If the FDC leaks fuel into the engine...

[TexAndy]

Wouldn't running a bunch of WMO somewhat mitigate the problem?

I only ask because I'm fixing to run alot of WMO in mine and the FDC has not been bypassed. Not sure yet if I want to bypass it as I'm not sure what kind of power it would generate on 50% - 75% wmo with the FDC bypassed.

So, semi-serious question, I guess. If you ran alot of WMO and you had an FDC that was allowing fuel to weep into the guts, do you think it would have considerably less negative impact than if straight diesel was leaking into it?

 

[AceHigh]

In my opinion if the FDC is leaking it should be fixed.

 

[cranetruck]

In my opinion if the FDC is leaking it should be fixed.

Right, the leak could add 1qt of fluid/1,000 miles to the crankcase.

The FDC piston rod begins to leak when impurities in the fuel mar the surfaces of the lapped-to-fit mechanism. WMO is probably going to make matters worse as far as the leak goes (=not clean).
Too many dirty and rusty fuel tanks out there IMHO.

 

[gimpyrobb]

Wouldn't running a bunch of WMO somewhat mitigate the problem?

I only ask because I'm fixing to run alot of WMO in mine and the FDC has not been bypassed. Not sure yet if I want to bypass it as I'm not sure what kind of power it would generate on 50% - 75% wmo with the FDC bypassed.

So, semi-serious question, I guess. If you ran alot of WMO and you had an FDC that was allowing fuel to weep into the guts, do you think it would have considerably less negative impact than if straight diesel was leaking into it?

That would mean your running 50-25% non-oil through your bearings.

 

[Floridianson]

In my opinion if the FDC is leaking it should be fixed.

Silly boy.

For real bypass the FDC now and be done with it. You don't need it. Won't need it and never will need it. Got it?

 

[gimpyrobb]

 

[TexAndy]

What kind of power difference are you guys getting between 50% WMO/Diesel and straight diesel?

I know bypassed deuces do not generate much power with 50% or more gasoline in them. I had to buy some to keep from running out of fuel on a different truck so it turned out to be around 50/50 gas and diesel with a quart of new 30 wt motor oil. The truck would not break 40 mph on level ground.

 

[gimpyrobb]

My truck runs BEST with diesel. That being said, it runs good enough on WMO that I run 100% WMO most of the time.

 

[Flyingvan911]

I agree, bypass your FDC. No good can come from letting it lead and adding liquids to your crankcase.

 

[randini]

I really dont notice a power difference. I run anything from almost straight WMO to almost Straight Diesel. I do mix gasoline with WMO, about 1 gal gas to 5 gal WMO.

 

[reloader64]

My truck still has the FDC, and it seems to run a little better on straight diesel fuel. However, at about $4.00/gallon, I've been putting a lot of WMO in it lately. I don't know how big each factor is, but with about 75% WMO, pulling a MKT-85 into a 30 mph headwind with cargo cover on, a highway overpass could have me down to 30 mph.

Scott

 

[russ132]

Please forgive my ignorance... what purpose does the FDC serve if not allowing the abilty to run different fuels? I run mostly WMO. Do I not need my FDC? What would be the benefit of removing it?

 

[DieselBob]

From TM 9-2910-226-34

"The fuel density compensator (when used) is
mounted on the governor housing. The fuel density
compensator automatically varies the quantity of
fuel delivered to the engine so that the maximum
power output of the engine remains constant
regardless of the type of fuel being used."

 

[tco3129]

Uncle Sam removed my FDC. I am running a near 100% oil mix (WMO & surplus new oil of varying viscosities) with no noticable difference from diesel

 

[russ132]

That is what I had read, so why disconnect if you have plans on running anything other than diesel?

 

[DieselBob]

The real "Multi-fuel" part is the design of the combustion chamber, piston top and injector. The FDC would only very the maximum amount of fuel delivered depending on fuel type to help keep the power output of the engine at the rated spec.

 

[davey8943]

The fuel density compensator is technically a fuel VISCOSITY compensator. The mechanism in the compensator allows more fuel to flow when the fuel viscosity increases.

Think of it as if you were running straight gear oil. The FDC would allow the much more gear oil to flow, than if it were regular (much thinner) diesel fuel.

The idea is that (generally speaking) heat content of the fuel increases as the viscosity liquid increases.

As long as you keep the viscosity of the fuel mixture somewhere close to that of diesel, the FDC makes absolutely no adjustments.



Dave

 

[russ132]

I am sorry guys... Why disconnect it?

 

[davey8943]

Russ,

Thanks for pointing out that I completely failed to answer your question!

There are seals internal to the FDC that seal crankcase (pressure oil return) from fuel (where the viscosity sensing takes place). If these seals leak, your engine will begin "fueling" your crank case and thinning out your lubricating engine oil (making it too thin to hold proper rifle pressure).

The basic idea is that there is little pay off for leaving it hooked up, but the risks are trashing your engine are real.

Dave

 

[russ132]

Awesome, thank you... What type of fuels would fuels would endanger your engine. Lower viscosity like gasoline or higher viscosity like oil. Or is it just dangerous in general? Is it possible to replace the seals in the FDC or is it necessary to replace the whole FDC? Aside from filling your crankcase is there any other symptoms of a leaking FDC? Sorry for the flurry of questions and thank you for the information.