1.WHAT CAN I DO IF CHOKED AIR SUPPLY TO CARBURETTER .
Problem: Generally sluggish running and excessive consumption of petrol. Sometimes accompanied by black smoke from the exhaust, and sooty plugs.
Remedy : See that the carburetter gauze is clean and the air supply unobstructed. If the fault is structural, which will not be the case in a good design, try a spare carburetter jet, and (beginning with it very small) slowly enlarge it until better running is obtained. If no success is met with, replace old jet. Do not tamper with the original jet. See that the induction pipe, where it envelops the exhaust pipe, has not become loose and fallen on to the exhaust pipe so as to restrict the openi
2.WHAT CAN I DO IF COMPLETELY CHOKED AIR SUPPLY TO CARBURETTER. Unlikely except where the carburetter has been intentionally tampered with.
Symptoms : Engine will not run at all except where simultaneously with the fault a large leak has opened into the induction pipe, as, for instance, where a flange has come loose and has allowed a leak of air through the flange, whilst at the same time completely blocking the intake by allowing the induction pipe to fall on to the exhaust pipe. Will show flooding of the jet chamber, possibly one or two explosions at starting, and then complete stoppage.
Remedy : See that the carburetter gauze is clean and the air supply unobstructed. If the fault is structural, which will not be the case in a good design, try a spare carburetter jet, and (beginning with it very small) slowly enlarge it until better running is obtained. If no success is met with, replace old jet. Do not tamper with the original jet. See that the induction pipe, where it envelops the exhaust pipe, has not become loose and fallen on to the exhaust pipe so as to restrict the opening.
3.WHAT CAN I DO IF CHOKED JET OF CARBURETTER (completely choked). This is not usual ; the jet is usually only partly choked.
Symptoms : Complete stoppage of engine, and will not give a single explosion after flooding. Will be obvious on examining jet and flooding carburetter, as no petrol will flow.
Remedy : Clear jet carefully, not with a steel instru- ment, but with a stem of grass or a broom bristle. Choked jet of carburetter (partly choked). Symptoms : If very slight causes loss of power, pro- bably accompanied with popping in the carburetter. Under these circumstances the obstruction will be scarcely visible to the naked eye, and can be easily overlooked. If more complete, engine stops, and after tickling or flooding carburetter, engine starts up and takes one or two revolutions, and stops again. The appearance of the stream from the jet on flooding carbu- retter will indicate chokage, as stream will only just show instead of leaping up two or three inches. Remedy : Same as in last paragraph, but obstruction can often be blown or shaken out (on to the back of the hand preferably, as this admits of its being examined, and the nature of the obstruction may enable precautions against a recurrence to be taken) . yatricar.com has known one case of a four-cylinder engine fitted with an ordinary mushroom auxiliary air valve, where a choked jet acted precisely as a governor. The engine would run up to about 600 revolutions with the throttle open, and beyond that it would not go at all, though it appeared to have plenty of power below this point. The reason of this action is not very obvious, but there is no doubt about the facts being as stated. There was no sign of popping in the carburetter or of unsteady running.
4.WHAT CAN I DO IF CHOKED AIR VENT OF GRAVITY FEED PETROL TANK.
Symptoms : Engine stops on the road through lack of petrol. Usually stops pulling for a few yards, pulls again apparently all right for a little while, fails again, and finally stops. These are the general symptoms of failure of petrol. Usually there is no intermediate state ; the engine is either pulling all right, or not at all. If float chamber be examined (by the position of its spindle) immediately engine stops it will usually be found empty If the obstruction to the vent is permanent, the float chamber will not fill again ; but if it be due to a cushion pressing on the vent (or similar cause), it is possible that the removal of the driver’s weight may cause it to clear, and the float chamber will fill at once. In all such cases, if suspected, it is well to turn off petrol immediately on the engine stopping, and then examine float chamber.
Remedy : See that the air vent in the tank cannot be obstructed. A small piece of stick laid across it will often be effectual in keeping a leather cushion off it.
5.WHAT CAN I DO IF CHOKED PETROL PIPE, FILTER, OR TANK OUTLET.
Symptoms : The same as with a choked tank vent, but in case of a choked filter the engine is sometimes starved for petrol before complete failure takes place, and “popping” may be noticed. This failure may be distinguished from a choked jet by the engine running much longer on restarting, as the float chamber will have leaked itself full, and on this the car will probably travel from 200 yards to half a mile.
Remedy : To locate, uncouple the union under the float chamber, and note the flowof petrol. This should be a steady stream the full bore of the pipe. If the flow is of this nature, the stoppage is not between this point and the tank, and must be sought in the float chamber or its admission port. Therefore, see to balance weights, float, and spindle. If the flow of petrol is only a dribble, uncouple a union further back, preferably the filter (if there is one) , or perhaps, better still, examine the filter at once if at all easy to do. If this shows a steady flow, the fault is between the first and second points examined ; if this also shows a bad flow, the obstruction is nearer the petrol tank, and the tank union may be examined, and so on. To remove : A long piece of wire will be the best way of clearing a pipe as a rule, but should this not be available, the pipe may be taken out and made nearly red hot for some time (provided it is not soft soldered) ; and if the obstruction is combustible, as it often is, it may afterwards be washed out. Where a filter is found full up with bits of fibre, hair, petrol, tin, paint, etc., and this trouble is of frequent occurrence, it is a fair proof that carelessness obtains in filling the tank, or a funnel without a filter is being used.