Compression Test.
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Senior User
Joined: Jan 2013
Posts: 317
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From: NW Ohio
Compression Test.
Ok so this is a new one for me. Tried to do some compression testing on the 300 in the garage. The gauge never moved. I have never had the needle not at least flutter. Same thing across cylinder 4,5 and 6. never bothered to try 1,2, and 3.
I figured well shoot my gauge must be messed up. So i went and got another. Sure enough needle would not even move.
Worn cylinders with a blown head gasket will atleast make the needle move.
My guess is something is afoot. I was able to turn the engine over with just a 1/2 inch ratchet. Now mind you this is with the engine suspended by the hoist. So stabilizing with one hand and cranking with the other. Past experience shows a good compression will require a cheater pipe or 24 inch bar, and some good effort.
I was hoping to not have to do a full blown rebuild right away. Something has to be up but Im not sure what.
I figured well shoot my gauge must be messed up. So i went and got another. Sure enough needle would not even move.
Worn cylinders with a blown head gasket will atleast make the needle move.
My guess is something is afoot. I was able to turn the engine over with just a 1/2 inch ratchet. Now mind you this is with the engine suspended by the hoist. So stabilizing with one hand and cranking with the other. Past experience shows a good compression will require a cheater pipe or 24 inch bar, and some good effort.
I was hoping to not have to do a full blown rebuild right away. Something has to be up but Im not sure what.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Compression test figures is probably only valid when engine is at Normal operating temperature, throttle wide open, charged up battery, each cylinder tested three times, take highest reading, etc. can't do that on a hoist.
Postmaster
Joined: Nov 2012
Posts: 2,806
Likes: 8
From: Langley, BC
Did you pull your plugs? If so, you have no compression which is why it was so easy to turn the engine over by hand.
How did you do the test? Walk us through this step by step as if we're stupid and somewhere along the line we'll be able to see what's going on.
For mine, I pulled out one plug at a time and screwed in my compression tester gauge. I disconnected the coil cable from the distributor and hopped in the truck. I cranked the engine over with the key until the needle on the gauge stopped climbing.
How did you do the test? Walk us through this step by step as if we're stupid and somewhere along the line we'll be able to see what's going on.
For mine, I pulled out one plug at a time and screwed in my compression tester gauge. I disconnected the coil cable from the distributor and hopped in the truck. I cranked the engine over with the key until the needle on the gauge stopped climbing.
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