[How to] Tell if your injection pump is installed correctly

[mrfatboy]

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 states 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 is installed correctly



Figure #4
Measurements with IP installed 180 degrees out of phase.



Figure #5


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
--------------------
Set engine timing to 20 ATDC #1 cam lobe up (very important)
Remove IP fuel line retaining clamps
Choose which injection line fitting you want to use (most front or most rear are easiest)
Remove your fuel line retaining nut (17mm) and slide it up the line out of the way
Remove IP piston fitting (19mm)
Remove Check Valve using a tool similar to this        http://www.sl113.org/forums/index.php?topic=16055.0
Place tape across hole
Insert toothpick and measure depth.
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 How To's to do that.
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!

[ja17]

Nice documentation !

Thanks!

[ctaylor738]

This worked very well to verify the pump timing on a 250SL.  I only measured the rear-most piston.  Rather than using masking tape, I slid a razor blade across the top of the pump up to the toothpick, and made a small cut.  Then it was easy to take the toothpick out and measure the depth.  Dank Gott it was 39 mm.

Cheers,

CT

[mrfatboy]

I'm glad it worked for you!  Good to know my documentation helped somebody 

[garymand]

Wow, what we do for grins and giggles!  I like the 5% comment and the razor blade modification.  It seems like no matter how cool we do something someone always comes up with a better way!

[saygold]

Does someone have the similar measurements for a R11 fuel injection pump for a 230SL?  Mine has been flushed and the rack moves smoothly both directions but the dimensions are less than the 250SL shown in the post.

Thanks,

Ken Deter
66 230SL 4-spd Euro

[Benz Dr.]

I once had someone call me and ask how to time the IP he just had rebuilt. I said 20 degrees ATDC on number one piston and that he should write it down so he wouldn't forget. He called back again a day later complaining about the pump rebuild and that the engine was smoking badly. I asked if he timed the pump the way I told him to.

 '' Yup, 20 degrees BTDC, just like you said.........''


   I'd say pump timing is kind of important.

[catjim813]

Which set of timing marks should you use when trying to find TDC and 20 degrees after TDC.   I used the set of numbers closest to the timing pointer when I removed my pump. But I also see a second set of timing numbers closest to the front of the engine. I removed my pump using the first set at 20 degrees after TDC I have had the engine removed before and I am not sure the timing marks on the balancer are aligned correctly.  The car was running strong but rich and the injection pump is leaking oil.  I just want to make sure after I have the pump rebuilt I can place it back in correctly.  Pump is out from using your great instructions.   The cam lobe appears to be pointing upwards on the first piston.  It just when I put the car at TDC using the first set of timing marks the number one piston is not at the top using either set of numbers at 0/0.   Thanks for all the help and guidance. 69 280sl

[ja17]

You can double check yourself by checking the camshaft timing marks and/or by carefully inserting something, that will no break off, in the front spark plug hole to see when the piston is on top! Find out which scale is at "0" TDC and use that scale to then move to 20 degrees ATDC #!.

[Peter van Es]

Content added to Technical Manual: http://www.sl113.org/wiki/Fuel/FIPTiming

Peter