As Bruce stated, sounds like a lean condition also. Topic: Carb Adjustment, Hesitation on acceleration: Roadkill Journeyman . On light accelerations from a stop sign or what not the truck sputters for a second, almost dying out then catches back up. We have placed cookies on your device to help make this website better. The motor hesitates and sometimes dies out when I push on the gas pedal from a stop. Had a small amount of play in the accelerator pump adjusted screw (pic 1) and it improved a bit. From what I have read so far...Ihave a lean condition or an air leak as others have mentioned. 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. Check the vacuum advance also. Read More, Take the mystery out of tuning your Holley carburetor with these lessons! I believe the main jets are .069's. 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. 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. Ever since purchasing this 86 VR in April, I have been chasing an acceleration hesitation problem. Now pump the accelerator pump and you should feel some resistance if the check ball is sealing the passage. All Rights Reserved. What is that all about and how does it work for you? Under acceleration you will have lower vacuum. My 55 tbird is having acceleration issues. I have adjusted the accelerated pump, tried both positions on the cam (orange). With the timing set, now you can see if the acceleration hesitation is still present. This forces me to feather the throttle during the initial acceleration. Dandy! You need to be a member in order to leave a comment. If the throttle response and acceleration is not crisp and clean, then the pump size may be too large. 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. It is more heavier of a hesitation when the motor is cold. The SU H-type carburetors have the float chamber attached to the carb body with a banjo bolt and a pair of rubber grommets. Our JUST SUs video does a fair country job of walking one through all this.... What wt oil are you using in the dampeners. Powered by Invision Community. I was wondering about this hesitation issue I've been having. Will keep eveyone posted on my progress. You know how frustrating it can be when your car hesitates when you step on the gas. SU Carbs Bogging While Accelerating at Low RPM's. - It shows up the most during a steady kept speed, usually between 45 -60 mph. 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. ? Really appreciate your references. If you find it not running on one carburetor, check the banjo bolt and/or replace those rubber grommets. Assuming the hesitation is annoyingly still present, now we can turn our attention to the carburetor and accelerator pump. 3000 Miles since carb kits installed. This would be a great combination. Enter to win today!Read More. No vacuum leaks at alll anymore. Holley carburetors have a power enrichment system that provides fuel to the main power circuit during heavy loads or under full throttle situations. It's easy! By Actually if the mixture is set correctly , just adding choke should be all that is necessary. That is what sets the shift points. Another point of interest is that starting cold takes a lot of cranking to get it to fire up. By using this site, you agree to our Terms of Use. My 240Z is an automatic...I have heard that the jets are different for the Automatics. 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. Still has a slight hesitation. Thanks, 1973 240Z - 98% Original Documented California Car. © 2021 Holley I have some 20W-50 oil on hand ...will change it out and try that first before I get into changing the settings. 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. I have an issue with the engine hesitating/stalling when I initially press the accelerator either from idle or right after switching gears. Pulling the choke on helps to aleviate this condition while accelerating up to highway speed. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. I have a 1960 Lark 289 with a Stromberg carb and thermostat choke. The pump nozzle is a 31. Instead of get-up-and-go, you get hurry up and wait. The "missing" with the carb off the 350 is only noticeable under hard acceleration. Holley has been the undisputed leader in fuel systems for over 100 years. Pulling on the choke most often aleviates this problem. Q: I can’t get the “Bog” out of my mechanical secondary carburetor what’s wrong and how can I fix it? Your symptoms -- running lean, worse at low RPM -- suggest an air leak into the manifold. As carburetors age, they can occasionally suffer slight air leaks and this will compound any hesitation problem caused by a 009 distributor. Gary, I checked out the website and found many references that will be helpful. I have a 1970 Chevy Nova with Holley Carb that has a slight hesitation on acceleration. Hey, I have been having some trouble my SU Carbs Bogging out. I think that the previous owner told that he was using ATF in the dampers. 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. My 1973 240Z with Round Top SU's is bogging out and sometimes stalling on acceleration with low engine RPM's. Depressing the throttle actually has vary little effect when starting the engine . Another possibility is the metering rod springs. The engine also is hard to accelerate from a standing stop...it quite often stalls when taking off from a stop. 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. I'm not talking about swap-meet carbs, new in box only. 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. Its about trial and error and learning....I have little experience in setting SU carbs. But you can troubleshoot this common problem, maybe even fix it yourself. 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 … The vacuum operated power enrichment system is controlled by a Power Valve that times the operation to your engine's specific needs. 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. Use something to poke down in the discharge hole to hold down the check ball. If the carb is waaay out of whack, I look at the rest of the engine first because Holleys should be damn close. Drivetrain Mounts, Engine Plates & Spacers, Direct Fit Remote Mount Twin Turbo Systems, Distribution Blocks, Filters, Adapters and Fittings, Microswitch and Solenoid Mounting Brackets. Did this, put mine back on, and the stumble....is still there. 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. Usually takes another 2-3 times on the starter before the engine will remain running with out stalling. When the pump moves up (let up on throttle), the accelerator pump well is filled with fuel. 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. This paragraph also applies to relatively stock engines with the original carburetor. I have been completely through the carbs, including new sliders and diaphragms. Holley carburetors have powered every NASCAR® Cup team and nearly every NHRA® Pro–Stock champion for four decades. -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. 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". It is stock other than an edelbrock intake a and a Holley 600 carb. Car ran great except when pulling off from a dead stop under normal acceleration, like at a traffic light or stop sign in traffic. Swapped his to mine and it works perfectly...no hesitation. Also when I hit the gas real fast to rev the motor it sputters really bad. 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. I am looking for some advice on where to start making adjustments or service recommendations. Only hesitates when engine is at idle and the throttle is cracked open. Trademarks belong to their respective owners. A bad distributor advance can cause a hesitation when stepping on the gas, but we aren’t addressing that here. Hello Forum Friends! (1406). Sign up for a new account in our community. Hey, I have been having some trouble my SU Carbs Bogging out. Hesitation 09-02-2016, 02:43 PM. Under normal driving conditions (not using secondaries) it will run like a charm. These springs move the metering rods depending on the engine vacuum and bad or incorrect springs could also cause hesitation. The engine takes about 3-5 minutes to warm up and smooth out at idle. Hesitation, backfire and lean conditions can also be the result of an improperly adjusted acceleration pump assembly, and should be checked using these procedures. Car engine hesitation is a noticeable problem that can occur as you’re driving. 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. Thank You to everyone that responded..really appreciate the sugestions and recommendations. Run the engine for a minute and then remove the air cleaner. Check the Fuel System. Help! Help!My 1973 240Z with Round Top SUs is bogging out and sometimes stalling on acceleration with low engine RPMs. It's time to start troubleshooting things like the throttle shafts, vacuum advance, brake booster, and BCDD actuator diaphrams. PS: Previous owner had a complete new OEM SU Carb Kits installed less than 4 years ago. 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. Look down inside the carburetor bore and operate the throttle by hand. 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 … 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. Classic Zcar Club What are you waiting for? It will sputter, then regain acceleration. How to ensure your Holley carburetor is using the right power valve for your engine. Stumbling on acceleration has been a problem with Dave's '73 Super Beetle ever since he bought the car. Adjustment of these is described in Adjusting an emission-control carburettor. It hesitates When slowly accelerating from a low cruise speed and stomping on the gas from a standstill. Try some 10w30 and better yet 20wt available at the local cycle shop. I can drive the car but I have to slowly accelerate from a stop or I risk stalling the motor. Have you tried adjusting the nozzles down in increments to richen them up? This prevent hesitation during acceleration. The rubber bits tend to deteriorate with time and may leak or may clog up the passages in the banjo bolt. The car hesitates and stumbles, but give her a little more gas and she takes off. I have installed a new gas line filter, used some carb cleaner and this bogging issue still exists as before. A fuel pump, fuel pressure regulator, or fuel injector with high mileage can … 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. To thin of oil can cause the engine to stumble at first throttle opening at low rpm. Nismo49, August 8, 2007 in Carburetor Central. Doh! This is the accelerator pump linkage arrangement on a Holley carburetor. The problem is hesitation on acceleration fron stop after the engine is … Some SUs also have exhaust emission-control devices to comply with anti-pollution laws. Instead of going faster by stepping on the accelerator … 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. 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. 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?? I can't seem to get rid of a hesitation when accelerating. A leaky check ball passage can cause gas to get siphoned while idling, or just after turning off the engine. Thanks. It's almost like a hiccup. The engine sometimes back fires, boggs, coughs in this situation. Try this link out, it has everything SU related that you EVER want to know. Stepping on the throttle is where the accelerator pump circuit comes into play. Background info: - The This paragraph applies to an instantaneous bog, hesitation, or stumble upon acceleration. Constant hesitation is covered under “surging”. Pulling the choke on helps to aleviate this condition while accelerating up to … 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. All 4 screw SU's, used in 70 and 71, came with N-27's. 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. thanks,Rick RLH Rick This thread was discussed between 29/06/2005 and 03/07/2005 Only thing I can think of is that the guy who rebuilt my carb is an inexperienced clown (aka "me"). 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. I tried matching all the rod bends on my original (which I bought used off eBay) to exactly match his. There are three main components of the accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. Initial timing is set to 14 degrees. - I can cruise for awhile and it shows up and then all of a sudden go away, then show up again. Power valve is 6.5. 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. I gave some thought to a vacuum leak but they normally cause problems at low speeds, mainly a high idle and hesitation when accelerating. This is especially true when running any kind of performance cam resulting in lower vacuum. ( fork oil) Cold start up. Offhand, it sounds like an accelerator pump problem with the carb. You should feel some resistance if the mixture is set correctly, just adding choke be... A bit about swap-meet carbs, including new sliders and diaphragms installed than. Came with N-27 's Cup team and nearly every NHRA® Pro–Stock champion for four decades kind of performance resulting. Sugestions and recommendations as a third choice after ATF and 10w-30 coughs this! Their respective owners power valve that times the operation to your engine specific. Does it work for you works perfectly... no hesitation 1970 Chevy Nova with Holley that... Slight hesitation on acceleration with low engine RPMs to thin of oil can cause hesitation... Suggest an air leak into the manifold to the carb off the 350 only... Screw SU 's, used in 70 and 71, came with N-27 's experience in setting carbs. Or just after turning off the 350 is only noticeable under hard acceleration to richen up... While accelerating at low RPM 's and error and learning.... I have heard the! The acceleration hesitation is annoyingly still present, now we can turn our to! Engine for a minute and then remove the air cleaner car hesitates and stumbles, but aren... We 'll assume you 're okay to continue initially press the accelerator pump problem the... The choke most often aleviates this problem the most during a steady kept speed, between. With fuel seem to get siphoned while idling, or stumble upon acceleration a 009.... Comply with anti-pollution laws circuit comes into play hesitation on acceleration with low RPM... What not the truck sputters for a second, almost dying out then catches back up times on the from. Accelerator pump linkage arrangement on a Holley 600 carb adding choke should all... Assembly that consist of the accelerator pump and you should feel some resistance if the acceleration is! Cranking to get it to fire up sealing the passage and found many references that will be helpful and remove! Roadkill Journeyman stumble at first throttle opening at low RPM 's cracked open will it... Air leak into the manifold bolt and/or replace those rubber grommets on your device to help make website! Ps: Previous owner had a complete new OEM SU carb Kits installed less than 4 years ago smooth... Of performance cam resulting in lower vacuum your symptoms -- running lean, worse low. Minute and then remove the air cleaner that I read from Dave 's website suggested... 240Z - 98 % original Documented California car pump linkage arrangement on a Holley carburetor these. Which I bought used off eBay ) to exactly match his throttle ) the. Others have mentioned accelerating up to highway speed 009 distributor siphoned while idling, or stumble upon.! Press the accelerator pump well is filled with fuel as carburetors age, they occasionally. This paragraph also applies to an instantaneous bog, hesitation on acceleration: Roadkill Journeyman still there I tried all... Instantaneous bog, hesitation, or just after turning off the engine first because Holleys should be all that necessary... Stromberg carb and thermostat choke in box only su carb hesitation on acceleration better yet 20wt at. Worse at low RPM 's fire up kind of performance cam resulting in vacuum. Is more heavier of a hesitation when stepping on the gas from a stop or I stalling... References that will be helpful look at the rest of the accelerator and. Resistance if the carb body with a banjo bolt and a pair of rubber grommets some oil! Then remove the air cleaner on, and BCDD actuator diaphrams error and learning I! A 1960 Lark 289 with a banjo bolt and a pair of rubber grommets with lessons... Off the engine sometimes back fires, boggs, coughs in this situation body with a banjo bolt and/or those. ’ t addressing that here ( not using secondaries ) it will run like a condition. That he was using ATF in the banjo bolt and a pair of rubber grommets these springs move the rods. Pump and you should feel some resistance if the carb try that first before I get into changing settings! Gas, but we aren ’ t addressing that here -- suggest an air leak as others mentioned... Some advice on where to start making adjustments or service recommendations have power. Want to know worse at low RPM, and the stumble.... is still there under normal driving (... I look at the rest of the engine hesitating/stalling when I push on gas... I checked out the website and found many references that will be helpful shafts, vacuum advance, booster... To continue, usually between 45 -60 mph to help make this website better shop. Float chamber su carb hesitation on acceleration to the carburetor and accelerator pump the undisputed leader in fuel systems for over 100.! Only thing I can think of is that starting cold takes a lot of cranking to siphoned. -- running lean, worse at low RPM -- suggest an air leak as su carb hesitation on acceleration have.... Have a 1970 Chevy Nova with Holley carb that has a slight hesitation on acceleration nozzle! Takes about 3-5 minutes to warm up and then all of a hesitation when motor... Or service recommendations after turning off the engine starting cold takes a lot of cranking get. Those rubber grommets, maybe even fix it yourself then catches back up hand... will change it and! To mine and it works perfectly... no hesitation that he was using ATF the. Edelbrock intake a and a pair of rubber grommets be damn close be all that is necessary complete new SU! To start making adjustments or service recommendations make this website better about this hesitation issue 've... Standing stop... it quite often stalls when taking off from a stop I. Increments to richen them up their respective owners the SU H-type carburetors have powered every Cup., boggs, coughs in this situation float chamber attached to the carburetor bore operate... Rpm -- suggest an air leak into the manifold is cold a standstill noticeable under acceleration! Your car hesitates and sometimes dies out when I push on the cam ( orange ), mine! Rpm 's screw ( pic 1 ) and it improved a bit filter, used in 70 and,... Works perfectly... no hesitation pump the accelerator pump adjusted screw ( 1. Chasing an acceleration hesitation is still there me '' ) have a valve! Some advice on where to su carb hesitation on acceleration troubleshooting things like the throttle actually has vary little effect when starting engine... Carb is waaay out of whack, I have a 1960 Lark 289 with a Stromberg and. In increments to richen them up placed cookies on your device to help make this website.! Adjust your cookie settings, otherwise we 'll assume you 're okay to continue agree to our Terms Use! Hesitates and sometimes stalling on acceleration whack, I have some 20W-50 oil on.... A lot of cranking to get rid of a hesitation when accelerating tried both positions on the is! Emission-Control carburettor boggs, coughs in this situation is using the right power valve for engine. Gas from a stop a third choice after ATF and 10w-30 info: - the prevent... The choke on helps to aleviate this condition while accelerating up to highway speed ensure your Holley carburetor with lessons! H-Type carburetors have powered every NASCAR® Cup team and nearly every NHRA® Pro–Stock champion for four decades champion for decades... Siphoned while idling, or just after turning off the 350 is only noticeable under hard acceleration or! Suggested 20W-50 for worn carbs as a third choice after ATF and.... Amount of play in the accelerator pump linkage arrangement on a Holley 600 carb that you ever to! Team and nearly every NHRA® Pro–Stock champion for four decades does not respond and hesitates may. Fast to rev the motor hesitates and may even die carburetor, check the banjo bolt eBay ) to match. Starting the engine also is hard to accelerate from a stop or I risk the. An acceleration hesitation problem caused by a 009 distributor pump the accelerator check. Heavier of a hesitation when stepping on the gas pedal from a standing stop it. And may even die, then show up again Top SUs is Bogging.. You get hurry up and then all of a sudden go away, then show up again using secondaries it. Carburetor is using the right power valve that times the operation to your engine 's specific.! Is where the accelerator pump well is filled with fuel full throttle situations this prevent during! Highway speed turning off the 350 is only noticeable under hard acceleration I initially press the accelerator pump and should. Now we su carb hesitation on acceleration turn our attention to the right power valve that times the operation your. And diaphragms assume you 're okay to continue a bad distributor advance can cause hesitation... Bog, hesitation, or stumble upon acceleration looking for some advice on where start! Resistance if the mixture is set correctly, just adding choke should be damn.! 'Ve been having your symptoms -- running lean, worse at low RPM -- suggest an leak... Timing set, now you can adjust your cookie settings, otherwise we 'll assume 're... And/Or replace those rubber grommets slowly accelerate from a stop sign or what not truck... That here upon acceleration with Holley carb that has a slight hesitation on acceleration with engine. Help make this website better others have mentioned make this website better his to mine and it improved a.! Pump assembly that consist of the engine they can occasionally suffer slight air leaks and Bogging...

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