Bypassing the FDC

[2deuce]

As a general rule do you guys do the bypass or do you leave it alone until you notice a problem?

I just changed the oil and I was trying to detect any diesel smell, but could not. The oil looked to be a lighter weight than the oil I drained from my CUCV, which I also drained today. The lighter weight could be because of a lighter weight oil or from some fuel mixed in, I can't tell for sure. The oil from the CUCV was 10/40 Delo 400, I don't know what was put in the Deuce. One other difference... I noticed how the bubbles created from pouring disappeared much quicker in the old Deuce oil. The oil from the Deuce is many years old but fairly clean because it just was not run for the last 8 years. Any ideas about this are appreciated.

Thanks

 

[gimpyrobb]

The fdc is a known weak point to let fuel into the crankcase. It is also ONLY a hindrance to power output. I'd bypass it if it were my choice.

 

[cattlerepairman]

Agreed. The FDC has no effect on the multifuel capability of the engine. Its reason for existence, as I understand it, is to help compensate for the different energy density of different fuels, based on their viscosity. When you are running straight #2 diesel (energy dense), the FDC reduces flow (that is why you see a "power gain" when you bypass it). When you run gasoline (less energy dense) the FDC would ramp up flow to compensate for less energy contained per unit of volume.
This is nothing that you could not do yourself with the fuel pedal.

 

[NebraskaFan]

Agreed.
This is nothing that you could not do yourself with the fuel pedal.

^ And an EGT gauge, definitely worth bypassing it.

 

[gimpyrobb]

Yeah, I kinda missed that important info, my bad.

An exhaust temperature gauge is really one of the best things to add to your truck. It gives you insight as to how hot your combustion exhaust is so you don't melt your internals!

 

[brianp454]

Bypassing is best. My truck runs much better and I use mostly waste veg oil in the Summer and waste motor oil in the Winter.

 

[2deuce]

I went and bypassed the FDC yesterday. I haven't ran the truck yet, due to it needing other issues resolved but it is getting closer. Thanks for the advice!