CAT C15 Fuel question

@AModelCat

 

Only thing ive noticed is if i leave it open when i change filters, its harder for the engine to fire up afterwards.

have no idea lol. Just know the engine fires up better afterwards if i close it during filter change.

 

04 mbn

 

I didn't have much time to do any digging. No mention of that valve in Cat's systems and operation. I did find it in the parts section so it is a Cat valve. I can't view some graphics with my phone and I don't have my laptop with me at the moment.

@spsauerland or @pushbroom might have a better idea of what its for.

 

AFAIK i think its for heating the inlet fuel with hot return fuel. Ball valve lets fuel down to the thermal valve by the pump to maintain temp. They got rid of the system shorty after so I would just leave it shut.
@spsauerland is more gifted in years then I am and might remember more

 

Here is what Cat said about the fuel recirculation system operation:

Later models will not have a temperature regulator for the fuel.

The fuel regulator valve is located in one of the return fuel lines. The fuel line runs from the fuel filter base to the fuel transfer pump. The fuel regulator valve is controlled by the temperature of the fuel. The valve is in the open position at temperatures below 21 °C (70 °F). The valve closes at temperatures above 27 °C (80 °F).

The temperature regulator for the fuel is used to supply the injectors with warm fuel during cold operation. Fuel is delivered to the injectors by a fuel passage in the cylinder head. The injectors are supplied with an excess of fuel. The excess fuel removes heat from the injectors. This heated fuel will mix with the cold fuel in the fuel tank. The fuel regulator valve in the return fuel line mixes fuel from the fuel tank with the excess fuel that is returning to the fuel tank. The warm fuel increases injector life.

Like @pushbroom said, they did away with it very early on with ACERT engines. This is from Truck Engine news 01/08/2004 :
The fuel recirculation valve and the fuel recirculation lines are used on the heavy-duty engines with ACERT technology. The fuel recirculation system is no longer required on these engines that have the ACERT technology.

In July, these engines will be shipped without the fuel recirculation system. The following instructions and components can be used if there is a problem with the fuel recirculation system on these engines.

I believe the shut-off was to be used when changing fuel filter or priming system. Only had one truck with it and removed it causing air intrusion issues in fuel. Cat does not offer replacement regulator tee, so if you have an issue you just bypass it.