Wiring an electrical fuel pump safely

There's been some recent posts on here about wiring up electric fuel pumps.

I posted up some diagrams from Mr Whippy on Volksworld describing a 2 relay system that automatically disconnects the fuel pump if the alternator stops turning (ie engine stops)

http://www.volkszone.com/VZi/showthread.php?t=448416&highlight=electric+fuel+pump+wiring+diagram&page=3

I think the setup has some issues, the biggest one is power is fed to the fuel pump via an ignition switched feed still. This means you could have problems with the ignition circuit caused by voltage drops from sharing the same ignition switched feed. The idea of a relay is primarily that you use a small amount of power to switch a larger amount of power.

Looking around I think using a fuel injection pump relay is a much better way to go.
The relay allows a direct feed to the fuel pump from the battery (has a built in fuse for that circuit)
Uses a sensor wire that connects to the - terminal of the coil. the sensor wire connects to a built in timer which disconnects the pump in under a second unless it receives a pulse from the coil. Engine stops, pump stops

Ratwell's page describes it well:

http://www.ratwell.com/mirror/sfraser/relay.html

The part number of the relay is:

321 906 059 C

You can get them from VW Heritage for about £35.

I think (not sure) you can get a socket for it from here:
http://www.thetoolboxshop.com/relay-and-flasher-sockets-346-c.asp

Alternatively, get one from your local scrappy from an old Scirocco, Jetta, mk 1 Golf etc. For peanuts.

If you want to wire in a priming circuit for when you run out of juice because of the '$£** fuel gauge, wire a push button between terminals 87 and 30


A good electrical pump to consider designed for a twin carb setup that wont break the bank is this one:

http://www.dellorto.co.uk/merchandise/products_details.asp?PartNo=WFP502&CategoryID=8&PartsectionID=18




Has a built in regulator and filter and comes with all the fittings (see the data sheet)

I've read so many posts from people who've had trouble with facet pumps I wouldn't touch them with a barge pole.

I'll post up some pics of my setup soon.

Cheers

Steve

 

Great post Steve, thanks.

 

You're welcome 8)

 

I like to keep it simple.

I install a bog standard relay £3 and take a feed from the alternator warning light wire and then put a over ride switch on the relay.

When the engines running and turning the alternator this brings on the the relay and brings the pump on.

There is enough fuel in the carbs to get the engine started normally and if you do run them dry you can use the switch to run the pump to fill the carbs.

 

Same odds really except the FI relay will get you home if the alternator fails.
One advantage of an electric pump over a mechanical is it's pumping full speed at cranking speeds so shouldn't to have to crank the motor too long before the carbs fill up
Cheers
S

 

whats the problem with electric pumps..
when i had an old moggy it had a leccy pump. when you turned the ignition on you could here it pumping for a couple of seconds and then stop, hence fuel at the carb. then you knew it was gonna start.
if wiring via your altenator if it packs up does your pump stop straight away.
where as if it was wired via a battery/ignition you would have enough power in your battery to get to the next garage or a safe place to park up.
I suppose if your fan belt brakes you come to a halt before you damage your engine...being wirered to the alternator.

 

Can you just confirm where you're taking the power feed from for the pump and for the relay to switch on?

Might be missing something but if the pump takes power direct from the battery, and the relay cuts power when alternator lights, what happens when ignition is off. Is the pump running all the time?

Obviously I need to sort out my pump wiring so want to get it right.

 

When the alternator is running it puts a pos to the dash lamp so by using this wire it switches on the relay so switching on the pump when the engine running.

If the alternator packs up you wont be going far anyway but you can always use the bypass switch.

The idea of a relay is that if you have a accident the fuel pump does not keep running you can buy proper shock switches put these are expensive and can be a pain to set up.

 

Ahhh, as you can see I am on there from my VZI days, since that thread I have been running mine with two relays one normally closed getting a neg signal from the oil pressure switch and a normaly open one getting a pos signal from the starter solenoid picking up an ignition live from the coil for the pump and it has been running fine.

 

Problem with the alternator exciting a fuel pump relay is that it only gets power to the pump once the engine is running fast enough for the ignition light to go out (ie power to the fuel pump relay relay). If you have a twin carb setup and you don't run it for a week or so you'll need to prime it.
Using a FI relay (with a coil connection), which allows the pump to run when there is an ignition pulse at cranking speed, means the fuel pump is running when the engine is actually turning over on the starter. No need to prime (electric pumps run at full pressure all the time unlike mechanical ones)

Cheers
s

 

ok so im gonna buy the fused relay from vwh.
im not electicly minded so is it as simple as connecting the live wire of the pump to the relay, connecting a live from the battery to the relay and connecting a wire to the relay from the - side of the coil?
which numbered connections on the relay for what?

 

bought this fuse from VWH today

its not the same as the one in the link in the first post. its meant to be but the numbers are differant and so is the diagram on it. i assume its right ?

any ideas on which number terminals i use for
1 wire from fuel pump
2 live from battery
3 sensor wire to coil
cheers

 

anyone??

 

Here you go...always handy

http://www.type2.com/library/identifi/bosterm.htm

 

What a faff. Think I'll stick to the mech pump.

 

Talk about make an easy job hard.

I have my electric pump wired to switch live so that once the ignition is turned on the pump starts. Simples.

 

Can't see how it is a bodge.

 

retired dads are usefull. he found this today while i was at work
so panic over :