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  #1  
Old 02-03-2008, 12:01 AM
nevadarick
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Default help with weber carb

I have and 87 YJ with the 4.2L. I switched it to the Weber 34DGEC. After fixing all the vacuum hoses, new plugs, wires, rotor, fuel pump, fuel filter and nutter bi-pass. It still doesn't run good. It is fine when its cold but after it warms up and you go above 40mph it starts missing. If you accelerate hard it bogs down until you let off the gas. This get progressively worse until you can only go about 15mph. Sometimes it will just die when you come to a stop and is very hard to start. Are the jets running it too lean? How do you test it? What jets do you install? Maybe its not the jets.
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  #2  
Old 02-03-2008, 12:56 AM
Yogi_Bear
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Hello NevadaRick, I have an '88 YJ and it sounds like you have the same problem I had. I don't know about the carb, but what I found that fixed my situation was a large stress crack in my intake manifold hidden underneath the carb next to one of the bolts. After replacing the intake, $$$, it ran great but was still hard to start after driving it, still working on that issue.
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Old 02-03-2008, 06:38 AM
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Welcome to the board! We'll get you fixed up.

Weber carbs are very sensitive to fuel pressure, and need much less than the Jeep fuel pump puts out. You need a top quality pressure regulator, but I'm not sure what the pressure should be. Use the search function on the board and you should find it.

If that doesn't answer your question, we have a resident Weber expert, Sarge, who can tell you everyting you need to know about them. Send him a P.M. if he doesn't pop in soon - he must be busy in the shop and hasn't been around much lately.
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Old 02-04-2008, 07:06 AM
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I have an 88 with a weber and a GM HEI. You'll need to provide more info for the gang to help you. Are you running your vac advance off of manifold or ported vac? Running an EGR? Are you using the CTS? Is your choke electric or manual? Still running the pulse air system? What all else is or is not connected from the original emissions system?

For what it's worth, I've had my weber for probably 10 years now. It's a great carb. But I never had much luck with the stock ignition system, nutter bypass included. Since switching to the GM HEI, it's been a great simple jeep and I love it.

Sarge will definitely fix you up, and RRich and the gang will sort your electrical ignition issues. You've got a few options for optimum performance.

Good luck
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Old 02-05-2008, 07:20 PM
nevadarick
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I'm not sure what the CTS is. Is that the CTO valve?
The canister carb vent line is teed to the breather hose so both go to the bottom of the air filter. The tank vent line is connected. The 2nd canister line goes to the vacuum at the carb base and is teed to the PCV valve. The 1st canister line goes to the CTO valve.
I'm running distributer off what I call manifold vacuum (also tried the vacuum advance port). It is the same line that goes to the brake booster. This manifold vacuum line also tees off to a green plastic switch on the firewall. The adjacent white plastic switch then goes to the CTO valve. The manifold line also tees down to a vacuum canister under the battery which then goes up some sort of triple vacuum switch. Two of those are capped and one goes to a line that goes back to the transmission.

The EGR valve is disconnected.
The pulse-air was partially removed by someone else.
I hope this makes since to you.

Thanks for the help.
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Old 02-05-2008, 08:23 PM
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Step one - disconnect and plug that vacuum advance line to the distributor. Leave it plugged off till you get the rest straightened out.
With it connected to manifold vacuum, your advance is retarding when it shouldn't, and advancing when it shouldn't - backwards of what the engine wants.

Leaving it disconnected for now won't hurt anything.
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Old 02-06-2008, 09:45 PM
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I drove it with the vacuum advance disconnected and it didn't change much except it hesitated a little when starting from a stop.
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Old 02-06-2008, 10:17 PM
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Hey, I had the same problem since I bought the Jeep weber carb for the 4.2L,

After hard hours of tuning, finaly got it running smoothly.
My carb is not conected to anything, just The vacumm line to he distributor (advance).

Things to take care of:

a) Check any vacuum hoses
b) Install a Fuel Line return to the Fuel Tank, this will take any excess of fuel to the tank.
c) check for the correct Chiclers fo low and high rpm, had to change the lower, to much fuel was going through.
d) clean every port in carburator, the smallest dirt can cause to work bad.

After a lot of trial and error. finaly is running smooth.

Ricardo
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Old 02-06-2008, 10:24 PM
nevadarick
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Do you mean a return line from the fuel canister or the carb? What are Chiclers?
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Old 02-07-2008, 05:42 AM
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There should be a fuel line from somewhere real close to the carb that runs back to the tank. On my '78 the fuel filter has one inlet and two outlets; the extra is for the return line.

It's not for pressure regulation per se, it's to keep a steady flow of fuel from the tank to the pump and back to the tank. That ensures that the fuel in the pump doesn't boil causing vapor lock.

That won't give you pressure regulation good enough to work with a Weber - you still need a real pressure regulator. Some of them have a bleed port that gets connected to the return line. Others just have in and out ports.
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