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
Quadrajet Adjustment

Trouble Shooting the Monojet M MV Carburetor

Adjust the Idle Mixture


Recent Posts

The B&B or Ball & Ball Accelerator Circuit Gone Bad

checkballdischarge b&bpump check inlet

 

 

 

 

Here is the question. When I accelerate the engine bogs down, or dies.
Assuming the electrical system is OK, because the distributor advance will act the same way, so check that out also.
The first thing to do is turn the engine off and look down the bore of the carburetor. Pump the throttle and you should see a squirt of gas come out of the main discharge. This is located just under where the carburetor top mounts (see #28).
No squirt, or weak squirt indicates a blockage in the accelerator pump circuit. Remove the aluminum plug where the main discharge is located. See #27 in the illustration. This plug is included with our Carter B&B carburetor kits. Remove and clean the main discharge jet #28. Be careful removing this jet. They get stuck and will break easily and if it doesn’t come out easily, then leave it in and clean it out the best you can. Run thin wire through the jet to make sure it is clear.
Your carburetor may have an intake check ball located at the bottom of the accelerator pump well with a retainer wire holding it in the hole. If you don’t have the hole, then a check ball is not necessary here. The action of this part is as follows: When the pump returns to the top, gravity pushes fuel up through the bottom hole and lifts the check ball up, allowing the pump well to fill up with fuel. You can add some fluid into the float bowl and watch to see if this does happen. If your carburetor kit includes an aluminum check ball, then this is where it resides. If you can’t get fluid through this hole, then it is plugged up. Try blowing air through it. When accelerating this check ball will close keeping fuel from going back to the float bowl. Seat this check ball (only if not aluminum) by tapping on it with a brass drift punch.
In the bottom of the float bowl close to the accelerator pump well will be another check ball inside a small column. The column will have either a cap screw, or an aluminum plug covering the check ball (#29 & #30). This is the discharge check ball. When pressing down the pump, fuel will force this check ball off the seat allowing fuel to reach the main discharge.
Test the 2 check balls this way. Hold down the discharge check ball with a brass drift punch. With the pump well full of fluid press down on the pump. You should feel some resistance. If you suspect this ball to leak under this test, tap on the check ball with a brass drift punch to seat it. Now press down on the pump (full of fluid) and see if the fuel lifts up the discharge check ball.
  1. Work on Carburetor While On Car 1 Reply
  2. Tri-Power Carburetors Leave a reply
  3. Holley 1904 Problems Leave a reply
  4. International Shipping Leave a reply
  5. Carter B&B Carburetor Lacks Power From Idle To Cruise Leave a reply
  6. Rochester 2 Jet Loses Power Leave a reply
  7. Mercarb Marine Carburetor Getting Too Much Fuel Leave a reply
  8. Carter WA-1 Check Ball Placement Leave a reply
  9. The Truth About NOS Carburetor Kits 2 Replies