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Fuel Injection Pump Timing

The biggest mistake made during injection pump timing is installation of the pump 180 degrees off. The crankshaft turns two revolutions for every revolution of the camshaft. You must install the pump on the correct camshaft revolution! The number one plunger on injection pump feeds number six engine cylinder. Hence the engine must be set at 20deg after top dead center on the power stroke of cylinder #1, which is also intake stroke of cylinder # 6. A quick refference; both cam lobes over cylinder #1 are upwards and intake lobe of #6 is downward. Next align the marks on the pump and slide it into place. No precise drip timing necessary with this type of injection. Just get your crankshaft timing at 20 ATDC (on the correct revolution) and the injection pump marks aligned before installation!

Mrfatboy writes: While trying to diagnose my injection pump problems I came across JA17's post about how to check if you pump was installed correctly or possibly 180 degrees out of alignment without taking off the injection pump.

JA18's original post:

"I do have a method by which you can check without taking the injection pump off. You would need to unscrew some injection lines and remove one fitting and check valve in the pump to do the check.

Unhook the three rear injection lines. Remove the injection pump #4 19mm fitting (third from rear). Remove the check valve in the injection pump. You can now feel the position of the #4 plunger (piston) in the pump using a nail or such. When the engine is at 12 degrees ATDC (after top dead center of #1 cylinder)on the compression stroke (#1 cam lobes upward ), the plunger in the pump should be near the top of it's stroke. You can feel it travel upwared and downward as you turn the engine by hand. When it reaches the top of its stroke check the crankshaft timing.  During re-assembly be sure not to overtighten the 19mm fitting. 18 ft. lbs is the specified torque."

I have gone a step further and measured all of IP cylinder hole depths while I had a chance.  I also had a spare IP that I was able to verify my findings.  First I set my engine to 20 ATDC.  JA17 stated 12 ATDC but after talking with him we both agree that the 8 degree difference is attributed to the rounded cam.  In short there is probably an 8 degree amount of play at the top or bottom.  Anyway, the IP is supposed to be installed at 20 ATDC so that is where I set the engine and will base all my measurements from there.  At 20 ATDC the IP alignment marks should perfectly line up as in figure #1.  If somebody installed the pump at 20 ATDC with the #1 cam lobe DOWN the IP will be 180 degrees out of phase.  I have read in this forum that an IP installed 180 degrees out of phase runs rich and less power.  However, the car does run.


Figure 1: Correct alignment at 20 ATDC with #1 cam lobe up



Figure 2: Incorrect alignment at 20 ATDC with #1 cam lobe down



Figure 3: Measurements with IP installed correctly



Figure 4: Measurements with IP installed 180 degrees out of phase



Figure 5: Injection Pump


You can see from fig #3 and #4 that the measurements are exactly opposite of each other from correct to 180 degrees off.  I did the measurements with a micrometer.

Diagnostic steps

  1. Set engine timing to 20 ATDC #1 cam lobe up (very important)
  2. Remove IP fuel line retaining clamps
  3. Choose which injection line fitting you want to use (most front or most rear are easiest)
  4. Remove your fuel line retaining nut (17mm) and slide it up the line out of the way
  5. Remove IP piston fitting (19mm)
  6. Remove Check Valve using a tool similar to this: Valve tool
  7. Place tape across hole
  8. Insert toothpick and measure depth.
  9. If measurements match with the above pictue (fig #3) your pump was installed correctly.  If not, your are 5% of the way there to remove the pump all the way and realign it :) See other Removal of Fuel Injection Pump.
  10. Reverse steps to put everything back together.

From this new data, one only needs to remove the front or rear injection line to test if the pump was installed correctly.  That saves some time. Also, by using the piston depth numbers one could extrapolate if their IP was partially off and not the whole 180 degrees.

I hope this helps somebody!
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