Mercedes Coupes/Sedans/Wagons 1974-1984 Repair Guide

Injection Pump

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See Figure 1

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Fig. Fig. 1: View of a typical diesel fuel injection pump's components

In many cases of poor running, the injection pump itself is at fault. Fuel that is extremely gritty will cause wear of the pump plungers, and plunger springs can break in service. Accurate testing of the pump must be carried out on a test stand. Aside from testing the governor vacuum and control rod, little else other than visual inspection for broken or worn parts can be accomplished.

REMOVAL & INSTALLATION



See Figures 2 and 3

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Fig. Fig. 2: To remove the fuel injection pump, use a flare nut wrench to loosen the fuel lines ...



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Fig. Fig. 3: 1. Injection pump 2. Fuel lines ... then separate the fuel lines from their injection pump connections

  1. Unscrew all the injection lines, the vacuum line and fuel lines.
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  3. Plug the lines, then detach the connecting rod for the auxiliary mechanical control and the starting cable at the adjusting lever.
  4.  
  5. Turn the crankshaft, in the normal direction of rotation, to align the 45- BTDC mark with the pointer (No. 1 piston on compression stroke).
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  7. Matchmark the pump and flange.
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  9. Unscrew the nut at the bell-shaped support, then the front flange hold-down nuts. Pull the pump from the crankcase, then remove the coupling sleeve from the pump drive collar or driveshaft. New pumps do not come with the splined drive collar, therefore the old one must be removed if the pump is to be exchanged.
  10.  
  11. Using a puller, carefully remove the collar and woodruff key.
  12.  

To install:
  1. Make sure that the crankshaft has not moved from the 45- BTDC position, then insert the woodruff key into its groove in the driveshaft, making sure the shaft is dirt free.
  2.  
  3. Install the drive collar and hex nut, using a pair of pliers wrapped in tape to hold the collar while tightening the nut. It is extremely important that the splines are not damaged in any way during this operation.
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  5. Try sliding the coupling sleeve onto the drive collar. If it slides on easily, it can be pressed onto the driveshaft. Remove the oil overflow pipe plug at the rear of the injection pump and adjust the start of delivery position by aligning the marks. Apply light finger pressure to the follower in a direction opposite normal direction of rotation (left). This pressure should cause the drive collar to jump two teeth.
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  7. Grease the paper gaskets with petroleum jelly and install them to the side of crankcase, then install the pump, fingertightening the bolts in the slotted holes.
  8.  
  9. Turn the crankshaft in the direction of rotation to 24- BTDC and check the start of delivery, as outlined previously.
  10.  

 
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