Help reading and performing compression check and methods of doing the test

[akalawrence]

Hi all I have a post already subject Fuel Pressure testing help PLEASE truck starts wont gohttp://www.therangerstation.com/forums/showthread.php?t=101387

I thoguht i would post this to try to get more views on the paticuler subject and test im currently performing. you can check out my other post if you want to start from my first post.

So i rented a compression gauge and heres the results and method used.

so I got a compression gauge I warm truck up to operateing temp turn off unhook all wires and connectors and pulled the fuel fuse.. hurride as fast as i could to test each cyl while it was hot heres what i found 1234 and 6 where reading 148-152 150avg but 5 was reading 160-165 5 is same side dirty plugs. I triple check all reading and even went back to 5 to triple check again. I made sure all connection where tight i was takeing the highest reading after 6strokes. I did not go thru or remember other thangs like adding oil to each cyl. I cant remeber the compres on the first strokes and thank i should retest to pay attention on how it builds up. I thank i was hiting 150 by the 3rd stroke.

can anyone help me out on telling me what could cause number 5 to be 10-15psi higher and is there other methods i should do while i have the gauge. I need to know everyone thought on my compression test so i may return it and start with the next steps. I been constently checking my other thread but have`nt goton any replys thought i would bring attention the compression test

 

[tbirdsps]

The thing to remember is that + or - 10% is certainly OK. Are you sure that 1,2,3,4 and 6 aren't low? Just a thought. The numbers on those are really good. It could be that #5 has some carbon buildup on the piston causing it to be slightly high. Could that cylinder have been misfiring or running too rich?

I think your numbers are quite good. Adding oil is a way to discover whether the valves are leaking or the rings are leaking. An increase in the reading after adding some oil indicates the rings are leaking. No change would indicate valves are leaking or both the valves and rings are leaking. I would be more worried if one of the cylinders was quite low compared to the others.

 

[Rearanger]

I made sure all connection where tight i was takeing the highest reading after 6strokes.

Don't count strokes, just turn it over until it max's out at highest compression. Usually best to hold the throttle at wide open. What year and miles. Numbers look OK but probably show a little drop since new.

 

[akalawrence]

2002 model ranger v6 3.0 tremor/edge with plastic intake flex fuel model i thank. 230k miles ..... carbon build up on all 3 plugs on the number 5 side..
i dont under stand you say if i add oil and it dose nothing to pressure than could be valves if its high then its worn ring...... well what is suposed to happen when i add oil and everythang is ok is the pressure suposed to drop? or rise just a bit slightly.

I also forgot to hold the throotle wide open should i retest?

 

[Rearanger]

230k miles

Pretty good compression for that mileage.

i dont under stand you say if i add oil and it dose nothing to pressure than could be valves if its high then its worn ring

The oil is supposed to flow to the outside of the piston and down the cylinder wall to the rings. It acts to seal some leakage past the rings. Depending how much the pressure increases with the oil it may show that the rings are leaking pressure. If there is no or little change change then the leakage is just past the valve seats - less expensive to fix.

I also forgot to hold the throotle wide open should i retest?

I wouldn't do it over. The numbers are all pretty close and not bad for mileage. These numbers wouldn't cause me to do anything to the engine, except maybe de-carbon. Higher numbers on retest is not going to change anything. Just keep driving it.