Interdependencies--what the heck is that? on... I know I had to.

Interdependencies–what the heck is that? Well…read on… I know I had to.

Do you wonder about interdependencies? Me too!

a. Although the five circuits of the carburetor have been treated independently for the

purpose of simplifying the explanation, a word of caution is advisable here as to the interdependency of the different circuits. If the float circuit is not up to standard, the supply of fuel for the operation of the low speed, high speed, and pump circuits will be affected, and hence the operation of all three circuits may be hampered. It has been pointed out that the operation of the low speed circuit does not cease when the high speed circuit starts to function. Similarly, in some cases, notably on units built for Chevrolet Motor Company, since 1934 there is an interdependency between the high speed and pump circuits. On these units the pump circuit delivers a small quantity of fuel at part throttle and higher engine speeds, although the throttle is held steady and the pump plunger is not in motion. This is called “pump bleed” or “pump pull-over,” and the unalterably designed feature of this pump permits it to discharge this fuel in the same manner as fuel is discharged from the high speed circuit. When the unit is properly serviced, this built-in feature will take care of itself.

b. The interdependency of the circuit is not emphasized to add technical confusion to the mind of the service man, but rather to show that, for the absolute precision operation, of which the carburetor is capable, all five circuits must be carefully serviced. No snap judgment should be made in diagnosing carburetor trouble, and no “favorite” should be played when circuits are serviced.

Find out more about the early jeep history in – Jeep – Its development and procurement under the Quartermaster Corps, 1940-1942

Maintenance and repairs are easy with the correct information. Get the book!

Maintenance and repairs are easy with the correct information.  So don’t get all choked up while we look at the choke circuit!


a. Function. These carburetors employ a manual type choker illustrated in the figure above. When the choker is used, the mixture is enriched by cutting down the amount of air admitted through the carburetor. These carburetors use a choker valve with a semi-automatic feature, the choker is connected to the operating lever by a soft spring, the choker valve is also mounted off-center in the air horn. The incoming air tends to push the choker valve open (the longer section of the choker valve being on the lower side of the choker shaft), and the spring action tends to hold choker valve closed. Thus the. valve is allowed to “breathe” with the engine, which tends to lessen the sensitivity of the choker control. In addition to this feature, a poppet valve is provided in the valve to allow inward relief and hence lessen the danger of over-choking when the engine starts to run. The choker and throttle levers are connected by the choker link, which opens the throttle slightly during the choking period.

Find out more about the WW2 jeep in – The Complete WW2 Military Jeep Manual

Operation of the Choke Circuit

Don't choke!

Don’t choke!

a. The choke circuit supplies a ready means of restricting the amount of air passing through the carburetor. This restriction and resulting rich mixture is necessary when starting and warming a cold engine.

b. Chokes are of two types; manual and automatic.  The WO Carburetors described herein employs the manual type. The manual choke mechanism  in the conventional carburetor consists of a valve mounted on shaft in the air horn of the carburetor, operated by an external lever attached to the shaft. Manual operated choke valves of this type usually have a semi-automatic feature which prevents over-choking after starting. This feature is accomplished by spring-loading, either all or half of the valve, or by incorporating a spring-loaded poppet device in the valve. Some models use both means to improve choke action.

You can find out more about the WW2 jeep inner workings with this book – The Complete WW2 Military Jeep Manual.

I watch my weight and the jeep's too.

I watch my weight and the jeep’s too.

A girl’s got to watch her figure.  And back in the day the Army was watching the weight of the jeep.

Compared to today’s Jeeps the WW2 jeep was pretty light weight.

Do you have the manuals? It’s in there. IF you don’t have them yet then look at this – General Stats.

The Willys MB and the Ford GPW made up the bulk of WW2 production in "jeeps".

The Willys MB and the Ford GPW made up the bulk of WW2 production in “jeeps”.

 Net weight – 2,453 lbs.
173+ megabytes of jeep & related info.
I just hate it when someone torques me the wrong way. Don't you?

I just hate it when someone torques me the wrong way. Don’t you?

When you put your combat rims together you should use a torque wrench and set the bolt to 60-70 ft. lbs. But hey be sure set them ALL to the same torque reading!

 image109Combat wheels are identified by eight bolts holding together the two halves of the tire rim. When removing a tire, first remove the wheel and be sure to deflate the tire before removing the rim nuts. After removing the rim nuts, remove the outer rim nuts, remove the outer rim then remove the tire after which remove the beard locking ring and tube from the tire. Mounting the tire is the reverse procedure. Do not put too much air in the tube when mounting.
From TM 10-1513 Change No. 1, May 15, 1942. You can add to your WW2 jeep library by getting your own copy of the manual – Maintenance Manual, Willys MB: TM 10-1513.

Is Oil Viscosity a Concern?

Film thickness. Simplified equations have been developed to provide approximations of film thickness with a considerable degree of precision. Regardless of how film thickness is calculated, it is a function of viscosity, velocity, and load. As viscosity or velocity increases, the film thickness increases. When these two variables decrease, the film thickness also decreases. Film thickness varies inversely with the load; as the load increases, film thickness decreases. Viscosity, velocity, and operating temperature are also interrelated. If the oil viscosity is increased the operating temperature will increase, and this in turn has a tendency to reduce viscosity. Thus, an increase in viscosity tends to neutralize itself somewhat. Velocity increases also cause temperature increases that subsequently result in viscosity reduction. From EM 1110-2-1424 28 Feb 99.
Worried about viscosity?

Worried about viscosity?

Increased viscosity leads to increased operating temperature which is not good for either your engine or your transmission (or other mechanicals). That’s why it is best to use the viscosity recommended by the original manufacturers. For example for the L-134 engine use 10 weight in the winter and 30 weight during the summer…or using modern oils you might consider using 10w30. For the transmission, transfer case and differentials use 90 weight during the summer and 80 weight during the winter.

You might be interested in Military Maintenance for MB/GPW Jeeps 1941-45 which has a lot of WW2 jeep or period related topics that might be helpful to you in learning all about the jeep.

I just love that "Go-Devil" Engine! But what I really love is all the little details about the jeep--check out this book!

I just love that “Go-Devil” Engine! But what I really love is all the little details about the jeep–check out this book!

Here’s an announcement: Herbert R. Rifkind’s book “Jeep -Its Development and Procurement Under the Quartermaster Corp 1940 -1942″ is available. It is in the original manual script format. Photographs inserted were chosen to replicate the ones that Rifkind originally chose. Some were left out because I could not find the image or because the image appeared to be from a copyrighted source.

This edition contains the complete text which the 1983 and 1988 did not have. This version did not have as many pen and ink changes present as the 1983 version. I think you will find it more readable then the British (1988) version. You can find the book at on line booksellers like and–and it should be available everywhere on line. The retail price is 19.95. 228 pages (including an introduction that I added).

ISBN-10: 146370917X
ISBN-13: 978-1463709174

CreateSpace: Jeep – Its development and procurement under the Quartermaster Corps, 1940-1942

Amazon: Jeep – Its development and procurement under the Quartermaster Corps, 1940-1942


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