Diesel Engine Troubleshooting

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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.

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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

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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

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Ford 7.3L DI Camshaft Position Sensor

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Sensors for mid-1994 to 1996 models are marked C96 or C 97; C-92 sensors were used from late-1997 to the end of production. These OEM units can cause no-start, hard-start, erratic idle, and shutdown on deceleration problems unless shimmed 0.010 in. off their mounting surfaces.

Replacement sensors have been shortened and do not require shimming. The CMP for mid-1994 to 96 models carries International part number C92 F7TZ-12K03-A, and can be recognized by the tin-coated connectors. The latest C98-F7TZ-12K073-A 128 Electronic management systems version features gold-plated connectors, which gives one an idea of the problems associated
with these units. And while the newer CMP has better reliability than the previous type, its gold connectors present an electrolysis problem when mated with the tin connectors used on early 7.3L production. Replacement sensors cost about $100 from International. It’s good insurance to carry a spare.

The CMP mounts on the front of the engine, adjacent to the camshaft, and is secured by two 10-mm bolts. Trouble code 0344 will be flagged if sensor response is intermittent; 0341 means that enough electrical noise has been detected to affect engine operation. Check connectors for loose, bent, or spread pins and clean grounds. Code 0340 indicates the absence of a sensor signal while cranking. In this case, the engine will not start.

Written by Ed

February 14th, 2011 at 8:10 am

Ford 7.3L DI Air in Fuel Circuit

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Air leaks can cause rough idle, shutdowns on deceleration, and no-starts. The time required for air intrusion to make itself known depends upon the proximity of the leak to the transfer pump. For example, the engine might start and run several minutes before air entering from a fuel tank connection reaches the pump. Air entry closer to the pump has more immediate effects.

Multiple leak points—Schrader valves, bleed screws, fuel-line connections—make the filter/water separator a prime suspect. Use OEM clamps on hose connections, new seals, and dope screw threads with sealant. Surplus fuel from the injectors recycles back to the filter. The connection at the filter incorporates a check valve that closes when the engine stops. Should the check valve leak, air from the return line will be drawn into the filter as fuel in the canister cools and shrinks.

Written by Ed

February 14th, 2011 at 8:09 am

Ford 7.3L DI Air in Lube Oil

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Aeration often results in hard or no-starts, erratic idle, shutdowns on deceleration, and loss of rpm. CG4/SH oil helps control the problem. As originally specified, 1994-model engines held 12 quarts of crankcase oil. This specification has been revised to 14 quarts. The dipstick should be recalibrated or replaced with Ford PN F4TZ-6750-E.

Leaks at pump pickup tube o-ring can be detected by jacking the rear wheels 10 in. off the ground and overfilling the crankcase with three quarts of oil. If the idle smoothes out, replace the o-ring seal.

In addition to its effect on performance, air in the oiling system causes rapid injector wear. Whenever an injector is changed, the associated cylinder bank should be purged:

• Disconnect the CMP to prevent the engine from starting.
• Mechanical fuel pumps (pre-1998 models)—disconnect the return line at the fuel pressure regulator on the fuel filter. Crank the engine in 15-second bursts, allowing ample time for the starter to cool and until a steady stream comes out of the line.
• Electric fuel pumps—crack a vent port on each cylinder head and run the pump until air is purged.

If head galleries have been drained, prefill the galleries with pressurized oil as described under “Low oil pressure.”

Written by Ed

February 14th, 2011 at 7:58 am

Ford 7.3L DI Low Oil Pressure

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If you have not already done so, check the oil level in the pump reservoir, which should come to within an inch of the top of the unit. If the engine has been idle for a long period, oil drains back out of the reservoir, making for hard starting.

Verify that there are no leaks at the line connections, around HEUI bodies and into the fuel system. Remove the valve covers and look for cracks in the casting, caused by mis-drilled oil galleries. Small leaks can be detected bypressurizing each gallery with an injector tester or a grease gun and a 3000-psi pressure gauge. Charge the gallery with oil at 2000 psi and wait several hours for any leaks to register on the gauge.

The next step in the search for causes of low oil pressure is to check the IPR (functionally similar to the Caterpillar IAPCV). If the 5V +/_ 0.5V reference signal is present and the output circuit is not shorted or open, replace the regulator o-rings with parts available from Ford International or aftermarket sources. The DF6TZ- 9C977-AN Dipaco repair kit services IPRs used before and after engine SN 187099. If o-rings do not solve the problem, the regulator should be tested by substitution of a known good unit and, if necessary, replaced. Torque to 35 ft/lb and do not use sealant that could clog the orifice on the threaded section.

Written by Ed

February 14th, 2011 at 7:56 am

Ford 7.3L DI Erratic Idle

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A frequent complaint is a rough idle, which can originate from the fuel system or from one or more weak cylinders. Follow this procedure:

1. Verify that the disturbance at idle is not caused by exhaust pipe contact with the vehicle frame, a loose air-conditioner compressor, or other mechanical sources.
2. Scan for trouble codes.
3. Perform steps 1 through 9 in the preceding “Slow or no-start” section.
4. If you have access to a Ford factory tester, make a “buzz” test on the injectors, listening for differences in the sound. A bad injector often buzzes at a lower frequency than the others.
5. Remove the valve covers and, with the engine idling, watch the oil flow out the injector spill ports. Each time a HEUI closes, the oil charge above the plunger drains out the spill port. Thus, amount of oil spilling out of an injector relates to fuel delivery. Replace any injector that passes noticeably less oil than the others.
6. Test engine compression.
7. As a last resort, replace the injectors.

Written by Ed

February 14th, 2011 at 7:55 am

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Ford 7.3L DI Slow or no-start

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Begin with a walk-around the vehicle to determine that the tank is at least a third full, batteries are charged, battery terminals are clean and secure, and the radiator is topped off. Check the crankcase and high-pressure pump reservoir oil levels. Ford requires a 15W40 oil that meets SH, CG-4, and Mack E-0L specifications, and recommends that Motorcraft 15W40 “black-lid” be used because of its resistance to aeration. The oil level should come to within one inch of the top of the pump reservoir.

Question the operator to learn as much as possible about the problem and conditions that led up to it. Did it appear suddenly? After repairs to the engine? What parts were replaced? Does the malfunction occur at all engine temperatures or only during cold starts?

Mechanics differ about what checks to make first. But, however you sequence them, the main bases to touch with 7.3L are:

1. Replace the air filter and examine the exhaust system for restrictions. The exhaust butterfly valve, which should cycle closed on cold startups, may stick shut. The back-pressure regulator that controls this valve can also fail.

2. Retrieve active (current) and historical trouble codes. P1111 means that no codes are set and, as far as the ECM knows, things are normal.

3. Drain a sample of fuel from the filter while cranking. If water is present, drain the tank(s) and refill with clean fuel before proceeding. Inspect the water separator for oxidation damage and, if necessary, replace it.

4. Check the glow-plug relay, which is a high-mortality item and especially so in its original oval form. The newer round-case relay interchanges with the older unit. The red cable, connected via fusible links to the starter relay, should have battery voltage at all times. If voltage is not present, check the fusible links and connections for opens. The heavy 10-gauge brown wire going to glow plugs is hot when the relay is energized. One of the 18- gauge wires (usually red with a light green tracer) is the signal wire, energized by the lube-oil temperature sensor. This wire must have battery voltage for the relay to function. Depending upon the circuit, the “wait-tostart” lamp may signal when the glow plugs energize or merely count off seconds. Individual glow-plugs should have a resistance of about 0.1 to ground when cold and 2 or more after cylinder temperatures normalize.

5. Check fuel pressure while cranking for 15 seconds. If pressure is less than 50 psi, replace the fuel-filter element, remove any debris on the fuel screen and on the screen protecting the IPR deceleration orifice. See the “IPR” section for more information.

6. Check injector-oil pressure during cranking. A pressure of 500 psi must be present to enable the injectors. Expect to see 960–1180 psi at high idle and 2500+ psi during snap acceleration. If the computer senses that the IPR has malfunctioned, it holds idle oil pressure at a constant 725 psi. Trouble code 1280 means low IPR signal voltage, 1281 high signal voltage, and 1212 abnormally high (at least 1160 psi) oil pressure with engine off. See “Low oil pressure” below.

7. While cranking, check for the presence of an rpm signal. A failed CMP can hold oil pressure below the 500-psi injector-enabling threshold. Refer to “Camshaft position sensor” section below.

8. Check power at the injector solenoids with an appropriate scan tool. Zero pulse width on all injectors means a bad CMP sensor or IDM. Failure may trip trouble code 1298. The high power levels—10A at 115 VDC—put severe demands on the injector drive module. In addition, modules on Econoline 7.3L vans built before 4–11–96 have problems with water intrusion.

9. Finally, check for air in the circuit by inserting a length of transparent tubing in the return fuel line.

Written by Ed

February 14th, 2011 at 7:52 am

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Ford 7.3L DI Power Stroke

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Four engines, three of them built by International, go by the name “Power Stroke.” The first was the direct injection turbocharged 7.3L V-8. This engine, also known as the International T444E, powered F series trucks and E series vans between 1994 and 2003. The 32-valve 6.0L Power Stroke, or International VT 365, has been used on pickups and vans since 2004. Production of the 6.0 will end in 2007, when it will be replaced by a 6.4L V-8. The Ford V-6, aka DT17, has been used on low cab forward (LCF) trucks since 2005.

In many ways, the original 7.3L Power Stroke is the most interesting of the group. It carried Ford to first place in light diesel truck sales and generated a cult following not seen since the days of the Mustang. People have taken out second mortgages on their homes to buy these trucks.

The material dealing with the operation of HEUI injectors, the high-pressure oil pump, and the IAPCV also applies to the Power Stroke, although Caterpillar and Ford parts rarely interchange and pressure specifications vary. Table 6-4 translates Ford acronyms and describes sensor function. “Supply” is the voltage going to the sensor; “signal” is the sensor output to the computer (ECM).

AP Accelerator position sensor
Along with other variables, the ECM uses the AP signal to determine injector oil-pressure, pulse width and timing. Supply 5.0V +/_ 0.5V, signal 0.5–0.7V at idle, 4.5V at wide open throttle.
BARO Barometric pressure sensor
The ECM uses the BARO signal to adjust fuel timing, fuel quantity, and glow-plug on-time during high altitude operation. Supply 5.0V +/_ 0.5V, signal 4.6V at sea level, decreasing at higher altitudes.
CMP Camshaft position sensor
The ECM uses the CMP signal to monitor engine rpm and tdc for Nos. 1 and 4 cylinders. This Hall-effect sensor generates a digital voltage signal of 12.0V high, 1.5V low.
DTC Diagnostic trouble code
EBP Exhaust back pressure sensor
The ECM uses the EBP signal to control the exhaust pressure regulator (EPR). Supply 5.0V +/_ 0.5V, signal 0.8–1.0V @ 14.7 psi at idle, increasing with engine speed and load, decreasing with altitude.
EOT Engine oil temperature sensor
The ECM uses the EOT signal to control glow-plug on time, EPR, idle rpm and fuel delivery and timing. Supply 5.0V +/_ 0.5V, signal 4.37V @ 32°F, 1.37V @ 176°F, 0.96V @ 205°F.
EPR Exhaust back pressure regulator
The EPR operates hydraulically from oil taken off the turbocharger pedestal mount. When intake air temperature is less than 37°F (50°F on some models) and the engine oil temperature is less than 140°F (168°F on some models) the ECM energizes a solenoid valve that causes oil pressure to close a butterfly at the turbo exhaust outlet. The valve opens under load and as the engine warms.
GPC Glow plug control
The ECM energizes the GPC relay for 10–120 seconds depending on engine oil temperature and barometric pressure.
GPL Glow plug light
The ECM turns the “wait to start” lamp “on” for 1–10 seconds, depending on engine oil temperature and barometric pressure.
GPM Glow plug monitor
Used on 1997 and later California vehicles to report if glow plugs malfunction.
IAT Intake air temperature sensor
The ECM uses the IAT signal to regulate exhaust backpressure. Supply 5 V+/_0.5V, signal 3.90V @ 32°F, 3.09V @ 68°F, 1.72V @ 122°F.
IPC Injection pressure control sensor
The ECM uses the IPC signal to match fuel delivery with load and to stabilize idle rpm. Signal 1.00V @ 580 psi, 3.22V @ 2520 psi.
IDM Injector driver module
The IDM receives cylinder-identification and fuel-demand signals from the ECM, and generates a 115 VDC, 10A signal for the appropriate injector, varying pulse width as required.
IPR Injection pressure regulator
The ECM varies the duty cycle of the IPR to control oil pressure and the volume of fuel delivered. 0% = full return to sump (open valve), 100% = full flow to injectors (closed valve). Functioning is monitored by the Injector pressure control sensor.
IVS Idle validation switch
The IVS is an on-off switch that signals the ECM when the engine is idling. Signal 0V at idle, 12V off-idle.
MAP Manifold absolute pressure sensor
The MAP measures manifold pressure to limit turbo boost, optimize timing, and reduce over-fueling and smoke. Signal frequency: 111 Hz @ 14.7 psi, 130 Hz @ 20 psi, 167 Hz @ 30 psi.
MIL Malfunction indicator lamp
“Check engine” or “service engine” lamp that the ECM illuminates when certain system faults are present. Can also be used to retrieve trouble codes.
PCM Powertrain control module
PCM is the onboard computer that receives sensor inputs, calculates output signals to actuators, and generates diagnostic codes. The computer also controls transmission shift points, anti-skid braking, and other powertrain functions. Referred to in this text as the ECM.
PID Parameter identification
PID, or the data stream, is the sensor data read by scan tools.

Written by Ed

February 14th, 2011 at 7:46 am

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