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Re: Engine Shuts down on "Fuel Gas Correction Factor Low Limit Reached" in Combustion Mode

Hi AIH. Thanks for the detailed response. I will have to verify and execute some of your points.


In the meanwhile here are the responses for some of your points and queries:

- The fault appeared suddenly I'd say. This engine was removed from another nearby location (lets call it Location A) 2-3 months back for In Frame Overhaul. Once it was ready and the opportunity came, a normal operating engine (another G3612 A3) was removed at another location (lets call it Location B) and this was installed in its place. From the removal of older engine to the installation of this IFO'ed engine it took 3 days at Location B. At Location B older engine was operating just fine. 

- Yes this is a G3612 A3.

- The pressure module has already been calibrated a number of times. I will however re-do it.

- Inspected the wastegate as well, from the inside. In fact already replaced with freshly overhauled one.

- In all the starting attempts, once I was able to start and load this engine successfully as per requirement. It was as if the problem had disappeared altogether suddenly. The engine ran fine with all parameters as they normally are. Even the Fuel Correction Factor did not wander away from 100 much (minimum value 98%). It however shutdown on detonation 2 days later and started showing same behvaiour i.e. it starts up fine but rpms and fuel correction factor gets disturbed as soon as it achieves combustion mode (~40% load) and eventually shuts down on low fuel correction factor limit.



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Re: Engine Shuts down on "Fuel Gas Correction Factor Low Limit Reached" in Combustion Mode

When a G3600 shutsdown on this code, it usually means that the fuel gas btu has changed beyond the ECM ability to correct for the fuel change in btu.  I assume that this is a G3612 A3.  You don't say if this fault started suddenly for no reason or if some site changes occurred or if any of the wells in the system had received any nitrogen as part of servicing.


You have done a lot so I would say that it is time to start over with the basics, not necessarily in this order but in total.

1. The pressure module must be calibrated to the site uncorrected barometric pressure.  This must be accurate so that the ECM knows the density of the site air and can correctly make calculations to achieve the correct air/fuel ratio.

2.  Turn all the needle valves out from fully closed 5 turns.  This will be a starting point which will be used for tuning later.

3.  You said that all the valve lash is correct; inlet 0.020", exh. 0.050", GAV 0.025" are the correct settings.

4. A fuel pressure of 43 psi is okay but not exactly spec.  Spec is 45 +/- 2 psi.  I find that I have better results when setting the Fisher 99 to 46 psi.

5. You have checked all the linkages and they are adjusted correctly.  But you need to make sure that the butterfly for the wastegate and the choke are secure to the shaft and in place and working inside, not just outside.

6.  You need to enter the calculations from the Methane Number calculations of btu and specific gravity.  You will need to use the btu to adjust the air fuel ratio to obtain the correct NOx value when tuning the engine in PC CAL.  The correct btu is whatever value gives you the correct NOx: 50 ppm for a 0.5 g NOx and 70 ppm for a 0.7 g NOx rating.

7.  When the engine is in PC CAL with at least a 70% load, a) first adjust the btu in PC CAL to get the NOx near the target then 2) adjust the needle valves to get the actual burn time equal  to the desired burn time.  The engine average burn time should also be equal to the desired burn time or real close, if you do this correctly.  Before you take the engine out of PC CAL, note the inlet manifold pressure.  When the engine is back in combustion feedback, the inlet manifold pressure should not change more than 1% from what it was in PC CAL.

8.  If you still have an issue with starting, try starting the engine in PC CAL after doing steps above.


This is what I would do.  Most of what you have tested or changed should not affect the engine to generate this fault code.  It is good that you know those items are okay.  But I would start with what I have set out above.

Let me know how things go.


Best Regards,

Al Hunt

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Engine Shuts down on "Fuel Gas Correction Factor Low Limit Reached" in Combustion Mode

[ Edited ]

The engine under consideration is 3612 on gas compression duty. The engine was put back online after its In Frame Overhaul just 1.5 months back. Its fuel correction factor was noted to be 92% at that time. Otherwise the engine ran fine and took load normally.


Recently as the engine was nearing its 1000 hours PM mark post IFO, the engine tripped on the cause of “E885: Fuel Gas Correction Factor Low Limit Reached”


  • The Engine was restarted. Engine started reliably. Stayed in initial starting mode reliably. Went in to and stayed in “Exhaust” mode reliably. However during loading as soon as 40% load was achieved and Engine mode changed to “Combustion” the “Fuel Gas Correction Factor started to drop from 100%. It eventually reached 80%. After this engine failed to maintain its speed and speed dropped. And eventually the engine tripped again on “E885: Fuel Gas Correction Factor Low Limit Reached”. Sometime the engine would not tripped if immediately unloaded but would not go back to combustion mode.  (This has been the tripping behaviour for all start up attempts since yesterday)
  • As a remedial measure, a number of actions have been taken but the engine has been invariably tripping in the same fashion. Dominant cause is “E885: Fuel Gas Correction Factor Low Limit Reached”. Occasionally however “Unexpected Shutdown” is also seen.
  • All Actions that have been taken are listed below. Please note that several attempts to start the engine were taken after each action with slight variations in parameters/settings. Each of the actions listed below has thus far failed:
    • Adjustment of engine’s fuel quality by setting BTU & Specific Gravity. BTU have been adjusted in between the range of 700 to 950. Specific Gravity has been adjusted between the range of 0.58 to 0.62. A new setting has been tried on almost every startup and loading attempt.
    • Adjustment of pre-chamber fuel gas needle valves to make all cylinder exhaust port temperatures uniform.
    • Resetting of pre-chamber fuel gas needle valves as per user manual instructions.
    • Calibration of Air Fuel Ratio module
    • Replacement of Air Fuel Ratio module with new one and new one’s calibration (various value between range of 13.5psig 14.6)
    • Verification of all electro-hydraulic actuators (Air choke / Fuel / Wastegate), their linkages, connections, coils resistance, smooth movement.
    • Replacement of waste gate and fuel electro-hydraulic actuators with new ones. Replacement of one of the leaky hydraulic hoses on waste gate actuator.
    • Replacement of Inlet Air Filters with new air filters.
    • Main Fuel supply pressure was verified. Found to be 43psig.
    • Gas admission and exhaust valve tappet clearance verification of 3-4 random cylinders and was found ok.
    • Using various loading strategies for example: increase speed up to 860 first then load the engine, load the engine then increase speed, increase speed and load side by side, very slow loading of engine etc.
    • Tuning of Fuel Governor parameters conducted. 
    • Turbocharger inspection and gaps verification. Found ok.
    • Gas admission and exhaust valve tappet clearance verification of all cylinders. Valve lash inspection. Found ok.
    • Compression test of all cylinders. Found ok.
    • Spark plugs re-gapping
    • Engine web deflection verification and found ok.
    • Combustion sensors were replaced with new ones.
    • Fuel actuator valve body was replaced with new.
    • ECM/both ICSMs/RHS sensor harness/LHS sensor harness/Right side ignition rail have all been replaced with new spares. Same behavior of Fuel Correction Factor Low Limit.
    • Verification of fuel gas quality and entry of verified fuel gas quality parameters in to the ECM.
    • Calibration of burn times carried out in "Prechamber calibration” mode.
    • Checked ECM supply voltages & power connections in shutdown as well as running condition. Found normal (varying between 22.5 to 24.5 VDC)
    • Replaced RHS Ignition Rail with new one, as a major pinch point was discovered on previous one’s flexible harness side.
    • Set & verified rod end lengths for all electrohydraulic actuators (wastegate, fuel, air choke) as per user manual.
    • Replaced PCV on fuel gas supply line with a spare PCV.
    • Set fuel gas supply pressure on PCV outlet to 55psig.
    • Inspected upstream Fuel Gas Coalescer filters. The housing and filters were found to be normal.

Any ideas that would be helpful at this point are most welcome...