How to Clean a Car Carburettor
While all gasoline engines now have an electronic fuel injection system, many cars prior to the 2000s are powered by one or more carburetors, single or double-barreled.
Although the fuel system is equipped with several filters, some deposits eventually accumulate at the bottom of the carburettor’s constant carburettor tank. If they are too large, they may partially or completely block one of the nozzles and thus impair the running of the engine. The carburettor must then be thoroughly cleaned.
Removing the carburettor
On most cars, the air filter has to be dismantled before the carburettor can be accessed. There are as many modes of fixing air filters as there are types of cars, so the best way to find out is to check your maintenance booklet.
Once the air filter is disassembled, remove the return spring from the throttle control and detach the control, which may be by cable or rod . It is also necessary, of course, to remove the fuel supply pipe, generally engaged on a brass pipe. Note that on some cars, it is also necessary to remove the small rubber hose bringing the vacuum prevailing under the carburetor butterfly until the capsule regulating the advance. The latter is located on the side of the body of the ignition distributor.
The last operation, of the simplest, consists in dismounting the two nuts of the flange of fixation of the carburetors on the intake pipe. Most single body carburetors are held by two bolts, while double bodies usually have four, whether horizontal or vertical. Always take a suitable step wrench to avoid damaging the bolts (eg with a pliers).
Disassembling the carburettor
Before starting to disassemble your carburettor (s) it is absolutely essential to clean them externally . Indeed, a layer of sludge and dust accumulates with the kilometers on the body of the carburettor; and if you open it without precautions, you risk penetrating foreign objects inside, which is the opposite of what you are trying to do. To clean the exterior, there are some aerosol products that are very effective but relatively expensive. If you want to save money, the best way is to use gasoline with a brush. Fill a small container and place the carburettor in it, the petrol will begin to dilute the layer of sludge, while you will fine-tune the cleaning with the brush. Only when the carburettor is completely clean will the dismantling start.
On a conventional carburetor with fixed nozzles, the the tank is generally held by small split-head screws that simply need to be removed for access to the carburettor interior .
Cleaning the lid elements
The cleaning operation will begin by removing the inlet filter from the tank. This small copper filter is usually located underneath the fuel inlet pipe and is housed in a brass blind plug which will simply unscrew. Clean the filter in a clean gasoline bath and do the same for its plug at the bottom of which deposits accumulate. Then replace the filter in its housing and screw the plug back in place. Clean the float well .
The needle that regulates the supply of petrol is also in the tank lid. Disassemble it to examine its condition and to see if any deposit does not interfere with its proper functioning. The air inlet of the carburettor should be cleaned with a wire brush and petrol as the black deposits formed are quite difficult to remove. If this input has a starter flap, it must also be cleaned while ensuring that it rotates freely on its axis .
Also in the lid there is a small diameter passage from the joint plane where it communicates with the take-up pump to a thin copper pipe leading into the air inlet of the inlet. Check that it is not clogged and that its ends are perfectly clean. A clogged recovery pump passage leads to a “hole” at acceleration.
Cleaning the carburetor body
All the elements secured to the lid are now clean, and you can take care of the body of the carburettor. Examine the bottom of the tank very carefully, as this is where the deposits tend to accumulate. Several forms of deposits are found, either a very fine brown deposit which consists of tiny particles of rust from the oxidation of the fuel tank; a whitish deposit that forms when the car remains stationary for a very long time.
In the first case, simply clean the bottom of the tank with a brush and petrol to remove the traces of rust while in the second case the work will be more difficult, for it will then be necessary to scratch the bottom of the tank firmly with a wire brush or iron wool to get rid of the whitish deposits. The more you leave your car stopped in a wet place, the more these deposits will tend to form quickly. The nozzles may be partially or totally obstructed by these deposits; so they must be cleaned. But without using any metallic objects that might distort the bore. If they are really too dirty, the best solution is to replace them.
Note, however, that if you use your car every day, it is unlikely that this kind of deposit will be formed. As for rust deposits, they only begin to form when the car has reached a certain age, which varies according to the quality of each vehicle. The problem is that unfortunately we can not stop the phenomenon, and it will be necessary to think to clean its filters and its carburetor frequently. There will however come a time when your tank will start to run away, pierced by oxidation. It will then have to be replaced.
Cleaning the nozzle and venturi
Since the constant level tank and the nozzles are cleaned, it is now necessary to clean the nozzle and the venturi of the carburetor body always using iron wool and brush applied petrol. It will also be necessary to think of the different jets located outside the body, unscrewing in the form of a hexagonal bolt (Solex).
Cleaning the recovery pump
An essential element remains the recovery pump. It may be in the form of a brass piston sliding in a bore along the constant level tank in the body of the carburettor (Weber); or in the form of a membrane actuated by a rod secured to the throttle valve (Solex). In the first case, it is sufficient to remove the piston and to look at the bottom of its housing to ensure the cleanliness of the whole.