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Unread 08-27-2014, 09:55 PM   #1
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1975 CJ5 
Join Date: Apr 2010
Location: Gainesville, Fl
Posts: 46
304 hot/warm start issue

I have a 75 CJ5 with a fresh 304 and MC2100 carb. When cold, she starts on first crank. However, once at operating temp, she doesnt want to start. If I give it gas and keep cranking, it will eventually start. At oone point, I had to let her cool down before she would start. Does this sound like a vapor lock issue or a carb issue. Either way, where do I start trouble shooting. I did take the gas cap off, but never heard anything and it didnt seem to make a difference. Thanks for the help!

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Unread 08-28-2014, 01:29 AM   #2
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1982 CJ5 
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if a vapor lock issue is suspected, you don't want to keep giving it gas. push pedal to wot, hold, and start. if it starts noticeably easier then you most likely have a boiling issue.
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Unread 08-28-2014, 09:30 AM   #3
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1980 CJ5 
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do you have the fiber carb spacer on the motor or are you running alluminum only? Heat transfer may be an issue. Also, verify your choke position on warm start. Your choke bi-metalic spring may need adjusting.
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Unread 08-28-2014, 11:37 AM   #4
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1976 CJ5 
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Location: Bedford, NH
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I put a mean green starter on mine and wrapped it with an "exhaust blanket" and never had an issue... I was having tons of heat from the headers and it wouldn't allow the starter to kick over.


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Unread 08-28-2014, 12:30 PM   #5
Mike Romain
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1986 CJ7 
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Does the 75 tank have a return line? AMC went with a dual output gas filter to prevent vapour lock on a hot shutdown. The filter sits level with the return line off the top of it so any vapours produced get blown off the top of the filter back to the tank.

Also the choke setting should be verified as someone mentioned. Even warmed up it needs some choke to start up fast or a few extra pumps of gas are needed.
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Unread 08-28-2014, 02:51 PM   #6
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1975 CJ5 
Join Date: Jan 2013
Location: , MS
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The 75 did not have a fuel return line. I ended up putting one on mine and a wood spacer. They helped it a ton. I was having the same issues that you are having.
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Unread 08-28-2014, 08:45 PM   #7
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1975 CJ5 
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thanks for the responses. My CJ has a return line. I think one of the lines was a little close to the header. I moved that last night and today had no problems starting. I guess Ill see if that solved the problem. Thanks for the help.
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