Compression test problems and results

[muffin_man]

So a friend and I decided to test compression on my 92 Festiva. Everything went ok, except we could not trip the fuel pump switch, and didn't have time to disassemble the interior. Since it seems that people sometimes test with the fuel pump on without anything bad happening, we thought we could at least see how the cylinders performed related to each other.

With the fuel pump on, and all plugs out, we blew: 120-135-120-150

Here comes the idiot part (which usually involves me), I didn't screw the spark plugs back in very well. We start the engine, and it blows two of the plugs out of the engine, leaving them hanging by the plug wires over the grill. (hood open)

We carefully re-tighten everything. The car starts up ok, but while it's running, it's making a light puffing noise. Feels similar to before, otherwise.

What do you think?

[mechanicaldj]

Can you explain in further detail on what exactly is your car doing????

(before the compression check)

[miami man]

i think you are lucky that those spark plugs that blew out did not strip the threads in the head.

[WmWatt]

Haynes manual say 204 standard, 145 minimum.
I'd try again as first attempt readings may not be reliable.
Also, after checking the compression put a teaspoon of oil in
through each spark plug hole and check again, called a wet test.
The difference between the dry and wet readings tells you
if the rings are worn.

[FestYboy]

if those are cold readings, ignore them. retest with the engine up to temp and come back to us.

[MTBOX]

compression test

One other thing make sure your throttle body is opened all the way.When you run the test.

[muffin_man]

mechanicaldj -
There was nothing particularly wrong with the car before we did the compression check. It occasionally would die from idle when cold. But otherwise it ran well.

miami_man -
We were definitely lucky. I must have done a particularly horrible job of screwing them in.

WmWatt -
I didn't realize the minimum for these was so low! Well, I definitely want to do the test again, but I want to figure out how to turn off the fuel pump first. This weekend, I am going to take out some of the rear hatch plastics so I can see if I can actually apply some pressure to that button.

FestYboy -
They weren't cold readings, we idled and drove the car around for 10 or 15 minutes before testing.

MTBOX -
Is the best way to do that by holding the gas pedal to the floor while starting, or by holding the throttle open by hand?

One other thing I realize I screwed up, was not using a torque wrench, what are you supposed to torque the plugs to? I also really need a longer extension for my ratched, the 5 inches or so that i had was just long enough to make access very annoying.

Any thoughts on the puffing sound it makes when running now?

[KingFish]

We have a gasket on the ends of our plugs, so just get them finger tight (I use my extension without the rachet, ideal is to use a piece of rubber hose) then take them another 1/4 turn.

[miami man]

yep kingfish is right about the ruber hose because i have been doing it that way for 28 years and it keeps you from cross threading the spark plug holes.

[jglutz]

The puffing sound....
When the plugs blew out they may have taken a few threads with them thus making it hardw for the plug to seal....in any case you should consider pulling the plugs and checking the seat area in the head.
Years ago...they used to sell copper washers for just such a repair.

Usually when a compression check is performed....12v is connected directly to the starter solenoid so there is no need to use the key switch or worry about fuel. They make a switch kit for this...easy enough to make one yourself.