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4.2 CJ7 "surging" at 60 mph under load.....

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johnnyboy:
Engine pulls well in normal use, but under sustained load it loses power for a few seconds then picks up then loses power again etc.
Maybe 2 seconds of power loss then 2 seconds of power then 2 seconds of power loss....
Ease off and it is fine. Its like having a speed limiter.Not a problem in normal driving (it's too noisy to go much above 60 anyway) but off-road up a hill..... or even on a motorway up a hill....

It sounds to me like not enough fuel getting through to the carb under sustained throttle, but the fuel pump and filter are quite new (just a few hundred miles...).
 Standard Carter 2bbl, rebuilt a couple of thousand miles ago.
On general principles I gave it a new coil, distributor cap and leads (previous were possibly original....) and maybe the engine ran a bit better, but no change to the surging.
If it had a cruise control I would blame that....

Any suggestions welcome?

frosty 1:
still sounds like a fuel supply problem, is there a filter in the carb where the pipe comes in.

johnnyboy:

--- Quote from: frosty 1 on October 06, 2021, 04:56:05 PM ---still sounds like a fuel supply problem, is there a filter in the carb where the pipe comes in.

--- End quote ---

Hmmmmmmm.

gazjeep:
Bit out of left field but does your carb have a vacuum pipe to the engine ?

I know mine on an Essex V6 had a small hole which affected its running a little, not like your surging symptoms though, just throwing it out there as something to cross off the list of possible' s 

Dave The Sparky:
Another one for you.
I had a kinked fuel hose on top of the tank that made my Jeep do this, allowed enough fuel through to run normally 99% of the time but when you needed the extra power going up hill it just couldn't pull enough fuel through and stumbled, back off the throttle and it was fine again.

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