M35A2 fuel density compensator bypass, several questions

[Lenny]

Last week I posted a thread about my M35A2 https://www.steelsoldiers.com/showt...-Kaiser-M35A2-oil-pressure-problem&highlight=. I just barely made it home that night with failing oil pressure. The next day I checked the oil and according to the dipstick I found it to be about 6 quarts high. I was assisted by the good people on this group who offered various information as well as a few videos which provided a tremendous help concerning bypassing the fuel density compensator.
Yesterday my son and I completed the mod. In my case though we also had the arctic preheater and a small filter to deal with as well, not to mention a personnel heater that was right smack dab in the way of where we were working . But we got through it OK. The drained oil, all 9 gallons of it was the consistency of kerosene. Pretty scary to think that I had that in my engine...
In any case we took the truck out for a test drive and it now seems like it has a substantial increase in power. So I have a few questions I would like to ask.
1. Did I just imagine it or does doing this bypass have an effect on power, and if so why is this?
2. What actually is the cause of this dumping of fuel into the crankcase? On M37's a membrane in the cam operated fuel pump ruptures and this is the result. Is this compensator also driven off the cam and is this a similar situation?
3. What does this compensator actually do, and if at some time in the future I should decide to run for example waste oil or solvents would I need this thing to be operational?
4. I run 911 fuel treatment in the tank every Winter. I have never used the arctic preheater which we also disconnected and the truch has always started even down below 0 degrees F. What is the likelyhood that I would ever need this device to work?
5. It seems like from what I have heard most people are convinced that this compensator is the leading cause of this fuel dumping. One guy on video even went so far as to say that 90 percent of cases like mine are corrected by this mod. So I'm hopeful that we nailed it. Now I plan to take some short trips in the truck initially to see how everthing seems. And I will be diligent, (more than I've been in the past in checking the oil), but it's nagging at me. Just in case we didn't fix the problem would there be typical or predictable number of hours on the engine where this might fill up again? I have a 70 mile trip planned for the end of July. I just worry about being stuck on the road with a crankcase full of newly diluted oil and no oil pressure to drive it home. This problem just seemed to come on so fast it does worry me.
Thanks everyone for your help and advice with this. I don't know where I'd be without this group. Lenny

 

[cattlerepairman]

1) Yes, it does. Bypassing the FDC has the same effect as "turning the fuel up". Why? At startup, FDC bypassed, you begin with a fixed quantity for fuel delivery and increase from there as you press the throttle, basically what the FDC would do if you were running gasoline (a lower viscosity fuel). If the FDC is not bypassed, it wil adjust fuel quantity as per viscosity of the fuel - for the higher viscosity diesel fuel, it would adjust fuel quantity down.


The military, in the TM, sets the fuel injection quantity very conservatively, resulting in minimal turbo boost, up to 6-7 psi perhaps. By using an exhaust gas temperature gauge (EGT) that measures ideally the temperature of the exhaust gas the turbo gets exposed to (probe sits pre-turbo in the exhaust manifold), one can adjust fuel delivery up to a safe amount where power is increased but the risk of any engine damage is very low.

You, on the other hand, currently have no idea where on the "danger line" your fuel delivery is sitting. It could be perfectly fine or it could cause dangerously high EGT, especially when lugging it on a grade and stepping on it. Hence the strong recommendation to use an EGT gauge when the FDC is bypassed.

3) You can run any fuel authorized for the multifuel, with or without FDC. The FDC is a quantity adjuster that compensates for a unit of fuel containing more or less energy, according to its "thickness" (viscosity). The thicker fuels pack more energy per unit of fuel, so if you run thinner fuels, the FDC will inject a higher fuel quantity to keep the power up.
This does not change the ability of your multi to burn other fuels; it will just have a little less power running on gasoline versus diesel.

5) Try not to be paranoid. If the bypass is done as per instructions and you have a handle on the EGT, go and drive your truck! Enjoy. It is a 50 year old beast and stuff can break at any time. Most likely nothing will go wrong on your 70 mile trip.

 

[Floridianson]

Just keep an eye on making oil again because the FDC is not the only problem child on the motor.

 

[frank8003]

a little something to read..........

https://www.steelsoldiers.com/showthread.php?140095-Fuel-in-Oil-–-HELP&p=1734887#post1734887

Basically 5 ways to make a milkshake.

 

[Nomad1]

So since we're talking fdc is there really a need for egt monitoring if you bypass it on a non turbo?

 

[doghead]

no