4.3 merc . spring starup

[samurai1988]

almost seemed motor seized after 4 or 5 try's
starter would not Engauge . replaced starter , did compression test ,
right bank all about 125
# 6 125 # 2 75 # 4 100
sprayed all cylinders with 4d 40 let sit
test #2 75 #4 zero all plugs out turned freely
#2 and # 4 added engine oil and let sit tested #2 125 # 4 zero
any ideas thoughts
thank u

 

[Eric 3.7LX Alpha 1]

quick guess.. possible valve stuck open on 4.

 

[Lou C]

You can pull the valve covers and disable the ignition & just crank it over briefly (don’t want it to start will make a big mess) to observe of the valves open & close. But it seems like the heads are coming off.
Any water in the oil?
Possibilities:
Leaky manifold to elbow gasket let water drip down & corroded # 4 exhaust valve
Blown head gasket
The 125 results are low too normal on these is more like 150-165 psi.

 

[flashback]

On My old 350 I had a rocker arm stud come loose. In those days they were pressed into the head but I don't think they are anymore.

 

[samurai1988]

You can pull the valve covers and disable the ignition & just crank it over briefly (don’t want it to start will make a big mess) to observe of the valves open & close. But it seems like the heads are coming off.
Any water in the oil?
Possibilities:
Leaky manifold to elbow gasket let water drip down & corroded # 4 exhaust valve
Blown head gasket
The 125 results are low too normal on these is more like 150-165 psi.

no water in oil ... i think results are normal for this 4.3 at 125
but will check again on sites ... th u

 

[dubs283]

... i think results are normal for this 4.3 at 125

Um, but I thought #4 has zero, not 125?

 

[samurai1988]

quick guess.. possible valve stuck open on 4.

going to take cover off and look for possible bent push rod
will check compression again after cylinder soak .. and will remove the head if it continues
th u

 

[dubs283]

but will check again on sites ...

No amount of searching the net will change a zero compression cylinder, need to investigate your engine, not computer

 

[Scott Danforth]

Studs still pressed in

Normal compression numbers are 150 psi