Injection pump adjustment
After adjustment, refill the pump with fresh oil (about 1/2 quart). On the MW, the fill port is a plug on the top left side of the governor housing (The ALDA points its direction in the picture below). On the M, remove the shutoff actuator.
No idle compensation is required unless noted.
External Idle Screw
- Controls the fine idle speed.
*Set the engine between 700-800rpm.
- Limits fuel at low boost pressure to control black smoke.
*Loosen the 10mm locknut and adjust the screw CCW in 1/4 turn increments to increase low boost fuel until you see black smoke when the accelerator is floored from a standstill.
**This adjustment will NOT
increase your maximum horsepower. It is purely an emissions control device.
- Prevents the external linkage from forcing the internal linkage past set point.
*Make sure your external linkage is contacting the stop at WOT when pressing on the accelerator pedal. A cracked rubber bushing on the firewall can cause failure to contact.
**Loosen the 14mm lock nut and turn the 9mm screw until two threads
of the screw are visible.
***This adjustment will NOT increase your maximum power without first increasing the internal full load setting.
- Limits maximum engine RPM.
*This can effect the governing of idle RPM and idle quality if adjusted beyond 1 turn.
**Loosen the 10mm lock nut with a wrench while holding the screw stationary (Do not use a socket to loosen the lock nut, the screw will turn with the nut!
***1 turn equals approx. 250rpm, CW increases.
****This should only be adjusted if your engine is in top-notch condition. Increasing maximum RPM comes with a serious risk of throwing a connecting rod and/or floating the valves resulting in catastrophic engine damage.
- Sets the maximum rack travel while the engine is running.
*19mm and 9mm locknuts must be loosened and the 13mm nut turned CW to increase maximum fuel quantity.
**The rack limiter lever can be completely removed
from the pump for maximum power. See below for this procedure.
***Anyone that tells you NOT to remove the limiter is inexperienced. Removing the rack limiter is the ONLY
way to get maximum power from your engine. Leaving the limiter in place, by definition, will LIMIT your maximum power.
Idle Regulation Bumper Spring
- Adds idle unloading spring force against the flyweights to prevent loping/hunting.
*Should not be adjusted.
Coarse Idle RPM Screw
- Sets the idle speed in combination with the outer fine adjustment.
*Should not be adjusted except in conjunction with torque control capsule adjustment.
10mm lock nut.
Start Quantity Cutout
- Allows full fuel for start but not run.
*Also affects other internal functions. Do not touch.
Torque Control Capsule
- (Do not adjust
) Reduces rack travel with increased RPM.
*Reduces smoke at higher RPMs due to the engine's decreased volumetric efficiency at higher RPMs. It is not
used to increase power.
*Loosen 21mm lock ring and turn 14mm capsule CW to increase. Back out the coarse idle RPM screw by the same amount as you turned the capsule.
**A pyrometer is an absolute must if you are going to adjust this. Take it easy and only go 1/8 turn each time.
***Caution: Adjusting the capsule is strongly not recommended
. It will result in the engine becoming slow to return to idle and causes excessive heat (EGTs) at high RPMs.
Full Load Limiter Removal Procedure
An exhaust temperature gauge (pyrometer) is necessary for reliable long-term operation of the engine after this modification.
Do not exceed 1250°F in continuous operation or 1400°F in short bursts (under 5 seconds). Do not use any kind of sealer on any of the gaskets.
Anyone that tells you NOT to remove the limiter is inexperienced
. Removing the rack limiter is the ONLY
way to get maximum power
from your engine. Leaving the limiter in place, by definition
, will LIMIT
your maximum power by LIMITING how far the fuel rack can move towards maximum fuel. Adjusting the torque control primarily, as suggested by inexperienced people, will cause excessive heat (EGTs) at high RPMs. Adjusting or removing the limiter increases fueling across the entire RPM range
, the torque control will still function exactly the same.
1: Remove the oil-filter housing. This is optional, with a long screwdriver its very possible to adjust everything with the housing in place.
2: Remove the pump back plate including shut off actuator and rack damper.
3: Disconnect the vacuum device linkage and tubes. Remove the top lid screws, turn the top lid (or remove both the ALDA and top plate for best access).
4: Remove the limiter's screws and nuts.
5: Push the limiter from the adjusting screw into the inside of the pump.
6: The hardest part is "digging" the limiter out of the bottom of the pump. A small (1/4" or less) pen magnet is strongly suggested for this step. It can only exit through the thin slot on the top of the pump. You have two options- You can turn (rotate) the parts around inside the pump or you can punch out the guide pin the limiter used to slide on. The pin is no longer needed.
7: Once the limiter is out replace everything back in reverse order minus the limiter. Remember to use a new oil filter housing gasket and get the filter housing and block mating surfaces surgically clean. Be careful not to drop any gasket leftovers into an oil channel. If you get an oscillating idle this is a good place to replace the Rack Damper bolt with upgrade unit (upgraded one is gold anodized, the old silver in color) in the back plate of IP.
Note: No governor adjustments are necessary. The rack limiter only affects the maximum available throttle/fuel when the engine is running, it has no effect on any other governor functions.
When you are done, you should have 5 or 6 parts left over (depending on the removal method you chose). DO NOT DISCARD THESE PARTS in case you decide to revert the operation at a later date.
8: Advance the injection timing to 26* BTDC to compensate for the increased injection duration. (Listed near top of the article)
9: Increase boost pressure to the suggested level to provide the necessary air to burn the additional fuel. (Listed near top of the article)
Failure to follow steps 8 and 9 will result in high EGTs and possible engine damage!
The procedure should be the same for all OM601/2/3, pre-1996 OM604/5/6 and European OM616/7 engines, but the throttle linkage setups will vary between models.
17: Torque Control Capsule- Reduces rack travel with increased RPM.
23, 24: High Idle- Limits maximum engine RPM.
25: Full Load- Sets the maximum rack travel while the engine is running.
28: Coarse Idle RPM Screw- Sets the idle speed in combination with the outer fine adjustment.
29: External Idle Screw- Controls the fine idle speed.
50: Related to low idle adjustment (28)
Left- OM61x european models
Middle- OM60x non-turbo models
Right- OM60x turbo models
ELR (Electronic Load Regulation)
The lift rod (163) rests against the guide lever (2a). The actuator (Y22) is supplied by the electronic idle speed control unit with a clocked D.C. voltage in the frequency range of approx. 50 Hz. If engine speed drops (e.g. drive position engaged or power steering turned to full lock), the actuator is energized with a higher voltage.
This causes the lift rod (163) to press against the guide lever (2a) and the control rod (2t) to move in the direction "a" increased quantity.
As soon as the engine speed increases, the voltage is reduced and the control rod (2t) moves in the direction of “b” reduced quantity.
With the ELR unplugged, idle speed should be reduced to 500rpm. Idle speed is adjustable in 50rpm increments via 8-position switch (location varies by model)
Full load quantity (2f/25)
*To increase the full-load fuel quantity, loosen the jam nut, and turn screw 2f/25
(bottom left) out (CCW
). Make careful note of the position of the slot, before & after adjustment.
: Poor idle quality (1000rpm+ unloaded, 500rpm in gear) is known above 1.75 turns for the OM60x and above 5 turns on the OM61x. 2 turns CCW of the nut 2k/50
(idling auxiliary spring) will restore the idle speeds to normal.
***Whatever number of turns you made to full-load screw (2f/25), make the IDENTICAL
adjustment to the idle stop screw, 2b/28
(top/right). If you turn 2f/25
out 1.5 turns CCW, then also turn 2b/28
out 1.5 turns CCW.
****If screw 2b/28
is backed out too much, it can touch the intermediate plate behind the ELR. Check the spec per the FSM procedure if you must change any shims for clearance.
*Because you turned screw 2b/28
, which moved the external throttle lever towards the rear of the engine and rotating lever towards the valve cover, you now must adjust all throttle linkages. Lubricate the ball/socket joints with ATF or #2 multi purpose (red) grease before re-attaching them.
**Due to the number of vehicle models this guide crosses, linkage adjustment is not detailed in this post. Use the procedure in the factory service manuals to adjust your throttle linkages, just remember that the rod lengths specified in the FSM no longer apply after you internally adjust the injection pump.
Internal coarse idle adjustment (2b/28)
idle, CCW decreases
External fine idle adjustment (3/29)
idle, CCW increases
**If you run out of adjustment range, you must adjust the internal coarse idle screw to change the affected range.
Maximum RPM (2m/23)
*Loosen the lock nut of 2m/23
and turn the 10mm Allen screw CW
**One turn equals approx. 250rpm.
Torque Control Capsule (2e/17)
*For best drivability results, Do Not Adjust
**Loosen the 22mm lock nut of 2e/17
and turn the 12mm 2-prong capsule CW
***This adjustment will raise the RPM when the governor starts to pull back fuel (due to the engine's reduced volumetric efficiency).
****Adjustment is not recommended for the first time modifications. It will cause a slow return to idle (no deceleration fuel cutoff) and excessive EGTs above 3000rpm.
Yes, many diesels do have a throttle!
The procedure should be the same for all OM615 and pre-1976 OM616 engines; 200D, 220D and pre-1976 240D models.
The engine must not be started before the throttle and air pipe are installed and the injection pump diaphragm is checked for leaks. Failure to observe this caution can result in severe engine damage from overspeeding (run away).
OIL: This type of injection pump does not have a connection to the engine's oil system. The pump's oil should be changed at the same time as the engine's oil using the same type and viscosity of oil. The red cap is the fill location and the drain plug is located at the lower rear of the back.
Remove the plug midway up the side of the pump, fill the oil until it starts to come out this hole. It will take approximately 1/2 quart.
Synthetic oil will not harm this pump or the engine.
A good seal of the vacuum pipe and manifold is extremely important. Any cracks or leaks in the hose, banjo bolts, throttle gasket, throttle shaft bushings, intake manifold or diaphragm in the injection pump have a significant effect on the operation of the engine.
If a turbocharger is to be added, the throttle MUST
be relocated to the inlet side of the turbo. Having the throttle after the turbo can cause the engine to accelerate out of control (run away), not decelerate when the throttle is closed and/or be extremely sensitive to throttle movement.
Control, AKA, "Gorilla ****"
) - Stop
) - Run
) - Glow plugs
) - Start
There are only two adjustments on this pump. There is no direct maximum RPM, high RPM fuel reduction or altitude compensation on this pump. These functions are controlled by the venturi in the throttle body.
Maximum Fuel (N
): Adjust CCW to increase fuel. Adjust only 1/4 turn at most without an external source of air (turbo, supercharger, nitrous), excessive adjustment will cause high exhaust temperatures and engine damage during extended high throttle use.
Idle Stabilizer (Q
): Do not adjust unless the idle speed is unstable (hunting up and down in RPM) NOTE: Any air leaks in the control system will make idle adjustment impossible.
Idle Speed (U
): Adjust CW to increase idle speed.
Maximum RPM (T
): Adjust CCW to increase maximum RPM. NOTE: Like the mechanical governor pumps, increasing this setting does increase high-RPM power by delaying when fuel begins to be cut off, but it comes with significant risk of major engine damage from overspeeding.
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