is my motor fried?

[dickerrss]

i have a 90 gsx and had some no start issues after installing a new turbo and exhaust manifold. the car has spark and fuel, the crank is turning and all the fuses are good. my friend told me that he thought that it sounded like there was no compression which dumbfounded us because i had driven the car into the garage the day before and have been driving the car for 2 months since i bought it and its been starting up and driving just fine. the car is mostly stock except for k&n air filter and walbro 255 fuel pump. so i did a compression test, the directions say to perform the test when the car is warm but obviously wouldnt start. so here are the #'s keep in mind that all cylinders are supposed to read atleast 120lbs across the board:

cylinder#1: 60 lbs
#2: 30 lbs
#3: 35 lbs
#4 :70 lbs

leak down:

cylinder#1: 90
#2: 60
#3: 60
#4: 110

So from what I gather the rings are toast. What I just dont understand is why it would happend overnight. I was replacing my turbo cause of shaft play, but im assuming the reason it wasnt boosting is because the compression was too low. I can take the car to a mechanic to confirm this but do I really need to do that? would the #'s be so far off just because the car was cold? Anyway if it is what i am guessing it is I'll be stroking the engine, or buying a jdm motor. thanks for any help.

 

[fourreGsixty3]

Wow that is really low, the service limit on 1Gs is 121 psi, and the norm. is 164 psi. Did you do a wet test to see if it was your rings for sure? All you did was change the turbo? You didnt pull the head or nothing like that? My bet is that its the rings, but they must be beat to have that low of a compression.

Dustin

 

[dickerrss]

no i didnt pull the head, when i did the leakdown test i put a cap full of oil in each cylinder and it started to sound better but didnt start up. i just dont want to spend 100+ dollars on finding out something i may already know. thanks for replying.

 

[fourreGsixty3]

If the compression improved more the 15psi from dry to wet compression tests its your rings, get them replaced, and have fun with the new turbo.

Dustin

 

[matt98eclipse]

do the compression test again this time take out all four of the spark plugs so that the car wont get any spark at all. Then test each cylinder when you do this do each cylinder tell it stops

ps i just fried my rings over the weekend on my rst and when i did my first test i got
1,60 2,90 3,90 4,90

then i did it the way i was suppose to and this is what i got

1,55 2,180 3,165 4,155

it makes a difference when you do it like this and it aslo doesnt matter if its cold or hot

 

[dickerrss]

yeah thats what i did i pulled all the spark plugs, pulled the fuse for the fuel pump and disconnected the coil pack. looks like its time to get a new motor

 

[matt98eclipse]

yea thats pretty low compression all that im gonna do is put all new rings in mine