Fuel Pump Relays

I wanted a safe power feed for my electric fuel pump.

Someone suggested I use the blue wire from the voltage regulator to power the pump.
This gives the advantage of shutting off power to the pump, and therefore fuel flow, when
the alternator is not putting out charging voltage.
In other words, IF the engine dies in an accident, the fuel flow stops.

This is safer than running the pump from the coil like a lot of people do, but
it has disadvantages:

1. There's no guarantee your engine will stall in the event of an accident.

2. The pump gets no power while you're trying to start the engine.

3. The blue wire, which feeds the generator warning lighton the dash- board doesn't carry consistant voltage.

4. If your charging system fails, your van dies seconds later.

Not all that safe after all.

Think of it this way, your wife/partner may not be the gearhead that you are and runs the van out of gas.
No gas in the carb(s) means no start even after filling up. A relay is a lot cheaper than a tow and a lot
safer than not being able to start or get out of the way in case of an impending accident.

I know on no vehicle with a factory electric fuel pump which doesn't get its power via a relay.
If I'm wrong about that, feel free to let me know

What did I do?

Well, first I contacted SKORPIO and asked what he thought. He pointed out the inconsistant
voltage problem and suggested two relays. One for running, and one for starting.

Relax, it's not that complicated. Remember to install appropriate fuses.
By "appropriate", I mean a fuse rated for the pump's draw and with a lower rating than your wiring
(you could also install the fuses near the main power feed before the relays).

It's simple and elegant really.
I now have one relay which is triggered by the starter which makes the pump run while cranking,
and another which takes over once the engine is running.

The "running" relay is triggered by the blue wire I mentioned earlier.

Remember what I said? The relay trigger feed doesn't have to be powerful at all (or in this case, consistant)!

If you've been paying attention, you'll have noticed that there's still no guarantee that the engine will
stall on impact. I got in touch with Skorpio and asked him what he thought. He came through again.

If you feed your ignition coil and carb solenoids (if so equipped) to the setup above,
when the engine stops, power to the coil and carb(s) shuts off immediately. Clever.

Some smart people have added a fuel cut-off solenoid to their fuel tank outlet for further protection.
The really smart ones also have automatic fire extinguisher systems installed in their engine rooms.
I hope to do the same eventually.