cylinder compression loss


Asked by Apr 23, 2016 at 05:30 AM about the 1993 Ford F-150 XL LB

Question type: Maintenance & Repair

I have a 92 f150 with the 4.9 inline 6 in it it had sat for approx 5 years with
out running due to bad trans so i put lots of new parts on i ( plugs wires cap
batt air and fuel filter rear man on motor and front main on trans and rear
on trans starter iac silinoid and starter ) as well as put a new parts under
neath and once i was all done i started it it was fine everything worked and
drove good besides at about twenty mph and thirty itwould  loss powwer
shutter but once past the speed it was fine and im kinda at a loss here took
it to shop the said i loss all conpression on cylender 3 so my question
before i tear my head off what are all possabilitys

2 Answers


If it sat that long the chances are high that you lost or are loosing the tension in the piston rings, you will be able to see the cylinder walls after you get the head off, then you will be able to see if there is any etching of the walls, loosing compression is common for an engine that has sat extended periods, cause the top end completely drains dry of any lubricant, so when you do finally get it running valves get stuck and sometimes even pull the guides right out of the head. So once it is torn down look it over carefully. HTH


Do a dry and wet compression test before u take it apart to see if it's rings or just head valve leaking through

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