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| | | | Joined: Dec 2002 Posts: 127 Wrench Fetcher | | Wrench Fetcher Joined: Dec 2002 Posts: 127 | I seem to be posting a lot lately haha... I just pulled the plugs on my 235. All plugs were a little lean, but the #5 spark plug was extremely rich. Any ideas what could cause this? Going to do compression test tonight. Thanks! | | | | | Joined: Jun 2009 Posts: 2,201 Shop Shark | | Shop Shark Joined: Jun 2009 Posts: 2,201 | Dead plug or plug wire. The plug is not firing leaving the fuel unburned. | | | | | Joined: Mar 2005 Posts: 1,636 'Bolter | | 'Bolter Joined: Mar 2005 Posts: 1,636 | Be unusual for only one plug to run rich while all the others are "lean". You only one carb and it services all the cylinders.
I'm with friedgeentmater... likely a bad wire and the plug isn't firing.
Residue oily on that plug? Could be a bad ring on that cylinder letting a little too much oil by it. Or maybe a little oil coming around a valve stem. | | | | | Joined: Dec 2002 Posts: 127 Wrench Fetcher | | Wrench Fetcher Joined: Dec 2002 Posts: 127 | The residue was not oily, just black dust. I will check the plug and wire tonight. | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | | | | | | Joined: Dec 2002 Posts: 127 Wrench Fetcher | | Wrench Fetcher Joined: Dec 2002 Posts: 127 | checked compression on engine. #2 and #4 were at 115 but the rest were at 135. I rewired the coil and checked all wires. #5 cylinder seems to be better. still some popping on deceleration. might have to make carb a little more rich. plugs were a little light colored. | | | | | Joined: Apr 2008 Posts: 899 'Bolter | | 'Bolter Joined: Apr 2008 Posts: 899 | I've had success checking spark wiring using an inductive timing light. Clamp on each wire and check the rate the bulb flashes. They should all be about the same, if not you have misfire on that particular cylinder(s)
Ed
| | | | | Joined: Aug 2000 Posts: 1,438 'Bolter | | 'Bolter Joined: Aug 2000 Posts: 1,438 | You can also remove one wire at a time. If you have one not firing well, you won't notice much difference in the way it runs when it is disconnected.
40 Chevy 1/2 ton
| | | | | Joined: May 2012 Posts: 574 'Bolter | | 'Bolter Joined: May 2012 Posts: 574 | what about the spark plug gap, it may be a little wider or more narrow.......i had a lawnmower that did that, it was a simple and cheap fix.
1949 Dodge Coronet 1955 2nd Chevy 4400 1.5 ton 1955 2nd Chevy 3100 1/2 ton 1955 2nd Chevy 3100 1/2 ton 1957 Chevy 5400 LCF 2 ton 1966 Dodge D100 Sweptline 1968 Chevy P20 stepvan 1969 GMC LWB pickup 1972 GMC Sprint 1974 CP30 shorty bus There are three things that I've learned never discuss with people: religion, politics, and the Great Pumpkin.----Linus Van Pelt Trying to understand the behavior of some people is like trying to smell the color 9  | | |
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