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Unread Yesterday, 09:52 AM   #1
TroySh90
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Join Date: Jul 2014
Location: Carlisle, PA
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1978 cj7 fuel issues?

I have a 78 cj7 that's basically stock. It has a 258, auto trans, and carter carb. The thing will idle like a dream and drives fairly decent for a while. But, it has an intermittent issue with what I think is it running out of fuel. You will be driving and the thing acts like its shutting down. Usually I can put it in neutral, pump it a few times, and it picks back up and runs ok for a little. Sometimes though, it will shut completely down. When this happens, I can usually pull off the road wait a couple minutes and it fires right back up. The fuel pump has been replaced, lines checked, and carb rebuilt. This has probably been answered a few times but I couldn't find anything so I figured I would take a shot and see if anyone else has had the same issues. Thanks in advance for any help.

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Unread Yesterday, 10:15 AM   #2
Mike Romain
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1986 CJ7 
 
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Location: Off the Grid in Chester Grant, Nova Scotia, Canada
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How is the gas tank vented? Is the charcoal canister hooked up with a clean air filter on the bottom of it? Quick vent test is to crack open the gas cap next time it acts up, if all is well after, you know where to start.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread Yesterday, 11:16 AM   #3
TroySh90
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We have pulled the fuel cap before and no difference. It seems like the warmer it gets, the more often it will happen.
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Unread Yesterday, 12:16 PM   #4
dg6772
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1986 CJ7 
 
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My friend had this issue.....did the same as you did. We decided the eccentric on the cam for the fuel pump must be shot. Not sure if the 4.0 has this as well. Our solution was an electric pump......

Dave in Muskegon using JeepForum
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Unread Yesterday, 12:22 PM   #5
Mike Romain
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Quote:
Originally Posted by TroySh90 View Post
We have pulled the fuel cap before and no difference. It seems like the warmer it gets, the more often it will happen.
Someone else is having a similar issue. His problem is his gas filter isn't sitting level with the return off the top so any vapours that accumulated get blown back to the tank. His filter is tipped down and his return line is real close to the exhaust manifold creating a vapour lock in the top of the filter.

One other person is doing something similar and his stock rubber gas lines on top of the fuel tank had dry rotted from the ethanol in the fuel allowing the pump to suck air now and then.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread Yesterday, 02:16 PM   #6
TroySh90
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Thanks for the help. This is gonna give some direction.
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Unread Yesterday, 03:58 PM   #7
TroySh90
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Do you think it would help if we temporarily blocked off the return side of the filter? Tbh I am new to carbs lol. I try to stay away from them.
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Unread Yesterday, 04:50 PM   #8
1978CJ7Beast
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I too have a 1978 CJ7 that had intermittent stalling problems. When trying to figure out the problem, we'd park it, fire it up, and observe. it would idle for about 15 minutes (tops) then start struggling..then die. We dropped the gas tank, found rust in it, cleaned it out, reinstalled the tank..still had issues. Ultimately, we had two main problems: 1. There was rust on the TOP of the tank we didn't see due to the tank's design and our lack of a scope . We believe flakes of rust were coming dislodged from the top of the tank, mixing with the fuel, then eventually getting sucked up against the sock type filter at the end of the sending unit inside the tank. Rust particles eventually surround and cover the filter, cutting off supply of fuel...and it'd stall. 2. The new fuel pump installed was defective. Replaced the tank and added an electric fuel pump. Solved my problem.
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Unread Yesterday, 05:02 PM   #9
Mike Romain
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Quote:
Originally Posted by TroySh90 View Post
Do you think it would help if we temporarily blocked off the return side of the filter? Tbh I am new to carbs lol. I try to stay away from them.
No, the return line helps prevent vapor lock when the filter is installed correctly.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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