Step-by-Step_ How to Service a Car Carburetor
Auto Parts,  Cars

Step-by-Step: How to Service a Car Carburetor

A carburetor is an essential and necessary part of a lot of automotive vehicles, like cars. It essentially mixes air and fuel for internal engines so that the air-fuel ratio is done correctly, which is very important in the car’s functionality. Without a good carburetor, a car may become inefficient.  

How do you service a car carburetor? It is a straightforward 8 step process, from its complete removal to its complete reattachment. There is also maintenance, which can lengthen the longevity of your carburetor.

In this article, I will try to break down the step-by-step process as to how this is done, and ways that you can service it, along with maintenance protocol. Below are two processes that are different but will achieve you the same results. I have also included another process in servicing, which is a complete replacement, which is something you should consider given your scenario.  

What is a Car Carburetor?

Before I establish the steps necessary to service the carburetor for cars, it is important to get a baseline of understanding prior to repair, so that you, at least, know what that part does rather than dismantling it without purpose. 

Fuel and air make up the car’s motion from a carburetor. The same principle applies to trucks, aircraft, and buses, for example. Although they may not use a carburetor directly, a mixture of fuel and air is needed to get the vehicle in motion. 

Exactly how much fuel and air and air that an engine needs is going to vary from moment to moment, given a couple of factors. One of these factors, for example, is how long the machine has been running, or how fast the machine is going. However, most modern engines use a fuel injection to regulate this mixture or ratio of how much fuel and air you need. 

However, before that, all engines used the carburetor, which is sometimes referred to as a “carb”. Although I will not get into the science of this ratio, the car engine should have 14.7 parts of air to part of fuel. Too much air means that you burn “lean”, and too much fuel means you burn “rich.” In other words, too much air will give you a better fuel economy but sacrifice performance. Too much fuel will give you the opposite result. Both are bad for the engine. 

Gasoline engines are designed to take in the exact right amount of air so that the fuel burns properly, regardless if the engine is running from cold or hot top speed. Getting the mixture right is the job of the carburetor, a tube that allows air and fuel into the engine through valves. 

A prime example of carburetor usage was in the 1990s Chrysler model. This is the last year that a carb was produced by the Chrysler company. Now, however, we have moved on from that with the fuel injection mechanisms that accomplishes the same result. 

Before getting into how to service your carb, I need to note the importance of constant maintenance and cleaning. It is imperative to always be checking on the carb routinely. For example, look out for dirt accumulation. Once the carb is dirtied, it will negatively impact efficiency. This is why cleaning is so important.

Servicing and First Steps

When there are issues with the carb, most of its errors are found in small engines. Another issue it could stem from is the engine running for a very long period of time. These issues result in the fuel breaking down. Once that happens, you will screw over the fuel to air ratio that is needed for the car to function properly. 

However, this is only one example of many that could be the cause of your carb malfunction. Regardless of what that the reason is, before servicing, make sure the tank fuel is good prior to starting the engine. Here is the process of how to service the carb, regardless of what issue it has. 

First, we need to remove the carburetor completely. Before that, we have to turn the fuel valve off. Then, we track down the fuel line to the carb and remove the hose. However, if the line is very old, you would need to replace this to ensure there are no leaks. 

Now that this has been found, look for the overflow hose. The overflow hose should most definitely be removed. Next, we have to loosen the screws. This should be seen at the clamps, or at the front and back of the carb. At this point, the carb should be loose so that you could take it off with a twisting motion by hand. 

Now, with the carb visibly seen, take off the throttle cable by twisting the top cap. When it gets unscrewed, the slide should still be attached with it. Now, you should have the carb fully removed. 

Continuing Steps

To continue with this process, we need to remove the float, a part that is located in the bottom part of the carb. To remove, unscrew the four screws located there. However, do not just yank them out. It is imperative to remove with care and caution as this should strip off easily. Now, remove the float bowl. 

Now, we have to remove the float pin. This can be simply done by a needle-nose plier. So, first, we remove the float pin, followed by the bowl. In some modern carbs, a needle will be hanging on the float itself. If that is the case, it should fall off naturally. 

The third step differs from different carbs, but its jets need to be taken regardless. Most carbs have some splash plates in them, and those need to be taken off as well. These are screws that have a hole in the center of them. In turn, these holes are essential in making the fuel flow to mix with the air. 

The plates also have to be removed. To look for it, keep an eye for a short and flat screwdriver head that is either flat or has a hex head. There is also the pilot jet, which should be long and skinny. Finally, if need be, take out the fuel splash plate. Remove it so that the float needle can be cleaned and removed. 

Removing the Outer Parts

Before cleaning the carb(only possible after removal), we have to remove the last parts from the outside. The air screw and idle screw can be removed with a flat head screwdriver. Usually, this is located on the side of the carb. To identify them, the idle screw is the larger screw. This adjusts the idle when the engine is at rest. 

The following action that you need to take is to remove the air screw. The air screw is much smaller and should be much easier to identify. This adjusts the air flow through the carb when the engine is running. 

To recap thus far, the air screw is smaller and responsible for the engine when active, the idle screw is larger and for the engine when at rest.

Cleaning the Carb

Before we begin this step, remove all the parts and gaskets and O-rings. This is imperative for safety and efficiency in this process. The easiest way to clean the carb is to soak them in a cleaner. This cleaner should be specific and should be properly labeled as a “carb and parts” cleaner. However, that can be sometimes pretty expensive. You can always also follow the instructions on the can if you want to spend. However, you can opt to clean with a spraying carb and choke cleaner instead. 

Before heading straight on, be sure that you are wearing safety glasses, as well as gloves, for the cleaning. Parts should be scrubbed with a wired brush and finally sprayed with the cleaner. In terms of the areas that you want to spray on, do it on the holes that the jets, idle screws, and float needle come from. 

For jet cleaning, be sure to spray it into the hole directly. To make sure it is clean, look through them into a flashlight. This will assure that the part is cleaned the way you want it, and that there have been no items being broken off throughout the process thus far. If it is not as clean as you want, just blow compressed air through the hole to get rid of leftover debris. 

Then, we properly check if all the debris is removed from the carb itself. Dry it and all of its other parts through compressed air. Blow that into all the holes and blow off all the parts of the carb. When everything has dried down, install your new O-rings and gaskets back into the cleaned-up carb. 

Installation of the Carb

Now, we install the parts into the opposite order in which they were removed. In this case, the float needle, as well as the fuel splash plate, need to be removed. The jets and the plates are installed next. 

Next, we install the outer parts of the carb. This step should always come first when it comes to the reinstallation of the carb back into the vehicle. Start first with the choke, then the air screw, then the idle screw. Remember that the air screw is the skinniest screw out of the three. When installing this, screw it all the way then back the screw out a turn and a half. This would serve as the baseline for the engine, particularly when it is idling properly. 

Now, the idle screw should be screwed in just enough to hold it. Next, we install the float. To do this, line the holes up with the holes in the carb and slide the pin in. This process should be easy. The pin should be slid freely, but make sure it is nicely centered for security. To make sure that the float is working properly, move it up and down to make sure the needles move with ease. If it does not, it needs a replacement. Needles should not be that expensive on the market, so do not hesitate if a purchase needs to happen. It will cost more in the long run if you use bad needles in the carb.

Now, we install the float bowl onto the carb with the 4 screws at the bottom. The carb should now be complete, without throttle. 

Final Steps of the Carb

Here are the final steps. Install the throttle slide back onto the cable and put it through the top cap. Then, we put the needle in the slide and compress the spring/hook at the end of the cable. Before sliding it into the hole, make sure the slot in the slide is lined up perfectly with the idle screw. 

When all of this is lined together, you can proceed by sliding in the throttle. After that, screw in the top cap. Now, you should be looking down either hole or screw the idle that you have next to it. Naturally, the slide is going to rise. When that happens, screw in about half a turn. If you need more than a half turn to screw it in, that is fine as well. Just make sure to not force it too much. 

Now, we should be sliding and wiggling the carb back into the rubber. Tighten the screws on the clamps to hold it in place. Install the fuel line and overflow line back into the carburetor. Finally, adjust the air and idle screw by letting your engine running. If you want the idle to increase, screw it in.  

Another Process

Like many parts in the automotive industry, there are also different types of processes in how to service different parts.  

As we all know, the carb is found primarily in older cars and it is working smoothly is essential to its functionality as well as the functionality of the car itself. It should be maintained and cleaned on a regular basis in order to make sure that we do not end up with a beat-down carb with huge fixing costs. Constant low-cost maintenance is always the key. The following process is a little bit shorter and simpler and should only take about a half hour. 

First, turn the engine off. Then, remove the air filter housing so that you have quick and easy access to the carb. Get a couple of rags in place, along with a spray lubricant and carb/choke cleaner. Thirdly, locate the throttle control which allows you to manually operate the engine faster. 

The next step is to place the rags around the base of the carb, since the chemicals may lead to painted surfaces. The rag, therefore, will stop the possible runoff. Afterward, we put on our safety goggles and spray the outside of the carb with a lubricant, or a carb/choke cleaner. Be very sure to spray the connections and moving parts, like the throttle linkage. 

Next, we let that fluid rest and wipe it up. If there is a heavy buildup, clean with a small wire brush before the spray dries up. Before starting the car, spray a tiny amount of it into the carb itself. After this, remove the rags themselves and any tools from the engine and start it. Do not ever spray the lubricant into the inside of the carb, only the outside. 

Now, we can properly start the engine and use the throttle, since you want to be able to run at a higher pm while you spray more carb fluid in there. This way, you can push the cleaner through and will avoid stalling out the engine. Spray this in short bursts, run the engine faster, then slow it to a normal idle. Repeat the process a few times. 

Finally, just let the car go on idle for a few minutes. After, turn off the engine completely and reinstall the air filter. Now, it should be good to go when driving. Drive it for an initial 10 minutes. This way, the cleaner is allowed to run through the system. Even if there is no significant improvement that you feel in the performance, this process that you went through has done tremendous amounts in carb preservation,

Knowing when to Replace

Now, given proper maintenance and cleaning processes, the carb can still be so bad and out of shape that you would need a new one completely. I will now talk about how to replace the carb when this happens.

When working with a system like this, always disconnect the battery to avoid any sparks that could be caused by touching the connections. This is very important, since these sparks can come in both liquid and gas form. To do this, locate the battery and remove the cables. To secure the cables, you are going to need a shield in a way that they cannot make contact with the posts while repairment. 

Now, we need to remove the air cleaner and any air intake ductwork. Most carbs on cars have an air cleaner that covers the air intake of the carb interior. This mainly keeps dirt and debris out of the engine. To find it, it is like a folded paper element or spongy material. The cover is held by screws or bolts. Once you identify this, remove the air cleaner and all ductwork. 

Disassembly of the old Carb

The next step is to remove the vacuum hoses and other connections. The way a carb functions is that it reads signals and helps out the engine load. The signal is transmitted through the intake manifold. There could be one or more of these hoses connected to this apparatus. Before detaching, take pictures of the hoses in their original position so that you can reassemble later on. 

Now, we have to remove the linkages. This is what controls the butterfly valve on the carb. The linkage and bracketry should be coming off next. To do this, disconnect the throttle linkage and any other bracketry and secure it on the side.

Now, disconnect with the fuel supply line. Typically, there will be a hose or metal tube, which is the supply line we are looking for. This line can either be held onto the carburetor by a hose clamp or threaded directly into it due to the metal line. 

Finally, we move on to the last steps. Release any residual pressure found in the fuel line. Depending on the type of fuel that you are using, there might still be pressurized fuel in the line. When doing a removal process, make sure you have something that could catch that escaping fuel. The next step is to remove the line and drain it out to avoid leakage. 

Removing the old Carb

After this, remove the carburetor. The carb should be held onto the intake manifold by any combination of nuts and bolts. The first thing to do here is to identify and remove the carb hardware. Now, we have to use the appropriate tools to remove it. These tools can be screwdrivers of many sorts, like a flathead or a hex. Either, given the carb model, should be fine. Then, we separate the carb from the intake manifold. Lift the carb out of the manifold. If there is any resistance, use a screwdriver. 

Be careful with this step, however. The body and flanges are fragile and can be damaged if you do not use a cautionary measure. Never force anything in this entire process. This can cause unnecessary and unwanted damage to the carb and even the car itself. Some consequences might be vacuum leaks or rough running later on down the road. 

Then, we block off the manifold opening by placing towels in the, to keep debris from falling through. Do not place them as far that they cannot be retrieved when it is time to install the replacement carb. The fourth step in this is to remove the old gasket between the carb and the manifold. 

Now, note that the gasket rule only sometimes implies. Not all manufacturers of carbs use a gasket in their system. If you do not have a gasket, that is fine. If there is a gasket there, use a razor blade to remove it. Please remove gently so that it does not damage.

Preparing for re-installation

The next step is to prepare for the new installation. First, we have to clean the carb and the intake manifold mounting flanges. Using a light solvent, clean them both rigorously. Also make sure there is no dirt or debris. Then, we can install a new gasket. Place it onto the manifold so that it is between the manifold and the carb itself. Now, compare the old carb v the new one. Take a few minutes to just analyze them making sure the features are similar, as well as the fuel inlet style and mounting points. The fourth step in this process is to transfer parts from the original carb to the new one. Finally, remove any other towels that may have been placed into the manifold. 

Now, we can install the replacement after our prep. Set the new carb onto the intake manifold. Then, we can complete the installation. At this point, follow the removal process mentioned above, but in reverse order. You want to make sure that the vacuum hose and fuel line have been reinstalled. 

The next procedure for this phase is the most important. Here, I should be checking for leaks. As you may have noticed we have been taking a lot of precautions regardless of the processes we are talking about. It is important to do this so that you and your car are in good shape. First, reconnect the battery to its positive and negative ends. Now, we should build pressure on the carb itself. Depending on the type of fuel system that you are working on, apply fuel pressure.  

Finally, we look out for carb leaks. Listen for any type of whistling sound around the carb. If it is detected, shut off the engine and do not cause any sparks. The next step is optional. If there were any leaks found, repair them by tightening any fittings or fasteners. Now, we can restart the engine and check the new carb’s functionality. 

Installation and Test Drive

Now we go on to the final steps of the installation. First, we reinstall the air cleaner and any other ductwork. Give a final visual inspection. Take some time to look at the new work that has been done, and make sure that the area is safe. The final step is to test drive the car. This is to just test out its functionality and if it is working the right way. If a fuel smell is detected, however, pull off on the side and shut the engine as soon as possible. Inspect the vehicle for leaks and repair as need be.