Author Topic: Top Dead Center Compression Stroke  (Read 682 times)

jtwoods4

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Top Dead Center Compression Stroke
« on: 10 November 2019, 03:55 PM »
hey guys I'm doing a rebuild on an om617.950 engine. The engine was completely disassembled and put back together. Right now I'm trying to make sure the camshaft pulley is correctly aligned with the timing marks on the balancer.

How do I determine if top dead center is on the compression or the exhaust stroke? there is a small timing mark on the back of the camshaft sprocket that lines up with the timing mark on the camshaft tower. I'm pretty sure those marks need to align when the engine is at top dead center on the compression stroke.

right now the marks line up at top dead center but I don't know if it's on the compression or the exhaust stroke.
1980 300SD

UTn_boy

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Re: Top Dead Center Compression Stroke
« Reply #1 on: 10 November 2019, 07:16 PM »
If the camshaft marks are aligned when the harmonic balancer is on TDC then all is well.  When the camshaft is disconnected from the chain drive top dead center of the crankshaft is top dead center.....exhaust and compression stroke are one in the same when the camshaft isn't linked to the crankshaft with the chain.  What you need to worry most about is if the injection pump is timed correctly to the crankshaft.  And then after that the injection pump must be flow timed to the position of the crankshaft. 
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jtwoods4

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Re: Top Dead Center Compression Stroke
« Reply #2 on: 10 November 2019, 07:17 PM »
Got it! Thank you! My injection pump was refurbished at a Bosch service center and is on the way back to me this week.
1980 300SD