Compression

1998 DODGE VAN
140,000 MILES • 3.9L • V6 • 2WD • AUTOMATIC
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KEVEN WATTS
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Just did compression check on the Ram van 1500 listed above. All the cylinders have around 120 to 130PSI. But the number four cylinder only has about 30/32 PSI and number 6 cylinder is at 105/110. I believe I'm right on firing order from inside the cab looking forward I was told passenger side back to front 1,3,5 and driver's side from inside cab looking forward 2,4,6. Thanks, I hope it's just stuck. Sat for 5 years. Came out of California. Runs good just rough idle once you get it up a little speed it runs smoothly. Thank you much.
Keven Watts, Indianapolis
Jun 16, 2022 at 6:54 AM
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SQM
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Hello,

The number one cylinder is the front right (if you are facing the engine). Attached is the firing order below for your reference.

As for the low compression on that cylinder, it could be due to stuck valve as you are suspecting, but it can be also due to worn or broken piston ring. You can try the oil method to check if it is the ring. Pour about a teaspoon of oil into the spark plug hole with the plug removed. Then check the compression to see if it goes up then the issue is the ring.

Here is a helpful guide:

https://www.2carpros.com/articles/the-reasons-for-low-compression

Let me know of any questions.
Thank you.
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Jun 16, 2022 at 8:26 AM