Carburetor hesitation on acceleration can be frustrating and dangerous, causing your vehicle to stall or perform poorly when you need it most. This issue is often caused by a problem in the fuel system or carburetor, which can be difficult to diagnose and repair without the proper knowledge and tools. In this guide, we'll take an in-depth look at carburetor hesitation on acceleration, including its causes, symptoms, and solutions. By the end of this guide, you'll have a better understanding of what causes carburetor hesitation on acceleration and how to fix it.
Understanding Carburetor Hesitation on Acceleration
Carburetor hesitation on acceleration is a common problem that affects many vehicles, particularly older models. This issue occurs when the engine hesitates or stumbles when you press down on the accelerator pedal, especially when starting from a stop. The problem can range from a mild hesitation to a severe stumble or stall, depending on the severity of the issue.
Causes of Carburetor Hesitation on Acceleration
Several factors can cause carburetor hesitation on acceleration, including a dirty carburetor, clogged fuel filter, clogged passage, or a faulty accelerator pump. Other common causes include a vacuum leak, low fuel pressure, or a malfunctioning choke. In some cases, the issue can be caused by a faulty ignition system or a worn-out engine. Be especially mindful of the distributor advance.
Symptoms of Carburetor Hesitation on Acceleration
The symptoms of carburetor hesitation on acceleration can vary, depending on the severity of the issue. Some common symptoms include a rough idle, hesitation or stumbling when accelerating, and a loss of power or speed. You may also notice that your engine is running rich or lean, causing excess fuel consumption or a burnt exhaust smell.
How to Fix Carburetor Hesitation on Acceleration
Fixing carburetor hesitation on acceleration can be a challenging task, but it's not impossible. The first step is to identify the root cause of the issue, which may require a diagnostic test or inspection. Once you've identified the problem, you can take the necessary steps to repair or replace the affected components. These may include cleaning the carburetor, replacing the fuel filter or accelerator pump, or repairing a vacuum leak.
Cleaning the Carburetor
Cleaning the carburetor is often the first step in fixing carburetor hesitation on acceleration. This process involves removing the carburetor from the engine and disassembling it to clean the various components. You can use carburetor cleaner or a specialized cleaning solution to remove any dirt, debris, or varnish buildup that may be causing the issue.
Replacing the Fuel Filter
A clogged fuel filter can also cause carburetor hesitation on acceleration. To fix this issue, you'll need to replace the fuel filter with a new one. This is a simple process that can be done with basic tools and a little know-how.
Repairing a Vacuum Leak
A vacuum leak can cause carburetor hesitation on acceleration by disrupting the air-to-fuel ratio in the engine. To fix this issue, you'll need to locate the source of the leak and repair or replace the affected components. This may include replacing a damaged hose or gasket or repairing a cracked intake manifold.
Preventing Carburetor Hesitation on Acceleration
Preventing carburetor hesitation on acceleration can be achieved by taking a few simple steps. Regular maintenance, such as changing the oil and air filter, can help keep your carburetor and fuel system clean and free from debris. You should also avoid driving with low fuel levels, as this can cause sediment and dirt to be pulled into the carburetor and fuel system. Additionally, using high-quality fuel and additives can help keep your carburetor clean and functioning properly.
FAQs About Carburetor Hesitation on Acceleration
Q: What causes carburetor hesitation on acceleration? A: Carburetor hesitation on acceleration can be caused by a variety of factors, including a dirty carburetor, clogged fuel filter, or a faulty accelerator pump.
Q: How do I know if my carburetor is causing hesitation on acceleration? A: Some common symptoms of carburetor hesitation on acceleration include a rough idle, hesitation or stumbling when accelerating, and a loss of power or speed.
Q: Can I fix carburetor hesitation on acceleration myself? A: Yes, you can fix carburetor hesitation on acceleration yourself with the proper tools and knowledge. However, if you're not comfortable working on your vehicle, it's best to take it to a professional mechanic.
Q: How do I prevent carburetor hesitation on acceleration? A: Regular maintenance, using high-quality fuel and additives, and avoiding driving with low fuel levels can help prevent carburetor hesitation on acceleration.
Q: What should I do if my carburetor hesitation on acceleration persists? A: If your carburetor hesitation on acceleration persists after trying the solutions outlined in this guide, it's best to take your vehicle to a professional mechanic for further diagnosis and repair.
Conclusion:
Carburetor hesitation on acceleration can be a frustrating and dangerous problem, but with the proper knowledge and tools, it's a problem that can be fixed. In this guide, we've outlined the causes, symptoms, and solutions for carburetor hesitation on acceleration, as well as provided tips for preventing the issue from occurring in the first place. By following the steps outlined in this guide, you can diagnose and repair carburetor hesitation on acceleration and get back on the road with confidence. Remember to stay on top of regular maintenance and take your vehicle to a professional mechanic if the issue persists.
Testing the Accelerator Pump
Testing the accelerator pump on the Edelbrock would be the same process as an AFB 9000, or Weber Marine. This test is best done with the carburetor off of the car. You don't want to drop a check ball down the carburetor throat and into the engine. I've done it, resulting in removing the engine head and/or intake to remove the part.
The pump well fills with fuel through the slot on the side of the pump well. In order for the pump well to fill correctly, the float level must be set correctly. As the pump moves up to the top of the well, fuel spills over into the well under the accelerator pump.
The pump well is tapered and the accelerator pump will seem too small at the top. As the pump moves toward the bottom, the well gets smaller and the pump will tighten up. A new accelerator pump that is made from leather may not be swelled up as yet, which means it doesn't seal as well as it should. Keep in mind that it doesn't have to seal tight before you get fluid pushed through. It shouldn't take much to pump the fluid through the passage.
To test:
Fill the bowl with fluid. Use something besides gasoline, which of course is explosive. We use mineral spirits (odorless) for all of our testing.
Insert the accelerator pump and push it to the bottom. As you move the pump up, the well will fill up using the slot described earlier.
Push the pump down and watch it squirt gas out of the main discharge. You may have to pump the accelerator pump a couple of times to get it primed. Also it may not squirt until the pump is part way down the well. The well is tapered and also the pump cup may not be swelled up yet.
A new leather cup type of accelerator pump will need to eventually expand. Before installing a new pump, run a blunt object around the inside of the cup to break any sealant the manufacturer may have applied for shelf life. Apply a couple drops of oil to the pump. It will eventually expand to fit. Please note, it may never fit tight and isn't supposed to. Avoid soaking the pump in oil overnight. This will make the leather too spongy and will probably fail.
For rubber cup pumps, apply a dab of lithium grease to the cup. This will help lubricate the well. Today's gas has very little lubricant causing premature pump failure. Polishing the pump well with crocus cloth will also help. The pump needs a smooth gliding surface.
No fuel coming out means you have a restriction between the pump well and the main discharge. Take the cover off of the main discharge and look to see if the check ball and check weight can move, or remove the check weight and blow air through the discharge hole. The air should go through to the pump well. There may be a restriction in the passage. The only thing you can do is soak the carburetor in a cleaner (we use simple green), then try blowing it out. Also don't discount the discharge cover. The small holes may be plugged.
Next test is to see if the discharge check is working. There may be a check ball with a small check weight above it. Some AFB's, or Weber Marine use a check ball and a spring. Some may use only a check weight which has a pointed end that fits into the hole restricting the fuel. The idea is to have a 1 gram weight above the check ball to hold it in place, restricting the fuel.
Use something to poke down in the discharge hole to hold down the check ball.
Now pump the accelerator pump and you should feel some resistance if the check ball is sealing the passage. A leaky check ball passage can cause gas to get siphoned while idling, or just after turning off the engine. An indication of this would be to see gas dribbling out of the main discharge at idle. That should not happen.
Gently tap on the check ball so that the trough forms to the check ball. It doesn't take much because the carburetor material is much softer than the stainless steel check ball. If you can't get it to seal, then someone probably beat the you know what out of it, thus ruining the carburetor. There is no way to fix it at that point.
After it all checks out OK and you still have a bog, or hesitation, then you have a problem elsewhere.
The distributor advance may not be working correctly. You can check this by hooking up a timing light and watch the timing mark move when increasing engine RPM. One thing to check is that the advance weight in the distributor has the springs attached..
One other possibility is the idle discharge. Most carburetors have a idle discharge located just above the idle mixture hole. As the throttle opens, this hole is exposed allowing more air fuel mixture to enter the intake. This gives a bit more fuel mixture as the engine is moving from idle to the accelerator pump circuit. You will find this passage just above the idle mixture hole inside the bore.
