'72 CJ5 feels like running out of fuel and sputtering

Last fall my son's (17 year old) 1972 CJ5 acted like it was running out of gas. Had an old carb on it (pretty bad shape), was told that was probably the cause, could rebuild or replace. Many dollars later and a new Weber, jeep still ran badly. Turns out a 30 dollar fuel pump was what it needed. All was fine through the winter but started to do the same thing again. Starts beautifully, idles great (maybe a bit fast) but starts sputtering and kicking up a fuss after just a bit of driving, 1/2 or so. Fuel filter is also new and has fuel in it. Gas tank is pretty ugly and soon to be replaced. Figured maybe a bad fuel pump so replace that again. Did great for one little excursion out but back to feeling sick. Suggestions? I am going to put it up on stands and go through it from end to end (tired of dinking with little things all the time) and tidy everything up.

One other question, I was told you can adjust the idle on the carb but there is no way to adjust the fuel intact. True?

Thanks,

Peggy

 

Nobody?

 

Patience... sometimes you get quick responses, sometimes not.

If the Weber is like other carburetors, the off-idle mixture is only adjustable from inside the carb, either by replaceable jets, tapered needles, or something similar. You usually have an idle mixture adjustment screw though. I presume you have the progressive Weber, which has a primary and secondary venturi. If so, you should only have one idle mixture adjustment screw on the primary venturi. This will be in addition to the idle stop (idle speed) screw.

The Weber carbs are fairly sensitive to fuel pressure. It might be that the carb is not lean, but instead flooding through the bowl vents due to excess pressure. What do the spark plugs look like?

 

I will assume that you have a 6 cyl. engine because you mentioned a weber carburetor. There should be a strainer (filter) in the fuel tank which would make the engine run like it is starving for fuel if it is restricted. If there is rust or trash in the fuel tank it will stop up the strainer. If there is an air leak in the suction line between the fuel pump and the fuel tank that can cause the fuel pump to suck air instead of fuel. I am not clear on your question about adjusting the carburetor.

 

Adjusting the fuel intact means changing the mixture without taking the carb apart, I presume.

 

Ok that makes sense, I have never heard it refered to that way. On some of the old carter carburetors (50-60) there was an idle fuel adjustment and idle air adjustment that didn't change the position of the throttle plate, but I havn't seen one of those in years.

 

Thank you . Am checking all those things. When "I" drive it, it does sound like it is getting too much fuel and choking out. Will check the lines, I know the gas tank is in horrid shape. Just didn't look forward to pulling it out. And yes, it is a straight 6.

 

So, there are two theories about this ... first, you aren't getting enough fuel, ie the pump is kaput or the line or strainer is clogged. You can check this without pulling the fuel tank and lines. Just direct the pump output into a container - you should be able to fill a jelly jar in much less than a minute.

The other theory is too much fuel pressure for the Weber, so that it floods out due to overfilling of the float bowl. I think this would only happen while driving, since the float bounce would contribute. You can try to add a fuel pressure regulator between the pump and the carburetor... I recall something like 3 psi is optimal for the Weber? Do a search here and on google and you'll probably come up with some more info.

 

the weber likes low fuel pressure. i run mine at 1 psi, using a holley regulator.

also, check the inlet needle/seat assembly of the weber. you'll have to remove the top of the carb to do it. mine was loose from the factory, and allowed fuel to weep (actually pour) past the needle/seat, rendering the function of the float/needle/seat useless.