GM Celebrity/Century/Ciera/6000 1982-1996 Repair Guide

Injection Pump

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REMOVAL & INSTALLATION



See Figure 1

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner.
  4.  
  5. Remove the crankcase ventilation filter and pipes from the valve cover and air crossover.
  6.  
  7. Remove the air crossover and install special cover J-29657 or its equivalent. Remove the fuel lines, filter and fuel pump as an assembly. Cap all line openings.
  8.  
  9. Disconnect the throttle cable. Remove the return spring.
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  11. Remove the throttle and TV detent cables from the intake manifold brackets.
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Fig. Fig. 1: Right side view of the injection pump on a diesel engine

  1. Disconnect the fuel return line from the injection pump.
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  3. Disconnect the injection line clamps, closest to the pump.
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  5. Disconnect the injection lines from the pump. Cap all openings. Carefully reposition the fuel lines.
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  7. Remove the two bolts retaining the injection pump.
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  9. Remove the pump. Discard the pump to adapter O-ring.
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To install:
  1. Installation is the reverse of removal, with the following recommendations. Position the number one cylinder to the firing position. Install a new O-ring, then install the pump fully, seating it by hand. If a new or intermediate adapter plate is used, set the pump at the center slots on the mounting flange. If the original adapter is used align the pump timing mark and the adapter mark. Tighten the pump bolts to 35 ft. lbs. (47 Nm).
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  3. Connect the negative battery cable.
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CHECKING INJECTION TIMING



A special diesel timing meter is needed to check injection timing. There are a few variations of this meter, but the type desirable here uses a signal through a glow plug probe to determine combustion timing. The meter picks up the engine speed in RPM and the crankshaft position from the crankshaft balancer. This tool is available at automotive supply houses and from tool jobbers, and is the counterpart to a gasoline engine timing light, coupled with a tachometer. An intake manifold cover is also needed. The marks on the pump and adapter flange will normally be aligned within 0.050 in. (1.27mm).

  1. Place the transaxle shift lever in Park, apply the Parking brake and block the rear wheels.
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  3. Start the engine and let it run at idle until fully warm. Shut off the engine.
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If the engine is not allowed to completely warm up, the probe may soot up, causing incorrect timing readings.

  1. Remove the air cleaner assembly and carefully install cover J-26996-1. This cover over the intake is important. Disconnect the EGR valve hose.
  2.  
  3. Clean away all dirt from the engine probe holder (RPM counter) and the crankshaft balancer rim.
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  5. Clean the lens on both ends of the glow plug probe and clean the lens in the photoelectric pickup. Use a tooth pick to scrape the carbon from the combustion chamber side of the glow plug probe, then look through the probe to make sure it's clean. Cleanliness is crucial for accurate readings.
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  7. Install the probe into the crankshaft RPM counter (probe holder) on the engine front cover.
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  9. Remove the glow plug from No. 1 cylinder. Install the glow plug probe in the glow plug opening, and tighten to 8 ft. lbs. (11 Nm). Do not over tighten.
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  11. Set the timing meter offset selector to A (20).
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  13. Connect the battery leads, red to positive, black to negative.
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  15. Disconnect the two-lead connector at the generator.
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  17. Start the engine. Adjust the engine RPM to the speed specified on the emissions control decal.
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  19. Observe the timing reading, then observe it again in 2 minutes. When the readings stabilize over the 2 minutes intervals, compare that final stabilized reading to the one specified on the emissions control decal. The timing reading will be an ATDC (After Top Dead Center) reading when set to specifications.
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  21. Disconnect the timing meter and install the removed glow plug, tightening it to 15 ft. lbs. (20 Nm).
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  23. Connect the generator two-lead connection.
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  25. Install the air cleaner assembly and connect the EGR valve hose.
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ADJUSTMENT



  1. Shut off the engine.
  2.  
  3. Note the relative position of the marks on the pump flange and either the pump intermediate adapter.
  4.  
  5. Loosen the nuts or bolts holding the pump to a point where the pump can just be rotated. You may need a wrench with a slight offset to clear the fuel return line.
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  7. Rotate the pump to the left to advance the timing and to the right to retard the timing. The width of the mark on the intermediate adaptor is about 2 / 3 °. Move the pump the amount that is needed and tighten the pump retaining nuts to 35 ft. lbs. (47 Nm).
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  9. Start the engine and recheck the timing as described earlier. Reset the timing if necessary.
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  11. Reset the fast and curb idle speeds.
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Wild needle fluctuations on the timing meter indicate a cylinder not firing properly. Correction of this condition must be made prior to adjusting the timing.

  1. If after resetting the timing, the timing marks are far apart and the engine still runs poorly, the dynamic timing could still be off. It is possible that a malfunctioning cylinder will cause incorrect timing. If this occurs, it is essential that timing be checked in cylinder 1 or 4. If different timing exists between cylinders, try both positions to determine which timing works best.
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