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Discussion Starter · #1 ·
I've worked on Spica enough to grasp the concepts, but...

One of the cars I worked on had one or more check valves in the fuel line(s). My current driver does not. I've not gone in search for guidance for whether these were original, later mods, optional, or what the purpose might be.

Any easy tribal knowledge?
 

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From what I remember from my 18 years at Alfa these dated from '78~81 Spiders and 78/9 Alfettes had them from factory. I don't recall them being on any of the dozen+ I owned prior to those years. The '78, 2-'79's and the 80 I owned had them in the feed and return line at the spica pump.

Somewhere I have a few of these, new in the bag......they could be hiding anywhere.
 

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Discussion Starter · #3 ·
From what I remember from my 18 years at Alfa these dated from '78~81 Spiders and 78/9 Alfettes had them from factory. I don't recall them being on any of the dozen+ I owned prior to those years. The '78, 2-'79's and the 80 I owned had them in the feed and return line at the spica pump.

Somewhere I have a few of these, new in the bag......they could be hiding anywhere.
That would line up with what I've run into. But, WHY did they add them?
 

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They are definitely factory originals. I think they showed up in '76 but I wouldn't swear to it.
They were on a 78 I did an engine change on a year or so ago, but not found on my own 77 ( built in 76), that I bought from original owner, and was always dealer serviced.

I'm most interested in what is their purpose?
 

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Definitely original checks on my '77 also....as to purpose, possibly to keep the Spica pump flooded i.e no draining back to tank on shutdown.
 

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Discussion Starter · #7 ·
Definitely original checks on my '77 also....as to purpose, possibly to keep the Spica pump flooded i.e no draining back to tank on shutdown.
Thank you. But to solve what problem?

My car istagged as meeting 1977 emission specs without a catalytic converter, and built in 76.

My fuel pressure light goes out nearly instantaneously with key-on. So... WHY. The check valves?
 

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I draw the analogy to keeping cams bathed in oil even though oil press is up almost instantaneously...fuel checked in spica pump means bathed in lubricant i.e. fuel
 

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Discussion Starter · #10 ·
I think people are guessing, which I've done plenty of. No hard knowledge here?
 

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For the 1976 model year Alfa 115 and 116 series Alfa/Spica decided to install fuel line check valves to both supply and return lines. The idea was to allow fuel to only flow in one direction (both to and from the pump) and prevent the lines from running dry. Basically to keep fuel as close to the pump as possible at all times, also keeping the pump well lubricated at the same time. More to the idea (and I think it was a good one) of the check valve was to do a better job of holding fuel pressure in the system, lower the fuel system's priming time (red light blink), and possibly help with cold and even hot starts. This is good when cars sit for a few days/weeks at a time. Fuel check valves are pretty common on diesel engines, hence the Spica systems pump. Did it make a difference? I don't believe so. I have pre-76 Spica Alfas and later Spica Alfas and I can't tell the difference, they both start up the same to me.
 

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I think people are guessing, which I've done plenty of. No hard knowledge here?
Most plausible explanation or guess I could come up with Don. We commonly use check valves in industry for the purpose of containing fluid or gas in the line and again for the Spica, given that the fuel is the lubricant for the pump also, wear at start up would've been the consideration.
 

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Discussion Starter · #13 ·
I'm not so sure fuel is the primary lubricant. There is pressurized oil fed to the pump, after all. My understanding is that fuel is in the piston overhead, helping to create a seal against the oil in the pump sump.

It's hard to resist conjecture. We all do it. But somewhere, certainly, is the actual Alfa reason for adding the check valves.

My car has a Bosch 044 electric pump with external regulator. The fuel pressure light extinguishes almost instantaneously. Still... the hot start is not so instantaneous as the cold start. I'll try the check valves and see what happens.
 

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Correct Don, oil is fed to the Spica's logic section however fuel lubricates the close tolerance pistons and barrels.
 

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Timely discussion! I have been working on a 78 trying to get it started, and found several PO oddities. Having not seen mention of these check valves in any documents I read, I figured they were something a PO did. I removed one while reinstalling the fuel lines that I found installed backwards to the SPICA pump. I hoped that I had figured out why it wouldn't start - how could it run with check valves in the lines, installed backwards!
But, that wasn't it.
Guess I'll put it back!
 

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I have these check valves in my '78 Spider as well. While replacing the rubber fuel lines I wanted to check their function so I just did a simple blow test. They both seemed to take quite a bit of effort to pass air through them in the fuel flow direction. I would like to replace them but have not found them available from the usual vendors. I just re-installed them with no seeming ill effect?
 

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So I happen to be talking to Wes Ingram yesterday and asked the question "what's the deal with these check valves". He said that in the late seventies they loosened the tolerances between the SPICA pistons and bores and experienced drainage in certain conditions (parked on a steep incline for days). It was cheaper to add the check valves then tighten the tolerances. When he rebuilds pumps from that era he returns them to the tightener tolerances and recommends eliminating the check valves.
 

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I've worked on Spica enough to grasp the concepts, but...

One of the cars I worked on had one or more check valves in the fuel line(s). My current driver does not. I've not gone in search for guidance for whether these were original, later mods, optional, or what the purpose might be.

Any easy tribal knowledge?
I read somewhere they were to prevent vapor lock. My 81 spider has them.
 

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The check valves are used to "Retain fuel pressure only in the mechanical pump stage", there are 2 valves, one before and after the Spica mechanical pump, when the engine is turned off the valves automatically retain the pressure there, the valves have an arrow flow direction and do not let that pressure escape. They are called ¨Non return check valve¨.
What is your function? ¨The engine starts fast.¨
Here I show 2 photos, one where the two aluminum valves are in the bench, and the other photo if you see i forgot placed the check valves in the system and it was there where I realized that it was difficult to start, I just placed them in the correct direction and wow .. starts immediately.
Another thing, these valves retain a high pressure, I don't know how much but enough to withstand 20 to 30 psi, or similar with what the system works. (Test a valve; Try blowing a valve like a jazz trumpeter.). ;)

Note: I work with Bosch K-jetronics and their system is very similar and they have something in common what for Alfa (Spica) are these 2 check valves for K-Jetronic is the pressure accumulator, they do exactly the same.

Reading something It is possible what GPROCKET says, there may be variations in tolerances. Remember that they are precision parts because they are mechanical, because everything that has friction has wear and what has wear loses calibration over time.

Something important, the Spica pump is lubricated by the engine oil, so the life of the Spica pump depends on that, you have to use quality oil and periodically change the small filter of the Spica pump.
The pump is very delicate and is a highly engineered precision rolex.

This is the only thing I can say specifically about these valves.

This is my story, my experience I hope it helps a little.

My Spider is US version, 1979. 🍀
 

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Curly - you're saying that by design, these valves require high pressure to allow flow in the direction of the arrows? I'm asking because the two I have require a great amount of pressure to allow air through in the direction of the arrow. I assumed they had gone bad, but maybe not?
 
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