TR2/3/3A Fuel pumps and Neg/Pos ground?

[karls59tr]

Are most newer electric fuel pumps Negative ground unless specified otherwise .ie Facet? When converting a car to Negative ground...if the fuel pump has one wire lead and the case is grounded then this pump should work OK without any changes when the battery terminals are switched over. Correct?

 

[dklawson]

I cannot say that the following applies to ALL aftermarket electrical pumps but in general it will be true.

If the pump has two wires, its frame is generally not part of the circuit and it can be used on either positive or negative ground. Just hook the two wires up appropriately. If the pump has only one wire, it was made for a specific ground application. To use a single wire pump on the "wrong" ground would require completely isolating the pump from ground and running a second wire to the pump's frame.

The Facet cube pumps use two wires and they can be used with either ground. Just make the correct wiring connections are made. SU electric pumps have a connection to the bakelite cap and typically a connection to their metal bodies. They are polarity sensitive.

 

[TR3driver]

I agree, except that some older SU pumps (eg the original pumps for my 71 Stags) were not polarity sensitive. Newer ones definitely are, though. The ones I've seen have a colored band with the polarity marked on it.

 

[karls59tr]

I cannot say that the following applies to ALL aftermarket electrical pumps but in general it will be true.

If the pump has two wires, its frame is generally not part of the circuit and it can be used on either positive or negative ground. Just hook the two wires up appropriately. If the pump has only one wire, it was made for a specific ground application. To use a single wire pump on the "wrong" ground would require completely isolating the pump from ground and running a second wire to the pump's frame.

The Facet cube pumps use two wires and they can be used with either ground. Just make the correct wiring connections are made. SU electric pumps have a connection to the bakelite cap and typically a connection to their metal bodies. They are polarity sensitive.

I have a 4" cylindrical fuel pump with two wires at one end. One wire is the power wire and the other wire goes to ground at the frame. If I'm switching over to Negative Ground to install an Alternator do I leave the wiring as is or do I switch the the wires around on the pump? A little dyslexic here.:confusion:

 

[dklawson]

I have a 4" cylindrical fuel pump with two wires at one end. One wire is the power wire and the other wire goes to ground at the frame. If I'm switching over to Negative Ground to install an Alternator do I leave the wiring as is or do I switch the the wires around on the pump? A little dyslexic here.

In general, yes, you would switch the two wires when switching the car's ground. However... you need to determine whether the pump body is also an earth connection before swapping the wires. Do you have a multimeter?

 

[TR3driver]

I have a 4" cylindrical fuel pump with two wires at one end. One wire is the power wire and the other wire goes to ground at the frame. If I'm switching over to Negative Ground to install an Alternator do I leave the wiring as is or do I switch the the wires around on the pump? A little dyslexic here.:confusion:

If you are certain that one wire goes to the frame, then you cannot swap wires. You need to do some research (ie find out the pump brand and model) to determine if it will run on reversed polarity or not. I'd say that it is more likely that it will; but certainly not guaranteed (where did you find a positive ground pump??); and it might destroy the pump if you just hook it up backwards.

OTOH, the pump is useless if it won't work in your new configuration, so it may not matter if you burn it up.

 

[Geo Hahn]

I have a 4" cylindrical fuel pump with two wires at one end...

FWIW - My emergency pump may be similar to what you describe. It has two wires and neither are connected to the body of the pump. Polarity sensitive so simply swapping the wires handles that. As I recall, '+' and '-' were stamped on the pump body near the wires.