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Discussion Starter #1 (Edited)
Dear all,

A stupid question related to Fispa Fuel filter / regulator

I've been owning carburetted Alfa's for 20 years now, without any problem 'fuel management wise'.
All of them started easily, had no flat spot or whatever miss and produced what they were supposed to do in term of torque/power. The secret is that they are bone stock ....;)

Now my question. I As far as the FRB-11 unit is concerned, I noticed that they are never 'full'. One could expect the bowl to be filled up to the top, due to flow and pressure produced by the fuel pump.
On my '67 Super, the level is something like 1" (2.5 cm) from the bottom. No more, no less, invariably, regularly

See this pic from the Alfa BB (sorry for borrowing) but the phenomenon is exactly the same as on my car.


I've never worried about that as the vehicle has always performed very well. But I recently installed a priming pump as the Super is used in very few occasions. I'm now able to fill in the bowl (with the priming pump) and I can clearly see the glass bowl emptying as the engine revs...
No visible or audible change in any thing whether the bowl is full (when operating the manual fuel priming pump) or nearly empty....

On the AlfaBB, I hear here and there about leaks from 'the Top seal' ... no risk for mine to develop a leak from this area !
Can the specialists help me about that. Do my car have a problem which I'm not aware of ??

Thank you in advance for your inputs

Best regards
Sébastien
 

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If it did not leak, and you have not used fuel containing ethanol, it is probably still good. Leaks are easy to spot with damp areas around the upper diaphragm (DO NOT over thighten the screws to fix this, you will warp the diaphragm seal area). The other leak area is the bowl seal which gives you a damp bowl.
In order to "overfill" the filter bowl, you need pressure. More pressure than the three pounds required for Webers to function correctly. This can be done with an auxiliary pump, as the Alfa mechanical pump delivers low pressure, and the Bendix type electric pump used by Alfa is likewise low pressure.
A crack in the original type diaphragm will allow an overfull bowl, and will vent fuel out of the air bleed hole in the FRB11 top.
The partially full glass bowl is INTENTIONAL as the air head absorbs fuel pulses from fuel pumps to avoid hydraulic hammering damage to the Weber float paddles by the needle ball top. Air compresseses where fuel does not. As such, some air head in the glass bowl is desireable.
From my experience.
 

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Discussion Starter #3 (Edited)
If it did not leak, and you have not used fuel containing ethanol, it is probably still good. Leaks are easy to spot with damp areas around the upper diaphragm (DO NOT over thighten the screws to fix this, you will warp the diaphragm seal area). The other leak area is the bowl seal which gives you a damp bowl.
In order to "overfill" the filter bowl, you need pressure. More pressure than the three pounds required for Webers to function correctly. This can be done with an auxiliary pump, as the Alfa mechanical pump delivers low pressure, and the Bendix type electric pump used by Alfa is likewise low pressure.
A crack in the original type diaphragm will allow an overfull bowl, and will vent fuel out of the air bleed hole in the FRB11 top.
The partially full glass bowl is INTENTIONAL as the air head absorbs fuel pulses from fuel pumps to avoid hydraulic hammering damage to the Weber float paddles by the needle ball top. Air compresseses where fuel does not. As such, some air head in the glass bowl is desireable.
From my experience.
Hi Gordon,

Nice to hear explanation from such a knowlegeable Guru... I really appreciate all your inputs and really learned a lot from them (camshafts, carb jetting..). Thank your for your participation in this thread.

All you said about damping fuel pressure pulsations damping make a lot of sense.
But I'm still confused: We all know (when periodically renewing these filters) that the fuel r pick-up to the carbs is on the TOP of the FRB-11 filter/regulator, where the filter is carrying the little black seal...



How can the fuel be driven to the carb when it does not even reach the pick-up...
It's a kind of mystery to me and I can't imagine that capilary action in the paper of which the filter is made could be the answer...

Thank you in advance
Best regards
Sébastien
 

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I think it has to do with "Italian Magic", Sebastien. Having restored 50 or more of these, I confirm your photos and logic. I did not have just the filter on hand to experiment with, but did have a vintage 275GTB Ferrari handy that has one plus 2 fuel pumps, and a double feed from the rear fuel pump.
Normally, you fill the system with the rear mounted electric pump, start it, and shut off the rear pump. The HUGE FISPA engine mounted pump then sucks from the tank and keeps the system full. In racing or very hot driving, you can run both pumps and the fuel volume avoids vapor lock. Both run through the FRB11 to modulate fuel pulses and maintain Weber pressure.
First I took 2 pictures from the parts book, front system and rear. Then for the sole purpose of developing a valid information base, (AND having a LOT OF FUN with a 15 mile drive on the highway at night) I drove the car.
The first picture is the FRB empty, pre cold start. The next picture, electric pump on, engine running at idle, front mechanical pump also feeding the system; the FRB11 is almost full, but does have the air head discussed. The final photo is after 15 miles on the highway, everything hot, just the mechanical engine driven pump running. Though the angle in my picture is poor, there is still about 3/8 inch air head in the FRB11.
As it ran, and was running, obviously the Webers had fuel. I will have to study the filter itself and see if I can figure out why.
Meanwhile, thanks for the excuse for a "test-drive" in the name of FRB 11 research!
 

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Hi Gents,

I know this is an old post, but it's a new problem to me. I have rebuilt my Fispa Fuel pump with an E10 kit from Alfa Stop. I had cracks in the original diaphragm which musty have wept out the vent hole as I had a strong gas smell for the last year. I finally had an issue where the car was extremely difficult to start. I measured the pump pressure using a gauge and "T" fitting between the pump and regulator to get about 3 psi max with lots of cranking, but an immediate drop to zero when the cranking stopped. Funny that the bowl in the Fuel Regulator was full and I'm thinking that's a good thing.

In any case, the rebuilt pump only givers me perhaps 4 psi but comes up to pressure quickly and takes a few seconds to decay. The decay part is what I am confused about. Wouldn't the valves keep the pressure in the section between the pump outlet and the input of the regulator? I didn't replace the valves because the ones in the rebuild kit were "homegrown" looking and the originals didn't look bad. Perhaps an error on my part, but I had heard the replacement valves often leak.

Still having some issues starting, but making sure it isn't something else before I blame the pump. Thoughts???

Best Regards,


Andy Amatruda
1964 Giulia Spider
 

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The valves are not seals and they will leak down quickly. The glass filter bowl does not need to be filled with fuel to work, and often you will see full filter bowls where the seal above the bowl is leaking, first air, then eventually fuel.
Four pounds fuel pressure at the pump is fine, and 3# at the Webers, engine running, is fine. Often hard starting with the Alfa system is a direct result of new "fuel" and Webers, in that todays fuel has soluble gasses, iso propane / iso butane, for easy start and idle with FI. With Webers, this increases the volatile nature of fuel as compared to gasoline, worse when warm or hot. FI fuel systems are sealed systems, where as carburetors ran gasoline and used vented systems. The end result is that if your car sits, even a few days, in a warm or heated garage, fuel level in the Webers will be low, and until the pump replenishes the fuel in the float bowls, you may have a no-start situation. The easy solution is to drive the car daily, or install an electric pump to fill the Webers after it sits a few days.
 

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Thanks Gordon. It's been idle for ~2 months as I waited for the pump kit to come in. Letting the battery charge up and I'll try it again. Started popping towards the end so maybe it just slow to fill.
 

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I wanted to update that after the long winter I am now back working this issue. I checked fuel flow before and after the regulator while cranking the engine. It goes from no flow to barely a trickle. The original issue was that the engine wouldn't start and it appeared to be because it's not getting gas. I need to confirm I am getting fuel to the pump. I haven't ever checked the status of my filter screen in the tank, but wonder if that is the issue if the flow to the pump is weak.

Andy Amatruda
1964 Giulia Spider
 

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Very possibly. I usually start at the tank and work forward. Modern fuel with ethanol will dissolve tank crud and plug the screen and do other nasty stuff along the way. BIG business today seems to be fuel tank repair / replacement on vintage cars, and some not that "vintage". A friends shop has a 50's 300 SL, a 60's Porsche 911 and an 80's AMG Mercedes all with tanks out being fixed or replaced.
 

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Checking fuel flow to the pump

Thanks for the input Gordon. I inspected the fuel lines from the tank to the pump. It is a metal line starting on the side of the tank that runs until forward until it gets close to the pump. It transitions to a short rubber line, then connects to the pump. I clamped the rubber line and removed the end at the pump. I put a gas can underneath the open line and removed the clamp. Initially I got no flow but eventually I got a steady but lazy flow. Considering the tank is almost full, I would have expected a fairly forceful stream. I confess I did leave the gas tank cap on, so I don't know if there are vacuum effects that might have slowed the flow, but is does seem that the pump would have to work pretty hard under these circumstances.

In any cases, can you comment on:

  • What should the gravity flow be like coming into the pump? Do I need to test with the gas cap off?
  • If the flow is restricted, what is the best plan of attack? I have a tank that's almost full, so draining will be the first hurdle.
  • How does the screen in the tank function? It seems to be over the drain plug based on the parts drawings, yet the fuel line is on the side of the tank. If it is dirty will it impede the flow?
 

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The screen surrounds the pick up line in the tank, and is removed with the drain plug assembly as they are one and the same. Siphon as much fuel as possible from the tank. The drain plug has a hex indent for removal. It will be TIGHT. Use a breaker bar if required. It once was lead plated, and is, I believe, brass. Don't pound on the hex. If the tank is truly rotten from rust, enough leverage may tear the tank. Thats a GOOD sign the tank was close to being history anyway. There is a quite expensive stainless steel tank available as a replacement. hope you don't need one as removal of old and install of new is most easily accomplished (factory build technique) with the car upside down! It can be done right side up but is a ... unpleasant... job.
Once the drain is out, note the screen is likely plugged with rust, or sometimes has either rotted away, or been removed by some previous owner. There are threads on the BB on how to construct a new screen, by resolute owners (talk to one) that have made (just) one.
With the drain out, and a flashlight (not a match), the interior of the tank can be partially seen. Usually just enough is visible that one regrets looking. If the tank is good, pat yourself on the back, and go have the beverage of your choice. If it's bad, check into the stainless replacement, and then have several beverages of your choice.
Fixing a bad thank involves R & R, and then the fixed one WILL go bad again. Then you get to do it again, and will regret not replacing it with new the first time.
Below is a picture from the parts book.
Let us know what you discover.
 

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There are a couple of sources. Last one I saw came from Ok Parts an Engineering in Germany.
 

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who makes the SS tank?
AlfaStop in the UK lists them as available in stainless steel, see here . At first sight, the price may seem expensive, but note that it seems to include the filter (which isn't exactly inexpensive, either).
 

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Arguably good news in that I was able to siphon some (not all) of the fuel out of the tank and successfully remove the plug. Quite a fun job covered in fuel while the last couple of gallons come out. From a quick inspection (since I am waiting for the fumes to pass) there appears to be a cylindrical chamber around where the screen would be. Alas, there is no screen section mounted to the plug.

There seemed to be no rust or particulate in the tank, however. The tank does appear to have some sort of epoxy on the outside so it is possible it had been serviced before I bought the car. The fuel line going from the tank to the fuel pump seems original and I guess it's possible that it has a clog. My thought is to try to blow it out with compressed air, but it may need to be replaced.

Since I have the tank drained, I will look into purchasing or making a screen for the drain plug. I haven't run a search yet, but hope to find a photo and/or dimensions for construction.
 

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Oddly the fuel lines don't plug up. They can be damaged from external rust, and I have seen the rust through. They can get crushed or bent to restrict fuel flow. No rust in the tank is GOOD!
 

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Just to wrap this up, since there was no apparent blockage, I tried to pull fuel through to the pump with a MI-T-VAC. It did flow through to the pump, so I reassembled, but still couldn't start. Then a mechanic friend of my blew into the tank while I had the line off where it enters the carbs and fuel did come through (not an approach I was aware of). With the plugs out and a charger on the battery, we cranked the starter and fuel flowed. A few drops of fuel in the cylinder, install the plugs and it started right up. Seemed like I was stuck at "close but no cigar". I don't know if this is considered priming the fuel system and whether its necessary, but it worked for me.

The bright side is that I know my tank is clean and I have dimensions in case I want to build a screen on the inlet line. Thanks to all for the guidance.
 

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Yes! Great!
 
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