Rochester Monojet Carburetor

The 1MV monojet carburetor is a single down draft unit using a triple ventuir in conjunction with the plain tube nozzle. The main venturi is 1 7/32″ in diameter and the throttle bore is 1 7/16″.
Fuel flow through the main metering system is controlled by a main well air bleed and a fixed orifice jet. A venturi velocity power enrichment system is used to provide good performance during moderate to heavy acceleration and at higher engine speeds.
An exhaust gas recirculation, E.G.R. system controls oxides of nitrogen emissions. The E.G.R. valve is operated by a vacuum signal taken from the carburetor throttle body.
A vacuum supply tube installed in the carburetor throttle body connects by a passage to timed vertical ports located in the bore of the throttle body and float bowl. The ports provide a vacuum signal to the E.G.R. valve in the off idle and part throttle operation of the carburetor.
The E.G.R. valve, mounted on the intake manifold, circulates a metered amount of exhaust gases to the combustion mixtures to lower peak combustion temperatures, thereby reducing oxides of nitrogen during these ranges of engine operation.

The E.G.R. system is not in operation during the engine idle.

A pleated internal paper fuel inlet filter is mounted in the float bowl behind the fuel inlet nut to give maximum filtration of incoming fuel.

The carburetor has an aluminum throttle body, a thick throttle body to bowl insulator gasket, and a internally balanced venting through a vent hole in the air horn which leads into the bore beneath the air cleaner. The float bowl is externally vented under extreme conditions through a pressure relief valve system.

The carburetor part number is stamped on vertical section of float bowl, next to fuel inlet.

An idle stop solenoid is used to control idle. The solenoid is electrically  controlled through the ignition switch. When the ignition switch is tunred off, the solenoid is denergized, allowing the carburetor throttle valve to close further, preventing the engine from running after the ignition switch is turned off. On manual transmission models, the  solenoid also deenergizes when the clutch is disengaged.

Rochester Monojet Identification

Monojet Identification

1980 Monojet 1ME Exploded View & Parts List

1981-85 Monojet 1ME Exploded View & Parts List

1985 & Later Monojet 1MEF Exploded View & Parts List

Float Level Adjustment

Monojet Float Level

Fast Idle Cam Adjustment

Monojet Carburetor

Vacuum Break Adjustment

Monojet Carburetor

Choke Coil Lever Adjustment
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Adjust the Idle Mixture


Recent Posts

VW Fuel Injection

By the mid 1960s, mechanical fuel injection had been successfully employed in Formula One and sports car endurance racing for more than a decade. But manufacturers were just beginning to install it on production cars. Volkswagen introduced it first in 1967 on what the company referred to as the Type 3: the notchback, squareback, and fastback models. It was a Bosch system called D-Jetronic. Volkswagen would not introduce fuel injection to the rest of its line-up until 1975, when they switched to the Bosch L-Jetronic system for their Beetle, Super Beetle, and Type 2, better known as the Bus.

Bosch had developed a direct injection system for gasoline engines as early as 1952, for the Goliath GP 700, a misnomer if there ever was one. The Goliath was a tiny car only 160 inches long, and production numbers were low. The VW Type 3 was the first production model built in sizable numbers to sport mechanical fuel injection on gasoline engines.

These were simple systems, but all systems break down over time. And forty years is a pretty long time. Today, parts are increasingly difficult to find, especially for the earliest D-Jetronic system. Even finding mechanics experienced with these early systems can be a challenge. Some owners prefer to go the DIY route. And some convert their engines to carburetion instead. There are useful manuals out there for the DIY-ers. One that is a little pricey but very helpful is Bosch Fuel Injection and Engine Management, by Charles O. Probst.




Several aftermarket companies make replacement “bolt on” fuel injection systems, but installation is typically far more complicated than merely bolting them on. They may require some drilling, fuel line modification, and perhaps welding of the O2 sensor. You have to be a pretty ambitious DIYer to tackle this job. And the initial cost of these systems can also be prohibitive. Some of these do come in kits, however, which help to simplify the process. For the truly ambitious DIYer, you can always build a system from scratch. But that will involve not only the new fuel line, but also the pressure regulator, electric pump, throttle body and its sensor, a computer, and of course, the injectors. And anyone ambitious enough to consider going this route has probably already replaced the Bosch system.

There are many paths you can take to put your VW back on the road, some far more elaborate than others. A lot of it is simply deciding what is best for you, your car, and your pocket book.

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