Yeah Spark plug testing

BIG MIKE

BIG MIKE

Senior Member
Look at my plugs today found 2 strange things , #125678 plugs have a tanish gray tip no carbon , #3 plug dosent even look like it even fired, kinda looks new? #4 plug wet lil dark , no oil but gasy smell. tell me is it crossed wires? Oh yes all plug wires Fire with nice blueish purple spark.
 
Unless plugs are examined immediately after engine is warmed up and operated under a full load it will be a matter of guess work to give you advice or diagnose any problems.
 
BIG MIKE said:
Look at my plugs today found 2 strange things , #125678 plugs have a tanish gray tip no carbon , #3 plug dosent even look like it even fired, kinda looks new? #4 plug wet lil dark , no oil but gasy smell. tell me is it crossed wires? Oh yes all plug wires Fire with nice blueish purple spark.
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Have your plugs tested in a spark plug testing machine that shows the
plugs firing and has compressed air to simulate compression. I have seen
lots of plugs that fire good with no compression but as soon as the
pressure gets to 25 lbs the spark is so weak the compression blows the
weak yellow spark out like a candle in the wind. If you can't find
someone to test them send them to me with return shipping costs. G.M.
 
I'm familiar enough with Big Mike to assume it's in his Bren Gun carrier. I would do a compression check first. Clean & bomb test the plugs as was previously mentioned. Checking wire routing on the older engines is difficult but not impossible. You will need to trace each one from the caps to the plugs. It can be done with an ohms meter but a high tension discharge tester would be better(but who has one of those?). A person can also check each one to ground after isolation of the terminals to see if there is a problem inside the harness tubes. You can also get cross firing inside the tubes so the leads have to be checked to each other as well. Those high tension leads have to be maintained in good condition. If they are old and weathered at all, I'd replace them.
 
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you got it Rotorwrench , Hey switched the 3 and4 Well that Fixed a problem also noticed I had a vacuum leak, I mean the plugs are brand new along with everything else i changed in the fall, but one thing when i looked in the plug holes i noticed the valves are a bright tan ? should I be concerned , OK GM Ill ohm meter them :)
 
Tan or coco color should be A-OK. Grey to tan is a normal carbon color for modern fuels. No carbon or black sooty carbon can show a problem from too lean to too rich respectively. Oil in the plugs can indicate either a non firing cylinder, a problem with rings, or valve guides leakage.
 
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