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Compression Test Question

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Old Dec 27, 2008 | 01:19 PM
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90RunnerRed
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Default Compression Test Question

Well I searched and I think I have the procedure down to perform the compression test, but the only question I still have is whether or not you need to disconnect the fuel line? Any help would be appreciated, thanks!
Old Dec 27, 2008 | 01:33 PM
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No, you shouldn't have to. You should disconnect the coil wire, though.
Old Dec 27, 2008 | 02:07 PM
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Thanks! From what I found you run the engine to operating temperature, shut off, disconnect the coil wire, remove all spark plugs, hold the throttle wide open and crank the engine until you get a max pressure. Anything else I'm forgetting?
Old Dec 27, 2008 | 02:09 PM
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You want to count the number of cycles it takes to reach max pressure as well. Ideally you should hit it at 2-3 cycles with a stock cam.
Old Dec 27, 2008 | 02:15 PM
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Humm, I didn't think about that, makes sense. Thanks.
Old Dec 27, 2008 | 08:43 PM
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Well I have one cylinder that is around 60 psi, I've yet to do the teaspoon of oil test. I really wasn't expecting this, the engine runs strong, no smoke, oil looks clean (no metal).
Old Dec 27, 2008 | 09:03 PM
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60 PSI is terrible. Make sure your gauge is properly seated. Hope your not using the press in type.
Old Dec 27, 2008 | 11:35 PM
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Originally Posted by 90RunnerRed
Well I have one cylinder that is around 60 psi, I've yet to do the teaspoon of oil test. I really wasn't expecting this, the engine runs strong, no smoke, oil looks clean (no metal).
one lame cylinder is hard to pick out in a v/8, oil test is probably gonna show you a bad valve.
Old Dec 28, 2008 | 11:19 AM
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I agree, that's odd. What are the other cylinders at?
Old Dec 28, 2008 | 12:12 PM
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The other cylinders are all around 130-140 psi. Yes, I am using the press in type, I know I know, not the best method, but it's what I've got. When I perform the test on that cylinder there is a definite sound difference. I am afraid it is a bad valve as well.
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