Posted by John Vardanian
Dear Tom,
I was experiencing fuel starvation so I rebuilt the mechanical pump and the filter/regulator unit. The problem persisted. Then I replaced the thick insulator block that is between the mechanical pump and the engine block with a paper gasket. I did this to increase the stroke of the plunger and thus increase the fuel through put. The problem went away but after about 30 miles of driving the pump busted from being hammered to hard. The little flat metal tabs that connect to the bottom of the plunger shaft shattered.
Can you offer any advice?
Fuel Starvation
Re: Fuel Starvation
Posted by Tom
Hi John,
You're talking about the part attached to the rubber membrane that shattered? I guess it's time for a new rebuild kit. Return everything back to the way it was, and lets figure out the REAL source of your starvation.
WHen does the starvation occur? During acceleration? Idle? When driving at steady highway speeds? When cornering? When on a hot day? Did you check the filter at the rear of the car by the electric fuel pump? Does your electric fuel pump work? Does it help the starvation problem when you turn it on? How new are the soft yellow hoses? There's a filter screen at he end of your fuel pick up that may be clogged? Rusty gas tank? I would check all these points before modifying Ferrari parts.
Tom  
Hi John,
You're talking about the part attached to the rubber membrane that shattered? I guess it's time for a new rebuild kit. Return everything back to the way it was, and lets figure out the REAL source of your starvation.
WHen does the starvation occur? During acceleration? Idle? When driving at steady highway speeds? When cornering? When on a hot day? Did you check the filter at the rear of the car by the electric fuel pump? Does your electric fuel pump work? Does it help the starvation problem when you turn it on? How new are the soft yellow hoses? There's a filter screen at he end of your fuel pick up that may be clogged? Rusty gas tank? I would check all these points before modifying Ferrari parts.
Tom  
Re: Fuel Starvation
Posted by John Vardanian
Tom,
The hoses and the filter in the back have all been replaced. So have the glass filter assembly and the internals of the mechanical pump. I also drained and flushed the tank.
The car runs okay with the electric pump on but with it off the engine hick ups under acceleration.
For testing purposes I removed the yellow hose that goes to the front of the fuel manifold and ran the engine (on the electic pump alone while the manifold was plugged up in the front so gas wouldn't pour out of it). I did this both with and without the insulater block that is between the pump and the engine block. With the insulator in place, gas barely trickles out of the open ended yellow hose but with the insulator it removed, gas gushes out. That is, with the block removed the stroke of the pump's plunger increases.
I am lost as to what to do. If I run the car without the insulator block the engine runs fine even with the electric pimp off. But the pump gets hammered too hard and the pair of flat metal tabs in the pump get shattered.
Thanks.
john
Tom,
The hoses and the filter in the back have all been replaced. So have the glass filter assembly and the internals of the mechanical pump. I also drained and flushed the tank.
The car runs okay with the electric pump on but with it off the engine hick ups under acceleration.
For testing purposes I removed the yellow hose that goes to the front of the fuel manifold and ran the engine (on the electic pump alone while the manifold was plugged up in the front so gas wouldn't pour out of it). I did this both with and without the insulater block that is between the pump and the engine block. With the insulator in place, gas barely trickles out of the open ended yellow hose but with the insulator it removed, gas gushes out. That is, with the block removed the stroke of the pump's plunger increases.
I am lost as to what to do. If I run the car without the insulator block the engine runs fine even with the electric pimp off. But the pump gets hammered too hard and the pair of flat metal tabs in the pump get shattered.
Thanks.
john
Re: Fuel Starvation
Posted by Tom
Hi John,
Just a thought, aren't there two check valves in the top of the mechanical fuel pump? Check their orientation. I've heard some people have shaved the spacer down a little bit to gain some more length on the stroke of the pump. Perhaps there is a happy medium where you can get enough pressure without bending anything by taking off some material off the spacer. I would find a suitable replacement material, and shave that down in increments.
There may still be a clog somewhere, and shortening the spacer only increases the suction and overcomes the clog.
Let me know how you make out.
Tom
Hi John,
Just a thought, aren't there two check valves in the top of the mechanical fuel pump? Check their orientation. I've heard some people have shaved the spacer down a little bit to gain some more length on the stroke of the pump. Perhaps there is a happy medium where you can get enough pressure without bending anything by taking off some material off the spacer. I would find a suitable replacement material, and shave that down in increments.
There may still be a clog somewhere, and shortening the spacer only increases the suction and overcomes the clog.
Let me know how you make out.
Tom
Re: Fuel Starvation
Posted by Andrew Brent
Hi John,
I recently posted the following, it pertains to the Mechanical pump and specifically a 250 GTE. I hope it helps.
------
Hi Rob,
I didn't see any responses to this yet, here is my 2c worth. I hope it helps.
[-] -----Original Message-----
From: Rob
Subject: FISPA mechanical fuel pumps
Fellow 12 cylinder technicians
I am restoring my FISPA mechanical pump and have a number of questions. I am told they are notoriously in effective but….I have a rebuild kit but am looking for insights or technical articles on how to setup and adjust.
[-]
I have learned that only original FISPA rebuild kits are worth buying. I of course learned this after buying another brand. Has anyone a similar experience?
[-]
No- I just put together what ever was sent to me from (Shameless plug) GT car parts in Aridzona. I don't recall it being an actual 'FISPA' rebuild kit, but it did work. All I asked for was a rebuild kit for the mechanical pump on a 250GTE.
[-]
Questions.
How much plunger activated movement is required to effectively drive the diaphragm?
[-]
Don't recall.
[-]
There is significant movement in the pump mechanism that produces no movement in the diaphragm.
[-]
I think it was about 1/8 of an inch.
[-]
Are there any specs?
[-]
Don't have them myself.
[-]
What is the optimal fuel pressure in /out?
[-]
Out, I think is 3-4PSI, but this is governed by the FISPA filter assembly on the inner fender wall, at least on 250GT's it is anyway. The manual calls for 3PSI at the Carb's.
[-]
Can the space be milled down? If so how much?
[-]
I did not mill the original Bakelite spacer, but I did replace mine with some Aluminum sheet with gaskets which ended up being approximately 2/3's the original thickness. This worked on my car.
[-]
Soaking the diaphragm in coal oil before assembly was advice I received to condition the diaphragm. Good idea?
[-]
No idea.
[-]
By directional valve test for correct orientation? Sucking on the inlet should result in closure of the first valve (evidence of elimination of reverse flow)
[-]
My pump would only go in the car one way, there is an arrow on the pump also, I think I remember an arrow, anyway you are correct if you are testing for correct operation of the inlet valves. They will shut if suction is applied to the inlet.There are two inlet and two exhaust valves on the 250GT mechanical pump.
[-]
Has anyone introduced a fuel pressure gauge into the system? If so where is the best takeoff point?
[-]
I'd like to know this as well, but I would think that it would be best at the fuel rail towards the front of the carburetors, the back of the fuel rail is fed by the electric pump, as I discovered the hard way after a prompt from Chris K.
Regards,
Andrew.
 
Hi John,
I recently posted the following, it pertains to the Mechanical pump and specifically a 250 GTE. I hope it helps.
------
Hi Rob,
I didn't see any responses to this yet, here is my 2c worth. I hope it helps.
[-] -----Original Message-----
From: Rob
Subject: FISPA mechanical fuel pumps
Fellow 12 cylinder technicians
I am restoring my FISPA mechanical pump and have a number of questions. I am told they are notoriously in effective but….I have a rebuild kit but am looking for insights or technical articles on how to setup and adjust.
[-]
I have learned that only original FISPA rebuild kits are worth buying. I of course learned this after buying another brand. Has anyone a similar experience?
[-]
No- I just put together what ever was sent to me from (Shameless plug) GT car parts in Aridzona. I don't recall it being an actual 'FISPA' rebuild kit, but it did work. All I asked for was a rebuild kit for the mechanical pump on a 250GTE.
[-]
Questions.
How much plunger activated movement is required to effectively drive the diaphragm?
[-]
Don't recall.
[-]
There is significant movement in the pump mechanism that produces no movement in the diaphragm.
[-]
I think it was about 1/8 of an inch.
[-]
Are there any specs?
[-]
Don't have them myself.
[-]
What is the optimal fuel pressure in /out?
[-]
Out, I think is 3-4PSI, but this is governed by the FISPA filter assembly on the inner fender wall, at least on 250GT's it is anyway. The manual calls for 3PSI at the Carb's.
[-]
Can the space be milled down? If so how much?
[-]
I did not mill the original Bakelite spacer, but I did replace mine with some Aluminum sheet with gaskets which ended up being approximately 2/3's the original thickness. This worked on my car.
[-]
Soaking the diaphragm in coal oil before assembly was advice I received to condition the diaphragm. Good idea?
[-]
No idea.
[-]
By directional valve test for correct orientation? Sucking on the inlet should result in closure of the first valve (evidence of elimination of reverse flow)
[-]
My pump would only go in the car one way, there is an arrow on the pump also, I think I remember an arrow, anyway you are correct if you are testing for correct operation of the inlet valves. They will shut if suction is applied to the inlet.There are two inlet and two exhaust valves on the 250GT mechanical pump.
[-]
Has anyone introduced a fuel pressure gauge into the system? If so where is the best takeoff point?
[-]
I'd like to know this as well, but I would think that it would be best at the fuel rail towards the front of the carburetors, the back of the fuel rail is fed by the electric pump, as I discovered the hard way after a prompt from Chris K.
Regards,
Andrew.
 
Re: Fuel Starvation
Posted by Deane
Mike Dunn (a well known ferrari fanatic, the MAD in MADEnterprises) mentioned to me that he had a similar problem on his 500 Superfast, even after rebuilding the fuel pump. I think he said that his problem turned out to be the tiniest backwards leak in a check valve in the pump. You might try reaching him by phone to get his exact experience, see www.madenterprise.com.
Mike Dunn (a well known ferrari fanatic, the MAD in MADEnterprises) mentioned to me that he had a similar problem on his 500 Superfast, even after rebuilding the fuel pump. I think he said that his problem turned out to be the tiniest backwards leak in a check valve in the pump. You might try reaching him by phone to get his exact experience, see www.madenterprise.com.
Re: Fuel Starvation
Posted by John Vardanian
I am glad to have found Tom's web site, mostly beacause it is for the real Ferrari enthusiast, i.e., those who work on their cars. I am trying to get my car raod worthy for the trip to Monterey for the car weekend. The one thing that concerns me is this fuel pump.
Thank you all for your advice on the fuel starvation. I am going to check for the leak in the check valve and will look at reducing the thickness of the spacer. Interesting that Mike Dunn was mentioned. He is actually the one that brought this car to US from Belgium back around 1968.
By the way, if anyone is interested I found that valve adjustment tool I had mentioned in my message of 7/23/01. I got it from a USAG dealer in Belgium. This tool provides the most effective way of holding the valve adjustment screw in place while you are tightening the 11 mm lock nut.
john
I am glad to have found Tom's web site, mostly beacause it is for the real Ferrari enthusiast, i.e., those who work on their cars. I am trying to get my car raod worthy for the trip to Monterey for the car weekend. The one thing that concerns me is this fuel pump.
Thank you all for your advice on the fuel starvation. I am going to check for the leak in the check valve and will look at reducing the thickness of the spacer. Interesting that Mike Dunn was mentioned. He is actually the one that brought this car to US from Belgium back around 1968.
By the way, if anyone is interested I found that valve adjustment tool I had mentioned in my message of 7/23/01. I got it from a USAG dealer in Belgium. This tool provides the most effective way of holding the valve adjustment screw in place while you are tightening the 11 mm lock nut.
john
Re: Fuel Starvation
Posted by Tom
Hi John,
I will be out in Monterey for that weekend too! I'd love to see your car if you can sort it out. E-mail me privately if you want to hook up.
Tom
Hi John,
I will be out in Monterey for that weekend too! I'd love to see your car if you can sort it out. E-mail me privately if you want to hook up.
Tom
Re: Fuel Starvation
Posted by dick mcbirney
My wife and I had an experience in the 1970's with my 1964 330GT2+2 on the way to the Annual Meet in Atlanta. I knew the car would vaporlock in hot weather, so I headed for Ferrari of Atlanta (aka FAF) on Tucker Lane, I believe. The car vaporlocked within sight of FAF, so we walked the rest of the way there. The mechanic said that was one reason for the electric pump, and to bring it in when it cooled down and he would fix it. He hit the electric pump with a hammer and my vaporlock days were over.
Did you try the electric pump?
My wife and I had an experience in the 1970's with my 1964 330GT2+2 on the way to the Annual Meet in Atlanta. I knew the car would vaporlock in hot weather, so I headed for Ferrari of Atlanta (aka FAF) on Tucker Lane, I believe. The car vaporlocked within sight of FAF, so we walked the rest of the way there. The mechanic said that was one reason for the electric pump, and to bring it in when it cooled down and he would fix it. He hit the electric pump with a hammer and my vaporlock days were over.
Did you try the electric pump?
Re: Fuel Starvation
Posted by Deane
Hi John,
Have you discovered the cause of your fuel pump problem yet? I'm curious to know what it was.
Hi John,
Have you discovered the cause of your fuel pump problem yet? I'm curious to know what it was.
Re: Fuel Starvation
Posted by John Vardanian
Hi Deane,
There were two things. One, the rubber seal that seals the rear filter canister was torn and two, the pair of flat metal tabs inside the mechanical pump connecting to the shaft of the plunger/diaphram were installed upside down, limiting the stroke of the pump. If you are interested which side is up I can explain further.
Hi Deane,
There were two things. One, the rubber seal that seals the rear filter canister was torn and two, the pair of flat metal tabs inside the mechanical pump connecting to the shaft of the plunger/diaphram were installed upside down, limiting the stroke of the pump. If you are interested which side is up I can explain further.
Re: Fuel Starvation
Posted by Deane
Thanks for the explanation. Glad you found it!
Thanks for the explanation. Glad you found it!
Re: Fuel Starvation
Posted by Tom
Do you guys realize that you'll both be at Concorso Italiano?
Tom
Do you guys realize that you'll both be at Concorso Italiano?
Tom
Re: Fuel Starvation
Posted by Deane
No kidding! I'm the blue 330 GTS. See you both there?
No kidding! I'm the blue 330 GTS. See you both there?
Re: Fuel Starvation
Posted by Tom
John, and Deane,
One week and counting!!!
Tom
John, and Deane,
One week and counting!!!
Tom