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TECH TOPICS | page 4

Injectors for 2003 and Newer Cummins HPCR Engines

by Joe Donnelly, TDR Contributor

Inside the Injector

We have looked at the pintle and nozzle with the remarkably tight clearance between them. Here are the components of the HPCR injector, first the bottom half with the nozzle nut, nozzle, pintle, and the main body to the right. Next is a photo of the top half with the armature to the left, check ball and seat in the center, and the solenoid and its nut to the right. Next is a close up of the armature that was on the left of the preceding photo. You can see the buildup of sludge on it from contaminated fuel. Finally, on a one-inch wide block you can see the fuel return seat, ball check (.053” diameter) and the end of the armature that fi ts to the fuel return check ball. A technician needs 500x magnification to inspect the ball, cup, and the seat in the armature for wear or erosion.

The electric fuel transfer pumps used in 2003-2004 engines [photo 72i5] may not be adequate for more than a gain of about 60-70hp over stock. The in-tank 2005-up lift pump has a slightly better reputation for fuel delivery and a noticeably better reputation for longevity. These lift pumps were covered in detail in Issue 56, pages 60-74. If your Turbo Diesel comes with an electric lift pump, add a spare to your “boonie box” and monitor the performance of your lift pump with an electric gauge (so you won’t have diesel fuel in the cab). There are also aftermarket lift pumps, with or without extra fuel filtration. The FASS 200 gallon per hour lift pump and filtration system was described in Issue 56, page 102.

The EGT range of most Turbo Diesel engines with stock turbos likewise may or may not remain safe with up to 60-70hp more, depending on load, altitude, ambient temperature, etc. However, these two components may be closer to “maxed out” with typical hop-ups on newer Turbo Diesels than the older trucks were. In part this is because the older trucks started with lower horsepower levels. Check your fuel pressure gauge and see if the lift pump pressure stays around 5 psi or so under full power. See if EGT get too high under full power and and/or heavy loads. Maximum EGT is 1450° for 2003-‘04 and 1500° for 2004.5-up engines. For safety, it is a good idea to stay well under these maximums, particularly for long pulls. With my BD compound turbochargers and intercooler, I can keep EGT below or at 1100° towing a 5000-pound trailer in the mountains at higher altitudes and 70-75mph.

Summary

In summary, the enemies of the HPCR fuel system are dirt, water, contaminated fuel, and excessive rail pressure. Have we covered everything you need to know? Not quite yet, let’s answer some questions and then finish the article with the removal and installation procedures.

Frequently Asked Questions

Rail Pressure versus Fuel Mileage
Q: In Issue 63, page 82, writer Joe Donnelly did an article about the 2003 and newer ECMs and reprogramming them using a “Smarty” by MADS Electronics. In that article we are told that added rail pressure does not give mileage gains and is “problematic to injector and injection system durability.” Then on page 110 there was a “Product Showcase” article where we are led to believe that increasing fuel pressure will increase mpg by 7%. What is the story?

A: In theory, it would seem that increasing rail pressure would help mileage, as noted by writer Gary Wescott in his “Product Showcase” about the Edge products’ Mileage Max product on page 110. In practice, neither Marco Castano (owner MADS, electronics/developer of Smarty), Mark Chapple (owner of TST, Cummins engineer for 33 years, developer of Power Kit and PowerMax products), nor I have seen any clear, verifiable mileage increase from raising rail pressure above the stock Cummins curve. Power adders do “cheat” the truck’s overhead console report of fuel mileage, giving falsely high readings because fuel is being added that the computer doesn’t know about. Mark Chapple told me he did see a nice torque increase in the 900-1300 rpm range from added rail pressure that was not achievable to the same extent by adding injection duration. As with some other products and approaches to modifying turbo diesels, “YMMV” in internet slang, or “your mileage may vary.” Remember that the Turbo Diesels with the lowest injection pressures, the First Generation trucks, were renowned for giving good mileage. (Then again, they were only rated at 160 horsepower/400 torque and the truck itself was much lighter.)

Finally, in another one of those all-encompassing articles, see the Turbo Diesel Buyer’s Guide, pages 80-99, “So You Want Fuel Economy,” for the bottom line on YMMV information.

Preventive Maintenance?
Q: What should I do for preventive maintenance on my 2006 Turbo Diesel? I have heard of many injector problems. Do I need a better fuel filter set up?

A: Here are some general things, my opinions:

• Keep exhaust gas temperatures down; I like to keep EGT under 1300° even though you can get away with a bit higher. Dropping a valve seat is expensive, and that is what usually happens first after a number of high EGT “excursions.”


• Change the oil regularly, using CI4+ rather than the newer spec CJ if possible. I like to change it at 4000-4500 miles.


• Keep rpm under 3000, but don’t lug the engine and drivetrain under high power below 1800rpm.


• If you raise rail pressure with a “box” or program, you should improve fuel filtration; 3 microns is a good level. Otherwise, you will probably be okay with the stock 7 micron Fleetguard filter. I like the FASS for its reliable fuel transfer pump and good filters.

Finding the Bad Injector
Q: My Turbo diesel has a lot of timing rattle noise and rough acceleration around 2000rpm under light throttle. When slowing down, the idle drops down to 500rpm and then recovers.

A: Since the truck is not lighting up the dash with diagnostic trouble codes, it is best to start parts-swapping with the least expensive items. Start with the fuel control actuator (FCA) on the back of the CP3 pump. The FCA is less than $120.

Let’s continue to discuss parts-swapping with the least expensive items. The following is a tip that I picked-up from TDR issue 62 where a TDR member wrote-in with a surging, rough idle and hard start problem. Unfortunately for the owner, he had already replaced the injectors, an expensive repair. The tip: “Try adding a couple of cans of ashless two-stroke oil to the fuel. If it clears up, it’s a defective fuel control actuator (FCA). The oil lubricates the FCA and the engine will idle until the two-stroke oil is depleted. It’s a cheap diagnosis method and only takes the time to run some treated fuel through it.”

To finish the story from Issue 62, “I was told that adding a fuel lube to check the FCA was a test that STAR (Chrysler tech assistance) was using some time ago. A friend who had a Turbo Diesel with a sticking FCA added fuel lube to it by accident and the truck ran fine. After a tank and a half of fuel without the additive, the rough idle, stalling, and stumbling returned. He had problems similar to yours and everyone was telling him it was defective injectors. As long as he kept the fuel additive in the tank, the engine ran fine. He tried different fuel treatments including Marvel Mystery Oil. I read about the fuel lube test, STAR, and the FCA and told him to replace the FCA. He replaced the FCA and the truck has been running like new without any additives.”

The owner tried the two-stroke oil and the engine did not stumble, but it still idled rough. The dealership replaced the FCA and the problem with the engine was solved.

To check individual injectors on the ’03-’05 Turbo Diesels, you could unplug one of the three electrical connectors at the head, while the engine is not running (the wires carry up to 50-volts). Once you see which pair of cylinders is at fault, you can remove the valve cover and remove one pair of wires at a time. Or, you could go right to the individual injector wires. You will get a trouble code, but you can remove it later. Since other injectors may be “weak” the best approach would be to send all six to a Bosch shop like Dynomite Diesel for testing. They are a Bosch dealer and could sell you new injectors as needed. Obviously, unplugging the injector will serve as a diagnostic method only if the electrical solenoid is at fault. If you have a mechanical failure, you would have to plug off one injector at a time or replace one at a time. DDP could test all six for you if that would be more convenient.

Other Injector Symptoms
Q: What are some of the other symptoms that I have an injector-related problem?

A: Often a truck will idle and run rough like it is missing. If it shows a diagnostic trouble code (DTC) P2149-“Fuel Injector Group, 2 Supply Voltage Circuit,” you’ll want to check for a fuel injector solenoid failure or the electrical connection through the valve cover gasket. To check for either problem, the valve cover must be removed.

Disconnect each injector in the bank affected which should be cylinder number 4, 5, and 6 and check the resistance with an ohmmeter. It should check less than 1-ohm and greater than 0 resistance. Look for the odd reading.

Disconnect injector harness outside the valve cover and using an ohmmeter, check each wire for continuity and resistance. The wires should be less than 1 ohm and greater than 0 resistance.