Hi Art,

I agree with you thoughts on the thread being long and cluttered with responses.
A lot of things have “circled the wagons” around the lack of fuel for sure.

We usually do not get this much feedback on a cars progression.
I’m not going to complain as I like the chat entertainment.
It’s the only thread moving along with lots of follow up. I appreciate him doing that.

As far as the testing, of my “one and only” failed check valve, it was off my 1978. It failed in the late eighties. So, I will say I don’t remember how I checked the new one.
The ball may not have moved either but it was different than my broken one.
I treat all check valves as with a go and no go of direction.
I had only the one car, not my collection today.

I was so young, I wouldn’t have know what a “necropsy” was either. Don’t know when I looked that up, probably, since seeing and knowing your posts, Art.
I definitely had less of a vocabulary let alone the experience to think with it sanely. (:-)
I may have sucked on a new one instead of blowing into it from either end.
That way, I would have about 15 lbs. of atmospheric pressure to assist in moving the ball. All I know it cannot leak, period.

I cut mine open and found the broken collapsed spring inside. I don’t think it even rattled but passed air.
I figured that since the valve is mounted horizontally the ball is subjected to gravity, in the mid or open position, inside the threaded canister.
It’s suspended in fuel on that spring fluctuating very minutely from the pulsating flow.
The spring gets distorted by having to support the weight of that steel ball horizontally.
I do not remember any kind rusting or having fuel additives issues with gas at that point.
The spring was fairly shiny and the coils were very thin.
A coil spring was even thinner where it cracked that could have reach the barrel of the fitting.

What I was trying to imply is that the check valve has more than a one way purpose.
By it just being in the line it should have “some” influence with the workings of the pumps pulsations.
Not so as it “is” an intentionally true purpose, but it does have a “mass in that is in movement” and it is a wear item in the process. It’s not static.
That tiny resistance, I believe can have a minor influence of how the pump can percolate gas through its clearances. Add age to those functions of wear and it what we will get.
A failed pre pump will shake the check valve even more, like running on an empty tank but it’s is 80% filled.
Nothing about the fuel pump system will get off lightly, in either case that causes cavitation.

Roller and vane (PS) pumps have some natural leakage and therefore don’t have as much suction capability. Power steering pumps are surrounded by reservoir or are gravity fed fluids
It’s simplicity and low costs.

The more traditional gear pumps, used for engine oil or piston pumps with valves are a different story.
On turbine vane pumps it’s the impeller diameter and the close fitting area of the volute, that makes for it to have large volume and suctions. Its capacity and capability is influenced greatly by the clearance tolerance of their wear rings.
In the Navy I repaired huge amounts of those for petroleum products and various type of waters aboard ships.

On a car, it’s the Size that matters with pressures needed versus a large volume output.
The roller pump has a simplicity of both designs but comes with compromises to get it so compact.
A compromise is to have the feed pump to keep it from cavitation.

Back in the K jet car, of 1978, a spring loaded accumulator was used for a slight back pressure and absorber of noise.
I think the pump was even slightly smaller in diameter.
The check valve still had to stay the same but untimely, an even larger filter was added lower or closer to the pump as a muffler.
The pumps increased slightly in size but so did the engines got bigger. Still the principles stated the same All through the LH s.

Yep it’s a long thread, maybe, slightly worse than my long posts, (:-) Nah it’s long!

Phil