91 2.9 compression problems - Ranger-Forums - The Ultimate Ford Ranger Resource

2.9L & 3.0L V6 Tech General discussion of 2.9L and 3.0L V6 Ford Ranger engines.

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Old 11-21-2015
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Join Date: Nov 2015
Location: Dayton nevada
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91 2.9 compression problems

New to fords just got a 91 ranger with a 2.9 and drivers side cylinders have 140 across and passengers side starting at number 2 has 0, 30, 90. I've been told numerous things from head gasket to collapsed lifter to a bad valve train I wanna see what others have to say about it that actually have a ranger. Thanks-Bob
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Old 11-21-2015
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2.9l shows factory 9.0:1 compression ratio

This would mean you would expect 160psi if testing between sea level and 2,000ft
I use 18 times ratio to get expected PSI, 18 x 9 = 162, some use 18.3 but unless engine is newer I find 18 is usually closer to reality, lol

But compression tests are not about high numbers since that varies with gauge, battery(crank speed) and testing methods.

So 140psi on drivers side would be OK

The passenger side reads like a problem, bad head gasket won't get down to 0psi, badly burnt exhaust valve or hole in the piston would, mis-adjusted rocker could be holding open a valve as well.
If you have an air compressor you can hook air hose to 0psi cylinder and listen at tail pipe or throttle plate to see where air is going.
Or dipstick tube(piston hole)

But in any case that head, both heads, will need to come off
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