two bad spark plugs?

nanuke · Post by **nanuke** » Sun Apr 19, 2009 2:27 pm

Truck has been running pefect and then suddenly yesterday Iwent to start it and it ran very rough. I pulled the plugs and the first two cylinders plugs were fouled but the rest were great. I checked wires, distributer, installed new points and condensor but still same problem. Any ideas?

Thanks

rixm37 · Post by **rixm37** » Sun Apr 19, 2009 5:11 pm

Next thing to do is a compression test. If there is low compression in both of the cyls in question then it could be the head gasket.

rixm37 · Post by **rixm37** » Sun Apr 19, 2009 5:11 pm

OOPS hit enter twice

MSeriesRebuild · Post by **MSeriesRebuild** » Sun Apr 19, 2009 5:11 pm

nanuke wrote:Truck has been running pefect and then suddenly yesterday Iwent to start it and it ran very rough. I pulled the plugs and the first two cylinders plugs were fouled but the rest were great. I checked wires, distributer, installed new points and condensor but still same problem. Any ideas?
Thanks

Was it oil fouling? If so there must be a ring/cylinder wall issue.

nanuke · Post by **nanuke** » Mon Apr 20, 2009 4:42 am

Both plugs appear fouled. I'm going to test the cylinder pressure and see if its a head gasket. What should the pressure be? This engine was rebuilt a couple of years ago(not by me though).
Thanks for the suggestions.

MSeriesRebuild · Post by **MSeriesRebuild** » Mon Apr 20, 2009 8:38 am

I don't believe from what you have said you will find a head gasket issue. Lots more likely cylinders 2 & 3 would be dead with a gasket issue as that's where the narrow area in the gasket is located & is typically where she blows. You will get a "0" reading on 2 adjacent cylinders if the gasket is blown. Good compression readings will be 120 PSI or higher with no more than 5 lbs variation between cylinders. 2 fouled plugs are no indication whatever of a blown head gasket anyway. If the engine build was done correctly, you should not have serious issues going on 2 years later, simply a guess, but I would first look at electrical or vacuum loss possibilities. Again, this is based on the little bit of info you have shared.

nanuke · Post by **nanuke** » Mon Apr 20, 2009 9:25 am

Thanks Charles for the help!
Can you explain a little bit more about vacuum problems. I had been driving my truck around town that day and we stopped for lunch. When I went to start it again it had to be with the throttle wide open. Once it started it was very rough and continues to be like that now. Plugs are 14 years old.
Greg

MSeriesRebuild · Post by **MSeriesRebuild** » Mon Apr 20, 2009 2:28 pm

nanuke wrote:Thanks Charles for the help!
Can you explain a little bit more about vacuum problems. I had been driving my truck around town that day and we stopped for lunch. When I went to start it again it had to be with the throttle wide open. Once it started it was very rough and continues to be like that now. Plugs are 14 years old.
Greg

Lets not get into the vacuum issue just yet, I'll be happy to if we determine that may be needed. I just feel like at this point the issue may be electrical. Have you got your timing set correctly, 4 degrees BEFORE TDC? If the plugs are that old, I'd suggest installing new ones gapped at .030". Are your new points gapped at .020"? Is your distributor shaft loose in the bushings? Is your inner distributor cap & rotor in good shape & clean? If it's years old also, I'd replace that as well. Any side ways movement of the distributor shaft is too much. Have you checked the condition of the spark at the plug cables? With points & condenser, it should be blue, & jump at least a 1/4" gap with a sharp pop. With an electronic module installed, it will jump 1/2" to 3/4" no problem & a much hotter spark. If it doesn't do that or the spark is orange or yellow, you have a distributor issue or a plug wire issue. Have you checked the plug cables with an ohm meter for resistance?

I should have asked this question sooner, do you have fresh gas in the tank? Gas that has been in the tank more than 30 days can cause some real issues with corroding & eventually sticking the intake valves in their guides. How long has the gas been in the tank? A possibility of a carburetor issue also exist, has that been torn down, cleaned, & rebuilt lately.

nanuke · Post by **nanuke** » Mon Apr 20, 2009 2:43 pm

Charles,

Boy, are you thorough! Reminds me of John down at Midwest Military. Your right on most accounts that I should check all of these things. Points and condensor are new and set at .020. Gas is new as is the fuel tank. Carb was rebuilt last year with kit from John. Timing was an estimate when I took out the distributor and put in new points and condensor(although truck ran better than it ever had just by putting distributor in same location as it was originally). Cap and distributor were clean and in good shape

Timing will be my first task followed by checking the plug wires and getting new plugs.

Thanks a million!

nanuke · Post by **nanuke** » Sun May 10, 2009 3:09 pm

Tried manually turning the fan while holding my thumb over the spark plug hole on cylinder #1 and no pressure at all. Removed head and found blown head gasket, replaced and it runs better than ever!!!

two bad spark plugs?

two bad spark plugs?

Re: two bad spark plugs?

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