TheSamba.com :: View topic - Proper way to wire an electric fuel pump?

Thu Sep 26, 2013 11:43 am

First off, to save some time, if I could use a stock mechanical pump on my bus, I would. But my 1600dp was built on an old German FI engine case, so there is no boss for a fuel pump on the engine, so I am forced to run an electric one.

I bought the Carter P60504 rotary fuel pump (same pump that CB Performance repackages and sells), which everybody seems to say works better (and quieter) than the clicking Facet's.

I have heard people running the power wire straight from the coil, but I feel that isnt the smartest way to do it. Are any of you guys out there running a wire all the way to the front of the bus to run the fuel pump off the fuse box? This seems like a decent amount of work considering its the complete opposite side of the bus, but if its the proper way to do it, nows the time for me to do it.

Just figured I would ask all of you who are running electric pumps how you wired them up due to not finding much info via the search function.

Thu Sep 26, 2013 12:13 pm

Don't know the year of your bus, but most buses have only one switched fuse (#2) and that is the terminal to which the coil is connected--though the coil is not fused.

I wouldn't see a problem using the coil wire to power a relay for the electric pump which could draw power, through the relay, from a hot fused wire directly to the battery/voltage regulator.

Edit: Maybe a better way. Power the relay from the terminal on the generator/vr that powers the idiot light instead of the coil. This would mean the relay would not switch over to power the pump until the generator is charging (idiot light connection is powered). This would act a s a safety device to shut down the pump whenever the engine dies or the generator stops charging--like a broken fan belt. There is ample fuel in the float bowl to start the car each time and get it running to kick in the fuel pump.

Thu Sep 26, 2013 1:53 pm

The right way.

I wouldn't see a problem using the coil wire to power a relay for the electric pump which could draw power, through the relay, from a hot fused wire directly to the battery/voltage regulator.

Thu Sep 26, 2013 3:13 pm

I like the idea of using the generator output to switch a relay to power the pump.
You might need an override switch in the case of generator failure or if the carb gets drained somehow, though.

Thu Sep 26, 2013 7:45 pm

That method is good.

As an alternative, if you're a 12 volt system, there's a module which only runs the fuel pump when the engine is running, not just when the key is on. This drawing shows what's inside the module and how it hooks up to the outside world:

It's triggered by the opening of the ignition points. The advantage of using this module is that if you're ever in a wreck, the fuel pump stops when the engine stops, even if the key is still on.

Thu Sep 26, 2013 8:22 pm

I run an oil pressure shut off switch. Pump only fires when there's oil pressure. I installed an inertia switch from a ford, which cuts power in the event of an accident.

Thu Sep 26, 2013 8:29 pm

That diagram seems pretty overcomplicated.
Looks like a good ol' LM7812 and a resistor off the D+ post to the relay coil would do it!
But I tend to ghetto stuff up like that.

Oil pressure switch idea is great!

Fri Sep 27, 2013 10:19 am

telford dorr wrote: It's triggered by the opening of the ignition points. The advantage of using this module is that if you're ever in a wreck, the fuel pump stops when the engine stops, even if the key is still on.

So is the VW 321 906 059C kept on with each trigger or once the first opening occurs does it remain on? If so what turns it off?

What is "31"?

Fri Sep 27, 2013 6:24 pm

telford dorr wrote: That method is good.

As an alternative, if you're a 12 volt system, there's a module which only runs the fuel pump when the engine is running, not just when the key is on. This drawing shows what's inside the module and how it hooks up to the outside world:

It's triggered by the opening of the ignition points. The advantage of using this module is that if you're ever in a wreck, the fuel pump stops when the engine stops, even if the key is still on.

It is a Rabbit fuel pump relay. It is a really easy set up to install, the schematic makes it look more complicated than it really is.

Tue Jan 28, 2014 8:58 am

ToolBox wrote: telford dorr wrote: That method is good.

As an alternative, if you're a 12 volt system, there's a module which only runs the fuel pump when the engine is running, not just when the key is on. This drawing shows what's inside the module and how it hooks up to the outside world:

It's triggered by the opening of the ignition points. The advantage of using this module is that if you're ever in a wreck, the fuel pump stops when the engine stops, even if the key is still on.

It is a Rabbit fuel pump relay. It is a really easy set up to install, the schematic makes it look more complicated than it really is.

Sorry if I am dragging this up, but I was searching electric fuel pump woes and ended up here.

The point I would like to make is... It is far better to use a simple Bosch Relay for the fuel pump than to us a Rabbit fuel pump relay. The rabbit fuel pump relay is probably the part most likely to fail on a rabbit and usually changed before any no start diagnosis begins. Not reliable. Also it is very tough to get a pig-tail for that relay.

Gordo.