Time For Your Injection!

              FAULT FINDING ON EARLIER DIESEL SYSTEMS

This information covers diesel systems without electronic diesel control, so this relates to most car and light commercials from 1960-1985. This information is a good source for locating any running fault you may have. The single largest cause of problems on early diesel systems is not poor fuel as you would expect, rather it is air, yes air in the fuel lines. This will cause all sorts of havoc with your engines performane so don't under estimate this. Although this is not extensive as there are so many different systems in operation, however I have been using these methods since 1972 and rectified problems on literally thousands of vehicles, it works!  Scroll further down the page you will find details on fault finding on common rail systems too.

Heavily carboned inlet/exhaust valves (Pressure & heat escaping past the valve seat) Compression test will not pick up this problem, you must have a cylinder leakage test carried out on the engine.

Injectors Hosing

Insufficient air, remove the air intake filter, does the exhaust run any cleaner.

If you have an EGR system remove the intake manifold and investigate for carbon build up around the cylinder heads intake ports.

Overfueling Injection pump.

Injection timing running retarded, check pump to engine timing marks.

Air in the fuel system. Install clear pipe from Injection pump to filter and observe for air in the fuel. Alternatively connect pipe from pump inlet to container of fuel (by-passing the rest of the system). If the engine runs OK, then investigate fuel supply from filter to tank.

Blocked fuel filter 

Blocked feed and return bolts.

Engine is burning oil, remove oil filler cap, crank engine, is the engine breathing heavily.

If in doubt carry out a compression test, rule of thumb 300-350 p.s.i most importantly uniformity across cylinders. 

Check fuel filter, is there any black oil residue on the filter, if the answer is yes the most likely source for this will be defective lift pump (if fitted). Defective fuel pump drive seal (if pump is gear/chain driven)

Glow plugs

Air in the fuel system. Install clear pipe from Injection pump to filter and observe for air in the fuel. Alternatively connect pipe from pump inlet to container of fuel (by-passing the rest of the system). If the engine runs OK, then investigate fuel supply from filter to tank.

Injector nozzle needle stuck in open position

Lift pump failure (where fitted)

Injection pump

Remove electrical connection to stop solenoid, if the engine stops have the wiring checked.

Remove the stop solenoid, any debris stuck under the stop valve, check with a magnet, if these are metal particles, this could be a sign the pump is breaking up internally.

If the engine is breathing heavily (worn piston rings) it is possible the engine is running on vapour.

Empty fuel tank. I know this is obvious but often missed.

Air in the fuel system. Install clear pipe from Injection pump to filter and observe for air in the fuel. Alternatively connect pipe from pump inlet to container of fuel (by-passing the rest of the system). If the engine runs OK, then investigate fuel supply from filter to tank.

Check timing, has the belt jumped.

Fuel pump stop solenoid. Remove the solenoid assembly, hold the valve and spring inside the solenoid with your thumb, apply approx 12 volts to solenoid (must be earthed). Valve should move in. If faulty replace.

Pump Failure.

Air in the fuel system. Install clear pipe from Injection pump to filter and observe for air in the fuel. Alternatively connect pipe from pump inlet to container of fuel (by-passing the rest of the system). If the engine runs OK, then investigate fuel supply from filter to tank.

Blocked return pipe

Blocked inlet or return banjo bolts.

Check adjustment of idle speed screw, also check adjustment of the anti-stall screw (If fitted)

Air in the fuel system. Install clear pipe from Injection pump to filter and observe for air in the fuel. Alternatively connect pipe from pump inlet to container of fuel (by-passing the rest of the system). If the engine runs OK, then investigate fuel supply from filter to tank.

Crossed feed and return pipes.

Blocked return pipe

Blocked inlet or return banjo bolts.

Injectors. If the misfire is noticeable at idle speed, place some rag or absorbant tissue aound one injector at a time, release the pipe nut at the Injector and listen for a tone change in the engine. If you can pinpoint the cylinder with the misfire, remove the Injector for testing or swap Injector with another from a 'good' cylinder and see if the problem moves. If the misfire is still evident on the original cylinder carry out a compression/cylinder leakage test.

                  FAULT FINDING ON COMMON RAIL SYSTEMS

I would strongly recommend you have the vehicles ECU code read, this normally varies in price from £35-£50. This will be money well spent and save you hours of fruitless searching.  Below is a list of problems with possible causes, in the event that there is no fault stored in the ECU and a code read is not possible I suggest these items are checked. Please note this is for Common Rail Systems Only These systems do vary so information should be used for reference purposes only. 

SAFETY WARNING

Do not attempt to enter the fuel system until the engine has been stopped for a minimum of 5 minutes. Under no circumstances should high pressure pipes be released while the engine is running.

These systems operate upto and over 2,000bar pressure, these pressures will penetrate skin tissue and could be fatal.