Virtual Mechanic

PURPOSE
The fuse box is designed to hold fuses and relays and there may be several of these around the vehicle.  It’s always a good idea to keep a few spare fuses, just in case.

THINGS TO LOOK FOR
When checking the fuses, it’s best to check the fuses with a test light and don’t rely on the fuse index map indicating where the fuses connect as they may be incorrect.  What is meant by the map is that sometimes when you pull the fuse cover off  you have an index on what the fuses represent eg. wiper blades, wiper motor and you go to check that and it is not the wiper motor fuse.  The wiper motor fuse is in another location.  The most important thing is replacing the fuse with the same amperage.  Also the fuse may look okay but it may not be okay.  The only way to check or test a fuse is with a test light with the ignition on and the engine off.

IS IT EXPENSIVE TO REPAIR?
Replacing a fuse is an easy task if it is a low amperage fuse up to 30 amps but if it is a high amperage fuse it may require a 6, 8 or 10 mm ring spanner to remove it and repair it.  The most important thing to remember is if the fuse breaks when you replace it, it is showing a definite short in the system.  This needs to be attended to ASAP.  Putting a higher amperage fuse in will only load up the wiring and may lead to a more expensive repair as the wiring may melt or be damaged.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The computer or ECM [electronic control module] or ECU[electronic control unit] is designed to manage the fuel system, ignition system, and depending on the design, it also manages the automatic transmission as well as turning on the air conditioning.  The computer is programmed to collect information and make about 11,000 decisions every minute.  It may also store fault codes for the technician to decipher and rectify problems as required.

THINGS TO LOOK FOR
The computer is located in a cool position away from the foot, usually around the passenger’s floor behind the kick panel or under the passenger seat.  The main cause for a computer breakdown are dry solder joints.  This may cause the engine to cut out, idle rough, non start or have poor fuel economy.  Another cause for computer breakdown is jump starting incorrectly and an open circuit battery.  These are enemies to the computer and need to be avoided at all cost.

IS IT EXPENSIVE TO REPAIR?
The average price of a computer will cost around $500.00 depending on the make.  It is possible to purchase a reconditioned computer from your local spare parts retailer for around $300.00.  When you purchase your computer make sure you receive a receipt and a warranty.  If you buy from the wreckers they may sell the unit without a warranty and it might not operate.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
Electronic fuel injection [EFI] is designed to manage the fuel system and inject fuel into the combustion chamber.  There are several types of EFI eg group injection, sequential injection.  All injection systems are designed to offer 95% fuel economy in normal operating temperatures.

THINGS TO LOOK FOR
Any EFI will suffer if the fuel level runs low.  This being a main focus as this will cause the EFI to fail. Because the fuel operates on pressure and when the fuel level is low there is a possibility of mixing air with the fuel thus creating a power loss. As the fuel system operates on fuel pressure it is easy to see if fuel leaks become apparent.  If the fuel is leaking, turn off the engine ASAP and, at this point, if a rubber hose is split around the injection rail it may be difficult to spot and get.

 
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The fuel pump relay is designed to switch the fuel pump on with a low voltage.  At the same time the relay is a heavy duty switch making it possible to switch on and off without wearing out the switch or preventing arcing in the switch.  A fuel pump relay is designed to switch off if overloaded.

THINGS TO LOOK FOR
When the fuel pump relay seems to be getting warm to hot, this indicates that it is either being overloaded or becoming faulty.  A hot relay is a relay in trouble.  Apart from being hot it may show physical signs of slightly melting around the terminals.  This may be the effect of the cause and the suspect cause being the fuel pump overloading the relay.  If caught early this can prevent a breakdown.

IS IT EXPENSIVE TO REPAIR?
Changing a relay is easy but the cost may range from $8.00-$120.00.  Therefore it is important to check with your auto electrician to make sure it is the relay and not something else causing the relay to malfunction.

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
If your relay is a common type it may be swapped with an air conditioning relay as they should both be identical, specifically for common type vehicles.  A common type relay may be bypassed as a more complicated type may be bypassed by both but it’s worth trying.  If you want to swap the relays over, make sure that they’re of the same amperage.  You should see 30 amps or 60 amps or 80 amps. They’re both either the same quantity of terminals or voltage or amperage or colour.

 
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The fuel pump fuse is designed to operate within a specification of between 10-15 amps and will break when it’s overloaded.  A fuel pump fuse continuing to break is not the fault of the fuse but is designed to protect the wiring looms in the fuel pump circuit.

THINGS TO LOOK FOR
A breaking fuel pump fuse could be an indication that it is being overload.  This may also happen when running out of fuel.  A fuse breaking more than once a year is a fuse letting you know that it is being overloaded and must be attended to.
IS IT EXPENSIVE TO REPAIR?
the fuel pump fuse costs only 50 cents but the cause may be a short circuit in the wiring of the fuel pump.  This may require the services of a good auto electrician.

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
If  you’re on the road and the fuse has blown it is usually 15 amps.  At your risk you may try 20 amps but this is only a temporary repair as the wiring may overheat costing you more than just a pump.  If the 20 amp fuse blows, protect the wiring and call a tow truck.  It’s a bigger problem than just a temporary repair.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The air flow meter is a component to allow the velocity of air through it and at the same time it measures the air passing either by a hot wire or a flap connected to a potentiometer.  This value is sent to the computer indicating the quantity of fuel required.  If the air flow meter is a hot wire type it also has a self cleaning process to keep the wire clean from the value interference.

THINGS TO LOOK FOR
The main thing to affect the air flow meter is the large ducting connected to the unit. Also any vacuum leaks will affect the air flow meter value.  A potentiometer may wear its contacts causing a possible flat spot or non start.  Its enemy is a backfire as this will twist the flap making it impossible to move freely.  A quick perusal will determine if the flap is twisted after a backfire thus requiring replacement.  The hot wire type may break, the wiring causing a non start.  The hot wire also has a self clean program.

IS IT EXPENSIVE TO REPAIR?
Either air flow meters are expensive to replace costing around $600.00 depending on the make.

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
Most common types of air flow meters are now reconditioned costing around $300.00.  Make sure you keep your receipt in the Virtual Mechanic folder, as air flow meters do play up from time to time.

 
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The EGR valve is design to recirculate exhaust gases but only after idle and before full throttle.  The EGR valve operates mainly on cruising. 

THINGS TO LOOK FOR
Over time the EGR valve may be responsible for poor idle.  EGR valves are sometimes difficult to pinpoint as being the perpetrator of a poor idle.  A quick inspection to see if the needle is moving or if any exhaust gases are coming from the valve may be determined by an electronic fuel injection specialist.
 
IS IT EXPENSIVE TO REPAIR?
The EGR valve can be expensive.  You can try the wreckers but nine times out of ten a new EGR valve is the best way to go as the second hand EGR valve would usually have been on the engine from when the vehicle was new.

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
Most EGR valves are not serviceable.  The EGR valve is specifically designed to eliminate or reduce exhaust gasses entering the atmosphere.  Tampering with an EGR valve may incur fines.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The throttle body position sensor is designed to send a value to the computer to allow the correct mixture of fuel required on that specific value.  The TPS is as a butterfly only it is an electronic butterfly that also sends a signal back to the computer on its position.  The TPS will suffer from clogging up as it has fine circuits or holes around the closing points on one side.  On the inlet manifold side of the butterfly it may be seen as being very dirty.  This must be serviced at least every 50,000kms to ensure a consistent idle.

THINGS TO LOOK FOR
The TPS is a component that should be serviced and an examination will determine its effectiveness.  A check inside the TPS will show a butterfly and on the other side of the butterfly if any muck or, blackness has built up around the venturi, this should be cleaned out with a rag and made spotless as this could affect the idle control.  The difference between a good idle and a poor idle is a clean TPS.
IS IT EXPENSIVE TO REPAIR?
The TPS rarely goes wrong except for the electronic potentiometer, attached to the TPS throttle, may malfunction or the contacts may fail or it may have a flat spot.  These are best calibrated and checked by your local auto electrician.  If the prices quoted for the TPS or the throttle positioner switch is a bit expensive, try the wreckers.  Remember to keep the receipt as the TPS is another component that could go wrong after it has been fitted.
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The cold start injector is designed to inject extra fuel when the engine is cold.  This is manipulated by the computer and also by the temperature sensor unit.

THINGS TO LOOK FOR
The cold start injector may leak or malfunction.  An indication of these problems is a hard to start in the morning.  Cold start injectors like other injectors should be ultrasonically cleaned at around 150,000km intervals for the best performance.

IS IT EXPENSIVE TO REPAIR?
A cold start injector is fitted to the vehicle in a different way to the normal injectors therefore it will be a little bit more expensive but ultrasonic cleaning is highly recommended first.

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
Cold start injectors are either cleaned or replaced.  But remember if the cold start injector is not working there may be another component interfering with the cold start injection program.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The injectors are designed to inject fuel and when the fuel injector is energised it should spray fuel.  When this happens the combustion chamber will burn it correctly.  Injectors usually run well for 150,000kms then they should be checked or ultrasonically cleaned to be sure that they are not gummed up and are spraying effectively.

THINGS TO LOOK FOR
It is very difficult to check an injector when fitted to the engine.  One of the indications of a faulty injector is that the vehicle is hard to start in the morning.  This may be the fuel injector leaking or the spray pattern may be causing poor economy or poor performance.  These symptoms are usually noticed at around 250,000kms.

IS IT EXPENSIVE TO REPAIR?
Fuel injectors are not cheap at around $30.00-$40.00 each. 

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
Fuel injectors are repairable in that they can be ultrasonically cleaned, spray tested and pressure tested to be sure that they hold the pressure and not leak under pressure.  These tests are performed by a specialist fuel injection service.  It is important to get a before and after report to prove that there was a difference made when the injectors were cleaned.  The fuel injector may also have a fuel injection cleaner poured into the fuel tank.
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009