How to Diagnose a Jumped Timing Chain The timing chain has the important job of
synchronizing the crankshaft rotation with the camshaft. This direct link
provides the timing of the valves during their opening and closing sequences.
Without precise timing,which a good timing chain in good working order
provides,the ignition and camshaft timing will not perform in the precise
sequence to complete a four-cycle combustion stroke. A timing chain will send
out a number of warning signs before it fails completely. An observant owner can
detect these warning signs by paying attention to a few peculiarities that will
affect engine starting and performance. Things you'll need Socket set Socket
wrench Timing light Rags Shop light Chalk Instructions Checking for a Jumped
Timing Chain 1. Open the hood. Place the vehicle in park with the emergency
brake set. Start the engine but be sure the battery has a full charge and is
operating at peak performance. Note the speed at which the engine tries to
start,comparing it with a normal start condition. An engine with a jumped timing
chain will show signs of very sluggish and slow starting. This happens because
the firing sequence is retarded due to a chain that has jumped a tooth. A chain
that has jumped two or more teeth may not start at all. 2. Listen for any
abnormal engine noises,with the engine idling,in the vicinity of the timing
chain cover. Chains that have slipped time have slackened and can sometimes
rattle during cold start or idle,or produce a swishing or scraping noise. Loose
chains typically hit the inside of the timing chain cover. A rough running
engine may accompany such noises. 3. Test-drive the vehicle and while slowly
accelerating listen for any backfiring (popping) noises. Try a rapid
acceleration and look for engine stumbling and backfiring. Any such symptom
means that the timing sequence has changed. Sometimes a rattling sound,stumbling
and backfire will all combine--a sure sign that the timing chain has skipped
position. 4. Park the car. Place it in park with the emergency brake set. Locate
the timing marks on your vehicle. They will appear on the crankshaft pulley and
on a small metal tang connected to the engine block right above it. Use a rag to
clean any dirt and oil from the mark. Look up your timing specifications in your
owner's manual. Use chalk to mark the pulley and the block scale. Hook up the
timing light to the number one cylinder and start the engine. Aim the timing
light at the marks Porsche
Piwis Tester II. If the timing marks do not come close to alignment or you
do not see any alignment at all,it means the chain has jumped position. 5.
Locate the top of the timing chain cover. Some vehicles have small inspection
plates that allow you to remove them to check the condition of the timing chain
and tensioner Car Repair Tool. Remove
the plate bolts with the appropriate socket and wrench. Hold a strong shop light
over the opening. Examine the chain and see if it hangs loose,or if the pads on
the tensioner have worn away. Sometimes tensioners will freeze up and not
provide the correct pressure against the chain. A loose chain will tell you that
the tensioner has failed.
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