90 B2600i FI Oil spewing out of #3 cylinder Why?

[bhowell]

1990 B2600i 120K miles 4x4 manual FI



I just bought this project truck. The trucks has been sitting for 3 years and the previous owner only remembers that it stated loosing power and he parked it.



I pulled the plugs and cranked it over and oil spewed out of cylinder #3. It didn't appear to have any water. I also drained the pan and no water. I get 150 psi in cylinder 1,2 and 4 and 220 in #3.



Does anyone have any ideas? Could it be a stuck fuel injector? I didn't notice any gasoline smell just oil. Could it be a valve? How could I determine this? Could it be a cracked block? Is so, how could I check this?



Thanks for the help

[wtousand]

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If the intake valve quits working or, more likely in your case, barely opens, it will create a chronic high vacuum in the cylinder at high engine speed and cause it to suck oil up past the rings and down the valve stems. In that case, excess oil may accumulate in the cylinder. It's the same as backing off the throttle at high speed but in this case the engine doesn't get to slow down.

Barely opening valve would allow a fairly high slow crank-over compression-build but also indicates the cam or some rocker part is likely shot. The excess oil makes the piston seal better and read higher. If you oil the other cylinders, they may also read higher, if the rings are worn. One other valve problem is steel valve seat inserts in aluminum heads that come loose and stick out only letting the valve open at the last part of its peak lift. If they slip back in place, you won't easily notice that they can do this but they will be loose if you carefully check.

When oil doesn't increase compression readings, it indicates the greater leakdown from when new, is in the valves.

Wes

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