1G no compression in cylinder 4

[sno_boarder4343]

So my car (1990 plymouth laser rs turbo) is running fine it sounds fine, but when i compression tested it today i got nothing out of cylinder 4, i held my hand over the spark plug hole and felt air coming out of it so i was getting at least some compression, but it was reading 0 on the gauge. so i put a little oil down the spark plug hole and checked it again and got no difference, so i guess the problem is in the head. So how do i properly diagnose what the problem is, and whats the easiest way for me to fix the problem.

 

[ineedagsx]

i had that same thing on cyl 4 on my engine, i had a spare head with a bad 3rd cyl so ripped my head off took out all 4 valves, took 4 off the spare head put it back together with a new head gasket and was on my way it'll take like 5 minutes j/k

 

[sno_boarder4343]

hahaha but isnt doing timing again a pain, and are there an other problems it could be before i go pulling off the head of my engine?

 

[BLINKY619]

bent valves? bronken ringlands?

 

[ineedagsx]

the timing isnt that bad, on the cam gears on the inside theres a dot and both of them should be facing up and then on the gears theres a groove on each side that should face eachother, get this as close as you can when you take the belt off because the oil pump is on a double turn and i dont feel like explaining how to tell where its supposed to be .

 

[95gst1]

I would do a cylinder leak down test if you can. It should be able to tell you alittle more of whats going on. hope this helps!!!

 

[NOSLO2PT0]

If you have 0 compression in that cylinder, I GUARANTEE your car isn't running "fine". Either your tester is broken, or you don't know what a car feels like when it's running on 3 cylinders.

 

[sno_boarder4343]

well the car is not rocking around any, the rpms are sitting right around 1000, the engine is not rocking around in the bay. it sounds just like a normal car and feels like it too, but for some reason we get no compression out of it what so ever. it stays at 0 while all of the others read up at like 145 so the tester is ok.

 

[mattylt1]

I would do a cylinder leak down test if you can. It should be able to tell you alittle more of whats going on. hope this helps!!!

i agree with both valves closed on that cylinder and you will find the problem

 

[cthab]

I would be willing to bet the valves wont close all of the way because they are bent.

You won't get any compression with bent valves unless they are very slightly bent...air will still flow from the pistons however it will not compress due to the air escaping.