Spark Plug Diagnostics
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From: Boise, Idaho
Spark Plug Diagnostics
Hi all,
Pulled my spark plugs today to do a compression test.
Not happy with how the spark plugs look. They've never looked like this before. Usually they're nice and clean with a slight tan to them (as they should be).
All six of my spark plugs looked exactly like this, so there weren't any stand out cylinders.
The compression test was good. All six cylinders were around 165 (not too bad for a 30 year old engine). The only oddity I noticed is that some of them, the pressure would drop on the gauge quickly, so I to be fast to see what the result was after cranking it a few times. This may have been a bad seal when I screwed the tester in, but who knows. The head was freshened up as of last year.
(No idea why some of these pictures are showing up rotated. They're straight in photobucket.)
Pulled my spark plugs today to do a compression test.
Not happy with how the spark plugs look. They've never looked like this before. Usually they're nice and clean with a slight tan to them (as they should be).
All six of my spark plugs looked exactly like this, so there weren't any stand out cylinders.
The compression test was good. All six cylinders were around 165 (not too bad for a 30 year old engine). The only oddity I noticed is that some of them, the pressure would drop on the gauge quickly, so I to be fast to see what the result was after cranking it a few times. This may have been a bad seal when I screwed the tester in, but who knows. The head was freshened up as of last year.
(No idea why some of these pictures are showing up rotated. They're straight in photobucket.)
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Joined: Aug 2010
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From: Sacramento
What kind of fuel do you guys run there when its colder outside, does it use oil ? Also how many miles on the plugs since you last checked, I've had winter fuel that have left my plugs with deposits all over them.
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From: Boise, Idaho
No idea on what kinds of fuel they switch to, but I pulled the spark plugs out of my wife's 84 (we drive both every day and fill up at the same gas station) and it didn't have any of the same deposits.
Plugs aren't that old. I think I looked at them sometime last year and have replaced them within the last 5,000 - 10,000 miles.
It does seem to use oil, but I'm not sure why. Great compression, and the head is freshened up as of last year.
The oddity that I noticed is that whenever I pull spark plugs from cylinders 3 & 4, there is oil on the spark plug's threads. The electrode is dry, but the threads are oily. Who knows, may just be a small drip from the valve cover.
Plugs aren't that old. I think I looked at them sometime last year and have replaced them within the last 5,000 - 10,000 miles.
It does seem to use oil, but I'm not sure why. Great compression, and the head is freshened up as of last year.
The oddity that I noticed is that whenever I pull spark plugs from cylinders 3 & 4, there is oil on the spark plug's threads. The electrode is dry, but the threads are oily. Who knows, may just be a small drip from the valve cover.
Postmaster
Joined: Dec 2006
Posts: 3,603
Likes: 10
From: Spokane, WA
They switch to so-called oxygenated gas for winter. The stuff sucks. Before I had my engine rebuilt with the mods it wouldn't run worth a crap on winter fuel. The current engine doesn't appear to know the difference.
AB: If you can find them, you might try a hotter plug or wider gap or even the EFI plugs. I use the EFI plugs with a 50 gap and haven't changed the plugs in 3 years. They've always been clean with a very light tan color although I'm going to change them out with a tune-up in the next week or two.
AB: If you can find them, you might try a hotter plug or wider gap or even the EFI plugs. I use the EFI plugs with a 50 gap and haven't changed the plugs in 3 years. They've always been clean with a very light tan color although I'm going to change them out with a tune-up in the next week or two.
Senior User
Joined: Aug 2010
Posts: 330
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From: Sacramento
I get oil on my spark plug threads, and I know my #5 burns oil through the guides, it could be a bit of oil usually if its just a tiny bit of oil being burned it gets pushed out, even burning oil I never have to add any being as it doesn't burn that much. However just because one truck runs cleaner then the other on the same fuel doesn't mean it isn't some type of additive, could just be one runs richer then the other.
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Joined: Jan 2008
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From: Trenton, MI
Anyone notice #2 picture of spark plug. Notice cremated is chipped. It look it was running LEAN to destroy cremated.
Check PVC's hose to see if there oil been sucked in.
Those spark plugs remind me of crap fuel in small engine.
Had you sniff in gas tank to see if it actually smell like gas or rot like old mix with fresh gas? What Fuel Filter look like?
Check PVC's hose to see if there oil been sucked in.
Those spark plugs remind me of crap fuel in small engine.
Had you sniff in gas tank to see if it actually smell like gas or rot like old mix with fresh gas? What Fuel Filter look like?
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From: Boise, Idaho
Thanks for the responses.
I cleaned up the plugs and reinstalled them. It removed a bit of low end bogging I was having, so I know the crud was causing some issue.
The '81 is set up a tad richer than the '84, so maybe that's why the other didn't have any deposits?
I'll look in to getting some EFI plugs and see if that helps too.
Milwaukee, the plug wasn't chipped. That was just the build up. Some of it was like a little bit of scale and had flaked off.
I'll check the PVC hose, I haven't looked at it in a while. I'll also see how the gas smells and how the fuel filter is. It's probably time for a new filter as is since it has one of those little in line ones.
The other odd thing is it's definitely going through oil. Maybe 2 - 3 quarts in the last 4 months? I hadn't been able to check it all winter because whenever I pulled the dipstick, it was all foamy from all the short cold trips day after day, but now that it's warmed up, my oil's back to normal, and it's barely touching the bottom of the dipstick. Yikes.
It doesn't leak since all the gaskets are new, and if it's burning oil, it sure doesn't show it in the exhaust.
I cleaned up the plugs and reinstalled them. It removed a bit of low end bogging I was having, so I know the crud was causing some issue.
The '81 is set up a tad richer than the '84, so maybe that's why the other didn't have any deposits?
I'll look in to getting some EFI plugs and see if that helps too.
Milwaukee, the plug wasn't chipped. That was just the build up. Some of it was like a little bit of scale and had flaked off.
I'll check the PVC hose, I haven't looked at it in a while. I'll also see how the gas smells and how the fuel filter is. It's probably time for a new filter as is since it has one of those little in line ones.
The other odd thing is it's definitely going through oil. Maybe 2 - 3 quarts in the last 4 months? I hadn't been able to check it all winter because whenever I pulled the dipstick, it was all foamy from all the short cold trips day after day, but now that it's warmed up, my oil's back to normal, and it's barely touching the bottom of the dipstick. Yikes.
It doesn't leak since all the gaskets are new, and if it's burning oil, it sure doesn't show it in the exhaust.
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Fleet Mechanic
Joined: Aug 2009
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From: Western Washington
You've got a catalytic convertor on your rig right? I've been told a cat can mask oil smoke by burning it up. Mom and Dad had a brand new car that would go through a quart of oil every 1500 miles, never saw a whiff of smoke.
Sam
Sam
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Joined: Dec 2007
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From: Boise, Idaho
I do have a catalytic converter.
Hrm.. I certainly don't want to be burning that much oil. If that much oil was getting past the rings, wouldn't that show up on a compression test?
Hrm.. I certainly don't want to be burning that much oil. If that much oil was getting past the rings, wouldn't that show up on a compression test?
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