Another compression thread.

[94dsm]

Sup guys, sorry if this is in the wrong place the search bar keeps closing when my keypad opens on my phone. Anyways, I was looking at a getting my second speed today, took it into the shop and did a compression test, car reached 180,180,179,180 ... my question is, it took almost 15,20seconds of cranking.. usually i can reach max in about 5-7 cranks. After throwing a booster pack on they all read between 190-195(seems high).. both rests cranked until needle stopped moving. But was moving just about 5psi each time... usually i get about half my max reading on the first crank when ive done tjis on other cars(non speeds). Was wondering if this is normal or something i should look into., I didn't have a leak down tester to further investigate. There was also oil on the plug threads leading me to thinking the pcv maybe causing excess pressure?!(failed). Tha ks in advance

[shamie]

Did they have the gas pedal to the floor to turn off the injectors?

[94dsm]

Yes, clutch and gas pedal pressed to the floor.

[GroceryGtr]

thats very odd, you get max comp after 4 rotations/1 cycle(well around since you could be mid way through a cycle). If its taking several cycles then I'd wonder if the rings are shot and its taking longer for oil/gas to wet the cylinders down to seal everything up.

[94dsm]

Kind of what I was thinking, weird it made solid and consistent pressure, but took so long to do it., like 20 cranks. Also why I mentioned the oil on plug threads, cars see getting alot of blowby but the pcv breather box was also caked in oil so I thought the pcv shit the bed.

[GroceryGtr]

well its making solid pressure after 20 cranks because its likely getting oil to seal the rings. This is why most people will do a dry comp run and if the numbers are low add a cap full of oil and run it again. If the numbers go up its the rings, if they dont its likely valves....or really really shot rings lol.

Dry comp check should be a 4 rotation count no more.

Or you have some incredibly gunked/carboned up valves and its just taking a ton of rotations to get a good/lucky seal out of one of those cycles.

[94dsm]

Originally Posted by GroceryGtr well its making solid pressure after 20 cranks because its likely getting oil to seal the rings. This is why most people will do a dry comp run and if the numbers are low add a cap full of oil and run it again. If the numbers go up its the rings, if they dont its likely valves....or really really shot rings lol. Dry comp check should be a 4 rotation count no more. Or you have some incredibly gunked/carboned up valves and its just taking a ton of rotations to get a good/lucky seal out of one of those cycles.

Agreed, I wouldn't doubt the valves are carbonated to shit it's at 108k miles probably never cleaned. Also maybe a dumb question but would I see a spike in psi per crank once they started getting oil? Seemed to be about 5-10psi per crank...one cycle puts that at 20-40psi per cyl, the engine wouldn't run.... and it seems to run fine. I wish I had access to a Leak down tester when I had the car in my possession. Thinking maybe the gauge wasn't sealing properly?!

[MSMS3]

I'd suggest that you pull the plugs and see if it still turns slowly when the starter is engaged. OP may have a starter that is on its last legs.

I'm not sure that a slow crank speed could turn the oil pump enough to get sufficient oil to the pistons to seal the rings.

Another thing to do is to re-run the test after you get the full pressure. If it is low compression until oil gets to the rings, then once there is oil there, retesting should reach max pressure in 4-5 cranks. If it still takes 15-20, I'd be looking at the starter or the battery or both.

[94dsm]

Doesn't matter anymore the car got sold, but there was a jumper pack on the battery.