Almost every day, we will receive a request to do a "Test as Received" (TAR) on EUI injectors.  While in some cases this may be the proper route to take, we have found that in most cases this only delays the inevitable, and that is injector failure.

An EUI injector is comprised of 3 different sections:

• Nozzle tip and stack-up:  The nozzle tip and associated parts are very similar to a conventional injector.  Nozzle opening pressures are normally higher and can be up to 5500 PSI in some injectors.  Nozzle pressure spring breakage is a common failure in this area, as well as nozzle tip seat leakage and poor atomization.  A TAR  of a complete injector does NOT check any of these areas as the nozzle can only be tested/set as a sub-assembly.  The injector may flow at the proper rate, but this does not guarantee that the nozzle is functioning properly.  The nozzle tip and the stack-up is most often the reason for a failed EUI injector.

• Control valve:  All EUI injectors have some type of control valve that determines when and how much fuel is to be injected.  These control valves are very complex, response time is critical.  Some injectors use a control valve that is a separate component, while others have a control valve that is integrated within the injector body.  Fuel contamination is the most common reason for control valve failure.  The TAR procedure will usually indicate if the control valve is functioning properly.  However, a broken nozzle spring or a leaking nozzle tip may  sometimes have the same types of symptoms as a non-functioning control valve during a TAR.

• Pumping plunger/barrel:  All EUI injectors also have some type of system to provide fuel under extreme pressure to the nozzle.  Most of these are engine camshaft activated.  This part of an EUI gives the least amount of problems, as many of these components utilize ceramics and other space age materials.  Injectors that have always operated on clean fuel show very little wear in this area even after a long service life!  Fuel contamination or improper installation can sometimes cause seizures in this area, and this problem is obvious during a TAR.

We recently acquired a new EUI test bench, and we now also have the ability to measure injector response time and PIP (Peak Injection Pressure).  Both of these values are important to a correctly functioning EUI, and are good indicators of an injectors quality.

So the question remains ...  When should I have EUI's  tested rather than repaired/rebuilt?  We have found that most EUI's have a service life of 750,000 - 1,000,000 km.  This is substantially greater than conventional injectors! 

If the injectors in question are approaching or have reached this service life, doing a TAR and reinstalling them in the engine would be questionable at best.  At this stage in an EUI's service life, broken nozzle springs and poor nozzle characteristics are very common.  If the springs are not broken, how long can they be expected to last?  Even if the nozzle springs are not broken, nozzle pressures can  be up to 2500 PSI too low!  A common scenario is for us to see the same customer 6 times in 6 months, and each time he is purchasing a single injector to replace one that has failed!  Obviously this is not very cost effective when you consider that labor costs to install 6 injectors is not much more than to install a single injector.

If the injectors in question are being suspected as the cause of a particular engine problem, and they are not at the end of the normal service life, then it may be advantageous to test them.  Sometimes a simple problem such as a poor electrical connection can be the culprit and is also easily repaired.

Fuel contamination, even in small amounts will almost ALWAYS result in injector failure.  If fuel contamination is obvious, some type of failure is inevitable and proper cleaning and repairs would be required prior to testing.

Another issue that we see is that a customer is rebuilding his engine, and wants to have the injectors tested before they are re-installed.  The life of a typical engine today would normally exceed the life of the injectors, and unless they were recently replaced our recommendation would be rebuilt injectors for the rebuilt engine!