Compression Question

[chriskinzel]

I have a jumper switch that I use. Never touch the key. No power to fuel pump, ECM or anything else.

Chris

P.S. This is because I have a 'No Start' solenoid that is mounted by the battery. Connection it right there.

[WARP TEN]

Using Dynomite's altitude conversion chart, at 5,000 feet it looks like you are fairly close to normal, about 195 to 205 or so. -- Bob

[scottfab]

Originally Posted by mike100

I'd expect 205-210, but it does make a difference on how many times you crank it. It may also make a difference if the engine hasn't run recently- put a little heat in it.

On most engines, you will see 90 psi on the very first compression stroke/ needle swing. On the LT5, it should be even more. I'd say warm it up a little, pull the plugs, and then crank it 4-5 times watching the needle rise on the gauge. All cylinders should behave the same- especially on the first rise of the needle.

watching and comparing the initial compression rise is like a poor man's leakdown test- easy to see the weak cylinder if there is one.

Right on all counts:
1 at least ~210psi on all +/- 10
2 ~90psi on first stroke is critical
3 watching and comparing compression rise on each stroke.

I'll add:
warm engine
forget altitude unless you're >5000ft
use 5 stokes
pull fuel pump fuses (both) and relieve fuel rail pressure.
and run each cylinder twice consecutively.