Can one completely dead spark plug cause hard starting on an O -235-C1?

[lndwarrior]

Trouble shooting a new hard starting problem on my 4 cylinder O-235-C1.

Electrical, battery, starter all seem good.

Found one completely dead spark plug on the bottom #4 cylinder.

Can this, alone cause hard starting?

It does start but after many attempts.

This is new problem not experienced in the 8 years since I installed her.

Before I put everything back together I'd like to know the answer to this question in case I should keep looking for additional issues.

 

[D-Dubya]

It for sure is a problem and might be the problem. Do you have an engine analyzer? If so, what was it showing for EGTs and CHTs on the last flight? What about during the mag drop test? A dead plug should have resulted in a rough running engine on one mag or the other.

You didn't say how you determined the plug was dead, so that leads to a few questions. Did you test the electrical resistance of all the plugs? Did you clean them and test them under pressure in a spark plug tester? High resistance and/or worn plugs can lead to hard starts. What do the other plugs look like (or how did they test)?

If the only anomaly you see is on #4, then I think you've found your smoking gun. Leave the cowling off and give it a try.

 

[mvs163]

If you have a key type start switch...they usually ground out the non-imuplse/right mag so you're only starting on the impulse/left mag.
If your dead plug is fired by the left mag then yes, you may be starting with 3 plugs only.
Swap that plug top to bottom and check the start.
But it should also give you a mag drop on that mag also ....

 

[Snowflake]

Could try just swapping the plug leads on that cylinder, and see if it makes a difference. If you're using the mag that's driving the dead plug you'll switch to driving a live one and you'll know if that's the issue.

How many cylinders are primed? Is it possible that is also the only cylinder with a primer line?