Diesel Engine Troubleshooting

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Detroit Diesel Injector Troubleshooting

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To determine if repair is possible or replacement is necessary perform the following procedure.

Flowchart for Repair or Replacement of Electronic Unit Injector

To remove the injector, complete the following steps: ?

  1. Loosen the injector wire terminal screws two full turns and remove the terminal wires.
  2. Remove injector hold down crab.
  3. Lift the injector from its seat in the cylinder head by inserting a pry bar under the injector body.
  4. Cover the injector hole in the cylinder head to keep out foreign material. Remove carbon from the injector exterior in the area where the tip joins the nut, using wire buffing wheel, J 7944 .

Disassembly of Electronic Unit Injector

On a Series 60 engine EUI, only the injector solenoid and seal rings are serviceable. The injector must not be disassembled. ?

Inspection of the Electronic Unit Injector

To clean and inspect the injector, complete the following steps: ?

  1. Clean the exterior of the injector with clean solvent and dry it with compressed air.Note: Do not test new or reliabilt ® remanufactured electronic unit injectors prior to installation in the engine. The Kent-Moore ® POP stand should only be used as a diagnostic tool on fuel injectors that have been removed from an engine.
  2. Test the EUI using J 34760 . Follow procedures supplied with this tool. Reuse or replace injector or injector and solenoid as indicated by testing.
  3. Inspect the O-rings for damage or foreign material. Replace O-rings.
  4. Inspect the fuel injector tubes at the injector seat. If required, replace the fuel injector tubes.

Repair of Electronic Unit Injector Solenoid and Seals

Perform the following steps for solenoid replacement: ?

  1. Loosen the injector wire terminal screws two turns and remove terminal wires.
  2. Loosen four hex-head screws and remove old solenoid.
  3. Perform the appropriate step for the DDEC unit used. For DDEC I and DDEC II, discard the solenoid, load plate, follower retainer, and screws. Do not reuse old screws. For DDEC III/IV, discard the solenoid, follower retainer, and screws. Do not reuse old screws. The load plate must be reused.
  4. Remove spacer and seals from injector body.
  5. Discard seals, but do not discard spacer.
  6. Install new seal in spacer groove and position spacer on body with seal facing down. Seal may be retained in groove with small quantity of grease.
  7. Install new seal in solenoid groove.
  8. Install solenoid on spacer.
  9. Install new screws through the load plate and follower retainer, solenoid, and spacer.
  10. Thread screws into body and tighten all screws until heads contact retainer and load plate with a slight force (less than 0.6 N · m [5 lb · in.] torque) in the sequence shown.
  11. Torque screws to 2 N · m (19 lb · in.) in the sequence shown.
  12. On DDEC II injectors only, etch the last four digits of injector part number on the load plate.

Installation of the Electronic Unit Injector

Perform the following steps: ?

  1. If the fuel system is contaminated with coolant:
    1. Drain the fuel tanks and refill with clean fuel.
    2. Replace both filters with new, and clean the fuel/water separator, if equipped.
    3. Inspect fuel injectors for damage and replace as required.
  2. If the coolant system is contaminated with fuel, flush and reverse flush the system.
  3. Using clean compressed air, blow out any fuel remaining in the injector bore.
  4. Detroit Diesel encourages the use of an additional service seal (5104701) that is impervious to both coolant and fuel. This seal should be used in situations where injector tube seal leakage or deterioration is suspected or confirmed. Place the auxiliary seal in the injector hole and seat it against the top of the injector tube with a 41.3 mm (1-5/8 in.) diameter wood or plastic dowel.
  5. Check to make sure the injector bore is thoroughly clean.
  6. Apply a thin coat of clean ethylene glycol to the injector seal rings and install them in the injector nut ring grooves. Make sure seals are properly seated.
  7. Insert the injector into its respective injector tube bore. Visually align the injector body for equal clearance between valve springs (there is no locating dowel pin on the underside of the EUI). After locating the injector, press down on the top of the injector body with the heel of your hand to seat it in the injector tube.
  8. Determine which type of hold-down crab is used by measuring the overall height.
  9. Position a 0.762 mm (0.030 in.) feeler gage between the crab and injector spring on the side of the spring that faces the intake manifold.
  10. Install the hold-down crab, hemispherical crab washer (flat surface up against bolt) and hold-down bolt to the injector. Ensure the clamp does not interfere with the injector spring or valve springs.
  11. Torque the hold-down bolt to 58-66 N · m (43-49 lb · ft).
  12. Install the EUI terminal wires by positioning the keyhole in the terminal over the screw in the injector solenoid housing. Pull the terminal end down so that the screw rests in the smaller slot in the terminal. Torque the terminal screws to 1.08 – 1.13 N · m (9.5 – 10.0 lb · in.). Do not bend the terminals down after installation.
  13. Install the rocker arm shafts, with rocker arms in place.
  14. Adjust the intake and exhaust valve clearances and injector height. 
  15. Install the inlet and outlet fuel lines to the fittings at the rear of the cylinder head.
  16. On DDEC III/IV engines, record the injector calibration code from the load plate with the proper cylinder location.
  17. Install the valve rocker cover.
  18. For one-piece valve rocker cover. For two-piece and three-piece valve rocker cover.
  19. Verify repair of electronic unit injector.

Written by Ed

October 24th, 2011 at 3:45 am

Detroit Diesel VGT/EGR

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The variable geometry turbocharger and the exhaust gas recirculation system are intimately related, with overlapping trouble codes. Depending upon its J 1587 addendum, flash code 48 translates as low air, fuel, or EGR pressure, or as low EGR, turbocharger inlet (TCI), or turbocharger outlet (TCO) temperature. A very low level of fuel in the tank or restrictions in the fuel supply lines generally account for loss of fuel pressure. EGR pressure is sensed upstream of the turbocharger. Consequently, low EGR pressure comes about because of leaks in exhaust tubing going to the turbocharger or because the EGR valve sticks open to pass more than the normal volume of exhaust gases.

EGR, TCI, or TCO temperatures are influenced by the heat content of the exhaust gases mixing with incoming air. Abnormally low temperatures result from exhaust leaks in the EGR cooler or inlet piping, or from failure of the EGR valve to open sufficiently.

Code 49 signals high TCI or TCO temperatures, which can be traced to a clogged air filter, excessive exhaust backpressure, or to the EGR valve. If the EGR valve were to stick open, the higher-than-normal input of exhaust gas would be registered as an increase in turbo temperature.

Fig. 6-28 illustrates the VGT turbo, EGR valve (7) and the tube-and-shell EGR cooler (1), which is distinguished from the earlier tube-and-fin type by its rounded contours. The newer, more efficient cooler can be retrofitted to earlier Series 60 engines with kit PN 23533985, an operation that calls for reflashing the computer on DDEC IV engines built before 06R0755298. The hydraulic EGR unit must be extracted from the original cooler and pressed into the replacement part. Kent-Moore supplies special tools for these operations, although press fixtures and a suitable extractor are not difficult to fabricate.

The EGR Delta-P sensor, which measures the pressure drop across the EGR valve, has also been revised. To install the replacement sensor kit PN 23532364, the technician must open the wiring harness, snip off the original Delta-P sensor connector, splice in additional wiring, and reassign pin functions. As originally wired, pin 1 supplied voltage, pin 2 went to ground, and pin 3 carried signal voltage. Under the new scheme, pin 1 is ground, 2 signal, and 3 supply.

Written by Ed

February 14th, 2011 at 8:25 am

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Detroit Diesel Electronic unit injectors

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Series 50 and 60 solenoid-actuated unit injectors are replaced as assemblies, using new seals, washers, and hold-down bolts. Disconnect the battery to protect the computer from voltage spikes, remove the hold-down bolt, and lift the injector free. Gentle taps with a rubber hammer should be enough to separate it from its sleeve. Kent-Moore catalogs an extraction tool (PN J47372) for stubborn cases.

If the injector is to be reused, carbon accumulations can be removed from the nozzle body with a wire brush, emory paper, or Scot-Bright. But keep abrasives clear of the nozzle orifices. Using a hand-held brush—not a power tool—clean carbon from the sleeve and vacuum up the particles. This procedure reduces contamination of the drilled fuel passages.

Lubricate components with clean diesel fuel, and install the injector with new seals, washers, and clamp bolt, as supplied under PN 2353711 (Fig. 6-25). Note that the flat side of the copper washer goes down, toward the cylinder head. Fit the clamp over its locating pin, run the bolt down finger-tight, and

• torque the bolt to 50 N-m (37 lb-ft),
• back off the bolt 60° (one bolt flat),
• torque to 35 N-m (26 lb-ft),
• tighten the bolt 90° (one-quarter turn).

Internal fuel galleries must be flushed before starting the engine. Prime the fuel system and, with the key “off,” disconnect the ECM at the fuse box or harness connector. Remove the combination check valve and pressure regulator, which are located at the rear of the cylinder head at the return-line elbow. Connect a hose to the gallery outlet, and crank the engine in three 15-second bursts, allowing ample time for the starter motor to cool between engagements. Once the galleries are flushed, replace the regulator, make up the fuel-return line and connect the wiring harness to the computer. Run the engine up to operating temperature and check for fuel leaks.

Detroit Diesel supplies an upgrade kit (PN 23528939) for Series 50 and 60 injectors that consists of a spring 11-mm longer than the original, a cam-follower retainer and new hold-down screws. Apparently, the original springs allowed injector plungers to “float” at high rpm. Remove the rocker-arm assembly, place it on a clean surface, and, working with one injector at a time to avoid mixing parts, remove the two 5-mm Allen screws that secure the follower retainer. Lift the retainer and the follower free (Fig. 6-26). Clean the parts in diesel fuel, and install the new spring, follower and retainer, using the screws provided in the kit. Torque to 25–28 N-m (22–25 lb-in.).

Written by Ed

February 14th, 2011 at 8:21 am

Posted in Electronic Systems

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Detroit Diesel

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Now in its sixth generation, DDEC (Detroit Diesel Electronic Control or “dee-deck”) was the first EMS designed for heavy-duty diesels. Later versions follow European practice by incorporating VGT, large amounts of EGR, and exhaust aftertreatment.

VGT generates boost across the whole rpm band. It also enables large amounts of exhaust gas to be recirculated under load, when EGR is needed most. Exhaust aftertreatment traps particulates and converts oxides of nitrogen, which are smog precursors, into nitrogen and water.

The complexity of later DDEC systems and a design philosophy that ties the product closely to service facilities severely limits what can be done without access to factory documentation and a DDR/DDL (Diagnostic Data Reader/Diagnostic Data Link). What follows pretty well sums up what a nonfactory technician, armed with a volt-ohmmeter and a generic J 1587 data-link scanner can accomplish. Table 6-5 lists Detroit Diesel nomenclature.

Figure 6-23 illustrates Series 60 DDEC V component locations and Figs. 6-24A and B illustrate schematics for injector and VPOD wiring. In addition to those called out in the schematics, DDEC V and VI systems incorporate sensors that monitor:

• Ambient air temperature and pressure
• EGR Delta-P and flow rate
• Turbo boost and rpm
• VGT vane position

Written by Ed

February 14th, 2011 at 8:14 am

Posted in Electronic Systems

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