Fispa fuel pump...

[TOMKIZER]

Since Kare hasn't answered yet, I'll post my question for everybody.

Back in 2008, Kare posted a question about the orientation of the FISPA mechanical fuel pump diaphragm actuator arms and received an answer. The two photos he posted are no longer available on the post. I am rebuilding my mechanical pump because it can't keep up with the engine fuel requirements at idle. The problem arose on my trip from Quebec, Canada to Cavallino in Florida. I would also like to know which orientation is correct. The orientation of the arms in my fuel pump is the orientation that would require the longest pushrod. That orientation, along with wear, may be the reason for my problem. I don't really know any other way to describe the two orientations of the arms. Flipping the arms over would move the contact pin in the direction of the rocker arm and cause the pushrod to start moving the diaphragm earlier. Which is correct?

Thanks for any help you can provide.

Tom Kizer

[250GT]

Since Kare hasn't answered yet, I'll post my question for everybody.

Back in 2008, Kare posted a question about the orientation of the FISPA mechanical fuel pump diaphragm actuator arms and received an answer. The two photos he posted are no longer available on the post. I am rebuilding my mechanical pump because it can't keep up with the engine fuel requirements at idle. The problem arose on my trip from Quebec, Canada to Cavallino in Florida. I would also like to know which orientation is correct. The orientation of the arms in my fuel pump is the orientation that would require the longest pushrod. That orientation, along with wear, may be the reason for my problem. I don't really know any other way to describe the two orientations of the arms. Flipping the arms over would move the contact pin in the direction of the rocker arm and cause the pushrod to start moving the diaphragm earlier. Which is correct?

Thanks for any help you can provide.

Tom Kizer

TomKizer,
I am not sure if I understand youre question correct.
I just overhauld two of those sup 150 pumps you are lucky.
I measured on a new pump how much the contact arm comes out in mm toward the basis
this is by me 3.5 mm
If the supply of fuel is to LOW you can reduce the pertinac spacer a few mm !!!!( due to wear on arm.)
A new spacer is 6.5 mm thick.
Hope this helps.
I have every internal part new so can look further.
Here as always some pics.
Look at the new replacement axel also: has attachment on one side on shaft: no possibility to get out, no loctite necc.
Well only little details but educative Ha

Cornelis

[250GT]

Tom Kizer,
After reading again you question
I maid some fotos of a new in the 80th repairset for you pump.
I think you mean the two metalplates in the middle with 3 holes probebly?
As you can see the holes are bigger on top.
so only one posiblility to put together.
Maybe you holes are severly wearn?
it is keep together with two pins with outside clips the third hole is fore the diagfragmapin see pic.

The best thing on old ferraris is that they are so unclomplicated, I know- Tom and Yale and orthers- dont see it like me.

But look at the last pics it took me 2 days holyday to come so far, and is still not out!
during my breaks I write some words here.
( clutchrepair ) by semiautomatic DS. 1964.

C.

[John Vardanian]

Hi Tom Kizer,

Hope this answers your question.

john

[TOMKIZER]

Thanks, Cornelius, for providing the photo.

And thanks, John, for adding the note and arrows.

That is the most perfect answer I could have hoped for. The answer is much clearer than the question I asked. It is exactly what I wanted to know. If I flip the two links over, like shown in the photo, the middle holes are farther from the ground and the rocker arm will contact the pin at a lower cam lift, thus providing a greater stroke on the diaphragm. I suspect it would also break something by over-stroking the diaphragm.

My sincerest thanks to you both.

[John Vardanian]

Hi Tom,

And conversely, if you install these tabs backward and increase the thickness of the Bakelite spacer (with added spacing) you would have range, where you get optimum displacement and force on the moving parts of the pump.

john

[250GT]

Tom kizer,
I hope you havenot finisched you 're pump already,
there is still one thing that you could do wrong. !
First: the fact that you can chance the arm in both directions implicate that the "end" holes have the same diameter
the big hole on top is for the long axel ONLY.
Someone -clever- has enlarged the other one in the past, to get more preformance at youre pump.
As I said already you can only put it to gether IN ONE WAY , when its original.
As you can see the big hole side has a dome top (compleet round end).
The orther side is also round, BUT with one flat surface on the lower side !...... look carefully.
this FLAT side goes also to the bottom side (even the rings has this flat side)
Orther wise the diafragma pin whitch goes down, touched the cap with tree screws.

Well this was a really holding hands repair.

John :
You are right by saing make the pertinac spacer thicker.
I own aleast 50 paperspacers !.... never know where the were used for.
thanks

Cornelis

P.S. some pics to controle

[TOMKIZER]

OK, guys. Your statements are in conflict.

John's little white on blue note with arrows is the way my pump was built. Middle holes closest the ground when installed and the flat spot on the side closest to the diaphragm. See my sketch labeled ALT 1. My sketches exagerate the hole sizes to show that it's not possible to swap the links end-to-end.

Cornelius' last post says the flat spot should be toward the ground to provide clearance to the three hole cover. See my sketch labeled ALT 2. That makes the middle hole nearest the diaphrage, not nearest the ground. I agree that the flat spot on the links looks like it should provide clearance to the three hole cover, and if I analyse the stresses in the two links, they are strongest with the middle hole closest to the diaphragm. That puts the thin cross-section of the link above the middle hole in compression and the thicker cross-section of the link below the middle hole in tension. That should make the links stronger.

NOW! I abdicate. I don't know how it should be built. Now I will let you two argue about it or maybe someone has a FISPA document that shows how it should be assembled.

Tom Kizer

[John Vardanian]

Hi Tom,

Nice diagrams. Alt 1 is the factory way and Alt 2 is a resort for a worn pump. If your pump isn't performing (even with new parts) with Alt2 you can afford yourself a whole new performance range, provided you start with thicker spacer.

john

[250GT]

TomKizer,

John V. is absoutly right,
But I think you overhaul an USED pump.
Untouched cars has on each side of the pertinac spacer one paperspacer.
I never try to use my new stuff ,its only referance for me.
my grading up is: not to replace these 2 paper spacers.
I though they were to pevent oil leaks.
the pin that comes out the timechaincover is also a bit damaged ,and has minimum oil pressure.
So with two paperspacers less I think the org. situation is returned.
But to be absolut sure you simple must test, how much fuelpressure is achived.

All the best,

C.

P.S.
perfect drawings by the way.
I was guessing all over the time what was realy wrong or changed .
There are a lot of dilletants working on those cars in the past.

[TOMKIZER]

Hallelujah! We are all in agreement. Life is good!

I rebuilt my pump as sketch ALT 1 and installed it. I am changing the trans output and differential input shaft seals, so I have not tried the pump yet. If it works well enough, then good.

If it does not work well enough, I will remove it, measure everything, and make the spacer thinner.

If that does not work, I will turn the links over and make another thicker spacer as in ALT 2. I hope it works as installed today, because I do not really want to start measuring everything to accommodate a thinner spacer for ALT 1 or thicker spacer for ALT 2.

Thank you both for all your help and explanations.

Tom Kizer

[John Vardanian]

Hi Tom,

Unless you have a milling machine, a good, clean way to reduce the thickness of the Bakelite block is by placing a router bit in the drill press and shifting the belt-pulley combination for max speed. The result is perfectly flat surfaces. Do not rub it on staionary sand paper, etc. You will not get a flat surface.

john

[250GT]

Hi Tom,

Unless you have a milling machine, a good, clean way to reduce the thickness of the Bakelite block is by placing a router bit in the drill press and shifting the belt-pulley combination for max speed. The result is perfectly flat surfaces. Do not rub it on staionary sand paper, etc. You will not get a flat surface.

john

Tom and John,

Tom to reduce spacer its important for you to use mouth and nose protection the dust is dagerous for you health
It would be a pity when you can enjoy it after repair.

John,
Bakelite was used in car industrie till 1920.
Pertinax or pertinac is used in the 50th and 60th often at electr. boards etc
you can find it also in you org front suspension -bushes- Ferrari.
its not so BRITTLE ( spröde) as bakelite but is a sistermaterial.

Cornelis

[John Vardanian]

Thanks Cornelis. I didn't know that about Bakelite.

john

[TOMKIZER]

OK! I got my Fispa mechanical pump all back together and installed. No change to the phenolic spacer. I even got the transmission and differential oil seals changed, so I was able to drive the car and test the fuel pump. I did change the 90 degree rocker arm lever with the pushrod pad on it. Mine was worn about 1/2 mm on the pad. I used a less worn one from an old defunct pump that I save for spare parts. Of the rebuild kit, the only parts I used were the square cut rubber O-rings that go under the check valves and the large rubber top cover seal. My square cut rubber O-rings were hard and deformed, and probably leaking past the check valves on the deliverystroke. The original check valves themselves were considerably lower pop-off pressure (intake stroke) than the new ones in the kit (I blew through them), so I reused the old ones that seemed to check well. I decided I didn't need to fight an increased intake stroke pop-off pressure with a pump that was already having a problme delivering enough fuel.

My pump is now working perfectly at idle (and all other speeds as well) and the sediment bowl stays full at idle without the electric pump.

Thanks for all the advice, everyone.

Tom Kizer