Going Back to Mechanical Fuel Pump

[mattyd7]

One of the PO's replaced the mechanical fuel pump on my car with an electric pump. I was fine with this, but I've read some posts on here regarding swapping to an electric and am realizing they did not do it very well.

My biggest concerns:
- They mounted it in the engine compartment rather than the trunk. So it is pulling rather than pushing the fuel from the tank which I understand is not so good to do.
- It gets power whenever the key is ON, so even if I just want to power the radio or lights to test them without the engine running, I can hear the pump going. Guessing this isn't great for the pump in general, but also I know this is dangerous in the event of an accident or mishap.
- It's old so probably it's days are numbered, and when it goes, well that is a bad day.

Now that I have the 1800 intake manifold installed, removing and replacing the mechanical pump is about 2 minutes of work. So I am thinking of buying one with my next order from one of the parts dealers and just doing it preemptively.

Questions:
1) Is there any disadvantage going back to mechanical?
2) Is it as simple as removing the electric pump and running a new fuel line from where the metal line enters the engine compartment to the fuel pump, and then up to the carb? Any other changes needed?
3) Do I need to add a check valve somewhere in that line? I think the electric fuel pump acts as a check valve now, right? So without one, would the fuel drain to tank? Is there a simple one you recommend?
4) Should I place the fuel filter before or after the mechanical pump? Right now it is between the electric pump and carb.

Thanks!

-Matt

[JEEPER]

Matt Fiat USA changed my mEchanical for an electric under waranty. My 79 was Vaporlocking before the swap. It is in the trunk. I had to replace it last year because I didn't have enough pressure (volume). The car runs great now.

[baltobernie]

An electric fuel pump in the trunk with a return line is your best defense against vapor lock, and also allows you to "prime" the carburetor.

The proper electric pump for a Weber-equipped Spider develops only 2 psi or so, so you don't need an external regulator.

Relocate the pump to the trunk, install (or retain) the prefilter, which will extend the life of the pump. Install one of these ...



... vertically to a secure panel, and wire in series to the +12 feed to the pump. This inertia switch was used on zillions of Ford cars and trucks, and is available new or used for pennies. The switch will stop current to the pump in an accident (it is shown in the "tripped" condition in this photo).

In the engine compartment, install one of these fuel filters ...



... with the 3 o'clock nipple attached to the return line. If you pause for a few seconds between On and Start, the electric pump will ensure a full float bowl and eliminate grinding the starter incessantly, particularly if the car has been sitting for a while. A functioning return line relieves excess pressure on the carb float valve and provides cool (-er) fuel to the carb; all good things.

[RRoller123]

+1 on the inertial shutoff switch. Here is another thread showing where I installed mine on the trunk wall, etc.

http://www.fiatspider.com/f15/viewtopic ... t=inertial

Pete

[carl]

Converting back to mechanical is as simple as you surmised. Most folks put the filter between the pump and the carb. I prefer an electric pump over mechanical as my Fiats don't get driven all that much and the electric pump primes the carb before starting whereas I used to have to grind away on the starter till the mechanical pump fed the carb so it could start. You can always install an on/off toggle switch for the pump to turn it off while doing electrical testing.

Bottom line, if done correctly either electric or mechanical pump should be fine.....in theory.