Some spark plugs not firing

[The_Handier_Man1]

From: sammut321  (Original Message)
Sent: 8/9/2003 8:43 PM

FOUND THAT MY # 6 AND 7 SPARK PLUGS AREN'T FIRING. GOOD WIRES. COMPRESSION 60 ON #7 & 80 ON #6. ANY IDEAS ANYONE?
THANKS FOR ANY HELP.



From: Tarsand traveler
Sent: 8/9/2003 9:46 PM

The compression sounds pretty low, have you tried grounding those plugs to look for spark.
Hugh



From: denison
Sent: 8/9/2003 9:49 PM

Compression that low could be from valves that are sticking, or have sticky lifters, or that are rusty from having been slightly open while the engine sat for years, or it could be stuck piston rings - or broken rings, though thats unlikely. Since #6 is the next to rear-most on the passenger side and #7 is the last one on the drivers side it couldnt be a head gasket. Plugs would easily foul with that low compression, so look at them, or try new plugs. Is it possible that wires #6 and #7 are connected in reverse? Check that you at least have a spark by pulling the cap off the plug and seeing if the spark will jump from a piece of metal pushed in there, and held 1/4 inch from the block. It should easily jump that far. It could be a bad distributor cap, though that would be rare, and it wouldnt cause low compression. Let us know what you find it to be. By the way, each time I take my plugs out I run a spark plug thread tap in, to clean up the threads. Also make sure you have the proper -reach- n the spark plugs.
If you cant get them to fire, giving it a nice trip, with clean oil, will go a long way to cure sticky valves, and if its rust, it should wear itself away - just don't run it where you have to keep the throttle really far open all the time. And let us know what you find it to be. denison



From: chip
Sent: 8/9/2003 10:49 PM

if you are still running points check dwell and gap.



From: leftyizme
Sent: 8/9/2003 10:56 PM

Hi, Denison has some good points, an easy way to determine whether the rings or the valves are to blame,(I agree with Denison, the compression is very low.) is to add one ounce of clean 30 wt oil using a syringe into the cyl., if the compression improves, the rings are bad, if it doesn't the valves aren't sealing.Marvel Mystery Oil added to each cyl. will sometimes free stuck rings if allowed to soak for a few days. There is a tool for doing a cyl. leakdown test that a good shop could do that would tell which is bad, it tests the intake, exhaust, headgasket, crankcase, and coolant passages for rate of de-pressurization (really long word for "leaks"lol) you didn't give the #'s for the other cyl. and are you removing all the plugs and holding the throttle wide open while cranking during the test? this will reduce the compression if you don't. --lefty