Timing chain alignment mark

Tiny
HIDDEN1
  • MEMBER
  • 2001 DODGE DAKOTA
  • 3.9L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 185,000 MILES
I noticed after replacing the timing chain, [marked an at TDC with dots in center] and getting the new chain and sprockets back in the exact position on the crank and cam guide keys, that the dot on the new top sprocket is a bit off to the right on new one. Looks like one tooth over. Is this typical and do I need to turn the top one to align?
I didn't recall turning cam as putting new sprocket in.

Any info is appreciated.
There's the before/after on pic.
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Tuesday, April 12th, 2022 AT 3:24 PM

3 Replies

Tiny
RANDY B
  • EXPERT
Dandy observation. This is your third photo. It's a little hard to see being at an angle, but it looks like the cam sprocket is off by one tooth. There's two things that can happen here. The first has to do with the spring-loaded tensioner. I posted the instructions, mostly to show how unclear they are. What they should have explained better was to set the chain tight on the right side, as viewed from the drawing, and with slack on the left side. Rotate the crankshaft two revolutions in the normal direction, (clockwise as viewed from in front), then check the timing marks. They should be lined up when all the slack in the chain is on the left. If that isn't done, and there's some slack on the right side, the camshaft is going to rotate counter-clockwise when the tensioner is released and takes up the slack. That will put the cam sprocket one tooth late, as it appears in your photo. This applies to all timing chains and belts that use an adjustable tensioner.

The second cause refers to your comment about not turning the camshaft. In almost all engines, when the belt or chain is removed, the pressure of the valve springs on open valves will push on the camshaft lobes and turn the camshaft, often without you noticing. When it comes to sticking the two sprockets on, both have to line up with their keys. The crankshaft didn't move, but the camshaft most likely did. Many people rotate the cam sprocket until it slides onto that shaft and keyway, then they use that orientation to install the chain. Some people do recognize the camshaft has to be rotated back a tooth. Most are confused as to why they had to do that.

You'll need to retract and pin the tensioner again, then turn the cam sprocket clockwise one tooth. That will put the camshaft in proper time, and it will put the chain's slack on the right side. Now slide the two sprockets forward just enough until you can drop the cam sprocket out of the chain, then rotate that sprocket clockwise one tooth on the chain. You'll need to rotate that sprocket back counterclockwise one tooth to slide it back onto the camshaft. The slack will allow you to do that by moving back to the left side.
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Tuesday, April 12th, 2022 AT 6:44 PM
Tiny
HIDDEN1
  • MEMBER
Thanks. Yes, I did realign the marks and got that chain back on fast with that new technique.
Balancer is at TDC mark an dots are aligned.
I torqued it to 135 ftlb.

I have it almost ready to try. With everything back on. Should I bump the motor once before first start up and is there anything else to do before start up?
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Thursday, April 14th, 2022 AT 8:35 PM
Tiny
RANDY B
  • EXPERT
I like to see my engines run before I button everything up. If you can run the engine for even a few seconds with the timing cover off, you'll have confidence in your work as you're putting everything together. This will be with no water pump, alternator, power steering pump, and given enough time, oil spraying around.

After you do enough of these, you become confident, and even complacent, and tend to stop paying such close attention to detail. That's when things go wrong and you have to take things apart again. The good news here is you don't have a lot of new technology to make this a confusing job. This is just a basic 318 c.I. With two cylinders lopped off. 318s never had the fiber tensioner on the side of the chain. Regardless, you're still looking for the same thing. Rotate the crankshaft by hand with a socket and ratchet two times, then recheck the timing marks. That's clockwise as you're sitting in front and looking at the front of the engine. If you're ever confused on another engine, just look at where the crank sprocket is pulling the timing chain tight, (right side in this case). When you're turning it the right way, all of the slack in the chain or belt ends up on the side with the tensioning device.

For future reference, while the 318 is not an "interference" engine, it's still good practice to rotate the crankshaft twice by hand, not with the starter motor. I can share that some of the Neon engines are interference engines. If the timing belt is off by just one tooth, the Engine Computer will see that, turn on the Check Engine light, and set the diagnostic fault code, "cam and crank sync". At two teeth off, the computer will shut the engine down to protect the valves. At three or more teeth off, the open valves will hit the tops of the pistons when they reach TDC. The valves will be bent, requiring a lot more work. My reason for sharing this is many people try to cut corners and don't replace the hydraulic and spring-loaded belt tensioners when replacing the timing belt. Improper installation procedures also can lead to the belt being off by three or more teeth. If you use the starter to try to start the engine in that state, it's strong enough to bend the valves, then a head gasket and valve job are required. If you were to rotate the crankshaft by hand first, you'll feel it come to a sudden, solid stop when the pistons hit the valves. You can't bend the valves by hand. That tells you the job has to be rechecked. But no damage was done.
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Friday, April 15th, 2022 AT 4:52 PM

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