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  1. Why diesel engines smoke and what that means for servicing them or possibly failing your next WOF.

    To let you "observe" when your diesel engine is saying "I need attention" I've brought together some basic views from those in the industry. The colour of engine exhaust fumes can often be a good indicator of engine condition, power output and economy. Even an engine in excellent condition will give off some visible fume due to the nature of diesel engines. However if it is excessive, you may be able to "read" what is ailing it by determining its exact colour.

    Diesel engine exhaust colours commonly seen are black, grey, translucent purple/blue and white or white/blue, these are commonly recognized as resulting from the following engine complaints.

    Too much excess diesel exhaust fumes and you could find yourself with a failed WOF

    Black smoke

    Or unburnt fuel in the exhaust system is commonly observed when powering up a hill. As the throttle position increases more fuel is injected into the cylinder faster than more air is inducted. This over rich mixture produces black smoke, which is acceptable on maximum throttle, but not otherwise. An over-fuelling injector pump will have the same result. Economy and engine life will be reduced. Black smoke can be the result of worn injector nozzles.

    If the spray pattern is imperfect the fuel does not atomise and the tiny droplets of fuel are too big to be completely burnt in the parcel of air which surrounds them. The air-fuel mixture then continues to burn down the exhaust pipe, power and fuel economy being lost. In a normally aspirated diesel only the fuel burnt in the cylinder before the exhaust valve opens will contribute power to the engine. Another cause of black smoke can be airflow restrictions such as a dirty air cleaner or insufficient airflow into the air cleaner.

    A side benefit of a snorkel fitment is the increased fuel economy, up to 15% depending on the model, the economy being derived from increased airflow"

    Cloudy white smoke

    Indicates incorrect timing or low engine compression. If the timing is retarded or advanced, ie the fuel is injected before the piston and valves are in the correct position, then this could be the injector pump incorrectly aligned or timed to the crankshaft so it delivers the fuel to the injectors either early or late. Or the injectors may have low opening pressure.

    With low opening pressure the fuel enters the cylinder before the maximum pump pressure is realised resulting in poor atomisation of the fuel, and it occurs so early that the air is below maximum temperature.

    With injection timing: Optimum timing = maximum air temperature = most efficient burn of fuel = maximum power

    Blue or grey smoke

    Can indicate a governor diaphragm problem. If the diaphragm is perforated it fails to control the rack and governor.

    With continued high rpm the rack moves to a high fuel supply position. When the throttle is quickly released the rack reacts slowly (due to the perforation) and the pump continues to supply fuel at the high rpm rate but the air is reduced quickly as the throttle was released. The blue/grey smoke is unburnt excess fuel.

    Translucent purple-blue smoke

    When starting first thing in the morning is unburnt fuel. This unburnt fuel may be the result of the glow plugs not preheating the fuel sufficiently or a timing issue.

    Light black smoke

    On starting the engine with no movement of the throttle. If with each repeated start-up, say 5 start and shut off's in quick succession, there is a puff of light black smoke it suggests the injector nozzle or pintle is worn and fuel is dribbling onto the piston top after the engine has stopped firing. This produces a hot spot on the piston top and will certainly reduce engine life.

    The radial clearance between the injector pintle and orifice is very small, between 0.02 to 0.05 mm. A deposit of only 5 microns thick can restrict fuel flow by up to 25%. Fuel gums, waxes and varnishes can easily build up on the critical surfaces of the injection system analogous to that of deposits of 'gunk' on the inside of human arteries. And we all know what that means!

    Water is the catalyst of injection problems. With water will come fungal growths, acids and corrosion. Water accumulates over time from condensation in the tank and can also enter the system with fuel. Use of a non-hydrocarbon based fuel system cleanser (Fuel Set) will mix with the water to carry it through to the injectors and finally be burnt. This maintains a healthy system but will not rebuild worn parts.

    Grant reckons most common repairs for an excessively smoking diesel engine are either failure to Service the diesel injectors after 100,000km or water in the diesel fuel or filter.

    All the above problems lead to reduced engine performance, engine life and fuel economy but please remember that diesel engines are extremely reliable and efficient when maintained correctly.

    If you are suspicious that your engine may have a problem then have the symptoms assessed by one of our diesel mechanics experienced with injection system problems

  2. G. Guy Motors has a professional workshop for servicing 4WD and non-4WD vehicles.

    In fact routine servicing, tune-ups and carrying out WOF checks for standard 2WD vehicles keep us very busy - you could say we're the one-stop-shop for all our customer's vehicle servicing needs, whether that's a specialist 4WD or a family sedan. Also as we are mta Assured - you can expect a quality service and great customer care.

    Electronic Fault Code Diagnostics

    We perform a full electronic fault diagnostic service using the latest engine and vehicle diagnostic computer scope. We use this to pin-point any problems you may have with your ABS, Airbags, Engine management or other computer control on your vehicle, a very useful service tool with all the computer-aided vehicles these days!

    So please remember, we don't just service 4WD vehicles - Also bring in your family car  for our full service treatment as detailed in our Service Check List

  3. Access to good quality offroad tracks is always a hot topic for discussion, particularly when 4X4 drivers see more and more land locked away from the hobby and sport.

    I'd like to share with you some good news about how well our hobby is served by clubs campaigning for all dedicated 4wheelers that appreciate access to our great outdoors. 

    In fact Wellington has a very active club, the Cross Country Vehicle Club. I'll leave you a link to their brochure for new members.

  4. We hear that question several times a week from prospective purchasers of new and used 4WD's

    We are happy to offer our experience to assist our customers make an informed choice when it comes time to short-list their vehicle options - but how do you really know the condition of a used 4WD vehicle?

    Get your next 4WD vehicle inspected before you buy!

    Our pre-purchase vehicle inspection service is a comprehensive mechanical inspection to enable you to gain the objective insight into the mechanical condition of a used 4WD so you know you're not buying a lemon. We are experienced in all areas of servicing and repairs for all makes and models of 4WD's. Our independent position enables us to give you an evaluation of the condition of the vehicle from an unbiased standpoint.

  5. For just about every 4WD vehicle make and model the 40,000km Service is a comprehensive preventative maintenance service that safe-guards your vehicle's future mechanical life.

    It is the only service where literally everything is inspected, everything adjusted that needs adjusting and all the oils and filters changed and fluids flushed.

    Both hubs and wheel bearings are stripped, cleaned and repacked with grease. All major transmission components are checked for wear, backlash, noise and feel, and all those tell tale sounds and driving characteristics spell out their story to an experienced 4WD mechanic.

    So what's the big deal?

    As a 4WD vehicle is not a 2WD - it has twice as many gearboxes and twice as many Diffs to carry or tow loads substantially more than any car could do without seriously stressing it. The preventative measures taken by performing a 40,000km Service so often wards off major repairs on vehicles and prevents major break-downs entirely.

    You'd be surprised just how much damage a little water can do while quietly sitting unnoticed in your wheel or Diff bearings, and you don't even need to be a tough-truck owner to suffer this damage. Many experienced 4WD drivers will tell you they learnt that lesson after going through too many avoidable bearing replacements.

    Many 4WD owners wrongly believe only deep water is a problem, but a single bogged wheel where the hub is below the water line is a typical situation to see a ruined bearing within weeks, not to mention water intake into the diff because the breathers don't stop the water from entering.

    If your wheel bearings weren't repacked in the last 40,000km and you drive offroad, I'd be expecting to see some signs of water entry

    Then why is the Service missed?

    Unaware first time owners of 4WDs

    They simply don't realise the Service is important until too late, treating their 4WD like their family sedan by expecting to Service it in a similar manner.

    Your routine inspection can be as simple as going through a 5 minute check-list to ensure your future trips will always be smooth and uninterrupted.

    Ownership of vehicles changes every 40- 80,000kms:

    The previous owner "leaves the 40,000km Service to the new owner" and it never gets done because the new owner assumes that it was done. The unfortunate fact is - it is extremely rare to find a used 4WD for sale that has received a complete major service.

    4WD owners that rarely go-off road don't do it:

    They often assume that their vehicle doesn't need it anyway or they'll get it done before their next big trip - maybe next year!

    Preventative maintenance on your vehicle is obviously a lot more involved than just taking the 4WD and getting it serviced. It also involves you taking on a routine of checking it for tell tale signs of issues or future trouble, especially after a day of offroad driving.

  6. If your 4WD has traveled more than 160,000 kms then have the transmission checked for any worn bearings.

    If you're not sure what worn bearings sound like then call in and we'll have a listen. Damage can quickly occur when bearings wear, producing minute particles of steel which move around with the oil to interfere with other components.

    Replacing the bearings before more expensive repairs are required makes good sense. Remember, prevention is better than a dead truck in the bush or a spoilt holiday

    In differentials it's common for the outer pinion bearing to become 'loose' or develop excessive free-play as a result of general wear and tear in the bearings. With thorough servicing it will be detected early and the bearing tension or pre­load 'can be adjusted correctly' to save further deterioration of the differential bearing surfaces.

    Landcruisers, Safari/Patrol and Hiluxes from 1994 to 1997 commonly require attention by now.