November 24, 2011 at 3:03 pm
filed under Car Care, Uncategorized
Tagged battery, brakes, car care, car maintenance, engine, fuel, gears, handling, performances, windscreen
Whether you are in a hurry or simply going for a quiet drive, nothing is more frustrating than a car which refuses to start or an enforced stop while you are en route. Finding the fault can be a lengthy and grimy undertaking, and calling out a garage or a recovery firm can be expensive if you do not already have the protection of breakdown club membership. However, many roadside faults are relatively easy to diagnose if you think logically and spend a little time trying to locate them.
For example, the symptoms leading up to an engine failure are very important when you attempt to make a diagnosis. If misfiring was evident just before the engine cut out, an ignition fault is indicated. Alternatively, coughing or spluttering point to the likelihood of fuel starvation.
This article is designed to help you locate some of the more common causes of roadside breakdowns, and illustrates how to carry out repairs that will enable you to drive home, or at least to the nearest service depot.
By far the biggest single cause of rough running or failure to start is a fault in the ignition system. If your car’s engine spins briskly but refuses to fire when you operate the starter motor, check first that all the electrical connections are tight, especially those at the coil, distributor and spark plugs. If these are satisfactory, the next step is to check that there is a spark at the plug electrodes. To do this, remove one plug, re-connect it to its lead and then rest it so that its body touches a bare metal component and is therefore earthed. Turn the engine by operating the starter setting. Tighten the base plate screw carefully so that you do not disturb the setting.
If the engine still refuses to start, check the faces of the points. Use a piece of fine-grade wet and dry paper, folded so that both external sides are abrasive, to saw between the points faces. If you do not have any abrasive paper, a metal nail file or an emery board can be used instead. If you succeed in starting the car using cither of these methods, make sure that you fit a new set of points as soon as you can.
On cold, misty mornings, the most common cause of failure to start is moisture on the spark plugs, electrical leads and distributor. One cure is to dry the components with a clean cloth or paper towels, but the easiest method is to spray the units with a proprietary water dispersant such as WD-40.
Motor; if the plug is in good condition a healthy spark should be visible. If there is no sign of a spark, the fault probably lies in the contact breaker (CB) points.
To check these, remove the distributor cap and then rotate the engine on the- starter to verify that the points open and close as they should. If the gap between them appears minimal, it may be the cause of the trouble. Widen the gap to the correct clearance by loosening the screw in the base plate and prising the points apart, making sure that the heel of the operating arm is on one of the distributor drive-shaft peaks. If you do not have a set of feeler blades, you can obtain an approximate gap by using a standard visiting/business card, which are usually about 0.3 mm (0.015in) thick—the most common gap.
Misfiring followed by the engine cutting out may be due to a cracked distributor cap which is allowing the high-tension (HT) current to leak to earth. The cap will have to be replaced as soon as possible but you may be able to effect a temporary repair by first scoring down the line of the crack with the point of a penknife or small electrical screwdriver and then across the crack at intervals of approximately 6 mm (l/4in) to interrupt the path of the leaking current.
A faulty coil can also be a cause of non-starting. To test the efficiency of your car’s coil, if you have a test lamp , remove the low-tension (LT) lead from the distributor and connect the lamp to the terminal and earth. With the CB points open, switch on the ignition and the bulb should light. If it does not, repeat the test on the other LT lead which comes from the ignition switch. If the bulb then lights, the coil is faulty and will have to be replaced.
If no current is coming from the ignition switch to the coil, you can bridge across direct from the battery to the coil with a length of wire. It may be that if no current is coming from the ignition switch, the starter motor will also be affected and will fail to turn. The starter can be operated manually in two ways. If there is a rubber button on it, pressing it firmly will over-ride the solenoid and the starter should turn. If there is no button, you can bridge across the solenoid’s terminals with a screwdriver with an insulated handle. If you do this, be careful not to let the screwdriver touch any part of the car.
It is possible for a solenoid to stick, thus preventing the starter motor from turning, and if you have a pre-engaged starter motor where the solenoid is mounted on top of the motor, try tapping it sharply with the handle of a screwdriver.
If nothing at all happens when you try to start the engine, it is most likely that the battery is not supplying any current. This can be due to several reasons. First, the battery terminals may be dirty or loose, so check that this is not the case. More serious is the possibility that the battery is exhausted. In the second instance the battery will probably have enough power to illuminate the car’s lights but you should notice that their beam is weak and yellow rather than bright in output. If this is the case, you will need to enlist the aid of an assistant, his car and a pair of jump leads to start your car. When using the leads, ensure that you connect the batteries positive (+) to positive and negative (—) to negative. With the leads connected, your assistant can start his car and keep it at a very fast idle while you start your car. Once your car starts, maintain a fast idle so that your car’s battery will receive a charge from its own generating system (this is more important with a car which has a dynamo as a generator than one which has an alternator as the latter charges the battery at low engine speeds anyway).
Although not directly connected to the ignition system, when nothing happens when you try to start the fault could be a starter motor which has jammed in mesh with the fly-wheel starter ring. It is sometimes possible to remedy this by putting the car in first or reverse gear and, with die ignition switched off, rocking the vehicle vigorously to and fro. In some cases the starter motor will have a squared end protruding from the motor body. By fitting an open-ended spanner on this you can turn the motor and free it. If neither of these methods work, loosen the starter motor retaining bolts (there are normally two), and move the motor out of mesh manually.
When an engine will not start despite good sparks at the plugs, a fuel problem is indicated. Tracing faults in the fuel system is simply a matter of following the path of the fuel from the tank to the engine until you locate the cause of the problem.
Begin your fuel line fault finding by checking that there is actually some petrol in the tank (do not rely exclusively on the fuel gauge to determine this, as it may be giving an incorrect reading). Next, slowly unscrew the petrol tank filler cap listening as you do so. If you hear air being sucked into the fuel tank, it means that the tank’s breathing system is blocked and a vacuum has been formed in the tank to the point where the fuel pump cannot draw any more petrol out. If your car’s fuel tank breather is blocked (it normally consists either of a small hole in the filler cap or a small pipe leading from the petrol tank to the open air) it must be cleared to eliminate the vacuum.
If the problems above are not applicable to your car, fuel may not be reaching the carburettor. To check this, remove the fuel pipe supplying the carburettor and activate the fuel pump (by turning the engine on the starter with a mechanical pump or simply by turning the car’s ignition on with an electric pump) which should result in fuel being emitted from the pipe. If there is no fuel flow it is probable that the fuel pump is faulty. Electric pumps can sometimes be stimulated into action by tapping them sharply with the handle of a screwdriver but if this fails the only remedy, as with mechanical pumps, is to strip the unit (consult your OTR index for details concerning the overhaul procedure for the various types).
When your tests show that fuel is reaching the carburettor and that the ignition is functioning properly, it is likely that a fault in the carburettor is causing the trouble. With most carburettors, removing the float-chamber is not difficult. A full chamber means that you have flooding problems (the smell usually betrays this even before you take off the float-chamber lid) in which case the spark plugs will be wet and will not fire. Dirt under the needle valve is a common cause of flooding but it is not difficult to unscrew the valve and clean the seat.
The float-chamber should be cleaned with non-linting cloth or a paper towel. Never try to clean jets by poking them with a pin or piece of wire; use either a bristle from a brush or blow through them.
If you strip down a carburettor at the roadside, store the parts carefully so that they can be replaced in the right order. Take special care when dismantling because some carburettors have spring-loaded accelerator pumps with a ball, and this can easily be lost.
If a car with a fixed-jet carburettor such as a Zenith or Ford unit runs roughly, stalls and refuses to re-start, the choke flap may have stuck in the closed position after a cold start. By working the operating lever you should be able to cure this without any dismantling.
A rare fault is fuel vaporization which only occurs in very hot weather. The cure here is to let the engine cool completely and when you re-start, to move the heater controls to “hot”. This may be uncomfortable for you and your passengers but it will lower the running temperature and can prevent recurrence.
Another unusual carburettor malady is icing up. This may happen in cold misty weather, causing the engine to cut out when the build-up of ice in the carburettor intake restricts the air flow. Left to itself, the engine heat will melt the ice which will pass into the inlet manifold and be steamed out of the exhaust pipe after re-starting.
The most common cause of overheating is a broken fan belt but warning should be given of this as the ignition warning light will come on. Although many cars are now fitted with electric fans, the belt is also used to drive the water pump and if this is not working water will not circulate properly and overheating will result.
If you do not have a spare fan belt with you, try the traditional makeshift repair of using a stocking or half a pair of tights. Tie the stocking around the crankshaft and water pump pulleys only to lighten the load. If the battery is fully charged you can drive quite a distance without the need for charging, the range depending a good deal on whether or not you have to use lights or other electrical equipment.
If you notice the temperature gauge reading higher than usual for no apparent reason, stop and check the cooling system. The first thing is to test the filler cap after allowing the engine to cool slightly. Protect your hand with a piece of cloth and undo the cap a quarter turn, and be careful of steam escaping in case it scalds your arm. As you undo the cap you should hear a slight hiss. If you do not, the spring on the cap is too weak or the sealing gasket has become perished, and the correct pressure is not being maintained. On cars which have sealed systems, the spring-loaded cap is on the expansion tank.
Having relieved the pressure, take off the cap and check the coolant level which should normally be about 25 mm (lin) down from the base of the filler orifice. In a sealed system, the level in the expansion tank should be about 65 mm (2iins) up from the bottom, but there is normally a mark to indicate the correct level.
If the level is down, check for leaks. Water seeping past hose clips can usually be prevented by tightening the clips while a split hose should be wrapped in insulating tape to form a repair. Small radiator leaks can be stopped by using preparations such as Bars Leaks or Rad Weld. Water coming from the water pump spindle shows that the gland has deteriorated and a new water pump will be required.
Thermostats seldom stick in the closed position but this can cause severe overheating. A tell-tale symptom of this is a loud thumping noise coming from the radiator caused by steam bubbles being forced through the bottom hose. To cure this, let the engine cool, take out the thermostat and drive home without one. Fit a new one as soon as possible.
A blown head gasket is also a cause of overheating and announces its presence by engine misfiring, loss of power and, of course, a rising temperature gauge. Earlier symptoms are finding water globules on the dipstick, oil in the radiator water, or both. There is nothing you can do as a roadside repair to remedy this. Simply allow the engine to cool and then drive slowly to the nearest garage.
If one of your lights become dim, the fault is usually a bad electrical connection, especially an earth connection. This applies particularly when only one light is affected. If all the lights are affected, the cause is more likely to be the battery. Either it is not receiving sufficient charge or the connections are loose and, probably dirty. Where the battery has lost power, first check the tightness of the fan belt. Assuming the belt is adjusted correctly, the generator is probably not charging properly. It is not recommended that you try is a short somewhere and if you still cannot find it, do not use that circuit until it has been traced otherwise there could be the danger of an electrical fire.
Diminishing oil pressure or the warning light coming on when the engine is ticking over could be due to a low level in the sump so that is the first thing to check. It could also be due to a worn oil pump but in this case it should have been apparent as decreasing pressure over a long period. You cannot repair an oil pump by the roadside but keeping the level in the sump on the high side will help.
Most engines will leak some oil as they grow older but excessive leakage should be investigated. If it is possible to let the car stand overnight with newspaper spread under it, you will be able to spot the places from which the oil is leaking. Curing lubrication faults is seldom a job to tackle at the side of the road; it is better to wait until you have time and reasonable conditions to work in.
Vibrations, especially when they can be felt through the steering wheel, are frequently caused by loose wheel nuts or front wheels which are out of balance or have been damaged by hitting a kerb. Checking for balance requires the use of a balancer but if a wheel is damaged or a tyre has a bulge in it, change to the spare.
A similar symptom can be a wheel bearing which is about to fail. To check, jack up each front wheel in turn and try rocking it in the vertical plane—any excessive movement at the hub means bearing wear. If you opt to drive to a garage, do so slowly avoiding sharp braking or acceleration and taking special care when cornering.
Roadside repairs on an alternator unless you are fully competent, but with a dynamo the trouble may be little more than a sticking brush or a dirty commutator. Getting at this does mean stripping the unit but it is not a difficult job.
Sudden light failure is usually due to a blown bulb but total headlight failure may be a blown fuse. Check first for obvious shorts were, for example, a wire has chafed on bare metal, before replacing the blown fuse, otherwise a new fuse will also be destroyed.
A slow indicator flashing rate often indicates a battery in a low state of charge, especially if this happens when engine revs are down. It can also mean bulb failure as can fast flashing or just a single flash from the light on the fascia.
In the unfortunate event of a collision, a wing may be pushed back so that it fouls a wheel. If you have no lever with which to pull the wing clear of the tyre so the car can be driven, the jack may be of help. If you wedge it between a solid part of the car—not the steering which might be damaged—and the damaged metal and then wind it open, you can usually force the damaged part free of the tyre.
In the event of damage to the rear it is often the rear light clusters that suffer. Legally, the only white light you may show at the back is a reversing light so if a brake light lens is broken, you should cover it with a piece of red material. Daubing it with lipstick is another emergency measure.
If a door has been damaged so that it won’t shut properly, open both windows on the same side (four-door cars) and tie the two doors together around the top of the door pillar then close the windows as far as possible. With two-door cars, you will have to find something like a grab handle to which to secure the damaged door.
Remember that whatever type of make-shift repair you carry out, in no circumstances should you attempt to drive a car which is in any way likely to be dangerous. In this connection, bodywork damage which has ragged metal edges could be held to be a danger to other road users and, therefore, illegal.
In theory, a well maintained car should never break down but the unforeseen can happen and the emergency repairs described are intended to help you to get home or to a garage. Remember though, that the repairs are an emergency measure and as soon as you are able you should effect a complete, permanent repair that will allow you to drive in full safety once again.
Useful equipment:
Insulating tape
Torch
Penknife
Warning triangle
Fine grade sandpaper
Plastic container of water 2-24 m (6-8ft) of 28/.012 wire
Roll of kitchen towels
Tow rope
Jump leads
Foot pump
Water dispersant spray
Spares:
Fan belt
Bulbs for headlights, stop/tail, indicators (one of each) Radiator top hose
Contact breaker points
Sparking plug(s)
Fuses
What to carry with you
A basic tool kit should consist of: 0.7 kg (llb) engineer’s hammer A set of five open ended spanners Medium screwdriver Electrical screwdriver Cross-head screwdriver Circuit tester
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