Jurjen's check valve

[jim]

Jurjen, can you explain a little about the check valve?  I thought the reason for having a return line was to let excess fuel return to the fuel tank rather than flooding the carb.  I can see that a check valve would prevent the carb from draining dry, but will the check valve not prevent the return line doing its job?  What becomes of the excess fuel?
Could you give us a picture of where and how you installed the valve?

[Jurjen]

Hi, Jim.
I did not want to "release" this feature yet, because I have not had it in there for more than a week.
I already made the pictures.

You are right, the free flow should go from filter return  to tank.
I try to make use from another physical quality of the check valve, the so called "cracking pressure" that is the pressure that holds the ball in the seat. My hope is that it will prevent the fuel filter from draining to the tank.
The cracking pressure is normally very low, something like 1 to 3 psi.

I have tried a two-way filter (so w/o a fuel return line) before, but had so much fuel pressure (I guess the "full" 7psi) that the carb would flood after switching the engine off. I tried a new float needle but that didn't help either.

I hope the pictures are clear enough, I bought a metal 1/4" check valve ($5) and put it in the rubber hose that runs from the filter return to the metal tube that runs back to the tank.



No, it is not the yellow thing in the vacuum line....


The old man in his YBR (yellow brick road) workshop (found that on the camera, picture secretly taken by my wife)

[ammachine390]

So has it been working so far? I was wondering, do you think it would work if you put the check valve on the line after the fuel filter before the carb? That way when the engine is turned off, the carb doesn't drain back to the tank through either the supply or return hose.

[Jurjen]

That is a very good idea, but has the same problem as the two-way filter: it keeps the high pressure on the carb, so it floods.

I don't know if it works like it is now, it takes about three days to drain back and I do sometimes use the car within that period (and then it starts-up right away).

But as said before, I will keep you posted.

[ammachine390]

That is a very good idea, but has the same problem as the two-way filter: it keeps the high pressure on the carb, so it floods.

If it was between the carb and filter (still using the filter w/return line), wouldn't it keep the fuel from draining out of the carb, yet still allow excess pressure to go through the return line. The check valve would only function when the engine is off.

[68AMXGOPAC]

That is a very good idea, but has the same problem as the two-way filter: it keeps the high pressure on the carb, so it floods.

If it was between the carb and filter (still using the filter w/return line), wouldn't it keep the fuel from draining out of the carb, yet still allow excess pressure to go through the return line. The check valve would only function when the engine is off.

seems like that would work correctly.

[Gil-SX4]

Jurjen keep us posted on any advances on this.
From looking at your pictures I would recommend changing all your rubber hoses, they are dry roted, and I can see some of them are the factory originals.

[Jurjen]

Thanks Gil, I saw that some of them were cracked, so I did change a bunch of them.

[Jurjen]

I last used the Eagle on Tuesday, today (Friday) it fired right-up. It looks like it is not draining back in three days any more.

The Pierburg company gives only two reasons for putting a non return valve in the return fuel line:

• NRV in the return line
- Used as a safety valve near the tank
in order to prevent it from draining if
a line ruptures.
- Used near the carburetor or before
the fuel vapor separator, to avoid
flooding the float chamber from the
return line if the vehicle tilts sharply.

Here is the link:
http://download.fwheel.com/KATALOG/PIERBURG/CD/catalog/BROSCHUEREN/PG/PG_Kraftstoffanlagen_en_WEB.pdf

When you study the schematics, you will find that some have a pressure regulator in the return line, or a non return valve and a flow restrictor with a 1 or 2 mm hole.

[vangremlin]

Hope this is helpful, I found this in the 1981 TSM, Page 1J-6:

"All AMC automobiles with six-cylinder engines have a fuel return system to reduce the possibility of high temperature fuel vapor problems.  The system consists of a line connecting from a nipple on the fuel filter to a nipple located on the fuel tank sending unit assembly.  The fuel filter is installed with the return nipple positioned at the top of the filter.  During normal operation, a small amount of fuel returns to the tank.  During periods of high underhood termperature, vaporized fuel is returned to the tank rather than entering the carburetor (fig. 1J-9).  Also a check valve in the fuel return system at the fuel filter hose eliminates any possibility of fuel feeding back to the carburetor through the fuel return line.

The in-line check valve has a stainless steel, spring-assisted, check ball to close the orifice (fig 1J-10).  Pressures of 0.1 to 0.6 psi (0.69 to 4.14 kPa) from the fuel filter side opens the check valve and permits normal operation of the fuel return system.

The check valve is bullet-shaped and located in the forward end of the hose/filter-to-tank tube.  If it is reversed, the fuel return system will not operate. 

AMC automobiles with four-cylinder engines do not have a fuel return system (fig. 1J-11)."

[rollguy]

  The fuel filter is installed with the return nipple positioned at the top of the filter. 

I wonder if the filter is positioned any other way, it would not work properly?    This could be what is giving jim's car the problem of not starting when hot.

[vangremlin]

After reading (and contributing) to this thread, I will now be recovering any check valves I come across in Eagles I find in the junkyards.  There is one that just arrived this week in Denver that I am going to check out tomorrow, plus another one that has been there for a couple months that I will see if it still has a check valve.

[Jurjen]

The in-line check valve has a stainless steel, spring-assisted, check ball to close the orifice (fig 1J-10).  Pressures of 0.1 to 0.6 psi (0.69 to 4.14 kPa) from the fuel filter side opens the check valve and permits normal operation of the fuel return system.

The check valve is bullet-shaped and located in the forward end of the hose/filter-to-tank tube.  If it is reversed, the fuel return system will not operate.

 

So  I put in what already should have been there.
Someone must have installed a new rubber hose at one point, and must have overlooked the check valve.

[autumnglen]

the only valves I have found in parts cars still have the original factory clamp on the return line on the fender. If a person is unaware that it is there, it will get thrown out with the old hose.
Rita

[Jurjen]

Here is the picture of the check valve from the TSM: