Isuzu Truck Repair Specialists! Your Isuzu dealership alternative
We have the tools and knowledge necessary to service your Isuzu medium-duty truck. From 5.7L and 6.0L gasoline-powered NPR's and mechanical diesel injection systems to the F-series, and the new 5.2L and 7.8L Common-Rail Diesels, we can accurately diagnose and repair your Isuzu truck.
Below are our 4,000mi, 20,000mi and 60,000mi Isuzu/Hino Preventive Maintenance Checks/Services forms that you will receive when each of these services are performed. These services take the manufacturer's recommended services and adjust them based on our ASE Certified Master Auto & Truck Technicians real-world experience.
Isuzu Tech
Here at Fleet Service Northwest, we dont just occasionally see an Isuzu medium duty truck every now and again, we service and repair these trucks on a regular basis. we have factory tools, training and and the information to do a proper repair on an Isuzu truck, sure, most facilities can change the oil and filter on this truck, but they lack the knowledge and experience to properly diagnose a fuel system, transmission or anti-lock brake issue and often times replace parts to try and correct a problem. this cost the customer in expensive parts and equipment down time.
We use only Isuzu genuine parts at Fleet Service Northwest.
Injector Failure 4HK1 TC common rail injection system
Injector failures on this platform have been attributed to fuel contamination, while many of these failures can be traced to "dirty fuel", the sheer number of failures would indicate another possibility, these injectors are garbage!, there I said it and it needed to be said. Isuzu's solution to this problem has been to add a secondary fuel filter. the problem with adding a secondary filter to this system is as of yet unknown. I will however speculate based on experience with similar systems, (duramax LB7/LLY/LBZ/LMM) that this can possibly add even more restriction to the suction side of the fuel system as both fliters become loaded with normal fuel debris, this will no doubt cause even more restriction the the suction side of the fuel system. to understand what effect this can have on a high pressure, common rail injection system, you must first have general understanding of how the system, this system in particular, works.
Fuel is drawn from the fuel tank via a tandem high pressure fuel injection pump. this pump contains a suction side and a high pressure side, it is in effect two pumps in one. the fuel is then drawn through the filter element up to the pump where it is directly fed to the high pressure pump which has the capacity to pressurize the fuel to 20,000+ PSI. this pressure is controled by the amount of fuel allowed to reach the pump. by the suction control valve, AKA pressure regulator. this fuel is then fed at high pressure to the fuel rail/s. the pressure is dependant upon signals recieved to the PCM which adjusts this pressure based on driver demand and other monitored factors such as coolant temp, transmission gear range status, calculated engine load, etc. the injectors recieve a signal to open from the PCM, the high pressure fuel is then distributed through the injector, directly into the combustion chambers, hence the term, "direct injection". this system also incorprotates a pre injection event which injects a very small amount of fuel in the compression stroke before the main injection event take place, this is to reduce engine noise and emissions. the tolerences within the high pressure fuel injection pump and injectors themselves are very close. these precision devices rely on diesel fuel as a lubricant. this level of precision will generate a certain level of heat due to friction between the moving parts. upon teardown and inspection of failed injectors, evidence of galling from this friction is present.
As you can see, lubrication of these parts is critical, and restriction in the fuel supply system can wreak havoc on the entire high pressure fuel system. there are safegards programmed into the system which will limit rail pressure and engine RPM's in the event of a detected fuel system issue, but over time, fuel starvation does it job.
Any dirt, water or debris small enough to make it past the filter media will destroy injectors as well. this is why it is critical to drain the seperator(mainly to check for water content) and change the filter on a regular basis. it's also a good idea to drain the fuel tank at least once a year and check for contamination, this can be done easily when the tank is low, by pulling the drain plug in the bottom of the tank, letting it drain into a clean container. the clean fuel can then be poured off and put back in the tank.
We have tried fuel additives and secondary filtration in an effort to reduce injector failures, has it helped? I believe it has helped but only time will tell. we are still testing. we are also working on a fuel supply pump kit. this would add an electric fuel pump to the system. this system would require a signal from one of the PCM sensors to operate a relay which would activate the pump in order to make it safe in the event of a collision. a lift pump would ensure a constant fuel supply to the high pressure pump under all load conditions regardless of some of the other fractors that effect the stock supply system. I believe this along with the double filtration would do more to add durability to the injectors than filtration alone. The cost of a new injector runs around $550.00 wholesale, multiply that number by four and add labor to replace, and consider we have seen multiple failures even after replacement!
You can be certain the staff here at Fleet Service Northwest will be on the leading edge of emerging issues concerning Isuzu Medium Duty Trucks.