So I just got a 69 duece last weekend. I drove it home and noticed that like most of the others it was making oil. So I bypassed the FDC and from what I read needed to turn the fuel down. Removed the metal cover that still had the wire and noticed that it looked like it had been turned up. So my question is how much of the threads on the adjuster should be showing if it has not been turned up? I am going to order a pyro the first of the week but really want to drive tomorrow and don't want to over fuel.
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FDC bypass question
- Thread starter sammi91
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Westech
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there is no set answer. Its set on a test bench. You need to get that pyro installed and then you can adjust the fuel settings to your engine's need and your preference.
you are still able to drive a Deuce with the fuel all out of wack or maxed out. Just dont be stupid and hold it to the floor till it explodes. You are able to feel the engine and hear and see what it is doing. USE YOUR HEAD and you will be fine.
you are still able to drive a Deuce with the fuel all out of wack or maxed out. Just dont be stupid and hold it to the floor till it explodes. You are able to feel the engine and hear and see what it is doing. USE YOUR HEAD and you will be fine.
Westech
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no it turns it all up. When you turn it down or up you have to adjust the idle as needed.
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Four threads showing is around what I have seen.
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Yes you can hard starting and to low boost at 1600.
Main fuel adjustment changes both fuel settings on the low side and high side. Need to boost gage it and if nothing else check low side boost and you might find it a little high if you increased main fuel low if you turned it down.
This is where readjustment of the droop is needed.
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The FDC is basically a movable stop for the fuel pedal. When you are running a thin fuel, such as gasoline, the stop moves to allow full pedal, and maximum fuel. When you are running a thick fuel, such as WMO, the stop moves to reduce the maximum pedal motion. The idea is the FDC controls the engine so that you get the same maximum horsepower for any fuel.
If you bypass the fuel flow through the FDC, the FDC will act as if it has a very very thin fuel, and will put the stop in the maximum fuel position.... just like it would for gasoline. If you then use some fuel other than gasoline, the injection pump (IP) will be capable of seriously over fueling the engine... lots of black smoke, lots of power, and lots of heat (Can you say meltdown? Sure you can!).
If you are a really disciplined driver, you could bypass the FDC, and drive with diesel fuel, by never going to full pedal... never letting the engine smoke much... I doubt that anyone is that disciplined.
There is a formula method for getting close to the correct fuel adjustment when the FDC is bypassed. That method is to adjust the nut on the compensator stop plate screw (smoke limit) 12 to 16 nut flats (sixths of a turn) clockwise (in the increase fuel direction), and to adjust the droop screw 1 to 2 turns clockwise(in the decrease fuel direction).
[For the stop plate, do not try to turn the threaded shaft. The outer nut is a jamb nut, and the inner nut is the adjustment. Count the nut flats as they pass by until you get to 12... your engine may be happy there, or may need a little more juice, up to 16 nut flats.]
The droop screw adjustment is hard to get at. It is part of the governor's fulcrum and is under the governor cover. It should only exist on the E type injection pumps on the turbo'd engines (I think). When you remove the FDC action, and adjust the smoke limit to compensate, it affects the governor action, requiring the droop re-adjustment for proper idle operation. Most folks that bypass their FDC's skip this step, and sometimes get problems with starting, and idling.
You should get TM9-2910-226-34 from the resources pages of this site before you touch anything!
-Chuck
If you bypass the fuel flow through the FDC, the FDC will act as if it has a very very thin fuel, and will put the stop in the maximum fuel position.... just like it would for gasoline. If you then use some fuel other than gasoline, the injection pump (IP) will be capable of seriously over fueling the engine... lots of black smoke, lots of power, and lots of heat (Can you say meltdown? Sure you can!).
If you are a really disciplined driver, you could bypass the FDC, and drive with diesel fuel, by never going to full pedal... never letting the engine smoke much... I doubt that anyone is that disciplined.
There is a formula method for getting close to the correct fuel adjustment when the FDC is bypassed. That method is to adjust the nut on the compensator stop plate screw (smoke limit) 12 to 16 nut flats (sixths of a turn) clockwise (in the increase fuel direction), and to adjust the droop screw 1 to 2 turns clockwise(in the decrease fuel direction).
[For the stop plate, do not try to turn the threaded shaft. The outer nut is a jamb nut, and the inner nut is the adjustment. Count the nut flats as they pass by until you get to 12... your engine may be happy there, or may need a little more juice, up to 16 nut flats.]
The droop screw adjustment is hard to get at. It is part of the governor's fulcrum and is under the governor cover. It should only exist on the E type injection pumps on the turbo'd engines (I think). When you remove the FDC action, and adjust the smoke limit to compensate, it affects the governor action, requiring the droop re-adjustment for proper idle operation. Most folks that bypass their FDC's skip this step, and sometimes get problems with starting, and idling.
You should get TM9-2910-226-34 from the resources pages of this site before you touch anything!
-Chuck
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Nice Stumps. Also read in the TM section Troubleshooting the 465. It is on second page 7th line down resources old Steel Slodiers. It has no number but easy to find.
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i am surprised no one mentioned the field expediant method of setting the ip. you need a boost gauge on the intake manifold, set fuel rate for max 9 psi at 2300 rpm. if you do not have a hill, use low gear and the brakes to keep truck at 2300 (full throttle) and have soldier #2 read the gauge.
tom
tom
The troubleshooting manual in the resources section is excellent. Do note, that it is geared to the LDS465, so there are some slight differences... most are just HP, rpm and timing specs, and the IP shown is the G type (IIRC), not the C,D,E types typical of the LD and LDT engines.
One thing I forgot to note. The way to test the FDC for leaks is to simply remove it from the IP casting (with all fuel lines intact), and turn on the Accessory switch in the cab. That will turn on the in tank fuel pump, and make the FDC start working. If it is dripping fuel in any great rate, it is bad. If it is a little wet, but not dripping, or is dripping no more than a couple of drops per minute, it is fine.
[The FDC has a piston that has fuel on one side, and a shaft that has no seal. The shaft is kept from leaking because of its tight clearance fit with the FDC casting. When it wears, it will let too much fuel leak by and significantly dilute the crankcase oil.]
So, before you condemn your FDC, test it. You should make that part of a yearly ritual if you have an FDC that hasn't been bypassed. Crankcase dilution can also be caused by a bad O-ring in the hydraulic head (HH) of the IP, and a bad seal in the IP's secondary fuel pump... and I seem to recall that it can be caused by the flame manifold heater too, but I have never had one of those, so I haven't paid much attention to them.
-Chuck
One thing I forgot to note. The way to test the FDC for leaks is to simply remove it from the IP casting (with all fuel lines intact), and turn on the Accessory switch in the cab. That will turn on the in tank fuel pump, and make the FDC start working. If it is dripping fuel in any great rate, it is bad. If it is a little wet, but not dripping, or is dripping no more than a couple of drops per minute, it is fine.
[The FDC has a piston that has fuel on one side, and a shaft that has no seal. The shaft is kept from leaking because of its tight clearance fit with the FDC casting. When it wears, it will let too much fuel leak by and significantly dilute the crankcase oil.]
So, before you condemn your FDC, test it. You should make that part of a yearly ritual if you have an FDC that hasn't been bypassed. Crankcase dilution can also be caused by a bad O-ring in the hydraulic head (HH) of the IP, and a bad seal in the IP's secondary fuel pump... and I seem to recall that it can be caused by the flame manifold heater too, but I have never had one of those, so I haven't paid much attention to them.
-Chuck
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chuck, thanks for mentioning the booster pump. i think it is greatly over looked. i recently had a booster pump seal that was putting 3 gallons of fuel in the oil in 5 minutes. it can be tested the same way, just let it hang by the lines and turn on the tank pump. be sure to get a NEW seal, not NOS, about $8
tom
tom
I got the clue about the booster pump from you, so I should be thanking you. Thanks!
At that rate, you soon would have a runaway on your hands. The in tank pump has a lot of capacity, and it will exploit any leak in your fuel system to maximum effect.
-Chuck
hdexpert
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Good info guys, I have some testing to do!!!
Try a quick search on FDC bypass using the search button at the top of the screen. How to bypass your FDC has been covered numerous times, even by me.
Or, you could look here: http://www.steelsoldiers.com/deuce/26917-fuel-density-compensator-pass.html#post280745
-Chuck
Or, you could look here: http://www.steelsoldiers.com/deuce/26917-fuel-density-compensator-pass.html#post280745
-Chuck
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I would argue that the pressure from the in-tank pump is insufficient to properly test the FDC, it operates on about 20 psi IIRC.
The sealing surfaces are honed (?) to fit and hard particles (=rust) from the fuel tank especially will mar the surface.
The piston in the FDC moves very little when in use, but micron size grains of dirt will cause a leak when moved from start-up position.
As a precaution, I now have a magnetic in-line fuel filter in the system...
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