Fispa Mechanical Fuel Pump

I'm in the process of installing my recently rebuilt Fispa mechanical fuel pump on a 275 GTB/2 and was wondering if anyone might provide some guidance as to how to properly achieve the correct spacing of the pump from the timing chest using the phenolic spacer and gaskets? Prior to rebuild, the pump was spaced with the phenolic spacer and one gasket totaling about 10mm in thickness. I have the small 3 screw front cover removed and have rotated the crank by hand to observe the pump lever's movement but I'm not quite sure how much travel is sufficient or exactly what I should be looking for. I've read that to much spacing and the pump won't work properly and to little spacing could cause internal damage to the pump. Any help as to what I should be looking for would be very much appreciated.

Ed

 

Thanks much for your help Timo. I sent a PM to DWR46 as you suggested.

Ed

 

Many thanks for your very helpful response John. I concur with you regarding PM's and making this information available to everyone. As such, what follows is the also very helpful response I received from DWR46.



Ed: Not an easy question to answer, but here goes-

1. If you look at the parts catalog, there are NO gaskets used with the phenolic spacer. They rely on an O-ring to seal the pushrod. I would recommend that you put a light smear of Locktite 518 on both sides of the spacer to make sure you have no leaks. But only do it after you have verified the correct pressure.

2. How many parts were replaced in the pump? The pivot arms, pivot shaft, what was worn, etc? All this will determine how much pressure the pump produces.

3. I would start by taking .015" off the phenolic spacer to compensate for general wear.

4. Mount the pump, get the car running, shut it off. That way you know the pump is pumping fuel and the carbs are full.

5. Remove the line from the pump to the glass bowl filter at the filter end (it may work better for you to remove the pump end). You can then run the car for a short time on the fuel still in the carb bowls.

6. Hook up a fuel pressure gauge and run the motor briefly to see what pressure the pump is putting out. Look for 3.5-5.0 psi. Up to 6.0 is OK. You will have to do some fiddling with lines, hoses, fittings, etc to make this all work.

7. You have to NOT include the glass bowl filter in the test because it has a pressure regulator built into it and it will lower the pressure to about 3.0-3.5 psi.

8. If your pressure is low (I doubt it will be high), then remove the pump and take off more material from the phenolic block in .015" segments till the pressure comes up to spec. Generally no more than about .030-.040" will get good pressure.

9.When you have the pressure you need, mount the pump with the Locktite 518.

Not a simple task and time consuming, but you will get a good pump when you are done.

Dyke

 

Thanks Jim for the very beneficial information. I will incorporate your approach into this process as well. Will be locally sourcing a banjo fitting with a barbed end today which will allow me to utilize my fuel pressure gauge to measure the pressure coming from the pump as suggested by DWR46 in steps #6 and #7. Will provide details when everything is up and running.

 

Thanks very much John B for your input as well as the pump diagram and rebuild instructions. I've been advised of an additional method to check for the correct initial amount of pump stroke and I'm wondering if anyone else utilized this as well when they installed their pump? With the pump mounted to the engine(phenolic spacer in place) and the 3 screw front cover and internal tension spring removed, you turn the crank by hand and observe the movement of the pivot lever in the pump (the end which the spring slides over) and simultaneously check for play (you can wiggle it up and down just a bit) as you rotate the crank. When the pin/shaft on the engine side is fully retracted in the engine, I can move the pump pivot lever up and down with ease. As I turn the crank and the pin/shaft from the engine side extends itself and contacts the lever,the lever begins to travel through its' stroke ending when the pin/shaft on the engine side is fully extended. At that point, the pivot lever (spring side) in the pump is very taught and can no longer be wiggled. I've been advised that there should be some play in the pivot lever at this point and that if not, gasket(s) should be added between the phenolic block and the pump body until this is achieved. The reason given was that without this slight play, there would be to much pressure being applied to the pump internals and one would risk damaging the pump. Obviously this is not a final adjustment but just a guide to prevent damage to the pump. Any input would be much appreciated.

Ed

 

Many thanks for the clarification DWR46. My thinking was similar in that if I could move/wiggle the pivot lever when the pushrod was fully extended, the pump rocker arm probably wasn't moving enough to adequately extend the diaphragm and the result would be less than optimum fuel pressure.

 

Fuel pump installed and putting out 6 p.s.i. On the high end of Dyke's recommended range, but after all the fiddling to get it properly spaced, I'm going to go with it. Ended up taking .040" off the phenolic spacer in 3 phases removing .015" twice and then .010" in my last pass. After removing .030" from the spacer, I was only getting a touch over 3 p.s.i. Was very surprised to see how much the fuel pressure increased when I removed the last .010". As Dyke noted, lots of fiddling and plan on taking some time to do this properly. Knowing a carpenter with the equipment to accurately cut the spacer down helped immensely. A visit to the local hydraulics shop where they made me a trick fitting that threaded into the outlet of the fuel pump and had a barbed end to slip the fuel pressure gauge hose over. Thanks to everyone for their help.

 

Thanks again for your advice John. Although I didn't run the pump very long when checking the fuel pressure, I did remove the front cover from the pump when I finished my test, which gave me a great view of the two flat tabs. Both appear straight and true. Plan to check them again after I've run the engine for a longer period of time.

Ed