Carb question

Time to rebuild the carb. The metering block on the 1900-series Holley carbs sometimes develops internal clogs, notably in the idle feed circuit. If you're lucky you can clean them up with a regular rebuild. If not...!

DS

My first guess would be that a bit of dirt or other crud is plugging the idle circuit. Closing the choke causes fuel to be drawn in through the main metering circuit, which is a different pathway within the carb.

Will it run with the throttle open?

Can you up it with the throttle and then open the choke?

How many carbs have you rebuilt in the past?

Did you put a kit in it or just clean it?

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Jas>

Did you buy a kit that comes with the new accelerator pump and the new ball bearings that work as the valves on the pump's gas flow?

Adjusting the float 'up a hair or two' just doesn't cut it!

The carb kits come with specific settings for the float and the accelerator pump and the new float needle and pump will 'not' likely be the same as the old ones.

I helped a gent do a carb rebuild yesterday and the new float needle and seat were 1/4" off the old set when it came to setting the float level. The needle was an 1/8" shorter than the old one so the floats needed to be adjusted 'way' up.

The two ball bearings are also different sizes. If you have the wrong one in the wrong place the accelerator pump won't work.

You also have to set the height of the accelerator pump properly or you will get a major bog between idle and speed. Moving linkage means shit, it is the internal movement of the pump that counts.

Here is an easy test. Start it up and shut it down. Then open the choke plate by hand and give the gas pedal linkage a slow shot while watching down the throat of the carb. You must have two nice sweet shots of gas over the complete travel of the gas pedal linkage. If not, then the pump or ball bearings are set wrong.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Jas>

Yup I bought the rebuild kit and replaced the rubber accelerator pump and the one ball bearing. There was only mention of one ball bearing in the rebuild kit, and yes, the one that I replaced was larger than the new one that came with the kit. However, I get nice smooth shots of gas when I work the throttle. I couldn't quite understand the directions for adjusting the float, so I just guessed. It said to invert the float assembly and line up the top of the float to the top of the bowl. I tried this method but just couldn't figure it out, so I adjusted it manually until the gas level was about to the top of the bowl. Do you know what the proper level should be for this model carb?

Thanks for all the suggesti> Did you buy a kit that comes with the new accelerator pump and the new

I wish I knew your carb.

I have 'never' seen the 'right' rebuild kit come with check ball(s) that were different sizes from the one(s) being replaced.

I would be suspecting the kit is for a different carb.

Also the adjustment on the accelerator pump is really important to make it run correctly.

The floats are 'usually' set according to the top edge of the float bowl. You hold the float in place and turn the carb upside down and put a straight edge across the float bowl. You then measure from this straight edge to the top of the float and bend the tab on the needle valve to adjust it.

The carb kit directions should give you this measurement as well as the measurement for the height of the accelerator pump.

Mike

Jas>

That's good, but you didn't mention an acceleration problem, but a "won't idle/won't run" problem, so the issue is not with your accelerator pump or its check ball. The rebuild kit does not come with parts or tools necessary to dissect the metering block, which contains additional springs and check balls and passages. The design of the metering block is such that even if you have enough spare carbs and parts that you can take it apart and clean it manually, you frequently cannot make it behave -- sometimes this part simply fails and cannot be made to work correctly again, in which case a carb or metering block swap is required.

Not critical, this is the accelerator pump check ball.

Whoah! No! That's going to cause all kinds of problems including *VERY* rich running. You need to go over the instructions until you understand them. The carburetor kit comes with a stamped-cardboard float gauge you need to use to set the float height correctly. Also be advised that the float in most 1940 carburetors is made out of a material called "Nitrophyll", which over time can absorb gasoline and become heavier than spec, causing improper running regardless of float setting. The same goes for brass floats, though less commonly -- they can leak, usually at the solder joint, and take-on fuel inside. Weighing the float (or simply replacing it if it looks crusty and old) is part of a careful carburetor rebuild; NAPA will still sell you a new one. Also, the float counterbalance spring must be present underneath the float arm.

DS

Agreed.

Mike, he's got a Holley 1940, not a Carter BBS or BBD -- these two pieces of advice do not apply.

No, just one. It's a Holley 1940. Don't send him looking for something he's not supposed to have.

DS

|> for adjusting the float, so I just guessed. It said to invert the float |> assembly and line up the top of the float to the top of the bowl. I |> tried this method but just couldn't figure it out, so I adjusted it |> manually until the gas level was about to the top of the bowl. Do you |> know what the proper level should be for this model carb?

As a general rule of thumb, the top edge of the float will be approximately level with the float bowl. With the cover inverted, the float will be parallel to the gasket surface. If fuel is at the top of the bowl, it's too high. 1/4" or so down is more llike it.

Hmmm... One of our books is wrong.

I always thought the model 1945 was just a divorced choke version of the model 1940.