Fuel Pressure gauge showing residual pressure

[AndyMenon]

[attachment=5066:GEDC0012a.jpg][attachment=5067:GEDC0021b.jpg][attachment=5070:GEDC0032c.jpg][attachment=5069:GEDC0042.JPG]

Hi all,

I just finished hooking up my fuel line. As I have a late model 305 in my ride, I put in a Holley black electric fuel pump with a Holley fuel pressure regulator to match.
Here are a few pictures of my set up. The pressure gauge is showing a residual pressure of 1.8psi. I noticed it a couple of days after I finsihed the fuel line. I unbolted the gauge, and let it bleed until the needle fell back to "Zero", and bolted it back up. But again, after a few minutes the gauge was back to showing 1.8psi!

Here are the facts:

1. As seen from the fuel-pum shot, the gas tank isn't in yet.
2. The pressure gauge was bolted to the carb inlet weeks before I completed the fuel line
3. To leak test the connections, I poured some rubbing alcohol down the fuel line until it pord out from the other end of the hard line, before I tightened up all the hose clamps. There is some amount of fluid in there.

Did I goof somewhere?

Thanks much!
-Andy

 

[Mike]

Does the gauge zero if you remove it from the system a second time? Is there enough alcohol left in the line to be creating a slight amount of pressure as it tries to flash off? I would tend to think ~2 lbs. would be a lot of pressure, but I suppose stranger things have happened. How about flushing the lines with some pump gas, draining it as best as you can and letting it dry out a day or two before sealing everything back up?

Did the gauge register anything prior to the test with the alcohol?

The angle of your photos make it a bit difficult to see, but that hose leading out of your regulator looks to be bound up like a boy dog. The short hose leading into the gauge fitting looks a bit crimped as well. Those hoses want to have gradual, relaxed curves in them and not to be crimped because of tight bends. Those crimps will end up as solid as hard line when you turn the fuel pump on. You may want to rethink that routing a bit. I would also try to get some more air space between the cylinder head and regulator, as well as between the hose and that front water crossover on the intake. There's no reason to heat the gasoline up before it gets to the carb. A needle and seat assembly can deal with raw gasoline well, but when that gas is already starting to flash off?

 

[AndyMenon]

Does the gauge zero if you remove it from the system a second time? Is there enough alcohol left in the line to be creating a slight amount of pressure as it tries to flash off? I would tend to think ~2 lbs. would be a lot of pressure, but I suppose stranger things have happened. How about flushing the lines with some pump gas, draining it as best as you can and letting it dry out a day or two before sealing everything back up?

Did the gauge register anything prior to the test with the alcohol?

The angle of your photos make it a bit difficult to see, but that hose leading out of your regulator looks to be bound up like a boy dog. The short hose leading into the gauge fitting looks a bit crimped as well. Those hoses want to have gradual, relaxed curves in them and not to be crimped because of tight bends. Those crimps will end up as solid as hard line when you turn the fuel pump on. You may want to rethink that routing a bit. I would also try to get some more air space between the cylinder head and regulator, as well as between the hose and that front water crossover on the intake. There's no reason to heat the gasoline up before it gets to the carb. A needle and seat assembly can deal with raw gasoline well, but when that gas is already starting to flash off?

Thanks Mike!

I think it's that hose that leads out of the pressure regulator that is causing this issue.
Let me re-route that and see if the problem will go away.
The short hose that leads to the pressure gauge however is not crimped. That shot is rather funky.
I have other pics but they are in my google picasa album. I will try to make that album public and publish a link to it here.

Andy

 

[AndyMenon]

Thanks Mike!

I think it's that hose that leads out of the pressure regulator that is causing this issue.
Let me re-route that and see if the problem will go away.
The short hose that leads to the pressure gauge however is not crimped. That shot is rather funky.
I have other pics but they are in my google picasa album. I will try to make that album public and publish a link to it here.

Andy

Ok, here's what I've done:

1. Opened up the fuel line on the fuel pump end and blew out all of the alcohol in it
2. Altered the fuel line to give it a more relaxed flow from the pressure regulator exit, and into the carb.
3. Made changes to the fuel line at the pressure regulator entry point so that the braided steel section clears the water pump hose.
4. Will post updated pics sometime over the long weekend.

But now, here's the fun part. I have disconnected the fuel line on the carb end and left it open to atmospheric pressure. To my knowledge, the pressure gauge must show Zero under atmospheric conditions. But I still see that stupid 1.8psi reading. A couple of days later it bled down to a lesser value, and I think it must be zero by now.

Not sure what the problem is :shrug2:

thanks,
-Andy

 

[one finger john]

If, when you crack the fittings, there is pressure in the line then find out where it is coming from. As Mike has said 1.8 lbs would be significant. But you say the system has not been pressured up so why is there pressure indicated? Where is it coming from? Replace the gauge. It should drop to zero immediately.

John

 

[Wild Mango]

Ok, here's what I've done:

1. Opened up the fuel line on the fuel pump end and blew out all of the alcohol in it
2. Altered the fuel line to give it a more relaxed flow from the pressure regulator exit, and into the carb.
3. Made changes to the fuel line at the pressure regulator entry point so that the braided steel section clears the water pump hose.
4. Will post updated pics sometime over the long weekend.

But now, here's the fun part. I have disconnected the fuel line on the carb end and left it open to atmospheric pressure. To my knowledge, the pressure gauge must show Zero under atmospheric conditions. But I still see that stupid 1.8psi reading. A couple of days later it bled down to a lesser value, and I think it must be zero by now.

Not sure what the problem is :shrug2:

thanks,
-Andy

Andy, I note the gauge you have is glycerine filled, which is a good way to get some vibration proofing into a bourdon tube gauge. Most glycerine filled gauges have a bung which you remove after ftting the gauge so as to vent the case to atmospheric. If that bung is still in, your pressure gauge is maybe trying to be a barometer, which is where the ghost readings are coming from.

 

[Mr T Bucket]

Had that happened to me. Bought some liquid filled gauges and forgot to crack the vent screw on one of them.

 

[AndyMenon]

Andy, I note the gauge you have is glycerine filled, which is a good way to get some vibration proofing into a bourdon tube gauge. Most glycerine filled gauges have a bung which you remove after ftting the gauge so as to vent the case to atmospheric. If that bung is still in, your pressure gauge is maybe trying to be a barometer, which is where the ghost readings are coming from.

Hi WM, All,

I hope you all had a Great Thanksgiving Weekend.

Yes, getting the vibrations out of the way was the whole idea. If I flip the gauge over, right behind the dial where the fitting meets the gauge body, there is a black rubber plug on the chrome body. Is this the bung? It looks like it is removable. But before yanking it off, I got to make sure.


Thanks again!
-Andy

 

[Chief-T]

Hi WM, All,

I hope you all had a Great Thanksgiving Weekend.

Yes, getting the vibrations out of the way was the whole idea. If I flip the gauge over, right behind the dial where the fitting meets the gauge body, there is a black rubber plug on the chrome body. Is this the bung? It looks like it is removable. But before yanking it off, I got to make sure.


Thanks again!
-Andy

I have a similar gauge. The plug is where the glycerin is added to the gauge. Do not remove unless you need to add glycerin. Just remember, there should be a small bubble on the face side which compensates for barometric changes.

 

[Screaming Metal]

Well guys....I see the guages are a playing' with ya. Yep, Mango, Chief-T, and Chief-T are correct.
You want about 3/4's to 5/8's face fill with the glycerin, just enough to Dampen the needle shake so you can read it. On the little rubber plugs, :whisper:, either drill a small .010 hole in the plug....it'll let the guage bleed off excess pressure should it build and allow it to breath, or get a jewelers file and put a groove along the side to do the same. Can't do it too much or your glyerin will run out if you've got it facing straight up. Also, it'll attract dust and if you pressure wash it, you could have your new guages sweating internally....WAIT! Its full of liquid anyway! Ha! :jawdrop:

 

[Screaming Metal]

The .010 hole will be drilled THRU that plug, but that hole will seal back up since the rubber will try to spring back. Don't worry....it should be enough to vent. Sometimes you gotta go to a .015....but I wouldn't go anything above that....