Locating Methods For Air Leaks In Mechanical Fuel Pump Fuel Lines

Boiling fuel

Boiling fuel does not mean you have an air leak. Boiling fuel will occur if you exceed the boiling point.

The boiling point will increase as pressure increases. What is your fuel pressure at idle?

The fuel will also boil if your block/pump is to warm. Was your engine/pump cold to the touch while fuel was "boiling"?

I have experienced fuel boiling with the new gasolines. A winter blend will boil very easy. In my case I took steps to reduce engine and underhood temps.

If fuel arrives to the pump under positive pressure then air can not leak into the fuel line. Some things that prevent positive pressure at the pump inlet:
1. Gas tank not vented.
2. Fuel line restricted or too small.
3. High pressure drop filter upstream of pump.
4. Fuel tank sock plugged.
5. Climbing a steep grade.
6. Fuel tank lower elevation than fuel pump.
7. Carb calling for more fuel than system can deliver.

If your system does not provide positive pressure to the pump suction then your pump may cavitate in severe cases then form bubbles and low flow. Your car should have positive pressure to the pump during idle, if your fuel level is higher than your pump and your tank is vented. Is your fuel level higher than the pump?

Your fuel was boiling at idle with a cold to the touch fuel pump?
In idle the fuel pump is not moving fuel most of the time; instead the pump is dead headed. If your fuel pump is cold to the touch and the fuel is "boiling" I would think it would be caused from the energy the pump is putting into the dead headed fuel; thus not the root cause of your engine stall.

That being said, you did not mention the possibility of a leaky diaphragm.
When you assembled the fuel pump was the pump spring in the correct tension state while installing the diaphragm? Was the diaphragm new or old stock?

Locating Methods For Air Leaks In Fuel Line

Thanks For Your Response.

When I Wrote Boiling I Did Not Mean To Mislead Anyone By My Choice Of Words But Should Have Rather Said, "hundreds Of Bubbles Appearing In The Glass Bowl As If It Were Boiling.

The Fuel Line To The Pump Is Not In A Bad Area For Heat Transfer; Under The Frame. The Fuel Line From The Pump To The Carb. Is In A Rather Hot Area, Crossing Over The Exhaust Manifold. I Have Wrapped The Exhaust Manifolds With The Latest Composite Material And Sleeved The Fuel Line To The Carb. With This Heat, Shields Up To 950 Degrees, Protecting Material.

When The Car Is Up To Speed And Under Load, These Symptoms Appear With A Simultaneous Drop In Fuel Pressure.

When I Was Working On This Issue, At My Home, The Engine Was Freshly Started, Cold, And With Both Sides Of The Hood Fully Opened. When I Noticed The Bubbles Appearing In The Glass Bowl, I Also Had A Loss Of Fuel Pressure.

It Takes A Little While For The Air To Get In, Where Ever Its Entry Point Is, But It Does Happen, Along With The Pressure Loss.

J.j. Lasalle