When I slow down to make a turn and try to accelerate after making the turn, the engines sputters and boggs untill I pull on the choke and then it will hook up and accelerate smoothly. Re SU needles -- The 3 screw round tops used on 72's came with N-58 needles in automatics and slightly richer N54's in 4 sp cars. Some get the fuel by filling over the top of the well through a slot on the side, others use a intake at the bottom of the well which is shut … If the throttle response and acceleration is not crisp and clean, then the pump size may be too large. Doh! Now pump the accelerator pump and you should feel some resistance if the check ball is sealing the passage. All Rights Reserved. When you go to step on the gas pedal to accelerate, you will suddenly feel like the power has been lost in the engine for a couple of seconds. If you find it not running on one carburetor, check the banjo bolt and/or replace those rubber grommets. Some SUs also have exhaust emission-control devices to comply with anti-pollution laws. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. Actually if the mixture is set correctly , just adding choke should be all that is necessary. Another possibility is the metering rod springs. Secondly I'd shoot carb cleaner at the throttle shaft openings and all the mounting flanges toward the head to search out any vacuum leaks. By using this site, you agree to our Terms of Use. Does anyone know what would cause hesitation on letting off gas or just starting off, i still have a zeinith carb in my 79, runs fine and not leaking a drop otherwise. Usually takes another 2-3 times on the starter before the engine will remain running with out stalling. Car engine hesitation is a noticeable problem that can occur as you’re driving. My 240Z is an automatic...I have heard that the jets are different for the Automatics. It's almost like a hiccup. This paragraph also applies to relatively stock engines with the original carburetor. Gary, I checked out the website and found many references that will be helpful. It will sputter, then regain acceleration. The engine also is hard to accelerate from a standing stop...it quite often stalls when taking off from a stop. The SU H-type carburetors have the float chamber attached to the carb body with a banjo bolt and a pair of rubber grommets. As carburetors age, they can occasionally suffer slight air leaks and this will compound any hesitation problem caused by a 009 distributor. Will keep eveyone posted on my progress. 3000 Miles since carb kits installed. Enter to win today!Read More. The vacuum operated power enrichment system is controlled by a Power Valve that times the operation to your engine's specific needs. This paragraph applies to an instantaneous bog, hesitation, or stumble upon acceleration. To thin of oil can cause the engine to stumble at first throttle opening at low rpm. This prevent hesitation during acceleration. There should be a brass discharge tube in the bore and you should see fuel spray from that tube each time you operate the throttle. Posts: 80 From: Chesterfield, Mi, 48047 Registered: Jun 2005: posted 09-08-2005 04:44 PM I have an autolite 2100 that I got from Pony Carbs, put it on a 302 V8. That is what sets the shift points. I can drive the car but I have to slowly accelerate from a stop or I risk stalling the motor. I have adjusted the accelerated pump, tried both positions on the cam (orange). The engine takes about 3-5 minutes to warm up and smooth out at idle. This is the accelerator pump linkage arrangement on a Holley carburetor. Your symptoms -- running lean, worse at low RPM -- suggest an air leak into the manifold. When the pump moves up (let up on throttle), the accelerator pump well is filled with fuel. Pulling on the choke most often aleviates this problem. You know how frustrating it can be when your car hesitates when you step on the gas. hesitation on acceleration carburetor Episode 480 We need to take our 1964 Falcon to the drag strip to get a base line for future modifications. - It shows up the most during a steady kept speed, usually between 45 -60 mph. It's time to start troubleshooting things like the throttle shafts, vacuum advance, brake booster, and BCDD actuator diaphrams. Stumbling on acceleration has been a problem with Dave's '73 Super Beetle ever since he bought the car. Dandy! Holley carburetors have a power enrichment system that provides fuel to the main power circuit during heavy loads or under full throttle situations. This would be a great combination. I think that the previous owner told that he was using ATF in the dampers. Have you tried adjusting the nozzles down in increments to richen them up? A leaky check ball passage can cause gas to get siphoned while idling, or just after turning off the engine. This forces me to feather the throttle during the initial acceleration. © 2021 Holley On light accelerations from a stop sign or what not the truck sputters for a second, almost dying out then catches back up. I am looking for some advice on where to start making adjustments or service recommendations. There are three main components of the accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. Stepping on the throttle is where the accelerator pump circuit comes into play. Read More, Take the mystery out of tuning your Holley carburetor with these lessons! I have a 1960 Lark 289 with a Stromberg carb and thermostat choke. But you can troubleshoot this common problem, maybe even fix it yourself. All 4 screw SU's, used in 70 and 71, came with N-27's. - I can cruise for awhile and it shows up and then all of a sudden go away, then show up again. The 009 distributor is notorious for causing hesitation on acceleration as they don't provide the shot of advance needed for a smooth increase in engine rpm which the vacuum distributors provide. Help! Pulling the choke on helps to aleviate this condition while accelerating up to highway speed. Thanks, 1973 240Z - 98% Original Documented California Car. Background info: - The Constant hesitation is covered under “surging”. I have been completely through the carbs, including new sliders and diaphragms. I was wondering about this hesitation issue I've been having. Instead of get-up-and-go, you get hurry up and wait. Hey, I have been having some trouble my SU Carbs Bogging out. Instead of going faster by stepping on the accelerator … With the timing set, now you can see if the acceleration hesitation is still present. Powered by Invision Community. Ever since purchasing this 86 VR in April, I have been chasing an acceleration hesitation problem. Hesitation 09-02-2016, 02:43 PM. As Bruce stated, sounds like a lean condition also. A fuel pump, fuel pressure regulator, or fuel injector with high mileage can … It is stock other than an edelbrock intake a and a Holley 600 carb. By Under acceleration you will have lower vacuum. Holding the accelerator pedal to the floor helps..and the choke fully on....it will take up to a minute of spinning to get the engine to fire the first time. How to ensure your Holley carburetor is using the right power valve for your engine. What is that all about and how does it work for you? I have an issue with the engine hesitating/stalling when I initially press the accelerator either from idle or right after switching gears. This is especially true when running any kind of performance cam resulting in lower vacuum. Well, keep reading and find out!Read More, It's true - Holley and Sloppy Mechanics are teaming up to fast-track your junkyard jewel Gen III or Gen IV GM LS engine's build from grime-covered lump to its true, turbocharged glory. If you have a double-pumper carb, the secondary accelerator pump nozzle must supply fuel for a sufficient time, so that the secondary main nozzles can begin to deliver fuel to the engine, after the secondary throttle plates are open. (1406). Run the engine for a minute and then remove the air cleaner. Also when I hit the gas real fast to rev the motor it sputters really bad. Thanks. Trademarks belong to their respective owners. Swapped his to mine and it works perfectly...no hesitation. Check the vacuum advance also. Its about trial and error and learning....I have little experience in setting SU carbs. A bad distributor advance can cause a hesitation when stepping on the gas, but we aren’t addressing that here. PS: Previous owner had a complete new OEM SU Carb Kits installed less than 4 years ago. ( fork oil) Cold start up. I believe the main jets are .069's. Hesitation, backfire and lean conditions can also be the result of an improperly adjusted acceleration pump assembly, and should be checked using these procedures. Hello Forum Friends! Starting hot usually is perfect..it will fire on less than one turn over if the engine has been shut off for up to an hour. I'm not talking about swap-meet carbs, new in box only. From a number of different sources, Dave has learned that the engine stumbling on acceleration (especially when accelerating through a corner) may be due to … Check the Fuel System. This hesitation could be potentially dangerous in situations like entering and exiting the highway from an off-ramp, where acceleration may be necessary to merge with traffic. http://www.teglerizer.com/sucarbs/index.html. The problem is hesitation on acceleration fron stop after the engine is … thanks,Rick RLH Rick This thread was discussed between 29/06/2005 and 03/07/2005 The car hesitates and stumbles, but give her a little more gas and she takes off. The motor does not respond and hesitates and may even die. If that line runs to the right rear of the transmission, that is connected to the "vacuum modulator valve". The engine runs great driving at higher RPMs (ie) 60 - 80 mph....or higher when the road is clear....it runs up to 120 mph...tail wind on nice level highway. What are you waiting for? I tried matching all the rod bends on my original (which I bought used off eBay) to exactly match his. If the carb is waaay out of whack, I look at the rest of the engine first because Holleys should be damn close. At the very least, you'll be able to give your mechanic a head start and save yourself the extra money it will cost for a diagnosis. The motor hesitates and sometimes dies out when I push on the gas pedal from a stop. The rubber bits tend to deteriorate with time and may leak or may clog up the passages in the banjo bolt. Offhand, it sounds like an accelerator pump problem with the carb. You need to be a member in order to leave a comment. I have some 20W-50 oil on hand ...will change it out and try that first before I get into changing the settings. Still has a slight hesitation. Nismo49, August 8, 2007 in Carburetor Central. From what I have read so far...Ihave a lean condition or an air leak as others have mentioned. Initial timing is set to 14 degrees. Sign up for a new account in our community. When we bought this car, she had an old tired engine and we did a turn up and replaced the intake and carb, the carb being the Edelbrock 1406. Adjustment of these is described in Adjusting an emission-control carburettor. Really appreciate your references. Try this link out, it has everything SU related that you EVER want to know. Only hesitates when engine is at idle and the throttle is cracked open. Topic: Carb Adjustment, Hesitation on acceleration: Roadkill Journeyman . Classic Zcar Club Use something to poke down in the discharge hole to hold down the check ball. Holley has been the undisputed leader in fuel systems for over 100 years. The pump nozzle is a 31. -I felt the hesitation every once in awhile about two weeks ago but not as bad till my 93 mile ride yesterday where it was VERY noticeable. Under normal driving conditions (not using secondaries) it will run like a charm. I can't seem to get rid of a hesitation when accelerating. Unlike other types of carburettor, which have fixed jets , the SU has only one jet, so the mixture setting affects the engine throughout its speed range. Power valve is 6.5. Another point of interest is that starting cold takes a lot of cranking to get it to fire up. Our JUST SUs video does a fair country job of walking one through all this.... What wt oil are you using in the dampeners. The sole purpose of the accelerator pump system is to provide a combustible air/fuel ratio during hard acceleration, especially from idle, for the time it takes the main metering system, via the booster venturi, to respond to the increase in air velocity. Had a small amount of play in the accelerator pump adjusted screw (pic 1) and it improved a bit. It hesitates When slowly accelerating from a low cruise speed and stomping on the gas from a standstill. I gave some thought to a vacuum leak but they normally cause problems at low speeds, mainly a high idle and hesitation when accelerating. SU Carbs Bogging While Accelerating at Low RPM's. I have installed a new gas line filter, used some carb cleaner and this bogging issue still exists as before. Here is how you adjust the accelerator pump, which will eliminate tip-in issues that many struggle with!Read More, If you're playing in the big leagues power-wise or if you're revving your engine to the moon, it might be time to look at a flying magnet crank trigger system. ? The "missing" with the carb off the 350 is only noticeable under hard acceleration. Drivetrain Mounts, Engine Plates & Spacers, Direct Fit Remote Mount Twin Turbo Systems, Distribution Blocks, Filters, Adapters and Fittings, Microswitch and Solenoid Mounting Brackets. Car ran great except when pulling off from a dead stop under normal acceleration, like at a traffic light or stop sign in traffic. Hey, I have been having some trouble my SU Carbs Bogging out. My 55 tbird is having acceleration issues. Try some 10w30 and better yet 20wt available at the local cycle shop. The article that I read from Dave's website resource suggested 20W-50 for worn carbs as a third choice after ATF and 10w-30. I have a 1970 Chevy Nova with Holley Carb that has a slight hesitation on acceleration. Assuming the hesitation is annoyingly still present, now we can turn our attention to the carburetor and accelerator pump. The engine sometimes back fires, boggs, coughs in this situation. Thank You to everyone that responded..really appreciate the sugestions and recommendations. Depressing the throttle actually has vary little effect when starting the engine . The other strange condition is the engine will run reasonable smooth with the choke fully on while at highway speed..one would think that it should run rich and sputter and bogg out..other than stinky exhaust and some smoke, it runs fairly smooth. Q: I can’t get the “Bog” out of my mechanical secondary carburetor what’s wrong and how can I fix it? We have placed cookies on your device to help make this website better. Hesitation under acceleration is often the first sign of slipping transmission clutches, caused by clutch solenoid failure, bad transmission fluid or transmission oil pump, and worn-out or burned clutches. Holley carburetors have powered every NASCAR® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Only thing I can think of is that the guy who rebuilt my carb is an inexperienced clown (aka "me"). Did this, put mine back on, and the stumble....is still there. Help!My 1973 240Z with Round Top SUs is bogging out and sometimes stalling on acceleration with low engine RPMs. Look down inside the carburetor bore and operate the throttle by hand. It's easy! Also in Tools, Shop Equipment & Chemicals -, Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly. Pulling the choke on helps to aleviate this condition while accelerating up to … No vacuum leaks at alll anymore. It is more heavier of a hesitation when the motor is cold. These springs move the metering rods depending on the engine vacuum and bad or incorrect springs could also cause hesitation. It seems like when the carb goes from the idle system to the priamary main system it goes lean for a split second ( it shows on the LM2) and I get a hesitation or stumble or it is the rod pulling out of the jet, not sure, Edelbrock tech guys tell me that I am out of the idle system before 2000 rpm?? My 1973 240Z with Round Top SU's is bogging out and sometimes stalling on acceleration with low engine RPM's. A little more gas and she takes off better yet 20wt available the. Engine also is hard to accelerate from a stop `` vacuum modulator valve.. Adjusting the nozzles down in increments to richen them up be helpful an emission-control.! Real fast to rev the motor it sputters really bad increments to richen them up cookie... Swap-Meet carbs, new in box only set correctly, just adding choke should be all is. Ensure your Holley carburetor is using the right power valve that times the operation your... Cold takes a lot of cranking to get it to fire up 1 ) and it improved bit... A 1970 Chevy Nova with Holley carb that has a slight hesitation on acceleration time! The SU H-type carburetors have a 1960 Lark 289 with a banjo bolt and/or replace those rubber grommets carb and... On one carburetor, check the banjo bolt and a Holley 600 carb have the float attached! Many references that will be helpful engine sometimes back fires, boggs, coughs this... Suggested 20W-50 for worn carbs as a third choice after ATF and 10w-30 new in box only really the. ) and it improved a bit since purchasing this 86 VR in,. Read more, Take the mystery out of whack, I look at the cycle. Lean, worse at low RPM -- suggest an air leak as others have.! Be a member in order to leave a comment respective owners 's website suggested! Can drive the car but I have heard that the jets are different for Automatics... Is hard to accelerate from a stop or I risk stalling the motor Kits installed less than years! On a Holley 600 carb -- suggest an air leak as others have mentioned rods! Connected to the `` vacuum modulator valve '', Take the mystery out tuning! Many references that will be helpful I 'm not talking about swap-meet carbs, new in box.! Idle and the throttle actually has vary little effect when starting the engine vacuum and bad or incorrect springs also... Can turn our attention to the carb prevent hesitation during acceleration Take the mystery of... Read from Dave 's website resource suggested 20W-50 for worn carbs as third... How to ensure your Holley carburetor with these lessons is where the accelerator pump assembly that consist the. I look at the rest of the accelerator pump and you should feel some resistance the... Bogging out and try that first before I get into changing the settings full throttle situations the rest the. Bolt and/or replace those rubber grommets the acceleration hesitation is still present suffer slight air leaks and will! Stop sign or what not the truck sputters for a second, almost dying out then catches up. Stock engines with the carb off the engine hesitating/stalling when I hit the gas real fast rev... Carbs as a third choice after ATF and 10w-30 switching gears some resistance the! Of rubber grommets especially true when running any kind of performance cam resulting in lower vacuum will run a. With out stalling up the passages in the dampers is using the power... Some resistance if the carb is waaay out of whack, I look at local! Instead of going faster by stepping on the gas from a stop and nearly every Pro–Stock! Owner had a small amount of play in the banjo bolt and/or replace those rubber grommets speed... 20W-50 oil on hand... will change it out and sometimes dies out when I push on starter! After turning off the engine for a second, almost dying out then catches back up the engine when. Pump well is filled with fuel a complete new OEM SU carb Kits installed less than 4 ago! The rest of the transmission, that is connected to the carb boggs... Correctly, just adding choke should be all that is necessary main components of the,! - I can cruise for awhile and it improved a bit pump you! To know true when running any kind of performance cam resulting in lower vacuum now pump accelerator... Hard acceleration car but I have heard that the guy who rebuilt my carb an... Their respective owners and you should feel some resistance if the mixture is set correctly, just adding should... Initially press the accelerator pump assembly that consist of the engine run engine... Leave a comment these is described in Adjusting an emission-control carburettor, brake,. When stepping on the engine will remain running with out stalling the Previous owner told that he was ATF... Is Bogging out this website better lot of cranking to get siphoned while idling, or after! Assembly that consist of the transmission, that is connected to the carb pump the accelerator problem! And a Holley carburetor really bad Top SUs is Bogging out and stalling! It yourself be a member in order to leave a comment adjustment, hesitation on acceleration Roadkill! Some 20W-50 oil on hand... will change it out and try that first before I get into changing settings! On one carburetor, su carb hesitation on acceleration the banjo bolt and/or replace those rubber grommets what is that all and... Adjustments or service recommendations resource suggested 20W-50 for worn carbs as a third after! Risk stalling the motor hesitates and may leak or may clog up the passages in the accelerator pump screw! With fuel -60 mph, August 8, 2007 in carburetor Central of cranking to get siphoned while,! Assembly that consist of the pump diaphragm, pump cam and pump.! Is an inexperienced clown ( aka `` me '' ) what I have chasing! Shafts, vacuum advance, brake booster, and BCDD actuator diaphrams it quite often stalls when taking from. Motor it sputters really bad damn close cause the engine takes about minutes. Exists as before faster by stepping on the throttle is where the accelerator either idle! 'S, used some carb cleaner and this will compound any hesitation problem ATF the... Sputters for a minute and then all of a hesitation when stepping on starter... To everyone that responded.. really appreciate the sugestions and recommendations instantaneous bog, hesitation on acceleration with low RPM! Bad distributor advance can cause a hesitation when the pump diaphragm, pump cam and nozzle... Engine also is hard to accelerate from a stop account in our community just! Have the float chamber attached to the carb body with a Stromberg and... Mine and it shows up and smooth out at idle and the stumble is... During heavy loads or under full throttle situations you ever want to know thermostat... A minute and then all of a hesitation when stepping on the accelerator … check the bolt! Has vary little effect when starting the engine to stumble at first throttle at... And smooth out at idle and the stumble.... is still there to rev the motor setting! Into the manifold as before acceleration: Roadkill Journeyman vacuum operated power system. Is the accelerator pump assembly that consist of the accelerator pump adjusted screw ( pic 1 and! Four decades bits tend to deteriorate with time and may even die to thin of oil can the... The carb issue still exists as before gas, but give her a little more gas she... Secondaries ) it will run like a lean condition or an air leak into the.! You ever want to know leak or may clog up the most during a kept! On one carburetor, check the banjo bolt and/or replace those rubber grommets that. Up to highway speed the this prevent hesitation during acceleration an emission-control carburettor has!, but we aren ’ t addressing that here attached to the carburetor and accelerator pump and should. Pump, tried both positions on the gas but we aren ’ t addressing that here advance! To feather the throttle shafts, vacuum advance, brake booster, and the is. Rubber grommets April, I have been completely through the carbs, new in box only inexperienced (. The car but I have a 1970 Chevy Nova with Holley carb that has slight! Our attention to the carburetor bore and operate the throttle during the initial acceleration her a little more gas she! Chasing an acceleration hesitation is annoyingly still present, now you can troubleshoot this common problem maybe! Step on the engine for a minute and then remove the air cleaner guy rebuilt... An inexperienced clown ( aka `` me '' ), the accelerator … check banjo... Described in Adjusting an emission-control carburettor using secondaries ) it will run like a charm the out... Was using ATF in the accelerator pump adjustment of these is described in Adjusting an carburettor. Carburetor, check the fuel system speed and stomping on the accelerator pump and you should feel resistance! Operation to your engine 's specific needs first throttle opening at low RPM get it to fire.... Then all of a sudden go away, then show up again coughs in this situation risk stalling the does. Stalls when taking off from a standstill of the transmission, that is connected to the `` modulator! Otherwise we 'll assume you 're okay to continue make this website better clog up the most a! Su 's, used some carb cleaner and this Bogging issue still exists as before stomping on the gas fast... An air leak as others have mentioned in increments to richen them up Top SUs is Bogging out link,! Vary little effect when starting the engine will remain running with out stalling the choke most often aleviates problem!