All information presented herein is purely for informational purposes only, I and MercedesForum
assume no liability for your or anyone else's actions. All procedures and adjustments in this guide are to be performed AT YOUR OWN RISK
. The pump can only be properly calibrated by a Diesel injection specialist on an injection pump test bench, this is not intended as a DIY at home pump calibration guide. Getting your engine into good running condition and installing an exhaust temperature gauge (pyrometer) is STRONGLY recommended before
you contemplate touching any injection pump internals. If you believe any of the following information to be incorrect please make a post or contact me through the forum PM system and it will be corrected asap.
Pyrometer, aka EGT gauge
If you skip installing a pyrometer you risk major damage to the engine and turbo from high combustion heat.
of more than 10-20 seconds can create combustion temperatures high enough to damage the engine. This damage is not instant, its cumulative. The longer you run hot the more damage excessive temperatures will do and it won't be obvious there is a problem until its too late. 1250*F (675*C) is a safe limit for continuous
output, 1400*F (815*C) is acceptable for short intervals
(under 5 seconds).
First off, more is not always better
The maximum useful boost pressure is determined by four factors:
1: How much fuel you're injecting
2: If you cool the charge air; Intercooler, water injection, etc
4: Pre-turbo exhaust pressure
A pre-turbo exhaust manifold pressure (EMP) gauge is very recommended to help determine the ideal boost pressure. The "no visible exhaust smoke" method works, but its like trying to assemble a jigsaw puzzle without the box picture.
An EMP gauge can be built by installing a brass ferrule fitting in the manifold before the turbo and using 2' of 1/16" copper tube (to cool the exhaust) with a standard boost gauge. The EMP gauge should read 2x that of your boost gauge for adequate measuring range.
When boost pressure is excessive
, drive pressure will be higher than 2:1 to boost pressure. This is caused by a lack of fuel to spin the turbo fast enough. Drive pressure higher than 2:1 has two major effects, it drastically increases exhaust temperature
and increases engine pumping losses
. Both increase stress on the engine and reduce
The perfect ratio is 1:1 but 1.5:1 is also very good. You have found your ideal boost pressure when your turbo is working in this range and there is no visible black smoke from the exhaust.
Some examples of boost pressures I recommend.
These are not guesses. They are based both on airflow calculations and real-world trial and error.
Stock engine: 11psi
Stock engine with an intercooler: 8psi
Rack limiter removed without an intercooler: 17psi
Rack limiter removed with an intercooler: 12psi
Note: These boost pressures are at sea-level (14.7psi-absolute). If you live above 4000ft elevation you will need more boost to make up for the lower atmospheric pressure (For example, Denver's barometric pressure is 12.1psi).
Here is an airflow calculator to help you determine the boost you need (its already programmed for a factory-stock OM617a): http://www.not2fast.com/turbo/glossa...torDutyCycle=0
Altering the air filter and exhaust systems do not provide any
benefits in power or economy.
The stock intake is already a true cold
air intake and the filter flows efficiently to 400cfm.
The stock mufflers are a straight-through, unbaffled, design and the diameter is already large even compared to modern cars.
Installing an aftermarket "cold" air intake, installing a larger diameter exhaust and/or removing the mufflers will produce a 0hp
change in power. The only change they will produce is noise
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.
- Prevents the external linkage from forcing the internal linkage past set point.
*Do not touch but make sure your external linkage is contacting the stop at WOT
**This adjustment will NOT increase your maximum power and can possibly cause internal linkage binding.
- Limits maximum engine RPM.
*This can effect the governing of idle RPM and idle quality.
**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 and should be completely ignored. 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.
*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 engines lower volumetric efficiency at higher RPMs.
*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 1/4 turn each time.
***Caution: Adjusting the capsule is not suggested. Adjusting it will result in the engine becoming slow to return to idle and excessive 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 alone will only result ing high EGTs above 3000rpm, not any more usable power.
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 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.
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
1: Remove anything blocking access of the rear of the pump. On the 86/87 603, this means pulling the windshield washer reservoir, all throttle linkages, the bowden cable and the cruise control actuator. The oil filter housing does not need to be removed on the OM60x or OM61x engines and the intake manifold can remain in place on OM60x engines.
2: Remove the ELR (round red device at the top-rear of the IP
). The Torx screws may be tight due to the factory locking compound on the threads. This does not apply to OM617 engines.
3: Unscrew the rear governor plate (6 screws). Early pumps have flat head screws, late pumps have Torx screws. When you pry of the plate, a fair amount of engine oil will spill out. Have rags handy to catch the mess.
4: Now you should have full access to the governor of the pump. To increase the full-load fuel quantity, loosen the jam nut, and turn screw 2f
(bottom left) out (CCW
). Make careful note of the position of the slot, before & after adjustment. Try 1.5 turns total for the first adjustment, or go in half-turn increments if you don't want to max it out. For the OM617, this will bring power near that of the stock MW-Pump.
: 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
(idling auxiliary spring) will restore the idle speeds to normal.
5: Whatever number of turns you made to full-load screw 2f, make the IDENTICAL
adjustment to the idle stop screw, 2b
(top/right). If you turn 2f
out 1.5 turns CCW, then also turn 2b
out 1.5 turns CCW. This decreases the idle setting but it also moves the external throttle lever.
After the idle adjustment, make sure the lever is not touching the pump body. If screw 2b 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.
: Make sure your new settings do not change when you tighten the jam nuts on both 2f and 2b. Make sure the nuts are snug, but don't over-tighten them... if you break something, you could end up pulling the pump to repair or replace.
6: If possible, use a new gasket for the rear cover, and a new O-ring for the ELR. They are available from Mercedes dealers at a reasonable price. Clean and dry the sealing surfaces, re-install the cover and ELR.
7: Because you turned screw 2b
, which moved the external throttle lever towards the rear of the engine, you now must adjust all three throttle linkages. Lubricate the ball/socket joints with ATF or wheel bearing 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.
8: Re-connect the transmission Bowden cable. Slacken to lower shift RPM, tighten to raise. Make sure the cable travel is not limiting linkage movement, you may need to bend the bracket slightly.
9: Press the pedal to the floor and inspect the lever at the back side of the pump, it should go through the entire range of motion from the idle stop to the WOT
stop. You can have a helper sit in the car or use a heavy object placed on the pedal. Be sure to remove it before starting the engine!
10: Reassemble all the items you removed to gain access to the pump.
OM60x: Leave the ELR wire off and start the engine. The idle should be ~500rpm. Re-connect the ELR wires and the idle should jump to ~650rpm if you have the trim plug set to #4.
OM61x: Use the external adjustment screw 3
to fine-tune the idle speed. CW decreases idle, CCW increases idle.
11: Test drive! With the engine fully warmed to 80*c during the daytime (not night), watch for black smoke. You will probably notice smoke when you mash the pedal from a stop.
OM60x: If smoke is visible until boost builds, lean out the ALDA setting by adjusting the screw CW
1/4 turn at a time or removing the shim, installing a thinner shim until the smoke is not clearly visible once the vehicle starts moving.
OM61x: These engines do not have an ALDA on the M-Pump. You will have to live with some smoke, adapt your driving habits to prevent it (with good throttle manipulation) or fabricate an ALDA using a 5-8psi wastegate actuator attached to the STOP lever.
No smoke should be visible at WOT
, after the turbo has spooled up, if you have the boost set at 14psi.
12: Watch your exhaust temperatures!
of more than 10-20 seconds can create combustion temperatures high enough to damage the engine. This damage is not instant, its cumulative. The longer you run hot the more damage excessive temperatures will do and it won't be obvious there is a problem until its too late. 1250*F (675*C)
is a safe limit for continuous output, 1500*F (815*C) for very
short intervals (under 5 seconds).
Most of the increased fuel feed from either of these pumps can be noticed between 2000 and 4000 rpm's, after that the high idle (maximum RPM) setting automatically starts to reduce fuel. Boost pressures above 14psi should not be needed although YMMV as to the exact boost PSI needed.
Loosen the 29(?)mm lock nut of 2m
and turn the 10mm Allen screw CW
One half turn = 150rpm.
Loosen the 22mm lock nut of 2e
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).
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