PART 6 - LEARNING TO LOVE YOUR COMMON RAIL DIESEL - FUEL INJECTORS

FUEL INJECTORS

There are 2 primary styles of injectors in CRD. Fig10

Solenoid type, have an electronic solenoid at the top of the injector. The solenoid is switched by the ECU sending a voltage pulse to the solenoid to open them. It can have many openings per injection cycle.

Piezo Type, use piezoelectric technology to open and close the injector at extremely high speeds and precision, with improved performance and efficiency over solenoid types.

When power is applied to piezo crystals they expand, they return to their original size as soon as the electric current is cut off. The expansion of one crystal is too small to see with the naked eye, so several hundred little piezo crystals are placed one above the other covering a more than half the length of the injector.

When current passes through these hundreds of crystals their combined expansion is enough to open the injector. The crystals expand downwards and an upward movement is required to open the injector, so two very small levers are used to reverse the process and open the injector and a spring closes it as the crystals contract.

Because of their operation, piezo injectors can open and close much faster than mechanical injectors, hence allow more precision in the injection process. The ECU is monitoring the fuel requirement to the milli-second, so piezo type also inject several times per injection cycle.

Just the right amount of fuel can be used at just the right time, so little or no fuel is wasted. Piezo type is more efficient and more durable than solenoid type.

Injector wear in CRD engines (usually from water issues, Section 8 above), is measured by reading individual ‘feed back’ values of each injector, with a high end scan tool. The ’feedback value’ is a measure of volume of diesel (in cc’s).

Excessive fuel leads to piston and ring failure due to excessive combustion temperatures. Feedback values upto 3cc’s are regarded as acceptable, in excess of 3cc’s is the industry standard for ‘Action Required’ immediately. At 5cc’s, it’s imminent engine failure…. Stop driving the vehicle! Fig9

Excess fuel is noticed by the casual observer in extra detonation noise, particularly when cold. As the excess fuel volume increases, the noise level increases and continues to be noticeable as the engine reaches operating temperature. 5cc’s feedback has a very noticeable noise when cold. However, noise when cold under light load, typical user description, is NOT a diagnosis of injector wear or failure. I am aware that many workshops, even specialists!, change injectors on report of noise, with no further investigation.

In one case, the owner of a KUN26 Hilux 1KD-FTV, changed the injectors twice, at 2 different workshops, for a total cost of $5000 – with no change to the noise. It was never the injectors in the first place! It was a blocked inlet manifold. Fig 4

The ECU knows when an injector is worn, when excessive fuel is being delivered to 1 or more cylinders. To complicate matters, the ECU then reduces the amount of diesel being injected by other injectors, to manage the balance or vibration of the engine. However, this masks the problem of over-fueling to an inattentive driver.

Fig9 Injector Feedback Values 1VD-FTV @ 160,000kms.

It is good practice to have your service agent read the Injector Feedback Values every 50,000k ms. Ask LTG 4x4 to do this at your next Service to determine the wear of your current injectors.

This tends to pull the injector to one side, ever so slightly. In doing so, the bottom sealing washer does not seal perfectly, carbon from combustion makes it way up the side of the injector, between it and the head.

Two things flow from this problem:

1. The injector can be dammed difficult to remove, to the point they pull apart (total destruction) during extraction and

2. The same carbon makes its’ way into the engine oil, as the injector passes from the head into the tappet cover cavity, and then through the cover to outside of the engine. Oil flow carries this debris from the tappet cover cavity into the sump, where the oil is recycled into the oil pump. The problem lies in the carbon debris building up on the oil pickup screen, eventually restricting oil flow. It is not uncommon to see engine failures due to oil starvation. Catastrophic failure. The likely cost is from $8000 to $15,000.

LTG 4x4 recommends changing the engine oil every 5000kms, and using an Engine Oil Flush with each change. The Flush breaks down the oil sludge trapped in the engine so it flows out with the used engine oil.

The crows foot style clamp is used in most 4x4 CRD engines, Landcruiser, Hilux, Ranger, Mazda, for example. It is good practice to check the oil pickup screen with every oil change interval. It is simply a matter of looking into the sump plug drain hole to observe the screen. A small amount of time spent here is a mighty lot of prevention!

Injector Mounting. Often CRD injectors are held into the head with a ‘crows foot’ style clamp. Fig 11

Another precautionary note is when tightening fuel return or drip rail pipes. On some models, eg 2007 to 2016 1VD-FTV engines this return pipe is inside the tappet cover. You cannot observe it with the engine running. If there is any amount of fuel leakage from an incorrectly fitted washer, or deformation of the rail, then leaking diesel accumulates in the engine oil. It dilutes the engine oil, the loss of viscosity can lead to premature wear of the upper mechanical components, like cam gears, timing chains and lash adjusters. I recently repaired an engine with just this problem, (1VDJ-FTV in a 76 Series, solenoid type), it cost in the vicinity of $9000 to rectify.

Changing the engine oil every 5000kms in CRD vehicles is also recommended due to the above. Ask GO 4x4 to check your oil pump pickup at your next Log Book Service.

Remember 2 things, It’s ALL about emissions (for 5 years) and Prevention is the best cure.

Thank you for reading the 6th installment of learning to love your common rail diesel! For the next installment on "Performance Upgrades" please visit www.ltg4x4.com.au

Cheers,

Tom from LTG 4x4