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Old 10-18-2003, 03:31 PM   #12
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Location: Colorado Springs, CO
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Default Re: Testing compression in an s-series

Originally posted by Saturn-Eh!
doing a compression test on an s-series is easy:

1) remove the fuel pump fuse, and start the car until it stalls. We want to remove any chance of fuel washing down the cylinder walls and skewing the results
Assuming the compression test is being done correctly, there is no need to remove the fuel pump fuse, or attempt to halt injector flow.

When the engine is turning less than 400rpm, and the throttle is greater than 75%, the PCM will close the injector(s), and as such, cease fuel flow into the cylinders.

Unless your TPS is screwy, fuel flow is automatically stopped when you try to start the car at WOT.
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