Quadrajet carburetor troubleshooting

Last UpdatedMarch 5, 2024

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Some of the conventional seats have holes or ‘side windows’ whose purpose is to supplement fuel delivery past the float needle when it opens. *new AC Delco R45TSX plugs gapped @ 0. c Rochester Quadrajet Technical Help. 590. Check the vacuum hoses for cracks or loose connections. Get Rochester Quadrajet carburetor parts here: https://www. Turns out the vacuum can that holds the secondary air valve shut was broken and the air valve was adjusted way too tight to compensate Jun 26, 2012 · Check for missing vacuum caps or bad seals between the carb, intake, and cylinder heads. Subject: Troubleshooting The QuadraJet 4 MC - 4 MV Carburetor Model and Year: All 1968 -1981 Corvettes Source: Delco Bulletin. Slowly unscrew the screw and count the number of turns it takes to make the engine run rough again. Secondaries come in after the primaries , and you are at a higher rpm where power usually just flattens out when they fail to open. Mar 22, 2010 · Corvette would not use Rochester carburetion until 1966, when the Quadrajet four-barrel emerged. 1968 - 1982 Corvette: Delco Service Bulletin: Quadrajet Carburetor Service Charts. This adjustment screw is for the ‘adjustable part throttle’ and is factory set, leave it alone. Jan 22, 2024 · Whether you're a seasoned mechanic or a DIY enthusiast, this video offers valuable insights and techniques to diagnose and address idle problems with your Quadrajet carburetor. It the engine does start when cold, but stalls after a few seconds, check whether the idle screw on the driver's side of the carburetor needs adjustment. Updated on 03/08/2021. 12 Bolt Eaton Posi w/3:73's. Hesitation off of idle can be caused by electrical, accelerator pump and a little known idle passage way. On some of the seats the Ultimate Performance, Tailored Precision. This type does not use a secondary lockout as shown above. Mar 8, 2021 · Quadrajet Rebuild. (2) The expanding fuel (increased volatility) creates pressure in the fuel line from the pump to the carburetor. These carburetors have the ability to self-adjust the air/fuel ratio by the use of a mixture control solenoid housed inside of the main bowl of the carburetor. The Quadrajet carburetor is a popular option for many classic and performance vehicle enthusiasts due to its reputation for excellent performance and reliability. You might want to check your fuel pump, as they get older they also don't pump as much gas to the carb, so you could change the carb and still have an issue. Idle speed is excessive. Jan 10, 2012 · This heats the choke stat when the engine is running, so that when you "blip" the throttle after some warm up time, the choke comes off. These were used only on some years and in 1976 and later. Check the choke plate during a cold Free shipping in US on parts orders over $100 (excludes carburetors and services) June 2024, Quadrajet rebuilds about 18 weeks, Quadrajet rebuild with re-color and plating about 14 weeks. Rochester Quadrajet, 4 barrel carburetor technical information. It offers maximum torque as well as horsepower and consists of high speed circuits. As already mentioned, you can’t test secondaries by blipping the throttle in the driveway. No new mods. Turning the screw down (clockwise) creates a leaner part throttle mixture. Install a good throttle return spring. Jan 10, 2021 · Carter Thermoquad Troubleshooting. Apr 28, 2016 · The number 5 designates an emission carburetor from California. 1135 Rob Loszewski January 25, 2015 Electrical and Ignition 0 1189. Connect the power source to the electric choke terminal. '68 el Camino SS 396/325 hp, 4 Speed, 3. Float level set incorrectly. Car used in this video is a 1976 corvette . The Rochester Quadrajet has gotten a bad rap over the years, often called a Quadrabog or Quadrajunk. Automatic Choke Adjustment. Some chemicals added to the fuel, or left in the carburetor can cause this. Team Chevelle Member # 3540. Check sealing of welch plugs, caps, plugs and gaskets. To set up the Sniper, just tap the Set-Up Wizard on the touchscreen, then follow the prompts: pick the correct Sniper unit, enter the engine displacement A Rochester Quadrajet carburetor is a type of carburetor that was produced by the Rochester Products division of General Motors. Run an engine compression test. GENERAL DESCRIPTION OF THE ROCHESTER QUADRAJET CARBURETOR. Ready to be installed. Find step-by-step solutions, tips, and advice for keeping your engine running smoothly. What is your technique for warm starting? Try turning the key without stepping on the gas. This can be done by running a wire from a fused 12-volt power source, such as an ignition switch, to the choke terminal on the carburetor. Letting the engine sit for months at a time is a sure way to damage the pump cup. One of the most common problems with Quadrajet carburetors is fuel leaks. Another cause which can be traced to the carburetor is a float level which Jun 9, 2021 · Jeff, I restore and rebuild Quadrajet carburetors for a living, CRK Carb and Performance. There are three basic carburetor models, the 4M, 4M, and 4MV. Because it is so common, many racetracks allow the carburetor in the stock Dec 21, 2023 · Quadrajet bog is usually due to improper settings for the idle and primary circuits, not the secondaries. The pump passage way to the main discharge may be plugged. Dialing in the Choke. Start the engine. Dis Assembly of the Accelerator Pump Lever. Jan 16, 2023 · This video explains what to look for when diagnosing a Rochester Quadrajet that is flooding over. Have someone operate the gas pedal while you verify full throttle adjustment at the carburetor. Sep 4, 2022 · We can't do any sort of carburetor video without someone bringing up the legendary Q-jet. I can’t seem to get the motor to idle smoothly. Say goodbye to As you rebuild your own carb, some of these issues might be things for you to watch for. May 6, 2021 · Quadrajet Aneroid Cavity. Jun 1, 2010 · Image 3 is the 840cfm carburetor. Carburtor leaks. Jun 29, 2022 · Vacuum Break Adjustment. The 4G 4-barrel, however, was used on other Chevrolet V-8 applications, while radical, high-performance applications retained the Holley 4-barrel. Make sure to use an appropriately sized wire for the current draw of the electric choke. May 13, 2006 · The Quadrajet was ubiquitous on practically every carbureted Chevy engine installed in a car in the '70s and early '80s. *new ACCEL P/N 35366 "ultra high-performance" ign. However, after reading this carburetor manual--I had the confidence of getting the job done successfully saving me a bundle of dough. Below you will find our Quadrajet rebuild video series. A few reasons why the 4 barrels don't operate on a Quadrajet Carburetor . And to be honest, the carb had some significant limitations for all-out racing use, including a small float bowl capacity and lack of adjustability. First i sometimes got a high idle when driving, i found Aug 5, 2013 · New Quadrajet, idling problems. May 2, 2019 · The Quadrajet by GM's Rochester Products Division is arguably the most popular carburetor ever produced. Repeat the process for the right side idle screw. If the carb is maintained properly, it will deliver years of service. Check one stream for one barrel carb and two streams for two and four primary barrels. Fuel Leaks. com/@DougsMessyGarage?sub_confirmation=1 I show ho Dec 12, 2010 · Sorry guys, I got the videos a bit out of order. 7. With the engine idling, look down into the carburetor with a flashlight. The cup curled, or is damaged. Quadrjet Identification. Apr 11, 2008 · Product Description. Except for the variation in choke mechanism, these three models are basically the same. Learn how the Rochester Quadrajet carburetor works and how to troubleshoot and repair common issues such as fuel leaks, poor idle quality, and rough idle. Feb 7, 2012 · Re: my theory on quadrajet starting issues It sounds like your carb doesn't have a choke or the choke isn't working. module. It was produced in many forms, including electronic-control from 1980-'90 Check the float level. Demon. You should inspect a stream or fuel bowl streams squirting in the throat. Apr 27, 2011 · The miles per gallon and performance both jumped as a result. However, like any other mechanical component, it can develop issues over time. Rochester Quadrajet Carburetor Chokes carburetors thermostats 4 barrel 4bbl Q-Jet - Carburetor Parts & Kits for Rochester, Carter, Holley, Edelbrock, Ford Motorcraft QJet, 4G, 2G, Mercarb Marine, AFB, AVS Thermo-Quad Carburetors Mar 20, 2015 · Engine starves for fuel at high speed (leans out) Check inlet needle and seat for condition and proper installation. Adjust by bending the lever at B. That's how it gets such a larger airflow. Percolation is fuel boiling in the carburetor and is minimized by reducing heat transfer from the intake manifold with an insulated spacer. I previously posted that it was running rich and appreciate all of the advice. Asking $785 plus shipping. Chevrolet Quadrajet carburetors would have a 0, 1, or even a 2. "Our Bottom Plug Repair Kit sells for $19. Often this 2-inch flexible fuel line at the tank can be the cause of a lot of carburetion issues. Jan 24, 2007 · Gauge should read approximately 18 inches at idle. The problem will repeat itself when the engine is brought back to idle. Nov 19, 2019 · 2132 posts · Joined 2006. The bottom plug issue on these carburetors was remedied in the late 60’s when the factory switched from the brass inserts to swaged aluminum slugs, bottom Jun 26, 2015 · In this video I show you what to check if you have a Quadrajet that is flooding or running rich. Rough Idle. The most notable failure in a Quadrajet is the secondary metering rod well plugs leaking fuel into the intake manifold air stream. When it came to the 1979 Z/28 V8TV was working on, the Quadrajet was well worn, showed some signs of rust and dirt seepage and ended up containing the wrong fuel filter. These carbs are more rare because the only Jan 29, 2019 · Be sure to also clean the lines and fuel pump, replace fuel filters and overhaul the carburetor. One major finding was that the carburetor’s upper plate was significantly warped, probably from the Mar 1, 2022 · Nope, the hot rodding community never fully warmed up to the Rochester Quadrajet, the ubiquitous GM four-barrel carburetor that was produced from 1965 to 1990. The metal tang that hinges the float and controls the inlet needle valve is loose at its attachment to the float. youtube. Shown here is a 1966 Quadrajet, carburetor number 7026260. Also, as highlighted on the previous pictures the "7041201" carb body does not have the bump out with the hole in it (as seen on the 7041200) for the bracket that holds that cylinder actuator thing that attaches to the front of the carb in 71. Here's how to check them out. Step 3: Connect the Power Source. Sep 4, 2021 · 18028 posts · Joined 2007. So I am sorting through the problems I am having with a quadrajet on a recently acquired car. It's easy to identify because it doesn't have the secondary booster ring. Jul 1, 2011 · The Fix. Worn engine parts such as valves, rings, or camshaft will cause a rough idle. Step 3: After checking, you can identify the primary problems in the Oct 18, 2007 · 524. This can be caused by several things, but there is one item often missed by the rebuilder and that is the idle tube. How to tune a Quadrajet carburetor? The first step in carburetor tuning is adjusting and checking the choke. The numbers speak for themselves. Attach a long (about 2’) vacuum hose to the pulloff. The search continues for a picture of a period correct (1971) 7041201 quadrajet carburetor. Make certain that it positively closes the throttle. Incorrect adjustment of these mixer screws is known to be the most common cause of rough idling as many faced when their Edlebrock idle mixture screws not Troubleshooting Quadrajet Carburetor Issues Using a Vacuum Diagram: Recap. Beginning in 1972 Quadrajets used a bowl vent connected to the EGR canister. First place to look is the choke fast idle cam and adjustment to see if the cam is moving to its off position or the fast idle screw needs speed adjustment. Base plate rebuild and Inlet repair service is typically about 1 week. Measure the gap between the rod and lever at B. Working on the ME4E Rochester Quadrajet is no picnic. #14 · Nov 20, 2019. JET Rochester Quadrajet Stage 3 Carburetor offers improved idle quality as well as instant throttle response. Here are some common problems that car owners may encounter with their Quadrajet carburetors. Updated on 12/14/2020. It is known for its durability and reliable performance, but like any mechanical system, it requires proper maintenance and occasional troubleshooting. Most other types are considered "square bore," with the primary and secondary venturis being roughly equal in size. 065". Solution #4: Examine the fuel filter. If the automatic choke's coil is not adjusted correctly or is malfunctioning, the engine might not get the right air/fuel mixture for a cold start. Unloader Adjustment. Dec 12, 2014 · This can result in a number of problems. Basically, this is Jul 21, 2015 · quadrajet Secondary throttle linkage. Screw the left idle screw into the carburetor until the engine starts to run rough. Sep 23, 2018 · The article was inspired by letters that we occasionally receive for our tech column that relay carburetor problems that are often blamed on the design of the Quadrajet itself. 4MC = automatic choke carburetor with the choke housing and coil mounted Accelerator pump itself may be bad. It was designed to meet the requirements for better fuel economy, improved emissions, and increased power. This video is about that passage way and how it works. The air fuel ratio that the carburetor is responsible for blending and metering is especially important and sensitive during cold starts. 4M = manual choke operation. The choke not only helps with cold cranking, but it also limits or enables secondary operation (4-barrel). Accelerator Pumps Quadrajet Q-Jet Rochester carburetor 4 barrel 4bbl 4MV - Carburetor Parts & Kits for Rochester, Carter, Holley, Edelbrock, Ford Motorcraft QJet, 4G, 2G, Mercarb Marine, AFB, AVS Thermo-Quad Carburetors Mar 18, 2020 · Rochester Quadrajet carb #7037263 (used on 67 PONT 400, and 67 GTO M/T), but will work and is visually correct for 68/69. The thermal plastic main body stopped percolation, but preformed like a Quadrajet. Open the throttle until the rod touches the lever at A. The videos are in 3 parts and while this is a video about the Quadrajet marine carburetor, it can be used as a general guide for any Quadrajet rebuild. It is not often that we see a serious innovation in the field of carburetor technology. Apr 24, 2021 · Possible causes : Fuel pressure too high, 5 to 7 psi is plenty. It's carb is a Quadrajet 7043242 (stage1) or 7043240. Dec 10, 2010 · Well said Tech. *new ACCEL 300+ spark plug wires. Crack the throttle slightly and push down on the divorced choke rod to close the choke fully. Float is leaking (brass) or soaking (plastic) fuel making it heavy and will not shut the inlet valve. Please d A Quadrajet linkage diagram is a visual representation of the linkage system found in a Quadrajet carburetor. 95 Chevrolet was the first and only GM manufacturer to use the 4M Quadrajet in 1965. Use this to further understand how your carb works. It shows how the different parts of the carburetor are connected and how they interact with each other. The Quadrajet quickly became one of the most popular carburetors in the automotive industry, and Oct 10, 2016 · The Quadrajet four-barrel carburetor was produced by the Rochester Carburetor Division of General Motors from 1965-'90. Engine lacks power at high speed. Is there a modification to eliminate the aneroid assembly, and, if not, is there a means by Feb 13, 2007 · I've experienced this three times in my '73 Riviera GS stage 1 455-4. This part is used to limit the amount of gas in the carburetor for evaporation emissions. One of the key components of the Rochester Quadrajet carburetor system is the vacuum lines. How to Adjust the Secondary. Once properly set, this will start like fuel injection. Aug 15, 2019 · Vapor lock usually happens in the fuel pump and prevents gasoline from getting to the carburetor. Has been in storage for 30+ years, just completely rebuilt with all new gaskets, seals etc, comes complete with throttle bracket and new filter. #2 · Sep 4, 2021. This cutting-edge kit ensures the longevity and endurance your engine deserves. He now works with brother, Craig, building carburetors, EFI systems and race engines. Replacement Rochester Quadrajet Carburetors Installation and Troubleshooting Guide 1968-1981 Corvette Thank you for choosing Mid America Motorworks for this high quality Remanufac-tured Rochester Quadrajet Carburetor. Solution #3: Airflow restriction can also cause an engine to idle poorly. By understanding the diagram, you can easily identify and troubleshoot any issues that may arise with the carburetor. Like. Hard starting. If you already removed it, turn it in until seated, then turn out 4 turns. Apr 1, 2021 · Replacing a Rochester Quadrajet needle & seat – diaphragm type. As always, if any of you have trouble with your Q-Jets, or if you need any assistance, feel free to drop me a note. For a number of years after leaving the Marines, he was a carburetor and EFI calibration technician at the GM Proving Ground in Mesa, Arizona. Learn everything you need to know about Quadrajet carburetors, including how to rebuild one correctly, what kind of performance to expect, and why they've go Hook up the throttle linkage and adjust for full throttle with someone depressing the gas pedal. The problem was the Plastic main body cracked because the long screws that held the Air Horn and Lets look at how a Rochester Four Barrel Carburetor functions. If vacuum is low, check condition and location of all vacuum hoses. Introduced with Chevrolet's new 396ci big-block for '65 and widely used by all GM divisions Oct 21, 2013 · Bend the rod so that the choke blade is fully closed. 3. I get lots of questions about poor running issues. May 21, 1999 · If so, the problem could be a saturated float causing the engine to load up at idle. See Vapor Lock. If any fuel can be seen dripping into the engine from the carburetor, the float is stuck or defective and must be repaired. The Chevy 350 Quadrajet vacuum diagram is a crucial part of the engine’s operation and performance. 66 Chevelle. It will idle OK for a little while, load up, and revving the engine will clear it up by burning up the excess fuel. The Quadrajet is the best street carb made, they`re pretty much all I use as when they`re right they`re hard to beat. The Rochester Quadrajet is a widely used carburetor in classic cars and trucks. The Rochester carb is the most common carb found in GM cars and trucks from the 1960's to the mid-1980's when they were replaced by fuel injection units. Same goes for inspecting the throttle linkage for wear where the controls are binding from wear induced miss alignments. Ethanol blends in gasoline today are responsible for many fuel system issues and carburetor failures on older Corvettes. Jun 26, 2022 · Except for the couple items above, a 50-year-old Q-Jet really can simply be replaced with a Sniper EFI Quadrajet and get all the benefits of modern EFI while leaving the rest of the car as is. Includes all Quadrajet models. Hi guys ! I got a Rochester quadrajet carburator with the choke coil mounted on the intake. The carb is mounted on a Chevy 350 SB. His knowledge has been gathered first hand. Jun 26, 2023 · The Quadrajet idle mixture screw setting is not complicated and doesn’t consume too much time. With a tailored fit for Buick 8-cylinder engines, the Rochester Quadrajet 4 Barrel Carburetor Repair Kit embodies the pinnacle of engine optimization. Oct 3, 2022 · Continue opening the throttle and electric fuel pump wide open for a thorough inspection of the carburetor. It needs to move up and down freely. High performance Chevrolet muscle era engines use Holley square flange 4150-series four-barrel Apr 2, 2008 · If it's flooding as bad as it sounds then you may want to double check the needle and seat and also reverify the float setting. A man with an experience will never be at the mercy of a man with an Dec 14, 2020 · Quadrjet Identification. Updated on 06/29/2022. Jan 5, 2016 · 4. Explains the do's and don't and the how's and why's. 516. Hold a thin blade screw driver, or something similar between the roll pin and the air horn. Any carb'd engine will require working the gas to keep it running until it warms up a bit if there is no choke to richen the mixture. To troubleshoot a Rochester Quadrajet carburetor, you can start by inspecting the fuel filter and lines for any clogs or leaks. 31, Buckets, AC, Black on Black - SOLD Gone to a new home. Engine overspeeds. 6,000 rpm. Cliff's High Performance has recently released a complete kit that permanently seals the bottom plugs of any '69-and-later Quadrajet casting. First let me mention my modifications: *new ACCEL 71105e electronic billet distributor. Low mileage very clean carb. Carburetor out of adjustment. I'm a huge fan of the Quadrajet and am running one on the slant six in my 65 Barracuda. If you have a carburetor with an electric choke, make sure the choke flap is opening properly and adjust if necessary. Sep 20, 2021 · Here's a video that explains how the secondary side of a Qjet works in general and what to look for if your carburetor won't run on the secondaries. If Jul 23, 2017 · Q-jet carb fast idle cam problems. Check carburetor base gasket and manifold gasket. Main metering jet may be the wrong size. It was first introduced in the 1960s and was commonly used on a wide range of GM vehicles. However, like any mechanical device, it can experience certain issues over time. Besides what tech mentioned, it`s also possible the secondary butterfly flap spring control is either broken or out of adjustment, what happens if the rear flaps open too fast too much air rushes in which results in a bog. This book is indeed a panacea! My hats off to Mike Stubblefield. As it deteriorates and cracks, it will leak. Our kit includes the small parts you see here: Part #31, the diaphragm is replaced by a regular needle. From the late '80s on through the early '90s, Bob Jennings increased the primary and secondary carb jetting to help the engine retain Apr 20, 2023 · The Rochester Quadrajet is a four-barrel carburetor that was first introduced in 1965 by the Rochester Products Division of General Motors. Look at the ignition system (plugs, wires, cap and rotor). If your Quadrajet has no functioning secondaries, or runs poorly when the secondaries are engaged, this video will help explain how to understand and fix tho Sep 23, 2018 · Wise is recognized as one of the country's top Quadrajet tuners. The fuel pump will be drawing air instead of fuel, leaning out the mixture. In fact, Here are some common reasons for hard starting, especially in relation to the Quadrajet: Choke Issues: The Quadrajet uses either a manual or automatic choke. This carburetor facilitates easy operation and installation. The problem is as follows: (1) After the engine is switched off, heat from the engine heats the fuel in the fuel line. May 1, 2008 · Because the Quadrajet was a mass-produced carburetor, it suffered from a few failure points in its basic design. Jan 10, 2021 · Secondary Adjustment on Some Quadrajets. To learn more, click: https://www. Here's our thoughts on the carb, it's good and bad points, and how i New Quadrajets. Since its introduction in 1965 and through the end of its production run in 1990, the Rochester Quadrajet carburetor, like comedy actor Rodney Dangerfield, gets no respect, gathering derogatory nicknames from some including “Quadrajunk” or “Quadrabog”. As we've stated previously, the Quadrajet is an excellent fuel-metering device, one that was very well engineered, allowing it to provide both economy and performance Nov 7, 2022 · Rebuild/Adjust the Quadrajet Idle Mixture Screws. Jan 15, 1999 · Great detailed sharp photos. These leaks can occur due to worn or damaged gaskets, cracked fuel bowls, or loose Sep 13, 2019 · Good used ECMs can be had cheaper than a overpriced f###ed up reman Qjet. (3) The check valve prevents the fuel backing up through the fuel pump. Dec 14, 2020 · Quadrajet Accelerator Pump. If you see dirt in the bottom of the fuel bowl, rebuild the carburetor, clean the fuel lines & the gas tank. Set the fast idle on the second step of the cam, usually approximately 1100-1200 rpm when engine is warm. 8. If the carburetor has any sort of issue that disturbs the air fuel ratio it may result in hard starting. Hook up fuel lines and vacuum lines if used. With Qjets, rebuilt and remanufactured are two very different processes. This system is designed to respond to the engine's actual demand for air and fuel, rather than opening at a predetermined rate or position of the throttle. Clean the carburetor thoroughly and inspect for any worn-out or damaged parts. Bulletin No: 9D-5T. Engine will not idle. The Quadrajet carburetor, also known as the Rochester Quadrajet, is a popular choice for Chevy 350 engines. This will make moving the pin back in place easier. Screw the idle screw back into the carburetor one half that number of turns. 350/400 Turbo. The Quadrajet carburetor was known for its durability, reliability, and its ability to deliver smooth and efficient fuel delivery. Dirt in the system - take the top off the carburetor. Remove the accelerator pump arm by using a small drift punch and beat the roll pin towards the carburetor air horn. The long-discontinued carburetor remains popular with performance rebuilders and tuners. Vacuum-Operated Design. In 1965, though, General Motors's Rochester Products Division came up with something truly special: the Quadrajet carburetor. It’s the original 400 motor, original ignition system, (which means points) and the motor has a mild cam in it – that’s it, no other upgrades. The Rochester Quadrajet carburetor comes with idle mixture screws to fine-tune the air/fuel ratio going into the engine during idling. The carb use to work nicely, but a couple of days after changing the thermostat housing it start to act weird. Sep 24, 2021 · Ep: 25in this video I show how to fix a hesitation and/or bogging issue with carburetors by adjusting secondaries. Rebuild is to restore the carb to original factory specs, reman is convert the carb to junk generic specs and hope it works good enough to fool the customer at best. But this wasn’t the only issue. Jan 25, 2012 · Take a look. Jul 21, 2017 · See All 4 Photos. The power valve may be sticking. The symptoms of leaking well plugs are a rich idle air/fuel mixture or a rolling idle caused by a fuel Rochester Quadrajet Common Problems and Decoding. The digit following the number 2 (or 5), will indicate the type of GM car it was originally installed. To adjust the type of Quadrajet secondary illustrated in the photo. Just installed a Shawn Murphy rebuilt Quadrajet on my brother in laws ’70 GTO (I know, not a Chevelle). A couple of jets can be seen in the front primaries. Dec 14, 2020 · Quadrajet Idle Circuit. Do a quick test of the accelerator pump circuit. Your Thermaquad TQ dies when hot and comes to a stop. The Carter Thermaquad was Carter’s answer for Rochester’s Quadrajet. Although your advice to check things with the engine, your advice on the carburetor is a bit off. The Quadrajet, a carburetor that was never intended to produce these types of numbers, can indeed run with the big dogs. If the idle screw is not screwed in far enough, the engine simply is not being supplied with enough gasoline to idle. Step 3. Understanding how the vacuum system works and the diagram itself can help in troubleshooting and maintaining the engine. Remove the short piece of vacuum hose attaching the choke pulloff to the vacuum nipple on the carb. I understand that this system is problematic but I would like to repair it. This time frame will vary. This basic design was typical of very early production Nov 27, 2023 · The Quadrajet utilizes an air valve secondary system, which is distinct from the mechanical secondary systems found in many other carburetors. Hard starting is another symptom commonly associated with a bad or failing carburetor. 1. A 4 would mean it is for a Buick, a 5 would mean Oldsmobile, and Pontiac carburetors usually have a 6 or 7. tu il gx zt fp rl it sh dv ps