Back to my fuel vapor in the lines.

[bigblock]

Tony you said you been fighting this problem for 5yr's, is it with the same fuel pump? the way you say it acts up sounds like it runs out of gas because the pump isn't keeping up the gas volume you need. You said you changed the line from the tank to the pump was it with hose or tubing , if its hose are the clamps to tight? If I had this problem for 5yrs I would look at the pump because it looks like it is pumping air because of the bubbles. The check valve in the pump seems to misfunction after its running awhile.

[chevynut]

Sorry but on that one I know your wrong. The internal size of the line is directly related to the amount of vacuum that has to be placed on the line to get fuel to enter the line.

I'm not following you on that one. Resistance to flow is a function of cross-sectional area and surface condition of the inside of the line. The larger the line, the less pressure drop no matter if you're pushing or pulling the fluid. It's the same pressure drop either way and is dependent on flowrate.

What does vacuum have to do with it?

A column of a fluid in a 1/4" line has the same pressure as the same fluid in a 1" line, as long as the height of the line is the same. The vertical distance is all that matters, not the column size. A 1 acre lake with an outlet 100 feet below the surface exerts the same pressure as a 10,000 acre lake with the outlet 100 feet below the surface.

[chevynut]

No it isn't the same when pulling the liquid uphill. The larger the pipe, pickup, whatever, the more volume. That means it's pulling more weight. Now once the liquid, say gas in a car, once it's sucked up then down again you have a siphoning action and it can level off. In the end after it's primed, it's determined by the height of the fuel in the tank compared to the height of the pump, or to it's final destination. As long as it's going uphill, the larger the line, the harder it is to pull.

No that's is not true. Line size has nothing to do with pressure of a fluid. As I said above, the only thing that matters is the height difference between the inlet and outlet. That's precisely why a siphon works.

Notice in the formula on this page the width or diameter of the column is not included...it's because it's irrelevant.

https://www.engineeringtoolbox.com/h...er-d_1632.html

[chevynut]

Sort of makes the idea of my fuel boiling a bit more of a possibility doesn't it?

Except after the pump the fuel is under pressure, so it's less likely to boil. And Rick's comment about why doesn't everyone (running a carburetor) in your area have the same problem? EFI systems don't have as much of a problem with vapor lock since the system is under much higher pressure.

[55 Tony]

No that's is not true. Line size has nothing to do with pressure of a fluid. As I said above, the only thing that matters is the height difference between the inlet and outlet. That's precisely why a siphon works.

Notice in the formula on this page the width or diameter of the column is not included...it's because it's irrelevant.

https://www.engineeringtoolbox.com/h...er-d_1632.html

You know, I was going to ask you what is harder lifting an ounce of water or a gallon, but it hit me. Although the line is larger therefore there is more weight to pull up, the surface area is also greater. So if the pump is pulling on an empty line with the end in liquid, the larger line would have the same vacuum psi, but it would also have more surface area so the same vacuum will indeed lift the fluid the same whether it's a 1/4" line or a 1" line. You are right, (and I don't mind admitting it).

[55 Tony]

I went for a ride and since it was colder today, it didn't act up at all. Besides not running out of fuel and stalling, the fuel pressure didn't drop either. When I came home I looked under the hood and saw just a few bubbles then it stopped, so I closed the hood and left it idle in gear for about 1/2 hour and checked on it. Yes I know the water went all over the place, but the garden hoses are put away for the winter. I'm certain I'd have the same results with water only on the pump. And before someone says that "the water sealed the leak so the bubbles stopped", watch again and notice how long it takes for the bubbles to stop. That's because the fuel is on the bottom of the pump and it took a while for that to cool down.

I say it was BOILING!

And I don't think anyone can convince me otherwise.

https://youtu.be/Jg8-z3nHjbE
https://youtu.be/ee-3spbjugY

[55 Tony]

Tony you said you been fighting this problem for 5yr's, is it with the same fuel pump? the way you say it acts up sounds like it runs out of gas because the pump isn't keeping up the gas volume you need. You said you changed the line from the tank to the pump was it with hose or tubing , if its hose are the clamps to tight? If I had this problem for 5yrs I would look at the pump because it looks like it is pumping air because of the bubbles. The check valve in the pump seems to misfunction after its running awhile.

BB, the pump was replaced and the problem stayed the same. And if the check valve was the problem, it just wouldn't pump well, it wouldn't allow air to enter, it would just let some fuel to go backwards.

And as far as this going on for 5 years, keep in mind that I had this problem ALMOST under control with a different fuel filter made to bypass vapor. It would only act up under extreme conditions. I changed filters to purposely make the problem worse, so I could track it down and hopefully eliminate the problem completely. I believe I found the problem.

[bigblock]

Good luck with your problem.

[BamaNomad]

What? What would the chrome do? Oh, maybe the seal would leak sucking in air? I have to run out for some things and I'm taking the 55. See how well it runs today that it's cold out.
It's a Holley pump, and the same one before it gave the same problem.

No, I was referring to the fact that chrome doesn't dissipate heat as well as a rough black surface... and you think the problem is heat related... normally a mechanical fuel pump would only heat from being in proximity to the block, not from it's own generated heat (which should be minimal).

[55 Tony]

My plan is back to an electric pump near the tank, and the fuel line in the engine compartment to be as short as possible. Maybe insulated.