Fuel Density Compensator by-pass

I'm looking for instructions on by-passing the Fuel Density Compensator...

Can somebody please direct me to the data?

Tnanks!

Stan

I'd like to know the opposite.

I have one that is setup for diesel only and I want my multi back.

As far as what I have been told, don't worry about the compensator. Several guys in here run whatever they want without worrying about the compensator w/no problems

The FDC does not make the truck a multifuel, the design of the motor is what makes it a multifuel. Search on SS for your question, this has been covered many times, and yes Steve, I still have your bridge plate.

kipman said:

The FDC does not make the truck a multifuel, the design of the motor is what makes it a multifuel. Search on SS for your question, this has been covered many times, and yes Steve, I still have your bridge plate.

Click to expand...

I assumed that it has been covered to exhaustion but cannot locate the thread(s)...

I don't mean to be a pain but I've spent a lot of time searching (I would never post a seemingly simple question otherwise) and have come up with no real information...

I ran multiple searches here in Steel Soldiers and elsewhere and can NOT find how to bypass the FDC. I find LOTS of talk ABOUT the FDC and other fuels etc but nothing specificaly on how to by pass it.

Can someone familiar with the worn out topic please help direct me to this data?

I would be forever grateful!

Stan

Thank you Thank you Thank you!!!!!!

Stan

Floridianson said:

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Where did these pictures come from and are the originals available online somewhere?

Michael said:

Where did these pictures come from and are the originals available online somewhere?

Click to expand...

They are from an old MVM article.
The reason for the looped tubing is to use what's available on the original set-up.
See the images below for a bypass using pipe plugs instead. Also, note the necessity for changing the fuel delivery after the bypass.

Thanks Bjorn. If you go to the old site and pull up topic 356 you get your old post with a larger picture you can right click and save. It is from MVM December 2002. Now to search and find out how to save and print your new pictures.

March 7th, 2009.

Just out of curiousity........

If the fuel density compensator is hooked up correctly, what benefit occurrs when cutting the unit out of the fuel system? While I know that it is the combustion chambers, and not the FDC that makes the engine a "Multifuel", I have also noticed that trucks that were
bypassed in the FDC ended up stencilled "Diesel Only"...., given the volatility of Diesel prices last year (and I bet when the economy recovers all around the world - it's gonna go up again), isn't it likely that the engines that aren't able to handle the different fuels are gonna be stuck with diesel only? It seems that when the M35A2's were converted to M35A3's they lost the ability to burn liquids like gasoline and unprocessed WMO, and I'm pretty certain that the modern civillian diesel trucks can't burn gasoline regularly in their furel mixtures.... or am I wrong?


Like the guy on Dirty Harry, "I gots to know"!


Cheers,

Kyle F. McGrogan

The Multifuel on the M35a2 is what makes the truck multifuel, the army might have stenciled diesel only to the tanks to prevent soldiers from dumping other amounts of fuel in that they didn't want to have burned. From i have read... the FDC only helps the engine burn other stuff more efficiently, however it works against you when you use Biodiesel. The FDC Does Not Make the Engine a Multifuel.

However other trucks now that are in the civilian world don't really have the capability to be a multifuel like a deuce, because of the engine design, however you can modify the engine (most likely diesel) to use other types of fuel. But that's costly or just a lot of work.

The M35a3 doesn't have a multifuel engine, diesel only.

if I'm wrong on anything please correct me, and i hope i didn't offend anyone.

I could be talking out my butt, but I thought the FDC just regualted the rate of flow to the IP based on the viscosity of the fuel? What makes it multifuel is the design of the motor. Basically it can still run all the same fuels just not as efficiently. It will have the same fuel rate whether it has a gas and oil mix, or diesel. If I am incorrect, someone please correct me. I don't like to be ill-inform or give out incorrect information.

D

saddamsnightmare said:

March 7th, 2009.

...While I know that it is the combustion chambers, and not the FDC that makes the engine a "Multifuel", I have also noticed that trucks that were
bypassed in the FDC ended up stencilled "Diesel Only"...., given the volatility of Diesel prices last year (and I bet when the economy recovers all around the world - it's gonna go up again), isn't it likely that the engines that aren't able to handle the different fuels are gonna be stuck with diesel only?...

Click to expand...

The ability to run on (almost) anything is like you say, in the engine. The pump is "calibrated" on the fly by the FDC, setting the maximum horsepower output based on the fuel used. More specifically, the energy per gallon of fuel is estimated mechanically by FDC, based on the viscosity (thickness) of the fuel. Thicker fuel decreases the fuel rate, and thinner fuel increases the fuel rate. Among the authorized fuels this pretty closely follows the energy content. Among all the possible fuels... Well, there are certainly exceptions.

When you bypass the FDC, it goes to "default mode". During the process, the main (and now fixed) maximum fuel rate is adjusted to match the desired performane, based on diesel fuel. So now, if one were to run another fuel in this bypassed engine, the engine still wouldn't care, but the horsepower of the engine will not be correct.

With that in mind, my opinion on why they say "diesel Only"... Simply put, the truck doesn't meet it's performance specifications with any other fuel. Too much or too little horsepower is out of spec and needs to be fixed. The fix is to only use diesel fuel, and the performance is correct. Hence they say "Diesel Only".

(IMHO) outside of the military, Maybe it's a little quicker from zero to sixty on one fuel than on another. If you've keep a deuce for racing purposes, you're gonna need to change a lot more than the fuel settings.....

Maybe this has been answered before as well, but what is the specific value of FDC bypass? Does it improve performance/power or fuel economy? Or does it just reduce point-of-failure? I'm sort of a fan of the old addage "If it ain't broke, don't fix it". Are we actually accomplishing anything with FDC bypass or are we tinkering just because we can? (putting on fire suit...)

Thanks!

Guy, read Jake's post a few times, it says it all.

Does anyone have a larger/clearer image of the article in Post #9? I am unable to make out what it says. What I am really after is exactly what parts are needed to convert from Multifuel to Diesel only. Currently my '88 is still setup for Multifuel and I don't want to have any issues of diluted crankcase oil. I know I need a couple T's, couple plugs, and it looks like a longer fuel hose running from the fuel filter housing to the IP. So does anyone know the size of the fittings needed for the T's, plugs, and what diameter fuel hose is needed? Is the fuel hose just an air hose? NAPA #'s?

Try opening it in some sort of photo manipulating program with a zoom feature. Might help.
BC

When bypassing the FDC, you pretty much just hook the line from the final fuel filter directly to the hydraulic head inlet, correct? (and then plug up the holes left in the FDC).

I ask because the hose in my deuce is not long enough.

MY pump seems to have had the FDC removed completly....

Would this have been done during a depot rebuild..?