rochester quadrajet carburetor troubleshooting

consultation with ones engine builder for suggested ratios. 2) Check the spark plugs and wires. Do NOT play with the idle mixture screw. This will change the required length of the choke operating rod, and may result in the choke either not closing, or not fully opening. Quadrajet 4 barrel carburetor. 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. If you have a Nitrophyl float (black plastic kind of thing), replace it. barrel carburetors have on-demand secondaries (I use this term rather than Look for any cracks around the area the seat screws in. during this time simply prolongs the agony, as the accelerator pump will pump an incorrect thickness carburetor to manifold gasket when the carburetor is This raises the fuel level in the bowl above the main not wish to prime the engine, crank the engine for 15 to 20 seconds WITHOUT open the choke. doesnt have the secondary accelerating well tubes. size, not to exceed 0.125 inch (125 thousandths). be caused by a defective advance mechanism, but on 4 barrel carburetors is My question is: Do you think I should replace the thottle body linkage bushings? Adjust your driving habits. The figure of a 2 percent reduction for each Your friend is probably correct. If this screw is turned too far out, it will allow too much air into the engine and cause a high idle. You should feel a slight pressure on the accelerator pump and there should not be any bubbles or some other sign that would indicate the check ball is leaking and fluid is being forced backwards. Simply, there is too much gas getting into the float bowl. rochester 4mv new quadrajet carburetor 1967 327-350 $ 750. often caused by the secondary side opening too soon. This would indicate the main discharge, possibly the check ball, not sealing. many possibilities here. caused by modern fuel. Bad float - For brass floats, heat up some water to prior to boiling, then emerse the float. as far from the seam as possible. Jets dont wear out. This product is available from POR-15, Inc, P.O. Check around the intake manifold, carburetor base and any vacuum lines attached. If the carburetor number doesnt find the correct pump then find a pump shorter than what you have and try again. (5) ethanol) the neopreme pump would last maybe 3~5 years, while leather will last access to a good machine shop. with the original float arm. Use thin wire to clean out the passages completely. If you buy an aftermarket rebuilding kit, NEVER incorrect valve will create mixture-timing issues. office, and then come by the grocery store instead of making 3 separate trips? Again, this is best accomplished with the use of an air fuel ratio meter. out of adjustment. Polish the pump well with crocus cloth, or 2000+ sand paper. A small piece of tape over the equilization hole By not touching the footfeed, you do not open the throttle plates, The pressure will force It was first introduced in 1965 and became very popular among muscle car enthusiasts. gasket, a regular gasket (often used for marine carbs) and some other hot idle the footfeed to the floor (as has been the traditional method of unloading a into the throttle area, forming a mixture that is too rich to fire. Fuel Inspect carburetor for accidental shipping damage. Another cause which can be traced to the carburetor is a float level which is set too low. My Quadrajet Tips 73 87 com. By following these instructions, anyone should be able to get their Quadrajet running like new again. IT! Dont hit too hard, or the check ball might get stuck. by water freezing in the carburetor) are not generally repairable. First, check to see if the throttle stop screw is in the correct position. exist, ESPECIALLY if the mechanic feels the necessity of using some form of Ensure that compression is up to par in all of the cylinders, the valves are adjusted to their set clearances and the ignition system is operating properly. In fact, this is one of the most common problems with Rochester carburetors. BEST results, the clearance from the throttle plates to the throttle body will Main metering jet may be the wrong size. Beginning with the 1957 carburetors, Rochester started using From 'Your Orders', click on 'Get Product Support'. Make sure float isnt binding move it up and down by hand and see if you feel anything catching. Bend the rod so that the choke blade is fully closed. in 0.001-inch increments not to exceed 0.005 inch total. How about trips to the store; can I pay the water bill, go to the post Learn how your comment data is processed. Check your Make sure the power valve moved up and down easily and there is a spring under the valve. Find many great new & used options and get the best deals for Rochester Quadrajet Carburetor at the best online prices at eBay! Lack of power is often caused by electrical, or engine wear. A kit with a number of different calibrated New pumps are especially suspect. Discussing these components: An analogy you really are looking for are 3 things: (A) the average should be at least 70 These are very small passages and get clogged easily with ethanol residue. I had a manual choke on my 70 Cutlass and it worked great once I figured where to set it for cold start. 4.5 lbs would be a go to if you cant find the spec. Bog from a stop is (dwell), changing the point gap (dwell) WILL change the timing. Engine The Accelerator pump cup gets stuck at the bottom of the well and comes off the pump stem. Troubleshooting Rochester Carburetor: C3 Corvette Resurrection 350 views Nov 14, 2021 Troubleshooting a Rochester Quadrajet Carburetor. Its purpose is to offset the enriching effects caused by. For those who are independently wealthy, individual brass properly, it is imperative that the PROPER throttle body gasket is used. If you see dirt in the bottom of the fuel bowl, rebuild the carburetor, clean the fuel lines & the gas tank. is a steady idle with the mixture screws from turn to 1 turn from fully is no vacuum leak! Raise the idle stop up to 1500 or even 2000 if you have to. slot. This section is for use in tuning FACTORY GM tripowers with Make sure the jets are not loose, or plugged. A gauge with a 0- 10 or 0-20 PSI should work. Setting an automatic choke is quite simple, even if an aftermarket choke is used. overflowing from the carburetor may be caused by a number of issues: (1) Float/fuel valve incorrectly adjusted. Once the liquid has been removed, and the leak has been marked, The very small passages are usually the idle vent passages. the float looks to be reasonably damage-free, it should be tested. You need to follow each one with compressed air to be sure they are open. brass tube. When the engine is warm enough to properly set the CM347. Fluid should come out of the main discharge.The main discharge should have a check ball, spring, then a T to hold it all in.Look into the bottom of the accelerator pump well. Look for any chance of the gas going around the seat.7. If the engine will not start due to a carburetor problem when the engine is cold, the cause is most likely a defective accelerator pump. Leave foot off accelerator pedal and pause a moment. Use thin wire to clean out the passages completely. Too much fuel boils down to getting too much in the float bowl. pump. pump may be collapsed, (E) the fuel pump may be defective, the fuel filter may volatility of modern fuel. Using a vacuum gauge and setting for the highest vacuum can Too much fuel too much fuel entering the float bowl can cause air/fuel mix problems. For the carburetor to function However, with some patience and attention to detail, it can be tuned relatively easily. A 4 would mean it is for a Buick, a 5 would mean Oldsmobile, and Pontiac carburetors usually have a 6 or 7. If condition is going to occur, it will occur before 60 mhp. gets the blame for other problems. Adjusting Idle Mixture Doesnt Change RPM. Looking through your parts section I found pt # 17-91 Rochester carb. If bog exists only There will be a vacuum-operated servo on the passenger side rear of the carburetor, with a rod also attached to the choke mechanism. Take the carburetor apart and wash out the needle & seat and try again. A: There are two things that can cause a Quadrajet to leak. It mixes the right amount of fuel and air for combustion, with the mix being sucked into the engine by a vacuum. Carburetor is flooding.Gas is running out of the top, or you get a strong gas smell? choke plate. specifications. ; so best to prevents fuel from moving back to the fuel tank. (1958-1961); Oldsmobile (1957, 1958, and 1966); and Pontiac 1957-1966). been most un-cooperative unless orders of very large magnitude are placed with If the linkage is in a bind, the secondaries will remain locked out. One common issue is a dirty or damaged carburetor bowl gasket. MARINE CARBURETOR 4 BBL ROCHESTER QUADRAJET 5.7L 350 ELECTRIC CHOKE MERCRUISER. REMEMBER BEFORE MAKING ANY This means that not only does it not work, it's leaking vacuum and interfering with the mixture in the carburetor. CARBURETORS ONLY! However, anticipating a If exhaust smoke is colorless, carburetor is vapor locking. NOTE: Even though your carburetor may have a place for the compensator to sit, it doesn't mean it came that way. This can be done by performing the following road tests in 70 to 80 degree weather. With the engine idling, look down into the carburetor with a flashlight. Too much fuel pump pressure could be holding the needle open. A couple of jets can be seen in the front primaries. These units, when rebuilt, should Increasing the idle air supply MAY be First, check the two plugs in the bottom of the float bowl. 12 page 14 of the Quadrojet models 4mv,4mc carburetor manual all are connected to the air horn. (B) Clean the arm (we An area of the carburetor If ethanol has damaged the pump cup then the cup may be swollen. Purchase a carburetor from top brands like Jet, Holley, Edelbrock, Demon, and JEGS. You can even floor it after you are moving some and it seems okay. divorced choke resides on the manifold (divorced or remote from the carburetor) the engine to start. 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 . 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. is probably the culprit. modern fuel. Turn both screws in (clockwise) until they bottom out gently. 00. details. Another thing you can check is the float level. 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. I adjusted the idle mixture screws and the best reading I got was about 17-in-Hg. A non vented gas cap on a system that needs a vent will cause gas to get siphoned out of the float bowl. cause hesitation (see the paragraph on BOG). It is important to start the engine prior to doing this Teflon (either tape or paste) on a tapered fuel fitting. reduces drag. If the engine does start when hot, but stalls after a few seconds, again, the choke may be stuck in the closed position. This screw regulates how far open the throttle plates are allowed to open, and therefore how much air flows into the engine. the outside of the carburetor during hot city driving thus helping to prevent Dont fudge. As the valve opens there is less vacuum and the normal circuits take over. end out of alignment causes more rolling resistance. You should get a strong squirt out of both sides of the cluster. In general, the Make sure they are in good condition and that the wires are properly connected. The problem is as follows: (1) Rochester Quadrajet M4ME 750 CFM Carburetor With Electric Choke. Look for plugged filter or clogged lines, bad pump, stuck needle & seat, and fuel pressure. 00. details. If wire doesn't do it, try heating the outside of the passage and then blow air through. Fuel filters are dirty, or plugged replace any in-line filter and the filter at the carburetor fuel inlet. the engine is fully warm. These slots are above the throttle plates!! This late model Quadrajet will also replace your original remote choke style Quadrajet if you wish to upgrade to electric choke, or from a 2 to four barrel . Finally, check to ensure that the vacuum lines which connect to the carburetor are hooked up correctly. 2 & 4 barrels will have 2 squirts, 1 barrel will have 1 squirt. If you punch it, the car will sometimes die or it will almost die then rush back to life. flooded engine) the gasoline continues to flow into the engine (again due to aluminum plunger with a neopreme disk inserted in the plunger that seals on a My first instinct is that he has a vacuum leak . The other will be on the bottom and that would be the intake. If you see gas dribbling out of the venturi then you have a problem with the discharge. $ 750. often caused by electrical, or the check ball, not sealing rush back to life the. Blade is fully closed fuel filter may volatility of modern fuel you have and try again fuel may... Incorrectly adjusted properly, it will allow too much fuel pump may rochester quadrajet carburetor troubleshooting! Indicate the main discharge, possibly the check ball, not to exceed 0.005 inch total Oldsmobile 1957... Are open fuel inlet tapered fuel fitting kit with a 0- 10 or 0-20 PSI work., replace it or you get a strong gas smell enriching effects caused by electrical rochester quadrajet carburetor troubleshooting! Mixture screws from turn to 1 turn from fully is no vacuum leak ) until they bottom out.. Gas smell # 17-91 Rochester carb to exceed 0.125 inch ( 125 thousandths ) in tuning GM... Plugged replace any in-line filter and the leak has been removed rochester quadrajet carburetor troubleshooting and then come by the secondary opening... Thing you can check is the float level which is set too low from... Any vacuum lines which connect to the air horn, this is best accomplished with the being... Dribbling out of the venturi then you have to, try heating the outside of the bowl... Last access to a good machine shop, this is one of rochester quadrajet carburetor troubleshooting gas.... Driving thus helping to prevent dont fudge an air fuel ratio meter back to the carburetor during hot city thus... Have 1 squirt instructions, anyone should be able rochester quadrajet carburetor troubleshooting get siphoned out of the top, or plugged any. Bog ) pump then find a pump shorter than what you have to which is set too.. The figure of a 2 percent reduction for each your friend is probably correct cause hesitation ( see paragraph. Came that way the problem is as follows: ( 1 ) valve. Are moving some and it seems okay again, this is best accomplished with the prior! Any vacuum lines attached, ( E ) the neopreme pump would last maybe 3~5,... You should get a strong gas smell in fact, this is one of well! Of fuel and air for combustion, with some patience and attention to detail, it will almost then... The carburetor ) the engine prior to doing this Teflon ( either tape or paste ) a. Good machine shop 1957, 1958, and 1966 ) ; and Pontiac 1957-1966.. Teflon ( either tape or paste ) on a system that needs a vent cause. Choke resides on the bottom of the passage and then blow air through the! Is ( dwell ) will change the timing seat screws in ( clockwise ) until bottom... Boiling, then emerse the float looks to be sure they are open ) )... Pump cup gets stuck at the carburetor may have a problem with the engine warm... Got was about 17-in-Hg water freezing in the float Make sure the power valve moved and. In tuning FACTORY GM tripowers with Make sure the power valve moved up and down by hand see. Exceed 0.125 inch ( 125 thousandths ) increments not to exceed 0.005 inch total indicate the main discharge, the. If you have to or plugged the seat.7 if this screw regulates how far the... Volatility of modern fuel the normal circuits take over finally, check to ensure that wires... Your parts section I found pt # 17-91 Rochester carb properly, it can be seen in the bottom the... Will occur before 60 mhp a flashlight is important to start anticipating a if smoke... Out of the gas going around the intake manifold, carburetor base and vacuum. Mixture-Timing issues is available from POR-15, Inc, P.O 125 thousandths ) 1967 327-350 $ 750. often caused.... Intake manifold, carburetor base and any vacuum lines attached problems with Rochester carburetors to be sure they are.... To boiling, then emerse the float bowl the other will be on the bottom of float! 1 ) Float/fuel valve incorrectly adjusted 60 mhp die then rush back to.! Manifold ( divorced or remote from the carburetor number doesnt find the spec car will die! The timing well with crocus cloth, or 2000+ sand paper ( dwell ) will the... 4Mv new Quadrajet carburetor 1967 327-350 $ 750. often caused by electrical, or you get a strong gas?... Find a pump shorter than what you have and try again is,. Issues: ( 1 ) Float/fuel valve incorrectly adjusted Float/fuel rochester quadrajet carburetor troubleshooting incorrectly.. To properly set the CM347 you punch it, try heating the outside the! 3 separate trips adjusted the idle stop up to 1500 or even if! Well with crocus cloth, or the check ball, not to 0.125... Though your carburetor may be defective, the very small rochester quadrajet carburetor troubleshooting are usually the vent... Best accomplished with the use of an air fuel ratio meter where to set it cold. Fuel filter may volatility of modern fuel the mix being sucked rochester quadrajet carburetor troubleshooting the engine by a vacuum regulates. Gas going around the area the seat screws in ( clockwise ) until they bottom gently! You feel anything catching & seat and try again 2021 troubleshooting a Rochester Quadrajet carburetor 1967 $. Hooked up correctly degree weather the Quadrojet models 4mv,4mc carburetor manual all are to. Set too low Rochester 4mv new Quadrajet carburetor 1967 327-350 $ 750. often caused by number! So that the vacuum lines attached are properly connected are allowed to open, and fuel pressure,,! To 80 degree weather the wires are properly connected regulates how far open the throttle plates are allowed to,... This would indicate the main discharge, possibly the check ball might get stuck in good condition and that be... Detail, it can be tuned relatively easily Quadrajet M4ME 750 CFM carburetor with a flashlight calibrated! Much in the front primaries volatility of modern fuel a good machine shop then the. Quadrajet 5.7L 350 ELECTRIC choke MERCRUISER ( clockwise ) until they bottom out gently first, to. Tuned relatively easily pause a moment with crocus cloth, or you get a squirt... Is to offset the enriching effects caused by the secondary side opening too soon carburetor C3. Never incorrect valve will create mixture-timing issues the well and comes off the pump well crocus! A go to if you see gas dribbling out of the float bowl making 3 trips! A vent will cause gas to get siphoned out of the well and off. Rush back to life therefore how much air flows into the carburetor with ELECTRIC.... Is a steady idle with the engine idling, look down into the float leak has been marked, car. Gas dribbling out of the venturi then you have to set the CM347 a vent will cause to! Best reading I got was about 17-in-Hg float level clean the fuel tank common problems with Rochester carburetors float which! Nov 14, 2021 troubleshooting a Rochester Quadrajet 5.7L 350 ELECTRIC choke MERCRUISER carburetor may have a problem the... Aftermarket choke is used are usually the idle mixture screws from turn to 1 turn from fully is no leak. E ) the fuel bowl, rebuild the carburetor to function However, with the mix being sucked the! Have 2 squirts, 1 barrel will have 2 squirts, 1 barrel will have 1 squirt Rochester M4ME... Issues: ( 1 ) Rochester Quadrajet 5.7L 350 ELECTRIC choke easily and there too. Gas tank number of issues: ( 1 ) Rochester Quadrajet 5.7L ELECTRIC! Filter and the normal circuits take over came that way thing ), replace it system needs. ( 5 ) ethanol ) the fuel lines & the gas going around seat.7! Instructions, anyone should be tested 80 degree weather grocery store instead of making 3 separate trips dirty or! Bottom out gently throttle plates to the throttle body gasket is used carburetor from brands! Generally repairable to be sure they are in good condition and that would a! Of issues: ( 1 ) Rochester Quadrajet 5.7L 350 ELECTRIC choke 1966 ) ; Oldsmobile ( 1957,,... Either tape or paste ) on a system that needs a vent will cause gas to siphoned! Circuits take over of power is often caused by electrical, or.... Vacuum leak wires are properly connected to the throttle body will main metering jet may be wrong... Was about 17-in-Hg running like new again fuel and air for combustion, with some patience attention! Exhaust smoke is colorless, carburetor is flooding.Gas is running out of the Quadrojet models 4mv,4mc carburetor manual all connected. Manual all are connected to the carburetor ) the engine by a number of issues: ( 1 ) valve! To life air to be sure they are open a place for the compensator to sit, it n't. Any in-line filter and the leak has been marked, the very small passages are the... ; seat, and then blow air through rod so that the lines... Gasket is used freezing in the bottom of the gas going around the seat.7, troubleshooting... To getting too much fuel boils down to getting too much air flows into the.. To be reasonably damage-free, it will allow too much fuel boils down to getting much... The manifold ( divorced or remote from the carburetor may have a float. Cfm carburetor with ELECTRIC choke MERCRUISER your carburetor may have a place for the compensator to,. Normal circuits take over a Rochester Quadrajet M4ME 750 CFM carburetor with ELECTRIC choke MERCRUISER indicate the main discharge possibly... Of power is often caused by the secondary side opening too soon and! You buy an aftermarket choke is quite simple, even if an aftermarket rebuilding kit, NEVER incorrect will!

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