Tech Support. Messages: 726 Likes Received: 0. We stock complete accelerator pumps, replaceable cups and springs. I've got a 79 z-28 with some upgrades, nothing crazy. Is the accelerator pump adjustable? Qty. Quadrajet Accelerator Pump; Quadrajet Adjustments; Quadrajet Choke Circuit; Quadrajet Float; Quadrajet Idle Circuit; Quadrajet Jets; Quadrajet Metering Rod; Quadrajet Needle & Seat; Quadrajet Rebuild; Quadrajet Secondary; Quadrajet Troubleshooting The accelerator pump orifice is also plugged. 79silverz28 Veteran Member. • Hook up the throttle linkage and adjust for full throttle with someone depressing the gas pedal. REPLACING JUST ACCELERATOR PUMP IN A QUADRAJET The accelerator pump is supposed to provide additional fuel needed during acceleration. . Operate the throttle linkage a few times to be sure nothing is binding. Usually, a faulty accelerator pump will result in a momentary lean condition, which can result in rough or sluggish acceleration, and even misfires. 247 Posts . PHOTO 11 To make the adjustment, connect a hand-held vacuum pump to the choke pull-off and pump it up to 18 to 21 inches of mercury. Consequently, is the Rochester quadrajet a good carb? 1982 . Check the gasket used between the float bowl and the base as you did for the air horn/float bowl unit. Then take the reading using the method specified for your carburetor. Comments: There are two holes in the accelerator pump lever arm for the lever arm rod to engage into: Inner and Outer. I use a small seal puller to push the roll pin out, away from the choke housing. Figure 30—Hot Air Choke System With Front And Rear Vacuum Breaks 356 323 320 For proper accelerator pump discharge (Olds engines) always use the inner lever arm position. After you pump the accelerator yes it should snap closed all the way. Correct for any Quadrajet application. Engine sputtering or stalling. Numbered bits are also available larger than #61- all the way to #1 (0.2280"). Carburetor Accelerator Pump Plunger #1982 for Quadrajet. Fast Shipping. Holley & Rochester Delayer Spring - 66-44. Products [16] Item In Cart. The outer hole produces a leaner pump shot, and can cause a lean stumble on engines requiring a robust pump shot. ACCELERATOR PUMP ADJUSTMENT; AIR VALVE SPRING ADJUSTMENT The Rochester Quadrajet carburetor is a two stage, four-barrel downdraft. Sep 18, 2006 #1. Measure the distance between the top of the choke valve wall and the top of the pump stem. In stock. The Edelbrock Hi-Perf Accel Pump & Spring kit. Skip to the beginning of the images gallery. Can anyone give me some direction? The “M” after that, is a style/model type. It appears that the Quadrajet has variable orifice jets controlled by the metering rods, so that suggests it might not have low-speed idle jets used in other carburetors. Early Rochester four. When the engine fires up it should then immediately pull open about 1/16 to 1/8 of an inch via the engine vacuum and the choke pull off. Close the vent valve and open the primary throttle until the vent valve arm touches the bi-metallic strip next to the valve. • Have someone operate the gas pedal while you verify full throttle adjustment at the carburetor. When the linkage is accurately set, the circuit will begin to squirt fuel from the accelerator pump very soon after the throttle is opened even a small amount. When discussing Quadrajet models, the number 4 means a four-barrel carburetor . Quadrajet adjustment for accelerator pump. Install the two metering rods down into their small barrels and attach the small support arm that holds them in position. What's the difference between square bore and spread bore? Accelerator Pump Rod Installed in Wrong Hole in Pump Arm Results in: Off-idle stumble or hesitation. Also put in a new accelerator pump … Most differences were due to minor changes in pump plunger stem lengths and compression spring heights. A Quadrajet equipped car is often distinguishable from other cars by the sound of the engine as the secondaries open. Adjust the float up or down by bending the small float support arms (tangs) on both sides, using a pair of needle nose pliers. • Install a good throttle return spring. There is a moment of quiet followed by a large increase in exhaust volume, sometimes described as a 'booming' noise. He also drills the accelerator pump discharge holes in the carb lid from 0.026 to 0.029 inch. The accelerator pump can also be used to prime the engine with fuel prior to a cold start. The TPS plug must be absent for a Q-jet carb to be used on the street without a computer, however the feedback type Q-jet can be used in race only applications by removing the metering rods and changing the size of the primary jets. Rochester Quadrajet accelerator pump catalog. The idle screws on a Rochester Quadrajet carburetor fine tune the air-fuel ratio going into the engine during idle. Make certain that it positively closes the throttle. Match the overall length and the cup size to be sure you are getting the correct accelerator pump. Three different styles of pump cups were used, but all Rochester Quadrajet carburetors use a 21/32" pump cup OD. For instructions any decent parts store should have a Q-Jet repair book. Jennings did mention that ethanol/alcohol will cause an AFB carb's leather accelerator pump to peel up over time. The Inner Workings of the Quadrajet | Hemmings For Rochester Quadrajets pick up a idle mixture adjusting tool at most any part store. quadrajet idle adjustment, Fast Idle Adjusting Screw B-09249 B-09251 c D. E. 320. FLOAT LEVEL ADJUSTMENT. Incorrect adjustment is the typical culprit. Discussion Starter • #1 • Jan 10, 2012. If it's not closing all the way on a cool engine, you can adjust it from the passenger side of the car. Joined: Jan 6, 2006 Location: Texas. IDLE VENT ADJUSTMENT. Ethanol ready, made in the US and meets or exceeds manufactures specifications. A Quadrajet carburettor car is often distinguishable from other cars by the sound of the engine as the secondaries open. A ... often the problem can be traced back to the accelerator pump system. Be the first to review this product. A 1/16" punch for removing the accelerator pump arm roll pin An adjustable T-square for setting float level A "pin vice" and a set of small numbered drill bits for measuring and making (or enlarging) small diameter holes. Most performance enthusiasts shun the Quadrajet … The most common cause of rough idle quality in engines equipped with this carburetor is an unevenly adjusted idle mixture circuit caused by incorrectly adjusted mixture screws. Anytime the throttle is opened, there is a transition time required for the carburetor circuits to operate. Place the small gasket shield back on the air horn top. Using a pump that has a short duration spring and a long stem so it can be trimmed allows you to set the pump cup just a tad above the fill slot. The carb is completely rebuilt including new throttle valve bushings and runs great. An accelerator pump is a component on a carburetor. Remove the idle vent valve cover from the air horn, if so equipped. Install the accelerator pump arm onto the rod, then position it so that a new roll pin can be pressed into the fulcrum hole. Accelerator Pump Cup: Quadrajet 21/32 - This is FLUORELASTOMER a special purpose fluorocarbon-based synthetic rubber. CALL TO ORDER 888-799-1135. The secondaries open and there is the slightest amount of delay as the accelerator pump richens the mixture. The tool bends which will make adjusting easier. Member; Posts: 224; Quadrajet accelerator pump problem « on: May 08, 2013, 08:55:24 PM » I have a poser for the group. BENEFITS OF BUYING DIRECT FROM EDELBROCK. I adjusted the float to specs, pulled it up about 1/8th inch higher than it was. 425. Rochester's timeless Quadrajet four-barrel carburetor can perform with proper tuning controlled power piston used … "One of the most important things we modify is the idle circuit. Place it on the base and mate the base to the float bowl. • Check for interferences at the accelerator pump linkage. STOP HERE and turn the carb over. The accelerator pump (A) sends additional fuel through a dedicated circuit to the discharge nozzle (B). Some pull-offs had an adjustment screw, while some older carburetors require the linkage to be bent to achieve the proper opening. The secondaries open and there is the slightest amount of delay as the accelerator pump richens the mixture. This assembly is 2.57" long. They are bought typically in sets numbered from #61 (0.0390") to #80 (0.0135"). 322. Arrow points to Dual Capacity Accelerator Pump plug; circled is where the TPS plug would be on an electronic or computer controlled Q-jet. There is a moment of quiet followed by a large increase in exhaust volume, sometimes described as a 'booming' noise. The accelerator pump … I rebuilt my Quadrajet this winter due to the secondaries not working properly. If there is any problem with the pump, then there will be a problem in the fuel mixture during acceleration. If the old roll pin was not removed and you’re installing a new roll pin, remove the old pin first. Excessive priming, like an improperly adjusted choke, can cause flooding. It fired up but idled high for a couple secs but just died.I tried giving it gas but it just idled high again and then died. Transitions Via The Accelerator Pump. Rochester Products produced many different varieties of accelerator pumps for the Quadrajet carburetor. It is a shorter style assembly that is great for performance applications. Skip to the end of the images gallery. PHOTO 15 To the side of the accelerator pump bore is a metal plate and below that is the discharge check ball. After the adjustment, put your fingers on the pivot and needle and check the measurement again. the only way to buy the accelerator pump is to buy the whole rebuild kit. Hello, I went out and started my 78 el camino today. Every time the float bowl is removed and replaced, this accelerator pump adjustment should be verified. How much horsepower can a quadrajet support? Bend to adjust. A hesitation or lag may result during this transition and influx of air. "We also change the accelerator pump and install a larger needle and seat," Valdez adds. $34.95. In Stock. Add to Wish List. Rods / Linkage Pulloff Rod. A minor clearance at curb idle between the arm and the adjuster is acceptable. Some Quadrajet builders of NHRA Stock and Super Stock Quadrajets do drill a third hole for accelerator pump travel but that's just part of getting the 21/32 maximum pump travel. screw down the carb air horn with the two center screws. Author Topic: Quadrajet accelerator pump problem (Read 8686 times) mikefam. I've rebuilt more Q-jets than I can remember and have never seen anything like this. It is commonly found on many older vehicles that are equipped with carburetors. It has wide chemical resistance and superior performance, especially in high temperature : 1309CP: $10.49: Availability: Check: Complete Acc. 455.4hp, 494hp, 514hp, and currently over 550hp. Accelerator pump assembly, New ethanol compatible 2.57" Complete accelerator pump assembly with ethanol compatible cup and garter spring. To adjust, open throttle so choke butterfly closes (when cold), connect a hand vacuum pump to vacuum choke pull off and pump it up both verifying the diaphragm is leak free and to cause the pull off to pull the linkage to the open/running position, and use a 1/4" drill bit to check the gap between the partially open choke butterfly and inside of carburetor air horn. 360. SKU. quadrajet adjustment help - backfiring/popping Discussion in 'Troubleshooting & Diagnosis' started by 79silverz28, Sep 18, 2006. For this purpose, the carburetor has an accelerator pump. This is when too much fuel and not enough air are present to support combustion. 220/230 cam, world product heads, 9.5:1 compression, etc. Acc Pumps Complete Acc. Is there an idle mixture adjustment like on other carburetors? 323. When divorced, a linkage connects the spring to the choke plate. ' noise due to minor changes in pump plunger stem lengths and compression spring heights the gasket used the! 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