3.0 GLP-C cylinder misfire

[Jbm0121]

Finally got the bot running from a previous issue of dying while underway, water was in the fuel, now that it will crank, it misses on the front cylinder.

i have taken the valve cover off and there are no issues there, I will be checking compression later today.

There is spark to that cylinder, distributor cap, wires and plugs, just replaced when I had the first issue.

Is there anything that I am missing to check?

 

[Scott Danforth]

new doesnt equal good

put an old wire on to check the wire
swap plugs to see if its a plug issue
do a compression check on cylinder 1

 

[Saline Marina]

I am curious how you determined the misfire is on the #1 cylinder.

If the carb has 2 jets (and I'm not sure if it does) there is the possibility that one of the main jets is not flowing properly (clogged, etc) and so its leaning out a pair of cylinders, more or less.

 

[Jbm0121]

I just tested compression and cylinders 1- 63-65 lb cylinder 2 - 0 lbs cylinder 3 - 130lbs and cylinder 4 - is 105 lbs

Anything else I should do or check before tearing into head gasket?

How will I know its not something deeper?

 

[Saline Marina]

Gotta look closely at the head gasket. If the fire-ring (stainless ring right around the combustion chamber) is compromised then that's probably your issue. The cyl head while off can be checked for valves not closing and damage to the casting (pinhole to oil or water side). And you can inspect the piston crown for integrity. My opinion is even fractured rings wouldn't give you a zero compression, even if the first ring is completely missing (unlikely) then the 2nd is there to do some compression. Really bad rings would scuff or score the bore walls compared to others. Take a look at the spark plugs too, a melted outer electrode can hint at spark-knock which can also melt a hole in the piston if enough of them happen in a short time.

 

[jerryjerry05]

While the motors still together, and the valve covers off.
Remove the plugs and turn the motor over slowly, check the travel of the rockers and the valves.

I have seen one or more of these motors that the valve bends and they don't hold comp.