1978 Cj 5 304 v8 engine trouble - JeepForum.com
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Unread 10-14-2013, 08:00 PM   #1
djmarine
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1978 Cj 5 304 v8 engine trouble

Have 1978 Cj 5 it's running on 6 cylinders? Can't figure out what's wrong with the 2 cylinders. They are getting spark i changed all the spark plugs. I made sure all the wires were working? Does any one have any ideas?

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Unread 10-15-2013, 03:27 AM   #2
uberxj92
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Could be a bad cam. Nit opening the intakes for them.
Is it smoking? Making noise? Maybe the springs or push rods. Do you which cylinders are dead?
Maybe the jeep wants a straight six now, lol. Just kidding trying to lighten the mood.
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Unread 10-15-2013, 02:49 PM   #3
djmarine
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It's cylinder 1 and 5 I believe. It back fires if I get on the throttle
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Unread 10-15-2013, 02:49 PM   #4
djmarine
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]It's cylinder 1 and 5 I believe. It back fires if I get on the throttle and there's no smoke
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Unread 10-15-2013, 06:33 PM   #5
uberxj92
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Well since they're both on the same side I would suggest disconnect the coil wire then pull that valve cover and have some one crank the motor over that way you can get a better idea of whether its push rods or springs or the cam.
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Unread 10-15-2013, 09:37 PM   #6
djmarine
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Sorry it was cylinder 8 and 5
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Unread 10-16-2013, 12:37 AM   #7
uberxj92
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Should still pull the covers you'll be able to see better
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Unread 10-16-2013, 12:45 AM   #8
djmarine
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Ok thanks a lot I'll do that tomorrow
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Unread 10-16-2013, 10:31 AM   #9
Red Rubicon
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Your first step should be to check compression.
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Unread 10-16-2013, 08:03 PM   #10
djmarine
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Compression was 90 at all cylinders
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Unread 10-16-2013, 10:02 PM   #11
djmarine
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Also when it started happening my fuel gauge and temp gauge stopped working not sure if that has anything to do with it but need to get that fixed to
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Unread 10-21-2013, 09:05 AM   #12
tineyhairs
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dead cylinders

is it back firing thru the carb or exhaust? intake would be intake valve not working or thru exhaust exhaust not working. as was said in a previous thread pull valve cover off and the coil wire. check the push rod if its there. check valve lash at bottom dead center for looseness. take all spark plugs out. crank the engine and watch the 4 intake and exhaust valves of the 2 cylinders in question. if they don't move or move little compared to the others, you have a bad cam lob. others reasons, v-springs rocker arms, push rods will be obvious. 1 more thing is if the lifter has collapsed the rocker arm may not move. reason for removing all s-plugs is the engine will turn over much easier as there will be no compression in any cylinder. gook luck. take your time and be thurl.
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Unread 10-21-2013, 09:12 AM   #13
tineyhairs
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cam

what cams have you all used in your 75 cj5 304? just want a little ruff idol compared to stock.don't want to change springs locks. the thumper cam is what i wanted, but they said i had to change the works and it would be around $500 bucks. cam and lifters is all i want. not looking for HP just a little ruff idol. tks for the help

have one on me
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