Originally appeared in TDR Issue 72
by Joe Donnelly
Fuel Injectors for 2003 and Newer HPCR Engines
Injector Removal and Replacement
You will need a few specialty tools to make the injector replacement easier. The aluminum plate at the top keeps the exhaust rockers in order and assembled. Under it at the left is a 15/16” socket cut down to 1” total length, with a connector tube nut in it. To the right of the nut is an orange painted tube that facilitates pressing the new injector into its well in the head. Next is a blue painted cover for the air intake hole after removal of the air horn. Over it and the aluminum plate is a 9” length of 3/16” brake line tubing and 1/4” OD vinyl hose for sucking diesel fuel from the piston bowl if some drains in a cylinder after removing an injector. To the left is a “lady foot” pry bar to remove the injectors. It has red paint on it. At the bottom are a length of 5/16” pushrod with the open end partially squashed to retain a Q-Tip, and a modified rifle bore brush and rod for cleaning out the injector tip hole in the head. These tools are discussed below in more detail.
You can use a nut of M14 x 1.5 thread and a screwdriver to pull the connector tubes in the head. In most cases, the tubes can be pulled just with fingers on the threaded end, or by nudging them with a screwdriver blade on the threads. It is helpful to have a cut-off 5/16” hollow engine pushrod with the cut end partially flattened so it will hold a Q-tip tightly. This tool enables you to clean the sealing surface in the head at the bottom of the injector well.
You will use 3/4″” (19 mm) and 7/8” open-end wrenches with total length not exceeding 6.5 inches to remove the injector line nuts from the ends of the rail. Get a small (about 5.5 inches long) “lady foot” rocker style pry bar to pull up the injector. (Make sure the nut and connector tube are out of the way so you won’t nick the end of the connector tube.) A ¾” or 19 mm flare nut crow’s foot and flex head ratchet will help remove the #5 and #6 injector line nuts. You also will want a 15/16” or 24 mm socket and flex head ratchet to remove the nuts at the cylinder head. A 3/8” drive socket cut down to 1 inch long gives better access for #3 and #6 connector tube nuts. In this engine, the injection line nut threads into the connector tube which is held in place by another nut that is threaded into the head.
Make up a steel or aluminum tube with an inside diameter of 1.15” to 1.25” and length of about 2.8” to press the new injector into its well. You may need to file it flat on one side if it is a thick walled tube, to clear the intake rocker. You don’t want any stress on the electrical studs or plastic end of the injector. Greasing the injector body O-ring helps a lot for pressing the injector into its well in the head. To vacuum out fuel from a cylinder, I use a piece of clear, flexible plastic (“Tygon” or vinyl) 0.25 inch outside diameter tubing, about 3.5 to 4 feet long with a 9 inch long piece of 3/16” brake line pushed into one end for about one inch. The ends of the brake line should be chamfered and the tube cleaned of any metal shavings. You will insert the 3/16” steel tube into the cylinder through the injector hole to suck out any fuel that drained into the cylinder and is in the piston bowl. The extra length of the plastic tubing allows a “belly” to form and trap the fuel that is withdrawn. If you prefer, it is safer to have a suction pump and trap attached.
First, remove the plastic cover over the engine and the breather assembly from the top of the valve cover (four bolts with 10 mm head and O-rings under the heads on 2003-2004 engines). Remove the valve cover lid (six bolts with 10 mm heads). You will remove the air intake for better access to the injector lines. It is held on with four bolts having 10 mm heads, plus one for the dipstick tube, and a 7/16” (11 mm) nut on the band clamp.
When removing the aluminum air intake horn from the head, it is easy to tear the gasket. Keep a couple of them around. Get Cummins part number 3969988 (the newest heat resistant type, replacing the 3938158 pink gasket that Cummins used in the past few years).
Plug the plenum hole in the head and the boost pipe so nothing falls into them. Be sure the areas around the lines at the rail and at the head are very clean. Remove the injector lines. Be sure to use a backup wrench on the nut at the head and on the ends of the rail to prevent damage to either the connector inside the head or the fuel rail. Keep the injector lines and exhaust rockers in order for correct re-installation, if you elect to address all six injectors at once. On many engines, the last digit of the injector line part numbers, etched on the engine end’s nuts, are in numerical order from #1-#6, for example 3957081, 3957082, 3957223, 3957084, 3957085, 3957146. Remove the nuts at the head and gently pull out the connector tubes about 1/2 inch with an M14 x 1.5 thread nut and a screwdriver on the nut. The tubes have balls peened onto their outsides to index them in the head.
Remove the exhaust rocker arms assemblies. A rocker assembly is shown but you will usually only remove the exhaust rocker. Disconnect the solenoid wires at the top of each injector. Be gentle! These studs are easily broken. Remove the two injector hold down bolts (M6 x 1.0 thread, 8 mm or 5/16” head). Pull the injectors gently with the “lady foot” puller.
If the intake valves were open, it may be necessary to loosen the intake rocker to get clearance to remove the injector. Listen carefully. If you hear fuel drain into the cylinder, you must vacuum it out with a hose through the injector tip hole in the head, as a piston bowl full of fuel will cause a hydraulic “lock” when you try to turn over the engine later. It is common to get two or three milliliters of fuel into a cylinder’s piston bowl when removing an injector. I use the tube described above in the “tools” paragraph and gentle mouth suction, letting the fuel settle into a “belly” in the hose—no one wants or should get a mouthful of fuel! Check the injector well in the head and if the sealing surface at the bottom of the well is contaminated, mop it clean with a Q-tip that is held tightly in the partly flattened end of a tube to gain the needed length (I use an old 5/16” hollow engine pushrod).
Clean the injector wells so that there is no grit at the sealing surface on the bottoms of them.
HPCR injector wells stay clean except for engine oil and deposits from the injector tips as they are pulled up through their holes upon removal. If there are heavy deposits making it difficult to install the new injectors, you can run a rifle bore brush through the holes into the cylinders to clean out the passages the injector tips go through. Wipe out the sealing areas where the copper washers rest on the bottom of the wells, with Q-tips. You can use a hollow 5/16” automobile pushrod that is partially squashed near the end to retain one end of the Q-tip so it can’t fall into the cylinder. The sealing ball area of the injector lines can get dirty or corroded, and subsequently leak. Usually cleaning with fine aluminum oxide or emery paper (600 or 800 grit) will take care of it. Be sure to spray off the area so no grit remains on the surface or inside the line. Don’t torque the line nut over 25-30 ft lb; put a little grease on the threads and back side of the sealing ball where the nut grips it, to get a smooth torque reading and to prevent the line from twisting.
Grease the O-ring on the body of each new injector. Push the injector into its well using the 2.8” long tube over the injector body, bearing against the hold down bracket that is captive on the injector body. The factory service manual specifies that you snug down the injector hold down bolts, then relieve the tension and tighten the connector tube nut to 11 ft-lb. Then, tighten the injector hold down bolts to 89 in-lb and tighten the connector tube nut to 37 ft-lb torque. I suggest using a thin film of grease on the threads and sealing surface of the nuts. I also put a bit of engine oil around the hole in the side of the injector where the connecting tube fits. Install the exhaust rocker, and set the lash. The lash generally does not change with this procedure, but if your engine has a lot of miles on it, you might want to set the valve lash on all valves. Valve lash specifications for the 2003-up common-rail engine are as follows:
|0.006 inch minimum||0.015 inch minimum|
|0.015 inch maximum||0.030 inch maximum|
|0.010 inch when resetting||0.020 inch when resetting|
I prefer to keep lash measurements as close as practical to the same in all cylinders, and generally use 0.010 inch on the intakes and 0.020 on the exhausts on 12- and 24-valve engine types.
Re-assembly goes in the reserve order of the removal procedures above. Torque specifications for re-assembly are as follows:
Injector Hold Down Bolt: 8mm (or 5/16”) head, 89 in-lb maximum; 80 in-lb may be “safer” if the bolts seem to be “stretching” excessively.
Injector Wire Nut: 8mm head, 11 in-lb. That’s a very light torque—the M4 x 0.7 studs are easily broken; gently snug is another way to describe it. You can use a nut driver (like a screwdriver) to help you get a good feel when snugging down these nuts). Note that the yellow or brown wire is closest to the intake side or intake rocker.
Rocker: 10mm head, 27 ft-lb
Connector Tube Nut: 24mm or 15/16”, 37 ft-lb
Injection Lines: 19mm or ¾”, 22 ft-lb
Valve Cover and Miscellaneous: M8 x 1.25 thread bolts with 10mm head, 18 ft-lb
Principle of Operation | Related Discussion in Previous Magazines & Aftermarket Processes
Upgrades and Preventing Failures | Inside the Injector & The Fuel Transfer Pump
Frequently Asked Questions | Injector Removal and Replacement