900ss

I have an Bosch 044 fuel pump that I want to wire up via a relay

What relay do I need to buy or use and can someone put up a simple guide of how to wire the pump relay
Car was n/a so I need to start from scratch

ta

cozmeister

iTrader: (1)

This thread has the answer to your question:

https://passionford.com/forum/genera...-044-pump.html

HTH

tabetha

As above use the relay numbers given, but don't worry if it doesn't have a 87a, the relay shown and mentioned wrongly is a changeover relay not a double throw at all.
You just need a SPST single pole single throw relay, 40 amp will be more than enough, the 044 locks out at 11.2L/min and 18amps anyway.
Don't foget to run the earth to the battery, this way you know for certain it's got decent feed, some put it down to the body, even underside of car so more corrosion and low voltage can build up!!.
The yellow relays as used on billions of fords would do the job, I put mine on a relay holder just behind the n/s/r seat back at the top, ther eis conveniently a 8mm hole there so bolted holder through here.
That way when you go to a show etc, simply pop relay out and carry with you, makes it a little bit harder for pikeys for no cost.
tabetha

joffy

iTrader: (1)

really easy to do aswell, i managed it!! lol

900ss

This isn't in a cossie but the idea should be the same?
Bit confussed about the earth part
I'm wireing in a pump via a relay and the instructions below I have from another site read as if the earth is via the ecu and not to the battery/ground ?

"The fuel pump signal wire you will be using for the ground on your fuel pump relay, this way the ecu has control of the fuel pump and will shut the pump off if the engine is not rotating, a good safety feature"

cjwood555

Tabetha that's cojones.

Voltage drop / series resistance is going to be MUCH greater down any size cable compared to a great chunk of steel. So long as care is taken to get good contact with bare metal over a large enough area (i.e. same size as terminals on pump), and protect it, then your point is moot.

I would be more worried about protecting another large diameter cable for the length of the car to be honest!

Neil S

iTrader: (1)

Wyn,

Have a look at my thread here.

I've used the output from the inertia switch to operate a new relay - this switches a new fused live direct from the battery through new wiring to the pump.

This keeps the inertia switch without adding extra resistance to the circuit

Neil.

tabetha

You'd actually be worried about "protecting" a earth wire, is this in case it touches the body somewhere!!
The slight amount of resistance will not make any difference to the pump but a bad connection due to rust etc can.
The body will still show a resistance, especially as at the ends of thebodt there is a terminal where the wire is connected to it.
tabetha

Spiky

iTrader: (1)

my ecu turns on my fuel pump using an earth, so just earths the relay and that switch's it on

if your ecu is feed your realy with 12v, then you need to wire it up slightly different to me

cjwood555

The series resistance of 4 or 5m of anything less than 4guage cable is going to be enough at 20A to see a drop of at least 2/3 volts at the pump.

The series resistance through a massive cross-section of steel and a short cable at each end would be significantly less so long as proper connections were made i.e. 'star'/gripper washers + nylocks/spring washers; and would also be significantly cheaper.

Protecting the cable not to prevent shorts but to ensure that the earth is reliable. Don't be cocky.

Chris

tabetha

Not a hope on hell would it ever be close to 2 or 3 volts at the pump.
Use the formula and do the math.
V = (25 x I x L)/CM
eg Use 28/030 cable, lets say 20 feet should be plenty, of stranded copper wire(thinwall) will carry continuously 25 amps or roughly double the pumps max will result in a resistance of 0.0536, and a volt drop after 20 feet of 0.6968 volts.
This is influenced by temperature, current carried(amps) material conducting and length.
Steel ie car body has a resistance of 0.00684 ohms/foot, resistivity ohm/cm of 11.8
copper has a resistance of 0.000999 resistivity ohm/cm of 1.725, so steel is OVER SIX times as resistive to current flow.
These are at 25C by the way better conductors than steel include ohm/cm,
platinum 10.0
iron 10.0
nickel 7.8
brass 7.0
iridium 5.29
aluminum 2.828
gold 2.44
copper 1.724
silver 1.629
All again at 77F
tabetha

cjwood555

Disregarding my failure to do the maths and basing my answer on personal experience; the cross-sectional area of the car body is far more than six times that of whatever cable would be used...

Points ref cost and reliability still stand.

joffy

iTrader: (1)

cost?? how much does 5m of cable cost to run back to the -ve compared with the cost of a rebuild when your corroded connection to your car causes low voltage to your fuel pump??

900ss

Many thanks for the advice

Does it matter what position/order the relay terminals are in?
I've found a few relays out but the terminals are in deffo order then shown here

https://passionford.com/forum/genera...-044-pump.html

I found one that is right but its 70amp, again will it matter?

tabetha

No doesn't matter the order they are in, the "DIN" numbers reffered to are the easier ones to identify, but others include letters uk/italian plus numerous others.
Again doesn't matter at all whether it is 40 or 70, so long as at least 30 or so.
Get a relay holder for around a quid(pm me if you need, and I'll send you one FOC), then as you insert the terminals after CRIMPING the wires terminals together just make sure from looking at holder and underside of relay they go in the right slots.
You can apply a dab of solder onto the end of the wire AFTER it has been crimped, but just a touch, solder makes the wire brittle.
Just be aware for 70 amp relay that they will have larger 30 and 87 terminals, but again pm if stuck.
The std size of terminals is 4.8mm, larger are 8.8.
tabetha

900ss

All good cheers
Thanks for the offer of parts but now I’ve half an idea what I need I should be able to find the parts from work.
Knowing what to look for is the thing now lol
Still i’ve found out a 30amp relay, as said diffo pin order but the 4 numbers are the same 30/85 etc

I’ve just dummy wired it up and the main 87 pump output goes live with ign on
But just a thought as its earth feed is via the ecu shouldn’t 87 only go live when cranked or running?
Or have I just wired it wrong lol

Also I've just bought a reel of 2.0mm 25 amp 12v cable
Is that ok to use for the main pump + cable?

tabetha

The 25 amp cable will be fine.
Assuming you want to keep your cut out switch(and you do) just take the live output after the cutout SW, to the relay.
Doesn't matter where the earth comes from but just take it from a ground, or the earth wire direct from battery that feeds pump earth.
The realy should be wired as this,
30 Live direct from battery(via a 25amp fuse)
85 Earth
87 Live output from relay to pump live
86 Live from/(after) cutout switch, make sure it is after or just use the original live that went to the pump.
I really would recommend a seperate new earth, but up to you, as otherwise you still leave a 20+ year old wire and connection on one side of the pump and earth is just as important as live, some take from a point inside the car alternatively though, which is still far better than the original wire.
All the ecu does for the pump is output a LIVE to the cutout switch then from there to the pump, the pump earth does not come from ecu, but from main loom earth points.
tabetha

900ss

Well it runs

Thanks for the help