Deuce keeps getting air in fuel system

[rustystud]

Was just adding the thing about the cooling in response to your comment to help education. Also the head has what is called the IP overflow valve not a bypass with a orifice in it to allow the fuel to always flow through the Head unit and also keep the pressure in the head correct when running. When not running fuel just passes through so we can clear the air after filter change in a correct system.
I have heard of microburst's but it was use to describe the newer injection systems the have controlled microburst's through out the cycle of the burn to better control the burn and not just dump a large load of fuel at one time like the mechanical injection do.

The "microbursts" I'm talking about are the small "explosions" you get from water and air that is highly pressurized like in a Hydraulic system or a Fuel Injection system. It is also known as "cavitation" . Of course cavitation is due to air entrapment while the water is more of a steam explosion, so I just used the term "microbursts" to describe both.

 

[rustystud]

Was just adding the thing about the cooling in response to your comment to help education. Also the head has what is called the IP overflow valve not a bypass with a orifice in it to allow the fuel to always flow through the Head unit and also keep the pressure in the head correct when running. When not running fuel just passes through so we can clear the air after filter change in a correct system.
I have heard of microburst's but it was use to describe the newer injection systems the have controlled microburst's through out the cycle of the burn to better control the burn and not just dump a large load of fuel at one time like the mechanical injection do.

View attachment Scan0027.pdfOK, I'll try to explain what I'm saying better. The fuel is used to cool the Hydraulic head that is true in all fuel injection systems. There is a lot of heat produced when pressurizing anything. Just check your air compressor line out and you'll see what I mean. So the Hydraulic Head has fuel "flow" around the plunger assembly. The pressure relief system which we where talking about allows over pressure to be released back to the fuel tank "and" it has a "metered orifice" to allow "trapped air" to escape. It has a secondary function of also allowing fuel to flow when the engine is at idle to keep the heat down at the Hydraulic Head. That is why the manual says "the opening ALSO serves" meaning it has a "secondary" function, not it's primary function.

 

[Floridianson]

View attachment 597221OK, I'll try to explain what I'm saying better. The fuel is used to cool the Hydraulic head that is true in all fuel injection systems. There is a lot of heat produced when pressurizing anything. Just check your air compressor line out and you'll see what I mean. So the Hydraulic Head has fuel "flow" around the plunger assembly. The pressure relief system which we where talking about allows over pressure to be released back to the fuel tank "and" it has a "metered orifice" to allow "trapped air" to escape. It has a secondary function of also allowing fuel to flow when the engine is at idle to keep the heat down at the Hydraulic Head. That is why the manual says "the opening ALSO serves" meaning it has a "secondary" function, not it's primary function. When the engine is at cruise speed that relief is not providing ANY cooling effect as the fuel is being used up too fast by the Hydraulic Head.

Is that almost not what I said before and never disagreed that it removes air running or not. I disagree that all the fuel is being used up at cruse speed there is always some fuel running through the overflow valve and returning to the tank. I just like calling things what they are so I say overflow valve so when the people read the tm's we are all on the same page. In fact you started calling it a bypass then a pressure relief when it is called the over flow valve but to me acts more like a metering valve to always keeps the correct back pressure on the head no matter what the pressure is.
If we were to split hair's the tm says first it's function is to hold back pressure in the head and over flow the extra fuel back to the tank. Then says air then cooling but in the real world it does all three at the same time no matter how you list it.

 

[daytonatrbo]

The "microbursts" I'm talking about are the small "explosions" you get from water and air that is highly pressurized like in a Hydraulic system or a Fuel Injection system. It is also known as "cavitation" . Of course cavitation is due to air entrapment while the water is more of a steam explosion, so I just used the term "microbursts" to describe both.

Cavitation applies to both. The "air" that you see in cavitation isn't air. Its basically steam (water vapor). Due to disturbances in the fluid, you temporarily see pockets of low pressure. The pressure in these pockets is so low that the water "boils" even at low temperature.

When these pockets of water vapor collapse, the wall of water closing in on the vapor travels at supersonic speeds and crashes into the metal so hard it pits.

Inside the pump, you see crazy turbulence and any trapped air promotes cavitation because it allows even more extreme pressure changes. But trapped water also allows it in the absence of air. The pressure at which water will flash to steam (at a given temp) is more easily achieved than that of diesel fuel. That's why straight diesel doesn't present an issue.

At 70° water will flash to steam at a pressure of 15mm of mercury. At the same temp, it takes a much lower pressure of 0.4mm of mercury for diesel to flash to vapor.

 

[ivbeenrokd]

Okay, I pulled it all back apart this morning and pressure tested the in-tank assembly. Found it leaking where the rubber hose meets the bottom of the 90 degree connector. Pulled the clamp and hose, cleaned, reinstalled, and it was still leaking but better. Repositioned the clamp and the leak went away completely even with signifcant air pressure. Did a 1 hour test run/drive and it's running excellent.

Thanks for all the help!

John

 

[Blackbear]

Congrats!

 

[Jeepsinker]

Good deal. Now when you put your new lift pump in, and remove that old pump, you will see a noticeable increase in power that you didn't even know was missing.

 

[Floridianson]

and as Garrett said before start reading up on the FDC bypass as that needs to be done next.

 

[Floridianson]

To be correct Rusty the overflow valve opens up at between 33 and 38 psi. When we start the motor the lift pump produces 35 psi then the valve will open and between the size of the orifice and valve the Head will flow all extra fuel out of it while holding the correct pressure along with expelling any air plus cool the Head. If there is a over pressure in the system that is taken care of by way of the secondary fuel filter bypass valve and returned to the tank or the lift pump bypass.
I just try and keep it simple for those who are just learning about the Deuce system so they can ask the right questions or understand the system and it correct parts.

 

[rustystud]

To be correct Rusty the overflow valve opens up at between 33 and 38 psi. When we start the motor the lift pump produces 35 psi then the valve will open and between the size of the orifice and valve the Head will flow all extra fuel out of it while holding the correct pressure along with expelling any air plus cool the Head. If there is a over pressure in the system that is taken care of by way of the secondary fuel filter bypass valve and returned to the tank or the lift pump bypass.
I just try and keep it simple for those who are just learning about the Deuce system so they can ask the right questions or understand the system and it correct parts.

OK this topic has gone down the rabbit hole. I never mentioned anything about pressures of any kind. I have been totally talking about the bleeding off of "air entrainment" in the fuel lines.

 

[rustystud]

View attachment Scan0028.pdf

Cavitation applies to both. The "air" that you see in cavitation isn't air. Its basically steam (water vapor). Due to disturbances in the fluid, you temporarily see pockets of low pressure. The pressure in these pockets is so low that the water "boils" even at low temperature.

When these pockets of water vapor collapse, the wall of water closing in on the vapor travels at supersonic speeds and crashes into the metal so hard it pits.

Inside the pump, you see crazy turbulence and any trapped air promotes cavitation because it allows even more extreme pressure changes. But trapped water also allows it in the absence of air. The pressure at which water will flash to steam (at a given temp) is more easily achieved than that of diesel fuel. That's why straight diesel doesn't present an issue.

At 70° water will flash to steam at a pressure of 15mm of mercury. At the same temp, it takes a much lower pressure of 0.4mm of mercury for diesel to flash to vapor.

No, there is actual air in the system. Here is what I'm talking about. I understand about water turning into steam, but there is also a problem with actual "air" in a system.

 

[Jeepsinker]

You guys are saying the same thing. Neither of you are wrong. The OP found his problem, so let's not clutter his thread up with arguing the same point.

 

[rustystud]

View attachment Scan0029.pdf

Is that almost not what I said before and never disagreed that it removes air running or not. I disagree that all the fuel is being used up at cruse speed there is always some fuel running through the overflow valve and returning to the tank. I just like calling things what they are so I say overflow valve so when the people read the tm's we are all on the same page. In fact you started calling it a bypass then a pressure relief when it is called the over flow valve but to me acts more like a metering valve to always keeps the correct back pressure on the head no matter what the pressure is.
If we were to split hair's the tm says first it's function is to hold back pressure in the head and over flow the extra fuel back to the tank. Then says air then cooling but in the real world it does all three at the same time no matter how you list it.

As far as calling the "overflow valve" a bypass valve or relief valve it really makes no difference. Do you call your Dodge differentials ring gear an "annulus" gear ? Well that's what they call it in their technical manuals. It still is a ring gear though. Now here's something to mess with your braincase. The overflow valve opens between 33-38 psi right ? Well then how is there any flow if the fuel pump only puts out 30-40 psi at 700 rpm ? The metered orifice cannot push that much fluid. This weekend I will be performing an experiment on my truck to find out where this fuel is coming from. Since I have that fuel shut-off valve in front of the injection pump I will also determine if the fuel filter bypass is allowing any flow back at idle speeds.

 

[Floridianson]

View attachment 597362
Now here's something to mess with your braincase. The overflow valve opens between 33-38 psi right ? Well then how is there any flow if the fuel pump only puts out 30-40 psi at 700 rpm ? The metered orifice cannot push that much fluid..

Remember we already said the valve has an orifice in it, The overflow valve /orifice does not need that much flow at low rpm as all the Head needs is it's correct fuel pressure to operate at specs. The orifice is large enough before valve opening to allow enough fuel to cool the head and expel any air, dirt and small children.
The IP injects cc's not gallons.

 

[daytonatrbo]

No, there is actual air in the system. Here is what I'm talking about. I understand about water turning into steam, but there is also a problem with actual "air" in a system.

I guess I should have been more clear. The first part of my comment was about cavitation in general. But I made exactly your point in the body of my comment.

Cavitation applies to both. The "air" that you see in cavitation isn't air. Its basically steam (water vapor). Due to disturbances in the fluid, you temporarily see pockets of low pressure. The pressure in these pockets is so low that the water "boils" even at low temperature.

When these pockets of water vapor collapse, the wall of water closing in on the vapor travels at supersonic speeds and crashes into the metal so hard it pits.

Inside the pump, you see crazy turbulence and any trapped air promotes cavitation because it allows even more extreme pressure changes. But trapped water also allows it in the absence of air. The pressure at which water will flash to steam (at a given temp) is more easily achieved than that of diesel fuel. That's why straight diesel doesn't present an issue.

At 70° water will flash to steam at a pressure of 15mm of mercury. At the same temp, it takes a much lower pressure of 0.4mm of mercury for diesel to flash to vapor.

 

[Floridianson]

Know it is hard to believe that a orifice 1.3mm will move fuel and air but it does. How much at 35psi I do not know but it could be figured so with that how much heat is removed. Guess what I do not know but it too could be figured. For removing how much air that too I would have to cracks the books as I do not know off the top of my head. We discussed the secondary fuel filter bypass before if you remember and it opened at 60 to 70 lbs. So I do not know what you are trying to show but I will hear what you type with an open mind and no pride involved as we all get schooled.
OK think I found the answer to your brain quiz. I will try and test more but the crack pressure of the overflow valve is less than 33/38 lbs.

 

[Floridianson]

You guys are saying the same thing. Neither of you are wrong. The OP found his problem, so let's not clutter his thread up with arguing the same point.

Yes and no Garrett any info only arms us and there are plenty of BS treads in other forms. More people flock to a thread that a woman starts that one with good info in it. Woof Woof

 

[daytonatrbo]

Yes and no Garrett any info only arms us and there are plenty of BS treads in other forms. More people flock to a thread that a woman starts that one with good info in it. Woof Woof

All credit to XKCD:

 

[Jeepsinker]

I like that. That's pretty funny.

 

[rustystud]

Actually having reread a lot of the past posts I see we all are on different subjects here. I started with the premise of too much air in the fuel system is a bad thing and that the overflow valve could not handle that much from a leaking fuel line. It quickly went down the rabbit hole from there.
I did try and test the overflow valve on my deuce today. What I found out was interesting though. With just the fuel tank pump on the overflow valve passes 750ml of fuel in 60 seconds. With the engine running at 700 rpm it passes 2250ml of fuel in 60 seconds. I wasn't able to test at any higher rpms due to the container getting pushed around and spilling fuel all over ! I need an assistant to check further.