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The pics in this post were taken from my Isuzu Injection Pump Service Manual.



The first shows where to find the ID labels for the injection pump, governor, and lift pump.




The other 2 show the labels for injection pump and governor, and the numbers that are of interest to us when de-coded. On the right side is an example number and under the relevant number or character is a number in parenthesis ( ) to indicate the position for the de-coding explanation.


Note that the pumps on the Isuzu 4B engines are made by a Japanese manufacturer under license to Bosch. They will be either Diesel Kiki or Zexel, but essentially they are Bosch pumps and governors.



For the injection pump:



  1. refer to the pic
  2. refer to the pic
  3. 'S' means the pump comes with a mounting flange, no marking is no flange
  4. number of plungers this will be 4 for our 4 cylinder engines
  5. injection pump size in our case 'A', for the 'A' type pump. Other engines may have 'P' or 'AD' if they have 'P', or 'AD' type pumps.
  6. this number is particularly interesting as it is 10 times the plunger diameter in mm. Usually it is 95 (9.5mm) for the 4BD1T and 4BD2T, but we are keen to find one with 10mm plungers.
  7. '/' has no meaning, 'C' is a design code
  8. this number tells the position of the lift pump if fitted
  9. this tells the location of the governor if fitted
  10. this tells the location of the automatic timing advance '0' if no auto timing advance
  11. tells the direction of rotation as viewed from the auto timing device end. 'R' for clockwise 'L' for counter clockwise.
  12. This is a design code.

For the governor:



  1. refer to the pic
  2. refer to the pic
  3. refer to the pic. Isuzu continued to use the 'RLD' governor for automotive use after Bosch bought out the simpler 'RQV' governor for variable speed and load applications – the problem being that the 'RQV' is too large across the housing where the flyweights are located and won't clear the block on Isuzu 4B engines, some Isuzu 6BG engines do have what look to be 'RQV' governors.
  4. this is the controlled speed range idle/max in pump rpm (half engine rpm).
  5. this is the injection pump size 'A', 'AD' or 'P' as above.
  6. This is an ID number for the flyweights and springs
  7. mounting position
  8. specific design number
  9. 'd' if equipped with a 'torque device', or no mark if no 'torque device'.
 

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The pump fitted to my 4HE1TC is S4MD110/41ALS2. If I understand the chart above, it would indicate 11 mm plungers. Should be big enough for some significant power :)
 

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John, excellent info as always, thank you. I do have a question though, as you mentioned the RQV is physically too large for our applications, is there another governor that has the supposed longer rack travel capability that might clear the 4BD series?
To my mind it was inconclusive that Schied had to change Randy's governor to the RQV type to get the required fuel rate, or that they simply didn't like working with the RLD governor (there is mention along those lines in Randy's thread). What else was modified in that pump was kept very secret. I'm not convinced it was only increased rack travel, because increasing rack travel simply turns the plunger barrels so the spiral groove that opens the port to finish the injection event occurs later, i.e. longer effective plunger stroke/displacement. Larger plungers and a regrind of the cam profile so that it lifts the plunger quicker, in conjunction with more rack travel is what I suspect.
 

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To my mind it was inconclusive that Schied had to change Randy's governor to the RQV type to get the required fuel rate, or that they simply didn't like working with the RLD governor (there is mention along those lines in Randy's thread). What else was modified in that pump was kept very secret. I'm not convinced it was only increased rack travel, because increasing rack travel simply turns the plunger barrels so the spiral groove that opens the port to finish the injection event occurs later, i.e. longer effective plunger stroke/displacement. Larger plungers and a regrind of the cam profile so that it lifts the plunger quicker, in conjunction with more rack travel is what I suspect.
Going from memory, I recall the concern being the ability to pull the rack "back" (decrease or less fuel) far enough with whatever setup they had.

I also remember Randy grousing a little about it might just be the RLD being a PITA to work with on that kind of application (non stock).
 

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Discussion Starter #7
I should re-read Randy's thread from time to time and refresh my memory. It's a pity they were so secretive. Looking at pics of a 6BG1 for sale, I noticed it had the injection pump was moved back, to center it about the 6 cylinders, with what looked like a drive shaft with flexible coupling behind the timing case, it looked like the timing advance was still in the normal position on the pump nose. It made me think it might be possible to do similar and move our pumps back and out a little so an RQV governor will clear the oil relief valve cartridge.
 

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My 1979 6BD1 is setup with the same IP drive. The pump is mid mounted, and connected to the front gear train with a prop shaft.

 

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The pump fitted to my 4HE1TC is S4MD110/41ALS2. If I understand the chart above, it would indicate 11 mm plungers. Should be big enough for some significant power :)
That is a Bosch 'AD' type pump (the 'M' after 'S4' should be an 'A', so S4AD110....), and some years ago I had an injection shop try 11 mm elements from an 'AD' pump in my 'A' pump but unfortunately they are an overall larger element and won't fit into the frame of an 'A' pump.
 

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Has anyone ever heard of a "RU" minimum-maximum governor? I have a 78 Dodge Pickup with a Mitsubishi 6DR5 in it and it has a Bosch "a" pump with a ND-EP/RU250-1780ARND173 governor.
 
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