JD Cold start Advanced timing sequence

[JMER817]

Is anyone familiar with how the JD Powertech engine operates during cold starts? I had a rough idle which was corrected by replacing the thermostat. Didn't get the complete explanation, but apparently the valves are designed to not open completely and the timing is advanced until the engine is warmed up. This is done by oil flow to the lifters somehow. Can anyone explain?

 

[AKfish]

Is anyone familiar with how the JD Powertech engine operates during cold starts? I had a rough idle which was corrected by replacing the thermostat. Didn't get the complete explanation, but apparently the valves are designed to not open completely and the timing is advanced until the engine is warmed up. This is done by oil flow to the lifters somehow. Can anyone explain?

Diesels burn/combust fuel with high compression. As such, improved combustion is achieved with warmer engine temperatures. In order to meet emissions standards, Deere increases engine rpm's upon startup to warm up the engine faster and reduce those initial, dirtier exhaust emissions.
With a cooler thermostat, it would take longer for your tractor to warm up and begin running smoothly and more efficiently.
All engines advance timing with higher rpm's.

AKfish

 

[jd110]

The 4024 and 5030 engines are the only ones that use oil pressure to the lifters to adjust valve timing. The thermostat involved is not the coolant thermostat. Although the coolant thermostat operating properly helps determines how long the advance is in operation. This is the theory of operation from the tech manual:

IMPORTANT:
By slightly advancing the injection event (pump timing), the injected fuel is provided more time to heat during the compression stroke and burn more cleanly in the combustion chamber when ignited. Without cold start advance (CSA), fuel injected into a cool or cold combustion chamber at cold startup takes longer to heat up and ignite. If this delay in ignition is too great, it results in unburned fuel (white smoke and “slobber”) and rough running or misfire until the combustion chamber warms.
The cold start advance on the Series 250 engine is controlled by oil pressure in the hydraulic roller cam followers, or lifters, for the unit pumps. During cold starting, engine oil is sent by the cold advance thermostat to the cold advance piston in the cam follower via the cold advance oil gallery. The oil pressure lifts the piston 1.5 mm, thus increasing the overall travel length, or stroke, of the unit pump plunger. This advances the pump timing. The increase in stroke of the plunger causes the cam to raise the plunger sooner. This change results in the injection timing to be advanced approximately ten degrees. The oil pressure needed to provide full cold start advance is about 35 psi. A ball check at the base of the piston prevents pumping forces from collapsing the advance.
The cold start advance thermostat begins to block the oil flow when oil temperatures reach approximately 80°C (176°F). When the oil supply port to the roller cam followers is fully blocked, residual oil in the piston cup bleeds out through a drain orifice located in the cup end of the follower. At approximately 15 psi oil pressure, the cold start advance is fully disabled. The follower piston returns to the lower position, returning timing advance to the optimum performance level for an engine at normal operating temperatures.

 

[AKfish]

Thanks jd110. I have both of the engines mentioned. They still belch a plume of white smoke at startup although likely not as long a period as would normally be the case at -10F.

I try to avoid working my tractors @ temps lower than that...

AKfish

 

[JMER817]

The 4024 and 5030 engines are the only ones that use oil pressure to the lifters to adjust valve timing. The thermostat involved is not the coolant thermostat. Although the coolant thermostat operating properly helps determines how long the advance is in operation. This is the theory of operation from the tech manual: IMPORTANT: By slightly advancing the injection event (pump timing), the injected fuel is provided more time to heat during the compression stroke and burn more cleanly in the combustion chamber when ignited. Without cold start advance (CSA), fuel injected into a cool or cold combustion chamber at cold startup takes longer to heat up and ignite. If this delay in ignition is too great, it results in unburned fuel (white smoke and “slobber”) and rough running or misfire until the combustion chamber warms. The cold start advance on the Series 250 engine is controlled by oil pressure in the hydraulic roller cam followers, or lifters, for the unit pumps. During cold starting, engine oil is sent by the cold advance thermostat to the cold advance piston in the cam follower via the cold advance oil gallery. The oil pressure lifts the piston 1.5 mm, thus increasing the overall travel length, or stroke, of the unit pump plunger. This advances the pump timing. The increase in stroke of the plunger causes the cam to raise the plunger sooner. This change results in the injection timing to be advanced approximately ten degrees. The oil pressure needed to provide full cold start advance is about 35 psi. A ball check at the base of the piston prevents pumping forces from collapsing the advance. The cold start advance thermostat begins to block the oil flow when oil temperatures reach approximately 80°C (176°F). When the oil supply port to the roller cam followers is fully blocked, residual oil in the piston cup bleeds out through a drain orifice located in the cup end of the follower. At approximately 15 psi oil pressure, the cold start advance is fully disabled. The follower piston returns to the lower position, returning timing advance to the optimum performance level for an engine at normal operating temperatures.

JD110. Thank you. Exactly what I was looking for.

 

[JMER817]

Do you think that if the engine was "stuck" in this advanced timing mode would it do any harm to it?

 

[buickanddeere]

It would probably operate better. Diesel timing has been retarded to cut NOX to meet emissions.

 

[JMER817]

The 4024 and 5030 engines are the only ones that use oil pressure to the lifters to adjust valve timing. The thermostat involved is not the coolant thermostat. Although the coolant thermostat operating properly helps determines how long the advance is in operation. This is the theory of operation from the tech manual: IMPORTANT: By slightly advancing the injection event (pump timing), the injected fuel is provided more time to heat during the compression stroke and burn more cleanly in the combustion chamber when ignited. Without cold start advance (CSA), fuel injected into a cool or cold combustion chamber at cold startup takes longer to heat up and ignite. If this delay in ignition is too great, it results in unburned fuel (white smoke and “slobber”) and rough running or misfire until the combustion chamber warms. The cold start advance on the Series 250 engine is controlled by oil pressure in the hydraulic roller cam followers, or lifters, for the unit pumps. During cold starting, engine oil is sent by the cold advance thermostat to the cold advance piston in the cam follower via the cold advance oil gallery. The oil pressure lifts the piston 1.5 mm, thus increasing the overall travel length, or stroke, of the unit pump plunger. This advances the pump timing. The increase in stroke of the plunger causes the cam to raise the plunger sooner. This change results in the injection timing to be advanced approximately ten degrees. The oil pressure needed to provide full cold start advance is about 35 psi. A ball check at the base of the piston prevents pumping forces from collapsing the advance. The cold start advance thermostat begins to block the oil flow when oil temperatures reach approximately 80°C (176°F). When the oil supply port to the roller cam followers is fully blocked, residual oil in the piston cup bleeds out through a drain orifice located in the cup end of the follower. At approximately 15 psi oil pressure, the cold start advance is fully disabled. The follower piston returns to the lower position, returning timing advance to the optimum performance level for an engine at normal operating temperatures.

JD110, do you know if this is a feature for all the 4024 since the initial launch of these engines or a recent change to meet emission levels?