What the devil was Ford thinking with these fuel lines?

Hi,
I am building a 300. I have finished my megasquirt and it tests fine. I had the engine re-machined and balanced. I have been reading tech articles and forums non-stop for the last few months, and I thought I was ready to put this thing together.
Then, I looked at the fuel lines and rails that the junk yard left me... I thought I would find a high pressure line, feeding a regulator at the end of the fuel rail, and then a fuel rail with injectors mounted in it. What I have, is two high pressure lines, each connected to one end of a looped fuel rail, a strange metal button in line on one of those lines, a weird thing that has a vacuum fitting on it in the middle of the rail, and no low pressure return line.
Does anyone know how this works?

It's quite simple, actually. The metal "button" is the fuel pressure regulator The end of the line which has the injector bungs between it and the regulator is the high pressure supply. The end which has no bungs is the return.

The fuel pump feeds the injectors through the supply line. Pumps do not produce pressure, pumps produce flow. The resistance to that flow if what causes pressure. The regulator provides that resistance. The pump supplies may more fuel than the injectors can use, the regulator allows the excess to flow back to the tank at lower pressure through the return line. At no time does any fuel which is going to the injectors pass through the regulator

The demand on the injectors is not constant. When you're cruising at high manifold vacuum, the vacuum line which connects to the top of the regulator pulls it further open and allows more fuel to bypass back to tank. When you crack the throttle body wide open, the vacuum disappears and more fuel is available for the injectors

That is what I had hoped, but it still seems a little strange. First, although I can see why the engineers who designed this would want to lower fuel pressure at idle - that way one could use a higher flow injector and the pulse width would not be so small that it would be difficult to maintain a nice, even idle. However, isn't that going to make it a little tricky to set the fuel injection up? Isn't the whole point of fuel injection to get away from a bunch of crap that is actuated by vacuum directly and control the engine through a central computer?
Second, there are two things inline with the fuel rail. The first has the vacuum fitting and I believe to be the pressure regulator, the second is a flat, little piece of stainless steel (which I called "a button" before) and I have no idea what it must do...
Third, there is braided stainless steel around both the fuel lines. Did Ford actually spring for stainless on a return line? I guess it makes sense, the line could get worn out and spray gas around the engine compartment, which would almost surely cause a terrible fire, but it seems a little excessive for a return line.
Also, although I don't really want to have a huge internet forum over semantics of fuel pumps, I must disagree with the idea that fuel pumps create flow, not pressure. I will concede that I would not be correct in saying that they produce pressure only, and would like to advance the idea that they produce hydraulic power which is the product of the pressure and the flow. Here is my reasoning:
If the pump is dead headed it will produce pressure, but not flow.
If the pump is dumping into a bucket it will produce flow, but not pressure.
Neither of these conditions will make my truck run, in order to make my truck run we must sustain a flow rate and pressure based on the needs of the engine.
Therefore, it is most useful to think in terms of hydraulic power, but I concede readily that it is easy to forget about flow when speaking about fuel pumps and regulators (or current as opposed to voltage when discussing a coil, or exhaust velocity as opposed to exhaust pressure when speaking of exhaust systems) and appreciate your insights and significant contributions to this forum...

I design hydraulic systems for a living. Trust me about pumps producing flow not pressure. It's the first thing they teach on the first day of Industrial Hydraulics.

The small fitting on the fuel rail is the Schrader valve

Pumps produce the volume or flow the restriction produces pressure. Yes you will raise pressure if you leave the lines the same size and raise flow, but the pump has just raised flow not pressure. Think of it like a garden hose you barely turn on your hose and you have a low flow, you stick your thumb over the end and you create higher pressure with that flow. Now you can increase flow and this would slightly increase pressure but the increase is only due to the restriction of the hose.

In other words Pumps=flow restrictions(change in Dia., regulators, etc)=pressure

StrangeRanger":fllgz32h said:

Trust me about pumps producing flow not pressure. It's the first thing they teach on the first day of Industrial Hydraulics.

Click to expand...

This is a very interesting way of looking at a hydraulic circuit, complete opposite of what we were taught in Hydraulic Engineering 101.

We were taught :
(Pressure produced by pump) x (flow rate through pump) = (power required drive pump)

If the pump does not produce pressure then it does not require power so what you describe is the perfect perpetual motion machine.

I've never heard that pumps produce pressure, L6. Granted, I'm no engineer, though I've taken some classes.

Now, pumps have a max pressure that they can operate at, sure. But they do not themselves produce pressure. A Roots supercharger is a positive displacement pump. Does it produce pressure by itself? No. It simply moves air from one place to another. The pressure builds up when the air is restricted by the heads, valves, and intake. This is why porting and polishing can reduce the "boost pressure" but horsepower goes up. Restrictions are removed.

You are using the equation to try and prove the wrong thing. The pressure is an external factor, not integral to the pump.

StrangeRanger":1vlqg67r said:

The small fitting on the fuel rail is the Schrader valve

Click to expand...

Could someone please tell me what end of the rail the schrader valve is located? (95' 4.9/300) I looked front to back but somehow missed it.

Edit: 2/18 Found it.

Before I answer anything you have to tell me weather you think a pump produces pressure or flow, or both...

Just kidding. The schraeder valve is on the pump side of the rail buried under the intake manifolds. It has a little plastic cap that further disguises it and keeps it clean.

By the way, if air is moving through a super charger, it is moving because of a difference in pressure. There can be no flow without pressure.

Also, If I understand the flow theory of hydraulic pumps correctly, then what you are saying is that any pump, no matter how small, will blow the fittings placed on it apart if we try to cap it because it will build up pressure until it reaches its magical flow capacity... Can that be right?

It would also follow that a pump of a given capacity will maintain that capacity even if we increase the pressure that it must overcome, so a 50 gallon per hour pump will produce 50 gallons per hour weather it is pumping across level ground or up to the top of a water tower and that the "head pressure" that pump manufacturers are always talking about has nothing to do with the pumps flow capacity, which is an unchanging and internal part of the pump design...

Before I answer anything you have to tell me weather you think a pump produces pressure or flow, or both...

Just kidding. The schraeder valve is on the pump side of the rail buried under the intake manifolds. It has a little plastic cap that further disguises it and keeps it clean.

By the way, if air is moving through a super charger, it is moving because of a difference in pressure. There can be no flow without pressure.

Also, If I understand the flow theory of hydraulic pumps correctly, then what you are saying is that any pump, no matter how small, will blow the fittings placed on it apart if we try to cap it because it will build up pressure until it reaches its magical flow capacity... Can that be right?

It would also follow that a pump of a given capacity will maintain that capacity even if we increase the pressure that it must overcome, so a 50 gallon per hour pump will produce 50 gallons per hour weather it is pumping across level ground or up to the top of a water tower and that the "head pressure" that pump manufacturers are always talking about has nothing to do with the pumps flow capacity, which is an unchanging and internal part of the pump design...

wallaka":2vbip91z said:

I've never heard that pumps produce pressure......

You are using the equation to try and prove the wrong thing. The pressure is an external factor, not integral to the pump.

Click to expand...

I have not responded in the hope that some one else might chime in to avoid what could appear as bickering between us, but that has not happened so I will say my piece then shut up.

I only know how to demonstate this by a mechanical analogy.

A company has an industrial trash compactor. It is the type where a plate moves horizontally to compress the trash against the end of the container similar to the system on a dumpster truck.

On this particular unit, the plate is pulled forward by two steel cables that wrap around the drum of a winch powered by a gasoline engine.

When the compaction cycle starts, the plate is pulled forward from the fully retracted position until it hits the trash. During that stage the winch only has to overcome friction effects so the tension in the cables is quite low.

After the plate reaches the trash, it can only continue forward if the winch increases the pull on the cables. The tension in the cables increases and as the winch is required to provide more grunt, the engine must provide more power and governor opens up the throttle. To continue compressing the trash the winch must provide an increasing amount of pull on the cables. The tension in the cables increases and at the same time you can hear the engine working hard as the governor opens up the throttle.

I doubt anyone would dispute the tension in the cable is created by the winch pulling the cables.

After years of service the gearbox is worn and the cables frayed so the owner decides to replace them. This time he installs a hydraulic ram that pushes directly against the plate, all the necessary hydraulic pipes and controls, and a pump driven by the old gas engine.

Now, when the compaction cycle starts, the plate is pushed forward by the ram from the fully retracted position until it hits the trash. During that stage the ram only has to overcome friction effects so the fluid pressure is quite low.

After the plate reaches the trash, it can only continue forward if the ram increases the force against the plate and this means the pump must supply oil at a higher pressure at the same time drawing more power from the engine. To continue compressing the trash the pump must provide fluid at increasing pressure, and as the pump needs increased power to do this you can hear the engine working harder as the governor opens up the throttle.

Sound familiar, just as the winch applied tension to the cables, the pump generates pressure to force the fluid through the pipes.

Any person still not convinced the pump generates the pressure should install pressure gauges all the way along the lines of a working hydraulic system. The highest pressure will be at the outlet of the pump, and it will progressively fall as the fluid moves along the pipe, around bends, and through control valves. If the pressure is generated by the constriction then it would be highest at the constriction and lowest at the pump.

So, the constriction does not “makeâ€￾ pressure, it creates a demand for pressure that is provided by the pump. If the pump fails to produce pressure or the engine stops supplying power to drive the pump, the system comes to a halt.

And there is a parallel to this which is quite close to home. Your kid needs $20 to go to the movies so you give him a bill from your pay packet. Did the kid “makeâ€￾ the $20, no he created a demand that was provided by the money you have because you worked hard last week. If there is not enough money left in the pay packet or you stop working, there will be no visits to the movies.

The practical effects of all this theory are that I left the darn thing in the circuit, because I thought it might save the life of the fuel pump and provide a little finer adjustment on the injectors at idle.
Now my problem is that my injectors are too small. I thought that using the stock FI throttle body, manifolds, etc. would limit things close to stock. But with no EGR, no smog pump, and a single straight exhaust, the 19lb/hr injectors are starving the engine and causing it to leanburn at open throttle above about 2500 rpm.
Now I need to figure out a way to use my magic flow producing pump to make some money for new injectors. I figure that since restrictions cause pressure, I am going to restrict it real good and make enough pressure to run a turbine and generate power. Then I can hook into the grid and use my old ford to make some serious cash. The exact amount will depend on just how restricted I can get the pump. If I can restrict it enough, I will get high enough pressure to run the whole county!