Fuel Density Compensator

[goldneagle]

Something that I have noticed with the FDC. On my 3 other deuces with FDC hooked up,they start right up in a second or two. The one truck that the military bypassed the FDC I crank on it and it sputters and dies. About the second cranking with the accellerator pedal pushed down it will start, but is kinda rough for a bit. Has anyone else had that problem with FDC bypassed trucks.

Well, I only own one Deuce and it has the bypass from the Military. She has sat for 3 months without starting. When I went to start her she kicked in with barely a touch of the starter button! She ran perfect! I think you have other issues in your fuel system.

Just my worht.

 

[FreightTrain]

Sputtering and dying on start and rough running for a second on second starts is a fuel leak not a IP turned down problem.your sucking air when the engine is shut down and it is running out of fuel when you crank it up.Find the leak and fix it first.

 

[WarCloud]

FDC

My truck fires up almost instantly, whether it's 100 degrees or 10 below. I got a good one.
My concern with the FDC is the stickers specifically pasted inside the hood telling me not to try to run multifuel without reconnecting the FDC..I'm not quite sure the manufacturer would develop the device if it were not needed. Seems to me that it would be completely necessary with low viscosity fuels (gasoline, alcohols, mineral spirits, benzene) to control the amount of that very carefully. Sure, if the density if your "emergency" fuel is similar to diesel (fuel oil, JP jet fuel, kerosene) I can see how the engine wouldn't see much difference. It's when you swing the fuel radically away from the normal fuel it's used to (like filtered fryer oil / peanut oil or corn oil which is thick, or mineral spirits which is very thin) that I see a potential catastrophic condition developing.
So just to bring my little thread back in line (ahem...)..who has experience here with mixing up all kinds of weird fuels and running their Deuce on it successfully? How far can I push the fuel density one way or the other with no FDC and still have the engine run?

This is not for everyday use. This is doomsday absolute emergency info only. As long as diesel is available that's what it gets fed, but that rainy day when she might have to burn something weird just might be closer than anyone thinks.

 

[Floridianson]

The Alternative Fuels section in the General threads is a great source for who, what and how well the alts. are doing.
Just remember by having or reconnecting the FDC you must watch for oil dilution.

 

[bottleworks]

Re: FDC

My concern with the FDC is the stickers specifically pasted inside the hood telling me not to try to run multifuel without reconnecting the FDC..I'm not quite sure the manufacturer would develop the device if it were not needed.

You don't have to believe those who speak here. It's your engine and you can break it if you wish.

The FDC is a convince item. That's why the manufacturer developed the FDC. It does not change the engine's ability to burn alternative fuels. That is a fact - plain and simple. The FDC has a long term durability issue. It leaks fuel into the oil. That is why many have been bypassed. I bypassed mine as PM. It did not effect my starting ability. I still can run 100% gas, bio, #2, UMO, whatever.

Those yellow stickers you see on the engine's oil canisters.... Keep in mind who they were written for. It's follows the same logic and reasoning as why these trucks are officially underrated for cargo capacity.

 

[Recovry4x4]

RE: Re: FDC

The original multifuel, the LDS427, didn't have an fdc.

 

[SasquatchSanta]

Floridianson wrote:

Hard to see. Yes the 465 troubleshooting manual second page 4th line I think. It also shows the most consistent way of putting a load on the motor using the brakes.

Thks for the clarification

I'lll check out the Trouble Shooting Guide. Hopefully it will also state what the droop screw actually does compared to the main fuel adjustment.

Thanks again.

 

[FormerNewMVGuy]

I posted the TM a couple of post back! some of the IP's didnt have a droop screw, cant remember which models right off hand.

 

[SasquatchSanta]

NewMVGuy wrote:

I posted the TM a couple of post back! some of the IP's didnt have a droop screw, cant remember which models right off hand.

I'm a real clutz when it comes to figuring out how to find the proper TM for a given problem.

Anyway, I'm ovbiously going to have to pay attention to the droop screw. I took my truck out for a spin today. After turning the main fuel setting (the double nut screw) down (counter-clockwise) two-flats I still can't tell a difference. It still runs like a scalded dog which is good BUT --- I still got more power than I need and I think turning it down more will save fuel.

 

[Floridianson]

Earine let us know 4 sure how it goes on the mileage. Do you have a boost gage installed or just a tune up one that you will be using. If you are willing to really do some tweaking it would be interesting to see how low on the boost at both rpm ranges you could go and still get what you want out of her. You could try 3 lb and 8 lb instead of 3.8 and 8.84. Maybe you could be the first to tweak out 15 mpg.

 

[SasquatchSanta]

Floridianson wrote:

Earine let us know 4 sure how it goes on the mileage. Do you have a boost gage installed or just a tune up one that you will be using. If you are willing to really do some tweaking it would be interesting to see how low on the boost at both rpm ranges you could go and still get what you want out of her. You could try 3 lb and 8 lb instead of 3.8 and 8.84. Maybe you could be the first to tweak out 15 mpg.

YES --- I'd like to take on a serious tweaking project and "yes" I do have a boost gauge and a pyro (see attach pics).

I've got a Vietnam Veteran buddy that's due in tomorrow for a two week visit so nothing will happen for a couple of weeks. As soon as he leaves I'll going to sort out what TMs to read up on. I would sure like to work with someone from an input standpoint on the fine art of fine tuning a multi. If ayone has any recommended reading suggestions please let me know.

 

[WarCloud]

FDC

Bottleworks:
I see your points.
Having begun my mechanical career quite litterally at the bottom..at 14 as the tear-down boy in my uncle's truck engine rebuilding shop..I have quite a bit of familiarity with big diesels from the crank out. I eventually learned machining and became an engine builder.

Diesels due to the high compression have a chronic oil contamination issue anyway. No matter how new the rings and sleeves, a certain bit of fuel will blow by into the bottom end, it's inevitable. So if the FDC for some reason has a design flaw which causes leakage into the crankcase, then you have a bit of advice I may just follow and forget about the FDC. As I said, it's not a device intended for every-day engine operation anyway. All-Fuel is an artifact of the Cold War, kinda like the Interstate Highway System (we don't habitually use those long flat stretches of highway as airbases, but if we ever NEED to..)

My concern was that the FDC was a necessity. If it isn't, then I'll leave well enough alone, because right now the truck runs like a well oiled watch. I don't want to mess with success.

 

[chazman21]

RE: FDC

Hello WarCloud,
Im new around these parts.

I have read what you and other's have stated. I would like to add something else.

I was reading in another topic "FDC Pump" The person had questions about the F.D.C. and seem to referance it to the pump.
He wanted to reconnect it as well. But also stated it was worn out.
Long storie short. I finally understood what he was talking about.
So, I added my .

You can read this in "FDC PUMP" topic

I came across some information months ago about, The LD, LDS, LTD,..etc 465 diesel engins on the WEST COAST. It was in a podcast I downloaded, For furture referance.
The engines had their F.D.C. by-passed &&&& the IP was retuned.

Yes, I do understand that the F.D.C., just doesn’t make the engine a multi-fuel. Its just one part in the works.
The main part would be the internal of the engine design.

The engines were retuned for better MPG & Emissions while running on diesel only.
The ones that were retuned should have a sticker or label. If it has not been removed.

For every action their is a equal an opposite reaction.

For the LDS-465-** engine to run on multi-fuels "same or a mix" over time.
Its not going to have the same power as if it were tuned for one fuel only.

Well, I gave this little info up and was SHOOT-DOWN by another member.
I understand what he had to say, And I agree because of were the information came from. Sort-of
If I read or hear of something. I just don't take it to hart. I research it. To understand it or to understand were others have gone wrong.
I hope to have the information in writting soon plus a Document stating, How to retune the engine back to factory settings.
If your interested, I still have the podcast.

What Im trying to say is.
Yes, Their might be something else wrong with the diesel engine to cause the symptoms stated in pass-submits.
But, If the engine was made to run with a F.D.C. and it is by-passed.
Some of the TM's information my not be useful in retuning for better MPG & Power, because the F.D.C. has been by-passed.

Then their is Muffys Law. If it can happen-It can. Some LDS-465 engins may just run perfect with out the F.D.C. and running other fuels.

Injoy!

 

[PawnShopEd]

The Alternative Fuels section in the General threads is a great source for who, what and how well the alts. are doing.
Just remember by having or reconnecting the FDC you must watch for oil dilution.

Ok so I just picked up a new truck - unlike my old truck I noticed it had a FDC on it still, beings I didnt have one before I'm not well versed in these. My old truck ran great this one runs great as well but if it can cause more of a reliability issue then I want to just remove it or bypass it. Is there any specific instructions to follow to remove? as well on this topic someone stated they can be worn out if it's not pertanent to remove it is there anyway to check for the amount of wear it has?
Thanks,
ed

 

[thehaas]

the pump with no compensdator is a g type under cap is diff but set up is done on injection test bench.the nut for fuel is under cap.droop adj is from back after hex head cap is removed.

 

[DawnandAlfie]

I have an M35A2 which is letting diesel fuel into the sump oil and thanks to the threads I have read on steel Soldiers I am pretty sure it is the FDC and have ordered a new one.
can anyone tell me when I fit the new one is it likely to need any adjustment or are these factory set ? If it needs adjustment, where and how can I do this ? What symptoms will be apparent ? Many thanks Alfie

 

[Floridianson]

I have an M35A2 which is letting diesel fuel into the sump oil and thanks to the threads I have read on steel Soldiers I am pretty sure it is the FDC and have ordered a new one.
can anyone tell me when I fit the new one is it likely to need any adjustment or are these factory set ? If it needs adjustment, where and how can I do this ? What symptoms will be apparent ? Many thanks Alfie

I do believe if you read many threads most all that know say we bypass it. It is not needed and can do more harm than good. Don't know how much the new FDC cost you but to bypass would have been around two bucks better spent.

 

[gimpyrobb]

I do believe if you read many threads most all that know say we bypass it. It is not needed and can do more harm than good. Don't know how much the new FDC cost you but to bypass would have been around two bucks better spent.

Ditto.

 

[Floridianson]

Do believe the best thing for our trucks is a pyro and a good tweeking after bypassing the FDC. Does not matter to me that I have to push the fuel pedal down a little farther if I run a weird fuel. I rather have better performance than a fuel leak into the crankcase.

To answer your question DawnandAlfie no the servo is set on the IP machine so no you could not change it. Also the servo is set up to run the fuels shown. I do not know how it would react to anything different or different viscosity.

 

[daytonatrbo]

Since this topic has been brought up again, I'll ask a dumb question.

My M109 has obviously had the FDC bypassed, with the fuel line routed straight to the IP and a loop from the "in" to the "out" of the FDC.

My M35A2 has the sticker on the oil filter saying the FDC has been bypassed, but it is still plumbed in.



Is there an internal method of bypassing the FDC, or has someone reconnected the FDC in my M35?