Engine I have a 1980 CJ7 258 with starting issues.

[cluckcj7]

I have a 1980 CJ7 with the AMC 258 i6 / 4.2l . I am having 2 issues: when I park the jeep overnight or for an extended period of time I need to crank if for 5 seconds several times before it will start, it seems like it is out of fuel. The second issue is primarily when it's hot out and I drive it on the freeway or offroad, when I shut it off and wait 5-10 minutes it starts really rough and seems to be loaded up. When I blow it through a few times it then idles fine. This was a problem before I replaced my engine and it transferred over to my rebuilt short block. I installed a 32/36 weber carb and new HEI distributor, this did not solve the issues. I am only utilizing the pcv system and charcoal filter system. I have a fuel pressure regulator running 2.4 lbs, I've tried fine tuning the carb idle and mixture and it runs great in all other conditions. Any ideas?

 

[Manic Mechanic]

Sounds like a carb issue. With the long cranking it's probably the fuel bowl is empty as if the fuel drained out while sitting. The hot condition could be vapor lock. I personally have never been a fan of the Webber carb. Before switching to EFI I used a MC 2100 for 15+ years and never had a problem. In my opinion it's a far better carb for the AMC 258 i6 / 4.2l . The other problem could be low fuel pressure as I'm pretty sure they need between 4.5-6.5 psi.

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[mdeluca]

Sounds like a carb issue. With the long cranking it's probably the fuel bowl is empty as if the fuel drained out while sitting. The hot condition could be vapor lock. I personally have never been a fan of the Webber carb. Before switching to EFI I used a MC 2100 for 15+ years and never had a problem. In my opinion it's a far better carb for the AMC 258 i6 / 4.2l . The other problem could be low fuel pressure as I'm pretty sure they need between 4.5-6.5 psi.

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You wouldn't still have that 2100 available for sale would you?

 

[Manic Mechanic]

You wouldn't still have that 2100 available for sale would you?

I can look but TBH I'm not sure. If you need one look for one from a 72 bronco with the 302. You will want the one with 1.08 Venturi

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[cluckcj7]

Thanks for the insight. I relocated my fuel filter and just read that the gas tank return port needs to be on top, my is not, so I will move my fuel filter and see if that does anything. I am also going to check my carb bowl vent line and see if anything is going on there between the charcoal cannister. Red line and Pierce Manifolds recommend 2 - 3 psi on the weber, it's easy for me to adjust so I'll play around with it. They also said they have had best results at 10 degrees from TDC with ported vacuum advance, my nameplate recommends 6 +/- 2 degrees. Thanks again.

 

[Manic Mechanic]

I've always had good luck with 9⁰ before TDC

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[Project86]

is there a wet spot that would indicate a leak under the carb?

 

[Patrick]

As for the hard starting condition when hot, remove your filter assembly when you are at Walmart. When you get home, let your vehicle sit for the amount of time you mentioned and try restarting. Do you still have the same issue?

 

[cluckcj7]

No visible leaking around the carb.

I will try disconnecting the filter and see if I have the same issue.

I did reposition my fuel filter to the top of the engine with the fuel tank return at 12 oclock. I'll let you know what I find.

Thanks all for the comments.