What is flooding? Upgrade your Rochester Quadrajet carburetor with our latest high performance ethanol resistant Quadrajet carburetor parts. Consult your repair manual for the specification, but 4 to 5 lbs is average for most carbs. I have this problem with the Q-Jets on my 1972 Electra and 1986 Chevy pickup. This can be caused by several things, but there is one item often missed by the rebuilder and that is the idle tube. Adding an affordable vacuum gauge to your toolbox is a good idea, but you can tune your Quadrajet carburetor pretty well without one, provided the carb and the engine are in proper running condition. Also watch the needle to make sure it is move straight up and down and not getting caught up. Fuel filters are dirty, or plugged – replace any in-line filter and the filter at the carburetor fuel inlet. The manual is not specific to marine however your video is and it shows all 4 tubes. On all carburetors, the vacuum created as air is moved into the engine sucks the fuel out of the passages in the carburetor. New viton tip needles sometimes are covered with residue, causing it to not seal until started several times. Quadrajet bbl.) This would indicate the main discharge, possibly the check ball, not sealing. We recommend using. And yet another troubleshooting guide here. You want to make sure the pressure is where it should be. Spray carb cleaner around the outside of the gasket. Idle Compensator is MissingThe Hot Idle Compensator, when used on 4MC and 4MV Quadrajet carburetors (View C) is located in a chamber at therear of the carburetor float bowl adjacent to the secondary bores. With the engine hot and off, look down the carburetor after 1st turning the engine off. He has owned an auto service facility since 1982 and has over 45 years of technical experience as a master ASE tech. Too much fuel boils down to getting too much in the float bowl. There will be a vacuum-operated servo on the passenger side rear of the carburetor, with a rod also attached to the choke mechanism. The Inner Workings Of The Quadrajet Hemmings Daily. Take the idle mixture screws out and see if they are plugged. Start the engine and make sure the choke opens a quarter of the way. If your carburetor hasn’t been rebuilt recently, then considering doing so. I have a Rochester Quadrajet Marine Carburetor #17059286. However, it's easy to flood the engine this way. Make sure float isn’t binding – move it up and down by hand and see if you feel anything catching. Top of the carburetor to the float bowl gasket may be leaking due to bad, or wrong gasket, or a warped float bowl, which is not uncommon on the Quadrajet. Use thin wire to clean out the passages completely. Move the throttle by hand just a little and see if the choke snaps closed. Float isn’t dropping far enough to open the needle fully. Did you put the fiber washer where the seat screws into the float bowl. If you are using a fuel additive that contains alcohol, then that will cause gas to evaporate more. The float pin may be worn. Rochester Quadrajet accelerator pump catalog. and customer satisfaction. Nitrophyl floats (looks like plastic), are tested by weight. $75.00. Looking through your parts section I found pt # 17-91 Rochester carb. Check the float for leaks – For brass floats, heat up some water and just prior to boiling immerse the float. Don Bowman has been writing for various websites and several online magazines since 2008. (Accelerator pump assemblies and accelerator pump cups.) If the fast idle isn’t working then the engine may die after starting. This is true for your engine in both performance and mileage. This causes the engine to run poorly. The Rochester QuadraJet, in its various forms and configurations, has been used by various GM Divisions for various applications since the mid sixties. As the engine heats up, the spring in the manifold expands and puts pressure on the choke to open the choke. It’s description states that there are 2 that stick out from of the bottom of the float bowel top. Too much fuel pump pressure could be holding the needle open. As soon as the engine starts, the vacuum servo receives a vacuum from the engine and pulls the choke off just enough to allow the engine to run. It should be around the outside of the arm. THE CARBURETOR SHOP Troubleshooting. First lets start by learning how to start a classic car with a carburetor. It is a good carburetor for up to close to 400 horsepower. or Best Offer. On a carburetor like the Quadrajet, the idle system picks up fuel from the main fuel well. Rochester Carburetor Troubleshooting by John Stevens J.D. Press the throttle down one time, then let up. The gas cap should be vented. The pump passage way to the main discharge may be plugged. Many rebuilds are ruined by a dirty fuel tank, or filter. The Quadrajet is a progressive four-barrel design with an air valve actuated secondary circuit. I assumed the carb needed to be rebuilt and the leaking was normal (from a drain in the carb) when flooded. You won’t have any problem unless you get into a high heat situation, or use your air conditioner.NOTE: Even though your carburetor may have a place for the compensator to sit, it doesn’t mean it came that way. We stock complete accelerator pumps, replaceable cups and springs. The float will heat up inside and if there is a hole, air will bubble out. Blow out with compressed air. There should be no bubbles. PHOTO 3 The Quadrajet is considered a three-piece design: air horn, float bowl and throttle body. When the engine is cold, the spring contracts and creates a pull on the choke to close. As mentioned above make sure the choke valve is closing. AdvertisementClick Here to Read MoreAdvertisement Introduced at the dawn of the emissions control era of the early 1960s, the “spread-bore” Rochester Quadrajet carburetor was considered leading-edge fuel delivery technology for the time. It is a good carburetor for up to close to 400 horsepower. Remove the air cleaner. Jets don’t wear out. Do the same to the other side and then repeat the process one more time. Rochester 4MC 4MV Carburetor Manual. Even if you're using an aftermarket intake, it might come in handy for making up your own bracket. Many times after rebuilding a carburetor and after re-starting the engine, crud from the tank and the fuel lines will rush up to the carburetor and into the needle & seat causing it to stick open. I rebuilt it using a kit I ordered from you. These quality pumps are the answer to today's E10 & E15 pump gasoline. There could also be a leak at the intake manifold. When the engine has just been started, there is obviously no vacuum--so no fuel is sucked into the engine to start. How does the Quadrajet idle work and what can I do when things go wrong. If not, the servo must be replaced because it operates with a rubber bladder inside and is leaking. My question is should I have the secondary accelerating well tubes and if I do is that the right part # ? New pumps are especially suspect. It has a spring located in the manifold with a rod running up to the plate. They have small primaries which lend well to atomization of the … Move the float up and down by hand to see if you feel anything catching. The last passenger car version of the carb appeared as an ECM-controlled carb in 1981. Bowman has a business degree from Pennsylvania State University and was an officer in the U.S. Army (aircraft maintenance officer, pilot, six Air Medal awards, two tours Vietnam). A: There are two things that can cause a Quadrajet to leak. Needle is sticking in the seat. The cup curled, or is damaged. Lack of power is often caused by electrical, or engine wear. Copyright 2021 Leaf Group Ltd. / Leaf Group Media. It was a stock GM carburetor for years on the company's performance cars, including the Corvette. A damage viton tip can cause this along with some chemicals added to the gas. Accelerator pump itself may be bad. It should go all the way closed, or the rod is bent or the spring is maladjusted. Using a solid gasket on a carburetor designed for the slotted gasket WILL result in hot idle issues. NOTE: Do not apply any pressure to the needle when adjusting the float. doesn’t have the secondary accelerating well tubes. The Quadrajet uses many moving parts, unlike most carburetors. However, I read a post online that said the fuel at the thottlebody should already be atomized, and should therefore not leak out the linkage,and that would indicate that the carb is flooding due to the float not being adjusted properly. All carburetors are installed on our test engine prior to shipping. 75 This will cause the gas to get siphoned into the engine resulting in no gas in the float bowl and too much gas in the intake. Rochester Quadrajet, 4 barrel carburetor idle. A couple of jets can be seen in the front primaries. Simple to test by loosening the gas cap after turning the engine off. He needs to have all four tubes, 17-91 is one of those numbers. If the engine runs OK except at an idle, the idle jets may be out of adjustment of dirty. A carburetor that has been sitting for 6 or more months can also be coated inside with gas that has turned to varnish. I set the float to 3/16 like the instructions stated. If the engine idles fine but will not accelerate when the pedal is floored and just falls flat, the accelerator pump is not working and the carburetor has to be overhauled. For example: Carburetor number 17058201 followed by a Julian date of 1238 would have been built the 123rd day of 1978. The bushings are replaced only if you have excessive free play in the throttle shaft. There is also a volume test if you can find the spec for that. If so, then the check may be leaking. Turn the screw out just until the RPM stops rising and turn the screw one half of a turn further. Take the carburetor apart and wash out the needle & seat and try again. Make sure float doesn’t rubbing somewhere. Can you see gas dribbling out of the main discharge, or venturi while at idle? Rochester QUADRAJET 4 Barrel Carburetor Parts Carburetor. Ethanol ready, made in the US and meets or exceeds manufactures specifications. This new carburetor was blended with what Rochester knew about carburetors, mixed with ideas from other manufacturers, (spread-bore design and vacuum secondaries). Our Marine Carburetor Catalog includes remanufactured marine carburetors for MerCruiser, OMC and Volvo Penta and also all inboard marine carburetors including Crusader, MasterCraft, Pleasurecraft, Ford Marine, GM Marine, Chrysler Marine, Gray Marine, Chris Craft, and more. Free shipping. Serving our valued customers Since 1980. Bad float – For brass floats, heat up some water to prior to boiling, then emerse the float. Find Summit Racing SUM-250218 Summit Racing® Remanufactured Quadrajet Carburetors and get Free Shipping on Orders Over $99 at Summit Racing! The idle mixture screws are located in the base plate for superior idle quality. Delco Carburetor TROUBLE — SHOOTING THE QUADRAJET 4 MC — 4 CARBURETOR (CONT'DJ BULLETN: 9D.ST DATE: AFTER goas wo, 131.132M, ex, GENERAL MOTORS CORR IN . Test your fuel pump – new pumps are especially suspect and often have too much pressure. What to look for when your Rochester Quadrajet is flooding. They absorb fuel over time. 1975 Chevrolet Carburetor Parts List Sheets Offers exploded view of Rochester Quadrajet carburetors. This is a sign of flooding. Look for any cracks around the area the seat screws in. Wiping with mineral spirits can help. Today’s gas has little lubrication. Rochester QuadraJet is a superior carb when tuned and set up right. Rochester Quadrajet 4 Barrel Carburetor 17080212. The accelerator pump will squirt an extra bit of gas into the intake. Now what to look for if you are having problems. Quadrajet 7040205 EH Carburetor. Some will open just slightly so it doesn’t choke out. Manually move the float up and down and watch for any kind of rubbing, or catching. Vacuum leak – Use spray carburetor cleaner and spray around the base of the carburetor and any vacuum lines. Make sure the jets are not loose, or plugged. These are just a few ideas, but bottom line is that too much fuel is getting into the float bowl. I reinstalled the carb and I’m having the same issue of fuel leaking from the throttle body linkages. Its purpose is to offset the enriching effects caused byexcessive fuel vapors during hot engine operation.In a perfect world the Idle Compensator should be installed on those applications that need it. 1904 Carburetor Info Page. I assumed the carb needed to be rebuilt and the leaking was normal (from a drain in the carb) when flooded. Because there are so many different combinations, we cannot possibly duplicate the vacuum signal New pumps are always suspect because they come from China and they don’t seem to care about specifications very much yet. This is more of an over rich condition than flooding, but flooding to one person may be different to another person. Carburetor Troubleshooting Tips Tech Article Chevy. The choke mechanism is the plate on the top of the carburetor. A Quadrajet is a unique carburetor in that it has small primary plates and huge secondary plates. Polish the pump well with crocus cloth, or 2000+ sand paper. Look for any fuel restriction – check for kinks in the fuel line. If the carburetor is losing too much gas overnight, then it may be percolation. Our Quadrajet manual has an illustration that shows where the air bleeds and other passages are. Test the fuel pump (new pump especially). QUADRAJET 4 MC — 4 MV CARBURETOR (CONT'D.) Products 1 - 6 of 6 Rochester Quadrajet Choke Linkage - Carburetor Parts & Kits for Rochester, Carter, Holley, Edelbrock, Ford Motorcraft QJet, 4G, 2G, Mercarb. KIPA Carburetor For 1901R Rochester Quadrajet 4MV 4MV Chevy 1966-1973 Summit Jegs Divorced Choke 1901-GG 4-BBL, Replace for Corvettes 1975-1979 750 CFM Vacuum Secondary Durable 4.0 out of 5 stars 9 $312.75 $ 312 . Move the float up and down by hand – Do you feel anything catching? I think this is what I need to do. This baby is the factory original Rochester Quadrajet spreadbore, PN7040202. It may take a few seconds of cranking to fill the carburetor (if low). Its limit in horsepower applications and ability to be modified was its downfall at the racetrack when horsepower climbed. This carburetor was made by Rochester , The Rochester Products Division of General Motors was located in Rochester New York and built carburetors for GM vehicles since 1949 . What I was referring to pickup tubes are call the main well air bleed tubes (2 inside tubes ) and secondary accelerating well tubes( the 2 outside tubes) fig. Make sure it is closing when cold. Immerse the float in hot water and if there are any leaks, it will bubble. $180.00. If the RPM changes then you found your problem. Power valve may be dirty, or sticking. 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. There may be a small air restrictor in the passage that makes getting through with wire difficult. QuadraJet Idle Problem from corvetteforum.com member lars Just thought I'd pass on a little tip to those of you running Q-Jets. This test is performed to ensure that all idle circuits and other carburetor functions are working properly. Most carb problems are attributed to dirt. Rochester Quadrajet Carburetor 1975 76 Pontiac Firebird Lemans 350" 400" 455" $400.00. I rebuilt it using a kit I ordered from you. If the RPM is too high, the idle circuit will be bypassed. Be sure the throttle body gasket isn’t leaking. Any chance you replaced the pump with a new one? Flooding fuel will leak out anywhere it can and onto the throttle valves and out the shaft is the 1st place fuel likes to go. Includes theory, diagrams, detailed specifications, tune-up data and complete overhaul procedures. Rochester Quadrajet Carburetor Cadillac 472, refurbished. It appeared to be flooding at idle and the fuel was leaking excessively from the throttle body linkages (on both left & right side). quick test of the accelerator pump circuit. Quadrajet Carburetor Numbers 68 and later Date Code Most Rochester built Q-jets used a four-number Julian Date code. $31.56 shipping. Complete service manual: Comprehensive factory service information for Rochester Quadrajet 4MC and 4MV carburetors. A whistle with air will indicate a clean passage. A non vented gas cap on a system that needs a vent will cause gas to get siphoned out of the float bowl. The first three numbers are the Day of the Year the carburetor was built; the last number is the Year. Just because a performance carburetor has been around the block or down the strip a few times, that doesn't mean that its days are over. Is the fast idle sitting on the higher step of the cam. If the RPM smooths out, then you found the problem. The carburetor is simply puking out too much fuel. Dirt in the system – take the top off the carburetor. In your youtube video (Rochester Marine Carburetor rebuild part 3 of 3) at 4:00 you mention not usually having to take apart the thottle body to replace bushings. Match the overall length and the cup size to be sure you are getting the correct accelerator pump. The throttle keeps it from closing as long as it is not disturbed. Main metering jet may be the wrong size. The number one problem to look for is leaks around the needle and/or seat. Simply, there is too much gas getting into the float bowl. Do you see gas dribbling out of the main discharge. ROCHESTER QUADRAJET CARBURETOR 4MV REPLACEMENT “mechanical / divorced choke” also known as “remote choke” 4 Barrel Quadrajet with “SIDE FUEL INLET”. 6.5 – 8 grams, depending on which float it is. I don’t have these. Tune up your automotive and marine Rochester 4 barrel Quadrajet carburetor with our USA made premium carburetor rebuild kits. The fuel is too high in the float bowl and is being sucked out of the jets into the engine, thereby flooding the engine. And if so, do you carry the kit? Inspect the choke system while the engine is cold. Did you test the (brass) float for leaks? Be sure to check out our USED Quadrajet Carburetor Parts. Rochester Quadrajet Part Numbers for 1965-1974 and Trucks to 1979 When getting a carb from another vehicle, whenever possible, get the factory cable bracket. If your flooding started after a rebuild, then skip this one. The power valve may be sticking. A Quadrajet is a unique carburetor in that it has small primary plates and huge secondary plates. My question is: Do you think I should replace the thottle body linkage bushings? Here is a list of items to check when this happens: Sorry about lack of knowledge and poor terminology. $41.32 shipping. Q: I have seen numerous Rochester Quadrajet carburetors that have a leak down problem when the car sits idle for a day or more. It is a good carburetor for fuel economy and still has stellar performance when required. These are very small passages and get clogged easily with ethanol residue. Free Carburetor Repair Manuals Mikes Carburetor Parts. Compatible with all Chevy/GMC trucks and cars 1966 thru 1973 Available for 327, 350, 396, 400, 402 or 454 Engines Bolts on to any Quadrajet/Spread bore GM style intake manifold If not, pull the hose off the servo and see if the arm extends and contracts when the hose is reinstalled. I've seen this problem so many times now, that I'm sure there are a lot of cars out there suffering this problem. Also make sure all old gasket residue is gone. My question is, how is the gas getting out of the float bowl, and how do you fix it? If wire doesn’t do it, try heating the outside of the passage and then blow air through. brass tube. Rochester carburetors were quite possibly the most widely used carburetor in the twentieth century, with over one million units produced by the Delco Carburetor Company, a division of General Motors. I have a Rochester Quadrajet Marine Carburetor #17059286. Make sure the power valve moved up and down easily and there is a spring under the valve. The solution is simple: Remanufacture it. If you see dirt in the bottom of the fuel bowl, rebuild the carburetor, clean the fuel lines & the gas tank. The choke valve will close once you step on the gas. For the carburetor to function properly, it is imperative that the PROPER throttle body gasket is used. Delco . The Quadrajet was actually the successor to the previously-built Rochester 4GC carburetor that was manufactured from 1952 to 1967. It appeared to be flooding at idle and the fuel was leaking excessively from the throttle body linkages (on both left & right side). Replace any fuel filters – There is usually one in the fuel inlet of the carburetor and often there will be an in-line fuel filter. It's been doing its thing for 40 years on my '70 L48 350 Monte Carlo--forever known as … It was used on vehicles with air conditioning. If you have been running the carburetor for awhile, then this won’t be the problem. It needs the extra gas and the extra air to start. My carb. This means that not only does it not work, it's leaking vacuum and interfering with the mixture in the carburetor. If the carburetor was sitting for many months, then the ethanol residue could be plugging things up. A little grease will help. When the engine is started, the throttle should be tapped just a little to allow the choke to snap shut. The Rochester Quadrajet was General Motors carburetor for dependable, performance four-barrel applications for almost 20 years. Float is catching when moving up and down. The engine needs a bit of help when cold. There is a pull clip that connects the float needle with the float arm. 12 page 14 of the Quadrojet models 4mv,4mc carburetor manual all are connected to the air horn. ROCHESTER QUADRAJET INSTALLATION These instructions cover all QUADRAJETS. It needs to move up and down freely. You can get your C3 Corvette—or any other carbureted vehicle, … Your problem is not bushings. Since the compensator part is not being produced you don’t have any choice but to run without it. QuadraJets are only slammed by people who know nothing about them. It was a stock GM carburetor for years on the company's performance cars, including the Corvette. The idle air bleeds and other idle passages are very small and can easily get plugged. Power valves – Rochester used a number of different calibrations and two different plunger lengths for power valves on tripower carbs along. The choke, when closed, creates the suction to pull fuel into the engine without pumping the gas. We won’t discuss here, instead we will concentrate on what problems the Quadrajet may have. However, it still creates a partial choke condition. Float level may be too low – set to specifications. Fuel pump pressure – check with your motors manual for the correct pressure. The Rochester Quadrajet carburetor is a two stage, 4-barrel downdraft carburetor . If you have a Nitrophyl float (black plastic kind of thing), replace it. This can be caused by one of several things, including electrical system problems. You need to follow each one with compressed air to be sure they are open. Pumping the gas a couple times can also start the engine, since the carburetor has an accelerator pump. Carburetor is flooding.Gas is running out of the top, or you get a strong gas smell? Adjusting Idle Mixture Doesn’t Change AnythingThis is usually indicative of a problem with either too much air, or not enough fuel (in the idle circuit). You can check this with the engine off by looking down the carburetor and pump the throttle once to see the squirt. First of all be sure you are adjusting the idle mixture at the idle RPM. Some chemicals added to the fuel, or left in the carburetor can cause this. Created Date: Ethanol blends in gasoline today are responsible for many fuel system issues and carburetor failures on older Corvettes. How to rebuild a Rochester Quadrajet 4MV carburetor Rochester Quadrajet Carburetor Kit - K7001 In Stock 77-79 Buick, 75-84 Cadillac, 77-79 Checker, 75-86 Page 5/10. The Quadrajet became an instant success. Grimsrud on troubleshooting and tuning Quadrajet carburetors. It is a good carburetor for fuel economy and still has stellar performance when required. Apply a couple of dabs of white lithium grease. Nitrophyl floats have to be weighed. If any fuel can be seen dripping into the engine from the carburetor, the float is stuck or defective and must be repaired. Be sure the clip is not routed in one of the small holes. Our carburetor rebuild kits feature online exploded view instructions and adjustment specifications, quality gaskets, ethanol resistant accelerator pump components and hi-flow needle and seats. 6.5-7.5 grams would be great. With the engine idling, look down into the carburetor with a flashlight. Using a small screwdriver and starting on the driver's side, adjust the screw in until the RPM starts to drop. Running up to the main discharge may be too low – set to specifications carburetor can cause a Quadrajet leak! Is used do not apply any pressure to the fuel bowl, rebuild the has! Caused by one of those numbers any leaks, it 's leaking vacuum and interfering with the engine start... For years on the company 's performance cars, including electrical system problems engine off and huge secondary.. Plates and huge secondary plates out and see if the RPM changes then you your... 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