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08-16-2010, 11:53 PM | #1 |
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One cylinder in my new engine not firing...any thoughts?
Just fired up the 21 stud flathead in my 33 pickup today. It had a load POP out the drivers side exhaust...further investigation showed that the rear cylinder (number 8) was not firing. It has compression, spark and fuel...so why would it not fire? After running for 20 minutes the plug was wet, but not a hint of firing. I put another plug in it (thinking it was bad), it made no difference. Any thoughts??
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08-17-2010, 12:06 AM | #2 |
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Re: One cylinder in my new engine not firing...any thoughts?
pull the plug and look in plug hole to see if valves are moving correctly....and closing all the way.....might have broken a valve....collapsed lifter??....good luck....Mike
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08-17-2010, 12:09 AM | #3 |
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Re: One cylinder in my new engine not firing...any thoughts?
When you say you have compression in 8, I presume it was normal. Look for a shut to ground somewhere in the ignition to that cylinder. LIte it up in the dark and you should be able to see where your spark is going.
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08-17-2010, 01:22 AM | #4 |
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Re: One cylinder in my new engine not firing...any thoughts?
Thanks guys. Yes, I pulled the plug and everything looks to be moving correctly. As far as compression, I don't have a gauge handy so I was just going by cranking it over with my thumb over the hole and feeling the compression. Cheezy, I know...but it's all I got
I fired it up in the dark and could not see any spark exiting anywere. I did pull the distributor/wires and am planning on replacing that stuff. It's a 46-48 distributor and I wanted to change to a crab I had anyways. So I'll pick some wires up for that tomorrow, button it up and see what happens.
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08-17-2010, 07:27 AM | #5 |
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Re: One cylinder in my new engine not firing...any thoughts?
Chris, What kind of headers are you running? Hope you get the spark issue resolved. Ken
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08-17-2010, 08:05 AM | #6 |
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Re: One cylinder in my new engine not firing...any thoughts?
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08-17-2010, 08:09 AM | #7 |
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Re: One cylinder in my new engine not firing...any thoughts?
plug wire not installed in the proper position in the distributor.
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08-17-2010, 09:48 AM | #8 |
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Re: One cylinder in my new engine not firing...any thoughts?
Chris,
I would beg or borrow a compression gauge to do a real test before opening up the engine. On Terry's lead could a pair of plug wires be crossed or an insulation break inside the harness tube. If there was a break inside the tube it might not show up running in the dark. |
08-17-2010, 10:34 AM | #9 |
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Re: One cylinder in my new engine not firing...any thoughts?
the easiest way to see if the plug is getting spark is to hook up and induction timing lite to that cylinder, if the lite blinks then its geting spark, another thing to check is the dist lobe on #8 cylinder, ive seen them worn so much that the points wouldnt open
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08-17-2010, 10:36 AM | #10 |
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Re: One cylinder in my new engine not firing...any thoughts?
while im thinking about your problem check inside the cap for carbon tracking, maybe a cracked cap
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08-17-2010, 10:43 AM | #11 |
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Re: One cylinder in my new engine not firing...any thoughts?
And take the plug out and ground it to the head to see if it fires.
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08-17-2010, 10:49 AM | #12 |
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Re: One cylinder in my new engine not firing...any thoughts?
What kind of load popped out? Oil? Or was that just an after fire (loud pop) like too rich a mixture getting into the exhaust. I hope nothing got left around to get into the intake to block the port.
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08-17-2010, 11:54 AM | #13 |
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Re: One cylinder in my new engine not firing...any thoughts?
DON'T pull it apart! As suggested, you need a compression test. Your thumb will not cut it. Also do as suggested by pulling the dead plug hook it up to the wire and lay it on the head, does it fire? You could also hook up a timing light to the wire with the engine running to see if there is any high tension there. Reprt back...
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08-17-2010, 12:18 PM | #14 |
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Re: One cylinder in my new engine not firing...any thoughts?
Like has already said .Check to make sure you don't have 2 wires crosed.
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08-17-2010, 12:32 PM | #15 |
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Re: One cylinder in my new engine not firing...any thoughts?
yopu got the same motor as in my tank! (bren Carrier) I wonda how much faster it would go if I did the same thing as you did Double carbs, I think you #8 wire is shot!
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08-17-2010, 12:33 PM | #16 |
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Re: One cylinder in my new engine not firing...any thoughts?
And who sayz your your thumb will not do the trick? it worked for me. best feeler even
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08-17-2010, 02:24 PM | #17 | |
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Re: One cylinder in my new engine not firing...any thoughts?
Quote:
I'll get a compression tester tonight and check. Yes, the plug gets spark when grounded out and running....maybe no spark under compression? I have the distributor and wires off now checking everything. Will report back if/when I find something. Thanks everyone so far, been a great help
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08-17-2010, 02:28 PM | #18 |
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Re: One cylinder in my new engine not firing...any thoughts?
Swap the plug and see if the problem follows the sparkplug.
If not swap sparkplug cable to see if the cable is the problem. |
08-17-2010, 08:38 PM | #19 |
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Re: One cylinder in my new engine not firing...any thoughts?
I hate to admit it but when I built my '46 flathead I got some gasket shellac or loctite or something on one of the valvestems and the valve hung-up just enough to keep it from closing all the way. It acted just like your describing your engine. Though it only took about 30 minutes to pull the intake, clean the valvestem and put the intake back on it was still a little embarrassing because I had a smarta$$ friend here to help me fire it and he never let me live it down. After cleaning the valvestem the thing purred like a kitten.
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08-17-2010, 10:45 PM | #20 |
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Re: One cylinder in my new engine not firing...any thoughts?
Try a new plug - it wouldn't be the first time that a new plug is bad
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