Auto Electrics Mobile Product Services Shropshire Tel 07703 558610


Diesel fuel injection engine diagnostics, Diesel Mechanic : Servicing & specialist repairs:

Breakdown mobile technician callout available to Shrewsbury, Shropshire & Mid Wales areas (subject to service van availability)


Diesel engine basic operating principle

Compression Ignition Diesel Engine

The four stroke diesel engine is a compression - ignition engine operating on the principle of air inducted through the engine intake valves sucked in by downward movement of pistons (induction stroke) then compressed on the upward stroke of the piston (compression stroke). During each engine piston compression stroke the air temperature increases to around 800 degrees centigrade. Diesel fuel is injected into the cylinder in precisely measured quantities as the piston reaches the end of the compression stroke BTDC . The highly pressurised injected fuel atomises as it mixes with the air and ignites ,causing the power stroke when the air fuel mixture combusts with an energy explosion which forces the engine piston downwards. Linear motion of the pistons uses connecting rods to cause rotation of the engine crankshaft and flywheel. Exhaust gas produced from combustion process is expelled through the exhaust valve as the piston rises on its exhaust stroke.

Fuel Quality, Fuel Contamination, and Fuel Filtration

Efficient diesel engine operation requires that mechanical diesel fuel injection equipment is maintained in good order and fuel is clean. All pipes and connections should be leak free to avoid diesel fuel leaking out of the fuel system and air being drawn in to the fuel system.

Diesel fuel contamination with other fluids, for example Petrol, Water,etc, or dirt is likely to cause damage to precision machined fuel injection equipment components leading to vehicle breakdown.


If the fuel tank has been inadvertently filled with incorrect fuel at the forecourt by mistake, such as Petrol put into a Diesel car, avoid attempting to start the vehicle as fuel system or engine damage may occur. Petrol does not have the lubrication properties of diesel fuel, and may remove protective coatings from certain high pressure components particularly in common rail fuel pumps, causing increased wear and deterioration of the fuel injection system.

A specialist industry ATEX approved fuel recovery company will have facilities to extract the contaminated fuel and purge the fuel system before the vehicle is refilled with the correct fuel.

Fuel Injection Component Supply

We supply a range of diesel fuel line equipment including :
fuel hose
sealing washers
Diesel fuel injectors
fuel pumps
diesel test equipment

Low Pressure Diesel Transfer Pumps

Low pressure diesel transfer pumps may be mechanical or electrical.
Diesel lift pump or primer pump moves diesel from fuel tank to high pressure diesel injection pump.

High Pressure Diesel Fuel Injection Pumps

Diesel fuel injection pumps operate at very fine tolerances to achieve high pressure, and require accurate calibration with highly specialised equipment.
Diesel injection systems are particularly susceptible to damage caused by use of incorrect or contaminated fuel.

Various types of high pressure diesel injection pump include :

  • Inline pump
  • Rotary distributor pump
  • High pressure Unit injectors combining pump and nozzle
  • Common rail injection pump
  • Mechanical Diesel Fuel Injectors


    Diesel fuel injectors are a key component in delivering diesel fuel into engine combustion chambers. Diesel fuel injectors spray diesel fuel at high pressure into engine combustion chambers to atomise the fuel air mixture. Periodic servicing / calibration of diesel injectors may prevent problems with engine misfire and uneven running, excessive exhaust smoke, etc. There is a variety of types of diesel injector depending on system type, for example , mechanical injector, common rail, high pressure unit injectors.

    Electronic Diesel Fuel Injectors

    Diesel injectors fitted to electronically controlled diesel engines often have specific calibration coding denoting flow characteristics.
    When replacement diesel injectors are fitted to an engine, the diesel control unit (dcu engine computer) may need to be informed as to which cylinder each specific coded injector is fitted by programming calibration information.
    We have computerised equipment enabling recoding of the engine control module when fitting replacement coded fuel injectors to common rail diesel engines

    Engine Cylinder Balance

    Correct, quiet and smooth engine running increases vehicle comfort and fuel efficiency.
    Smooth engine running requires even cylinder balance. Uneven cylinder balance may cause misfire which may be due to fuel pressure loss, faulty injectors, loss of compression, etc. and will cause excessive engine vibration,

    Diesel Service Parts Fitting


    We can supply & fit:
    Fuel filters, Filter heads, Lift pumps, Diesel fuel injection pumps, Fuel Injectors, Stop Solenoids (ESOS), Glow plugs, Heater plug relays, Cam belts, Diesel Diagnostics.

    Automobile diesel engine technology has progressed away from the association with sluggish performance, noise , and fume pollution, towards quiet running , fuel efficient ,low emission , high torque performance engines with sophisticated electronic diesel control.

    Reduced Diesel Exhaust Soot Emissions

    Low exhaust emissions and maximised performance requires diesel engine designs to use increased fuel injection pressures and precise control of the timing of  fuel injection in the engine operating cycle.

    Exhaust Gas Recirculation (EGR)

    blocked egr

    EGR systems are designed to route exhaust gases back in to the engine intake to reduce soot particulate emissions. EGR system problems may result from blockages due to build up of carbon, which in turn may be a result of a deteriorated fuel injection system or specific vehicle operating conditions. EGR system faults may cause difficult engine starting, running problems, and excessive black smoke particulate emmissions.

    Diesel Exhaust After treatment : Diesel Particulate Filters (DPF) ,Adblue, Eolys,Sintered Catalyst Reduction (SCR).

    Modern diesel powered vehicles include systems offering after treatment of exhaust gases by special filtration and chemical additive in the exhaust system to allow vehicles to meet strict european exhaust emissions legislation.
    The Diesel Particulate Filter or DPF forms part of the vehicle exhaust system containing a ceramic catalyst designed to reduce diesel soot emission.
    The Diesel Particulate Filter needs to be kept clean to operate efficiently.
    Typical dpf chemical additive fluids may be ammonia based. DPF systems can become problematic due to the corrosive nature, and crystallisation of additive treatment fluids causing blockage of the fluid treatment system, leading to subsequent soot blockage of the dpf exhaust gas filter which may be sensed by the engine control computer causing warning light illumination and limp home restricted mode activation.

    On vehicle DPF regeneration provides self cleaning of the dpf filter at high temperature to burn off soot.
    The Dpf regeneration function is often programmed in to engine control sofware by the vehicle manufacturer but will require certain conditions to activate for example certain engine temperature and driving conditions.
    The Diesel engine electronic control can sense blockage of exhaust dpf filter by measuring exhaust gas pressures before and after the filter. Diagnostic equipment can actuate forced regeneration of the Diesel particulate filter.
    Excessive Dpd soot loading can mean the regeneration functions will not operate, requiring removal and specialist cleaning of the exhaust filter or renewal.

    Lucas Laser 2000


    The Lucas Laser 2000 test equipment with specialist diesel software was a specialist tool used throughout the Lucas Service UK (LSUK) network in the 1980s and 1990s. We still have SUN Portable Data Link (PDL) / Lucas Laser 2000 test equipment and the Lucas Laser 1500 breakout box system, albeit a bit dusty, which can be used to fault find on older vehicles fitted with the Lucas Electronically Programmed Injection Control (EPIC) systems.
    The 'EPIC' diesel fuel injection systems were fitted to many turbo diesel vehicles including Ford Transit 2.5 Di turbodiesel, Leyland Daf vehicles (LDV) Convoy , Mercedes, Fiat , Peugeot, Citroen applications .

    We also have test equipment capable of fault diagnostic test applications with more modern vehicles common rail diesel fuel systems.

    Diesel Engine Fault Diagnosis

    Our mobile service has facilities to remove and refit diesel fuel injection equipment ,and also diagnostic equipment which can be used to diagnose and interrogate electronically controlled diesel engines, including systems from Bosch, Denso, Lucas, CAV, Rotodiesel, Stanadyne, as fitted to many makes of vehicle including cars , vans, minibuses, taxis, buses, commercial vehicles, tractors and construction plant.