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Author Topic: cj7 4.2 weber carb issues  (Read 204 times)

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  • Vehicle: cj7
  • Year: 1983
cj7 4.2 weber carb issues
« on: March 22, 2023, 09:35:05 AM »

Hello all, anyone here got experience of the weber carb conversion on the 4.2l engine?  basically my jeep starts idles and runs fine - until you try to open the second choke. it gasps and stutters then pulls through, but not very well and with not much power.
I'm guessing its a setup issue with not enough fuel coming through - does anyone know a decent set up for these carbs or anyone who might be able to help me tune it - carbs seem a bit of a dying art these days...
it also has the issue that on a steep gradient it stumbles and stalls. So I'm guessing float level isn't correct which also could be related to the flat spot issue  - but once again getting correct info on this seems difficult with many conflicting comments on the web...


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Re: cj7 4.2 weber carb issues
« Reply #1 on: March 27, 2023, 05:35:15 PM »

from my days playing with Escorts and Capris the float should be parallel to the top plate when held vertically as a good rough starting point, and check the pump jet diaphragm is working correctly, doesn't have a blocked secondary choke nozzle.


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Re: cj7 4.2 weber carb issues
« Reply #2 on: April 02, 2023, 05:02:08 PM »

I run a 36/36 webber on mine and the setup process is the same for a 32/36.

Bottom line is if the idel isn't correct, no matter what you do it wont run right. These surprisingly are very simple to setup and people often over complicate the process.
Base setting is mixture screw turned out to the point of idle increases then decreases, to a maximum of 1 1/2 turns out. any more then you need to increase the idle jet size.

the link below takes you to the weber setup instructions (Redline is the manufacturer).

Once the idel is set then the jeep will run with no issues, if the jeep is then hesitant on full throttle or delay in pickup then an increase in main jet maybe required.
Fuel pressure is also a key point and swapping to a 12v fuel pump capable of giving 7psi constant pressure (bypass may require installing for a return to tank for over pressure), anything less and you could see fuel starvation. A mechanical pump is fine but you have to rely on cranking speed for fuel delivery, whereas a 12v pump its there straight away (personal preference i think)
XJ 2.5 diesel - dead. XJ 4.0 6" lift - sold to some lucky person
CJ7 4.2 auto standard(ish)
Alfa 147 jtdm
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