Main.TrailIndexPage | Fuel System | Fuel Injection | Removal of Fuel Injection Pump

Removing the Fuel Injection Pump

Take a good look at the scope of the job first of all. The injection pump is attached to the block in the front by two nuts and one allen bolt/nut arrangement. One of the two attachment nuts is on the bottom front and is more easily viewed from below. The other attachment nut is on the front between the injection pump and block.

The 6mm head allen bolt is on the front side and besides attaching the IP it holds several brackets in place also. In the back, the 280SL has a two difficult brackets supporting it to the block. One hangs down from the heater pipe coming out of the head. It is attached to a bracket on the rear of the pump by a 6mm head allen bolt.

Another bracket is fitted to the bottom back of the injection pump and is attached to the block with a bolt in a difficult place between the oil filter canister and the block. In addition, there are a lot of fuel lines, water lines, an oil line, some wires which must be dis-connected or moved out of the way. Take a look at all the attachments and connections, to make sure you have the tools and ambition to begin the work.

We can help you get over difficulties, ask lots of questions. The 250SL pump can be the most difficult to remove since it has the added oil cooler directly under the injection pump, which makes space a little tighter.

You need to turn the engine to 20 degrees after TDC so that when you pull the pump out you can check the timing marks on the pump. Or you have to turn the engine to the same place later on before you put it back in. See Timing of Fuel Injection Pump.

Seems to me that I had to remove the cooler lines before I had all the room I needed. Takes about 2 hours to remove a pump. You remove them from the top and out. There's a lot of stuff in the way but it's possible. Take the injection lines off if you need to.

Steps

  1. Disconnect the negative post of the battery.
  2. Check to make sure your engine crankshaft couter-weight timing scale is visible and if it has two scales you need to identify which scale is to be used.
  3. I like to remove all the spark plugs so turning the engine is made easier.
  4. Remove all the spark plug wires with the distributor cap as a unit so they are not in the way.
  5. Set the engine to 20 degrees after top dead center (#1 cylinder compression stroke). This is commonly known as 20 degrees AFTDC #1. The camshaft lobes over #1 cylinder will be basically pointing upwards when the cylinder is on the compression stroke. If the lobes are pointing basically downward, then you need to turn the engine 180 degrees to 20 ATDC again so they are pointing basically upward. See also: Timing of Fuel Injection Pump.
  6. Drain the coolant, you will have some water lines to disconnect.
  7. If you are sending the injection lines off to be re-plated, then start by removing the linkage rods If you are not sending these out to be re-plated, removal is not needed. If they are taken off, take lots of pictures. They can be a real puzzle to re-assemble correctly.
    • Removing the valve cover at this point, makes the job easier.
    • Remove all the injection lines together as a set. You will need to unfasten the ends at each injector, unfasten the 17mm fittings at the injection pump and remove the one main 19mm attachment bolt for the injection line assembly at the front of the cylinder head.
    • Disconnect any coolant or vent lines which may also be attached and part of the injection line assembly. The injection lines now can be removed as an assembly.
  8. If you are not removing the injection lines from your engine, unfasten each 17mm fitting at the injection pump, one at a time starting from the rearmost line and working forward. Slide the fitting up the line and out of the ways before you move to the next fitting.
  9. Unfasten the 7th injector line (cold start line) which attaches to the "T" fitting near the pump. At this point all the lines at the pump are loose and can be moved away a bit.
    • optional for better access...... If your engine has the coolant pod at the cylinder head holding the thermo-time switch and temperature bulb for the temperature gauge , then remove the pod as a unit with all lines left attached. It unfastens with the one 15mm hex bolt. Carefully move the pod aside.
  10. Unfasten and remove the IP fuel intake line.
  11. Unfasten and remove the IP fuel return line.
  12. Unfasten the cold idle air hose at the back of the WRD (warm running device).
  13. disconnect the one or two electrical wires connected to the rear of the IP.
  14. disconnect the metal oil line (14mm fitting) at the engine block side of the IP.
    • optional .... I like to remove the fuel filter canister and its top mounting for much easier access to the lower IP mounting nut. Otherwise you may just want to remove the fuel canister and access the lower IP mounting nut from below.
  15. unfasten the three IP flange/eng. block attachments at the front of the IP (one upper nut, one alen bolt on the side, and another lower nut at the lower flange of the IP.
  16. slide the injection pump straight rearward and off! If yours a 250SL with the oil cooler below the IP, you will have to remove the rear bracket completely off the IP in order to clear the oil cooler metal line.

Be aware of the splined coupling between the IP and the engine. It can be removed but be sure not to forget it during installation. You may also want to have a new gasket or gaskets on hand for the IP/ engine block connection. If yours is a 250SL or 230SL make sure to check or renew the oil in the IP when it is off. Don't forget to fill or check it.

Pictures


Fuel Injection Pump on 230 SL



Fuel Injection Pump on 250 and 280 SL



Rear bracket



Rear bracket (late)



Fuel Injection Pump Attachment



Front Flange



Front Flange and Timing



Injection Line Assembly



Coolant Pod



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