# 5 cylinder DEAD!???

[Caliturbo88]

Well on the 86 i got, number 5 cylinder just died off one night driving home. Its a NA motor. We had all the injectors professionaly flowed and new spark plugs and wires(its getting spark and fuel). What would cause the cylinder to loose compression? i can tell its not getting nearly enough compression on number 5 because when you crank the starter, it raises and lowers rpm as it tries to turn over. Could it possibly be something besides worn rings or not sealing valves?

[mattfurlani]

Originally Posted by Caliturbo88

Well on the 86 i got, number 5 cylinder just died off one night driving home. Its a NA motor. We had all the injectors professionaly flowed and new spark plugs and wires(its getting spark and fuel). What would cause the cylinder to loose compression? i can tell its not getting nearly enough compression on number 5 because when you crank the starter, it raises and lowers rpm as it tries to turn over. Could it possibly be something besides worn rings or not sealing valves?

The raising and lowering RPM isn't a sign that the cylinder is dead. you need to do more testing before you can make that hypothesis

86.5 NA has 156 cranking PSI that's not what it runs at. Looking up the running PSI and the percent tolerance between one cylinder and the others will determine whether or not its bad. Losing compression can only be caused by a busted, burnt, or craked valve, worn rings, a hole in the cylinder itself. or the lack of the breathability of the cylinder. since you have fuel spark and air i'd do a cylidner leakage test.

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[Caliturbo88]

what size/thread pitch compression tester do i need?

[mattfurlani]

i don't remember. you can look it up online or try and find a manual or a factory manual. Its probably a smaller size.

ASk some of these other guys i'm sure they've done it a million times.

[mrnickleye]

Same size as the spark plug threads. I believe its 14mm. most compression gauges will have threads for both size spark plug holes. The gauge is a cheap tool, and everyone who works on his car should have one in his toolbox.