Rebuilding the Injection pump

[rustystud]

I just want to say one more thing about the FDC and it's function. Think of it as a "voltage drop" compensator. If you have a long electrical cable you will end up with voltage drop across the ends. So what the FDC does is build in a compensation for this voltage loss. Just like copper has one resistance per foot and aluminum has another so does gasoline compared to diesel fuel. So at a given pressure and flow of fuel we will have a different "resistance" for gasoline compared to diesel fuel. Since diesel fuel has more BTU's of energy compared to gasoline it will get a higher resistance to bring it down to the gasoline's level. This is one reason most people just eliminate the FDC completely. That and the fuel leakage problem.
Now as to how much movement the stop plate has, I don't have an answer. But I do plan on making my own tester later on and then I can determine if and how much movement there really is.
I know I have been a little testy answering some questions here. The reason is I did not want this thread to degenerate into an argument session. It was to be a stand-alone rebuild thread that I hoped could be sealed and put into the stickies. In fact I was hoping the moderators could go back to post #98 and delete everything after that and then seal this thread.
Then if anyone wanted clarification on any pump matter they could start a new thread and all discussions and arguments could be held there.

 

[Beyond Biodiesel]

Should we also replace the two hoses at the bottom of the IP at the time that we replace it? If so, is there a source for those two hoses?

 

[Scar59]

Should we also replace the two hoses at the bottom of the IP at the time that we replace it? If so, is there a source for those two hoses?

Contact Gimpy Rob, I believe he is in the process of have multiple sets fabricated for a bunch of us w/ needs

 

[jbayer]

I say yes to any hose if you don't know how old it is.

Multiple threads on both.

Here's one link for the IP fuel feed hose. This hose comes from the primary fuel filter, connects to the copper crossover line under front frame rail:

http://www.eriksmilitarysurplus.com/fuliasform3s.html

The oil hose:
https://www.steelsoldiers.com/showthread.php?169340-Injection-pump-oil-hose

 

[rustystud]

Should we also replace the two hoses at the bottom of the IP at the time that we replace it? If so, is there a source for those two hoses?

Yes. Replace all the hose's. I replaced mine with Stainless Steel wrapped Teflon hose. The shop charges me about $20.00 each. These hoses will last my lifetime and that of my sons.

 

[Beyond Biodiesel]

Thanks, Rusty, and others for this valuable thread. I have 2 questions regarding the injector pump, which might be off-topic for this thread.

1) I found the motor oil level in my deuce was rising, and I asked on another thread, and was told the probable cause was the hydraulic head (HH) had to be resealed, so I ordered a seal kit, and resealed it. I found no change in the chronic rising of the crankcase oil level, so I ordered an unused and newer model of the deuce IP. I found the chronic rising of the crankcase oil level continued.

So, the question is: "Since I do not run gasoline in my deuce, other than it blended with waste oils, is it reasonable to conclude that the fuel making its way into my crankcase is coming from the oil line that goes to the IP from the engine oil line? If so, how does everybody feel about disconnecting the oil supply to the IP, and connect the IP's oil line to the fuel return line, assuming that diesel fuel has sufficient lubricity to properly lubricate the IP? I I think is most likely does.

2) My second question is" I made the mistake of following a thread that was here, and does not seem to be anymore, which recommended cranking up the fuel flow of the IP to increase power of the deuce engine. In the process, I ended up breaking a component of the FDC causing my deuce engine now to run at high idle, which surely uses a horrific amount of fuel.

So, the question is: Can I simply remove the top cap of the FDC to pull the parts assembly of the FDC off my old injector pump and pull the cap off the top of my new IP and use tweezers to pull out all of the FDC parts that fell into the IP, and then put the FDC assembly from my old IP into the new IP, and expect to have fixed this problem?

 

[cattlerepairman]

Beyond, there are 4 ways fuel can make its way into the crankcase. The HH is one of them.

Making oil!

My deuce is making oil. What should I do first?

www.steelsoldiers.com

If you replaced the IP completely, you also replaced the booster pump, so you can likely eliminate that as the source. Flame heater, FDC?

 

[Floridianson]

The oil line that comes off the block and goes to the IP feeds the IP the oil it needs. Leave it alone or as said they both could stand to be replaced if never done but has nothing to do with fuel in oil.
I do not know what you have done to your FDC and dropping parts inside? What did you do? Is your FDC bypassed if not it needs to be done. Yes booster pump is a good place to get fuel into the oil if you have done replaced O rings in Head and fuel control unit assembly. Also do away with the flame heater and block off flame heater fuel line.

 

[Floridianson]

Now I' even more confused:

The droop screw, which can only rest against the stop plate, and keep the fulcrum lever from moving further towards the ''increase fuel'' position, does two things that are exactly the opposite?:






(Floridianson)
Makes sense:

The pressure inside the FDC only changes when a different fuel is used.
The pressure inside the FDC is the same regardless of engine speed, and does not change during engine operation.

How can the stop plate move during operation? And how would movement of the stop plate cause surging?


This already is my understanding of the droop screw's, and governor's, function. It is, basically, what i learned back when I was an apprentice at M.A.N.


Thanks. I'll see if I can access the manual at work.

Just for smitts and giggles I looked at the TM. Correct FDC only should move when fuel changes and on start up. Now if we go by the TM fuel goes to a pressure regulating valve as per TM that is 20 /21psi. So even at idle where we have a minimum of 30 psi or high idle 60 psi it will not be over 20 / 21 psi in the servo not 60 psi at servo.

 

[frank8003]

rustystud has rebuilt many FDC, listed all failure modes and the actual way it works.
His posting are in here someplace.

 

[Beyond Biodiesel]

Beyond, there are 4 ways fuel can make its way into the crankcase. The HH is one of them.

Making oil!

My deuce is making oil. What should I do first?

www.steelsoldiers.com

If you replaced the IP completely, you also replaced the booster pump, so you can likely eliminate that as the source. Flame heater, FDC?

I've replaced the injector pump, which means the booster pump has been replaced, and the flame heater died, so it has been removed, but I don't see how it could be a source of fuel entering the crankcase.

 

[Floridianson]

Was the booster pump rebuilt with a new seal when you installed the Injection pump?

 

[Beyond Biodiesel]

Was the booster pump rebuilt with a new seal when you installed the Injection pump?

The injector pump was unused and included the booster pump, but I still observed rising levels in the crankcase.

 

[Floridianson]

As per some you can check the booster with just the in tank pump and it's low pressure if the seal is real bad. TM tells us we need to push 60 psi through it to check for a failing seal with it removed from the IP. Unused to me is old rubber and still might be your cause. As for you asking about replacing inside parts on your installed IP. If you have one on the bench you could take the four bolts and lift the FDC up a bit and see if the rod that connects the wedge plate to the servo has a locking pin. I can not remember. If not then you should be able to disconnect the FDC servo from the wedge plate and see inside. I am guess you broke the stud off of the main fuel wedge plate. It might be tuff to replace it when IP is still installed on the truck. I have never tried it but I also have never broken the twin nut stud. It has been done and I even sent the OP the part to fix his broken wedge plate stud but I did not hear how he did it. I do not know why some of my post is under lined.

 

[brianp454]

I'm rebuilding a spare hydraulic head to swap it and the booster pump onto my engine when I'm confident they are as good as new. There's some kind of sleeve down inside under the 12 point screw that I haven't been able to fish out and clean. It seems to be held in by the oil on the back side. See pic. It turns with no force and a magnet cannot pull it out. Anyone ever removed this? What's behind it?

 

[rustystud]

I see people where still posting wrong information here after I left.
So again I will try and show you how the plate in the FDC still moves all the time.
As you can see from the diagram the wedge plate is connected to the piston which moves according to the pressure exerted against it. This pressure is variable due to the viscosity of the fuel being used and the main fuel line pressure. It's just a matter of how much it moves. The pressure on the regulating valve is not static but will give you a difference value of around 20 PSI . This pressure will change due to the main fuel pressure (anyone with any common sense can see that) but it will maintain this 20 PSI difference due to the spring pressure exerted against it. For anyone who still believes this regulating value just maintains 20 PSI, then explain to me why even have a FDC ? If your pressure is a constant that never changes what is it's purpose then ?
There are two constants in the FDC. The "orifice" in the top of the Servo and the "Servo Spring". In combination with the differentiating regulator valve and the "viscosity" of the fuel used you get movement to the plate which in turns pushes on the governor. There is a "needle valve" after the servo piston but it's purpose is to adjust or "Trim" the servo according to set spec's according to the fuels used. Mainly Diesel and Gasoline and Kerosene . Do not play with this needle valve. You need complicated equipment to set it correctly.

 

[rustystud]

I'm rebuilding a spare hydraulic head to swap it and the booster pump onto my engine when I'm confident they are as good as new. There's some kind of sleeve down inside under the 12 point screw that I haven't been able to fish out and clean. It seems to be held in by the oil on the back side. See pic. It turns with no force and a magnet cannot pull it out. Anyone ever removed this? What's behind it?

There is a pressure relief valve under that 12 point screw. You should remove it and clean out the hole.

 

[rustystud]

I got a personal message today about the "droop" adjustment. There has been a lot of confusion about this function so I decided to try and explain what the droop function is for. In one sentence "it maintains engine RPM " .
Now here's an example. In generators when your under load you can have loads drop off immediately. This can cause surging RPM's which can cause serious problems since the Hertz rate is determined by RPM. (In America the 60 Hz cycle is standard. That equates to 900 RPM ,1800 RPM, 3600 RPM's . You get the idea).
So we lost a load on the generator (say someone turned off an A/C unit ) now the generator RPM's is surging (this is bad) , the droop function immediately tries to govern down the engine to prevent this surge. Now lets say the generator is plugging along with a small load. Suddenly there is a air-compressor turned on. Now the engine's RPM's drop fast , the Droop function ramps up the engine's RPM's to compensate for this extra load. That is the function of the "Droop" adjustment in a nutshell.
In vehicle applications you normally don't even need a Droop function. Your foot on the throttle makes this decision. Why the militiary decided to keep this function on there injection pumps I'll never know. Why did they even add the "Fuel Density Compensator" ? Really it serves no useful function. All you guys who bypassed it know this is true. So unless the droop function is extremely out of whack just leave it alone. Playing with it will just add unneeded headaches.

 

[Floridianson]

Rustystud, I am not ''concerned'' with the droopscrew, I simply asked for clarification.
You made two statements:
That the droopscrew :
1. helps add fuel and 2. prevents excessive fuel delivery
I fully agree with number 2, but do not understand how the droop screw could ever ''help add fuel''.
It is clear that these are two things that are exactly the opposite.That's what my question, still unanswered BTW, was all about.
I am a certified diesel mechanic, so there is no need to explain to me how the governor functions, I learned that decades ago.
I am very familiar with bosch injection pumps, so you will not have to explain the principles of operation.
You can go directly to the droop screw and tell me how it causes what part of the governor to move in which direction in order to add fuel.


I know exactly when and under what conditions the droop screw comes into contact with the stop plate, and when the smoke limit cam does, but neither do I see how having been an apprentice at m.a.n. should make me realize the stop plate is curved, nor how it should be related to the FDC, and I could not find such explanation in the pdf either.
What I did see (and expected) is that the stop plate in the picture has two separate contact surfaces for the smoke cam and droop screw, having slightly different angles.
What I also see is that the pump in the picture is not a multifuel pump, and does not have a FDC. The governor operates on the same principle, however.
The code G pump's (LDS427-2) stop plate is perfectly straight. Smoke limit cam and droop screw are close together, and share the same contact surface.

The stop plates in the other multifuel injector pumps do also have two separate contact surfaces at slightly different angles.
If at all, the stop plate is rounded only where the 2 contact surfaces meet.


According to You, a droop screw ''has no more function'' with the FDC bypassed, as there are no more pressure changes, and the stop plate no longer moves, no longer causing surging.

My explanation, back in post#109, of how the FDC works :
''The pressure inside the FDC only changes when a different fuel is used.
The pressure inside the FDC is the same regardless of engine speed, and does not change during engine operation.''

Differs from yours:
''I think I know what the problem is here. Your not taking into account that the stop plate moves during operation. It is not stationary, but slides up and down according to fuel pressure.''''The stop plate is continually being adjusted according to fuel pressure at that time. Since fuel pressure is adjusted according to engine RPM then that means the FDC is constantly adjusting''

Well, got the tm out, and found this:
''The fuel supply is admitted to a pressure regulating valve where the supply pressure is reduced to a constant regulated pressure over the engine operating speed and load range''

This means the stop plate does not move during engine operation, and even if it did, it would only change maximum load fuel by an negligible amount, between the full load gasoline position, and the full load diesel position.

So your explanations did not answer my question yet.
Oh, and don't get me wrong.
Please keep in mind that my questions are of purely technical nature.
I truly appreciate Your threads. Lots of useful step by step information and heads up even for more experienced mechanics.

I am with you on this one and if you look at the Troubleshooting manual page 33 34 the droop is adjusted after the main fuel and only when we for some silly reason still have the FDC hooked up. It does not add any fuel or decrease any fuel and gen sets do not have an FDC but do have problems with load control so they need one or the other droop controls. When FDC is still hooked up and the wedge plate changes because of type of fuel the Droop should still be with in specs for fuel / boost. Now when we bypass the FDC the FDC wedge plate is no longer moving and all we can do is adjust the main fuel / twin nuts. So if FDC bypassed and you adjusted the main fuel then go to change the droop it will throw off the main adjustment you just set. Just to be clear when we for some reason we still have the FDC hooked up the droop screw if I remember still controls boost fuel from 1600 rpm to 2100 rpm is why it is there.

 

[rustystud]

I am with you on this one and if you look at the Troubleshooting manual page 33 34 the droop is adjusted after the main fuel and only when we for some silly reason still have the FDC hooked up. It does not add any fuel or decrease any fuel and gen sets do not have an FDC but do have problems with load control so they need one or the other droop controls. When FDC is still hooked up and the wedge plate changes because of type of fuel the Droop should still be with in specs for fuel / boost. Now when we bypass the FDC the FDC wedge plate is no longer moving and all we can do is adjust the main fuel / twin nuts. So if FDC bypassed and you adjusted the main fuel then go to change the droop it will throw off the main adjustment you just set. Just to be clear when we for some reason we still have the FDC hooked up the droop screw if I remember still controls boost fuel from 1600 rpm to 2100 rpm is why it is there.

Yeah, basically once the FDC is out of the picture you don't need to worry about the Droop screw again.