Electric Fuel Pump

[Otahuhu]

Could someone list the electrical wiring diagram for an electric fuel pump on a vintage car that is  foot started, and uses an oil pressure switch as a safe guard. Some time ago there was one on this site Thanks Len

[hook]

An oil pressure switch is good but your engine could still continue to run in a collision that severs the fuel line, and since most electric fuel pumps are placed in the rear it could shoot gasoline everywhere until the engines carburetor ran out of gas and the oil pressure drops. I like to place an inertia switch in line with the fuel pump power supply to prevent that from happening. It can also be used in line with an oil pressure switch for other problems. Just my 2 cents worth of safety concerns

[joe_padavano]

Actually, the correct oil pressure switch eliminates the need for the foot started button. Most cars with carbs and electric fuel pump use a switch that provides power directly to the pump when the key is in the START position, then when the engine starts and oil pressure rises, this switch holds power on but turns it off if oil pressure is lost. To Hook's point, an inertia switch in series with the oil pressure switch is the best of all worlds. The inertia switch would simply be installed in the wire from the "P" terminal on the switch to the pump in this diagram.

 

 

[joe_padavano]

Another version of the same diagram.

 

[Otahuhu]

Thank you for the reply .Maybe I was not clear enough. There is no solenoid on the starter motor The foot start  when pressed engages a switch on the starter motor by a lever  that then engages the   Bendix into the fly wheel. No solenoid is involved  Regards Len

[Bloo]

I've done a bunch of stuff like this but it was 20+ years ago. There are some gotchas and try as I may, I can't remember the details. To figure out a good place to start, we are going to need more info. For starters (no pun intended):

 

1) 6v or 12v?

 

2) Positive or Negative ground?

 

3) Can this have it's own oil pressure switch or will it have to piggyback on some existing switch for an idiot light (and not blow the switch up)?

 

4) Is there space available at the oil pressure port for a fancy switch like Joe Padavano posted or will it need to be one of the tiny single terminal ones?

 

It's almost a given that you will need a relay. You might need two.

 

 

[joe_padavano]

48 minutes ago, Otahuhu said:

Thank you for the reply .Maybe I was not clear enough. There is no solenoid on the starter motor The foot start  when pressed engages a switch on the starter motor by a lever  that then engages the   Bendix into the fly wheel. No solenoid is involved  Regards Len

Understand, sorry for the confusion. In that case, you just need power to the "S" terminal on that oil pressure switch when the starter is engaged.

[joe_padavano]

23 minutes ago, Bloo said:

It's almost a given that you will need a relay. You might need two.

The oil pressure switch I posted is designed and rated to carry the current for a conventional 6-ish psi fuel pump. Unless you're using some high pressure EFI pump with an insane GPM output, there is no need for a relay. Just be sure the wiring is rated for the current.

[Otahuhu]

Appreciate if someone could show the wiring details of the setup for an electric fuel pump as per attached drawing Regards Len

 

[37_Roadmaster_C]

Late to the game, but I will jump in before the others do...   One thing we will need that is not on your drawing is to know if there is a way to connect a wire to the starter MOTOR terminal. That would be where the actual motor gets power when the foot switch is pressed. There is a point within the assembly where this is but it might not be easy to access.  Also, it would be helpful to know what vehicle this and starter type and model if you know.

[joe_padavano]

4 hours ago, 37_Roadmaster_C said:

Late to the game, but I will jump in before the others do...   One thing we will need that is not on your drawing is to know if there is a way to connect a wire to the starter MOTOR terminal. That would be where the actual motor gets power when the foot switch is pressed. There is a point within the assembly where this is but it might not be easy to access.  Also, it would be helpful to know what vehicle this and starter type and model if you know.

 

^^^THIS! Somewhere on the starter is a contact that provides power to the actual starter motor windings when the foot button is pressed. That terminal needs to be connected to the "S" terminal on the oil PS-64 oil pressure switch. The rest of the circuit is exactly as I showed you in my first post.

Edited January 2, 2022 by joe_padavano (see edit history)