valve cover and attach a dial indicator to the cylinder head with the plunger inline with and resting on the pushrod side of the rocker arm. Remove the timing chain cover and temporarily remove the timing chain and sprockets to access the chain tensioner. Temporarily install the timing chain and sprockets without the tensioner, then slip the timing chain cover and vibration damper in place to provide timing marks. Turn the crankshaft clockwise until the number one piston is at TDC to take up the slack on the right side of the chain, then zero the dial indicator. Slowly turn the crankshaft counterclockwise until the slightest movement is seen on the dial indicator, noting how far the number one piston has moved away from TDC by looking at the ignition timing marks; if the mark has moved more than 6 degrees, install a new timing chain and sprockets. Position the number one piston at TDC on the compression stroke and remove the timing chain cover, avoiding turning the crankshaft during vibration damper removal. Ensure the crankshaft, camshaft, and balance shaft sprocket timing marks are aligned; if not, use the vibration damper bolt to turn the crankshaft clockwise until all marks are aligned. Remove the camshaft sprocket mounting bolt and camshaft position sensor drive gear without turning the engine, taking care not to allow the crankshaft to turn from TDC. Compress the timing chain tensioner with a screwdriver and insert a drill or Allen wrench as a retaining pin to hold it in the retracted position, then pull the camshaft sprocket/chain off the camshaft. If intending to remove the tensioner assembly, remove the two bolts holding it to the block. Turn the crankshaft until the key is facing up, drape the chain over the camshaft sprocket, and turn the sprocket until the timing mark faces down, ensuring the chain is positioned over the camshaft and crankshaft sprockets with their timing marks aligned before slipping both sprockets onto the camshaft and crankshaft. When correctly installed, a straight line should pass through the center of the balance shaft gear, the camshaft, the camshaft timing mark, the crankshaft timing mark, and the center of the crankshaft; do not proceed until the valve timing is correct. Install the camshaft position sensor drive gear, aligning the keyway with the Woodruff key on the camshaft, then apply a non-hardening thread locking compound to the threads and install the camshaft sprocket bolt, tightening it to the specified torque. Finally, remove the retaining pin from the timing chain tensioner and reinstall the remaining parts in the reverse order of removal.

It is very important not to rotate the crankshaft or camshafts after the timing chain(s) have been removed due to the possibility of harming the valves or pistons - special tools are required to lock the camshafts during removal. Start by using the number one cylinder with Top Dead Center and then pulling the spark plug and also taking out the negative cable from the battery. Next, the engine cooling fan should be removed as well as in certain models, the radiator should be taken off as well. Move on and remove the valve covers, drain the engine oil as well as take off the crankshaft pulley. Some models require also the removal of the water pump and its pulley, power steering pump, drivebelt tensioner, and idler pulleys. Remove camshaft and crankshaft position sensor connectors if necessary, and remove the air conditioning compressor without disconnecting refrigerant connections. Check all the connectors and brackets on the harnesses, and then undo the nuts and bolts that hold the timing cover and the cover away making sure that you do not use over torque. Take off the timing cover gasket and dowel pins, then timing chains between the crankshaft and the camshafts. For 1999 through 2004 two-valve engines, fit the camshaft and crankshaft retaining tools, to lock the camshafts at the TDC and protect them from being damaged. Take off the right and left timing chain tensioners and stationary guides, and if it is necessary - the camshaft sprockets. In 2005 and later three-valve models, the engine needs to be rotated to its proper position and the camshaft rocker arms should be removed in addition to making certain that the timing chain marks are easily seen before installing the timing chain guides and sprockets. For confirmation of its position, turn the crankshaft; next, remove dirt and grease on the joint surfaces; spread RTV sealant on the cover surfaces; grease the timing chains; bolt on the timing cover. Lastly replace the crankshaft front oil seal and continue with reversing the process put the right quantity of the engine oil and the coolant then start the engine to check for any possibilities of leaking.

The crankshaft or the camshafts cannot be rotated at any one time once the timing chain(s) have been removed as this will lead to serious damages to the valves and or the piston; there are special tools used to immobilize the camshafts during the removal of timing chains and it is always advisable to read through the entire procedure and ensure that all the required tools have been acquired. Due to it being an interference engine design, when a chain breaks, valves or pistons will be damaged and the cylinder head will have to be taken off. The timing system is quite intricate and mistakes made are can lead to heavey losses to the engine thus only professionals should attempt this process and all the work done should be cross--checked before starting the engine. It is done by pulling out the negative cable of the battery, setting the number one cylinder to TDC and then, the spark plugs are pulled out. Secondly, the valve covers, as well as the timing chain cover should be detached, and attention should be paid to the fact that there are two lengthy timing chains between the crankshaft and the camshafts. Crankshaft position sensor toothed-wheel must be unclamped and then retrieved gently to avoid damage otherwise when replacing the spur, it must be ensured that it is placed in the correct orientation. Fit in the camshaft and crankshaft retaining tools such that the camshafts cannot move as a result of pressures from the valve springs. When positioning the engine at TDC, lock the keyways on the camshaft sprockets to be at right angles with the valve cover mounting surface. For specific engine types camshaft retaining tools must be fitted and the camshaft(s) must only be retained at exactly TDC as any error can lead to severe engine damage. Rotate the crankshaft groove to 12:00 for 5.4L 3V engines and also there is a valve spring depressor tool been used to take off the rocker arms into their corresponding camshaft lobe positions. The tensioners should be removed and the chains lifted off the camshaft sprockets with the timing marks observed with the intention of being realigned in the correct manner. Remove crankshaft sprockets at both ends, and if necessary, lock crankshaft in position before removal; also both chain guides should be unbolted and removed if required too. Check sprocket teeth, chain and guide for wears and tears and replace them with new ones if they are badly worn. Early-style tensioners should be tested for operation and the presence of the oil feed hole should be ascertained, whereas later-style tensioners should have their seals intact and the plungers should move freely. In installation perform a manual rotation of the crankshaft up to two full turns to evaluate the resistance in the crankshaft which is suggestive of a problem. Place fixed chain guides, crankshaft sprockets and timing chains: the bright faces of the links engaged with the marks on the sprockets. To individual types of engines, it is necessary to complete such procedures as the installation of camshaft sprockets, timing chains, and tensioners with attention to the relative positioning of the timing marks. Last of all, take out any retaining tool, replace rocker arm if any before fully engaging the crankshaft to ensure the right assembly so as to end the process of the installation.

The oil pan should be removed and cleaned of all debris, and the oil pick-up tube screen should be checked.

Position the number one cylinder at TDC (Top Dead Center) and remove the spark plugs.

Align the bright link with the dimple on the camshaft, loop the timing chain under the crankshaft sprocket, and align the bright link with the alignment mark on the crankshaft sprocket.

Rotate the crankshaft in a counter-clockwise direction to take up the slack in the left side of the chain.

Rotate the engine 360-degrees CLOCKWISE, remove the rocker arms from the remaining cylinders using the special valve spring compressing tool, and rotate the engine 360 degrees CLOCKWISE back to the TDC number 1 position.

Add coolant, check the oil level, run the engine, and check for oil and coolant leaks.

Remove the retaining pin from the timing chain tensioner and reinstall the remaining parts in the reverse order of removal.

DO NOT proceed until the valve timing is correct.

Remove the engine front cover.