fuse box help

[Si316]

Hi guys and girls,

Im just finishing the wiring on my project and need some help with the fuse box. Im looking to wire my electric fan and facet fuel pump in via the fuse box using 2 of the unsued slots.

Does anyone have any diagrams or pictures of the inside of the fuel box? maybe someones already done this and can help me out?

Cheers
Si

[Brianmoooore]

For the fan, use the positions BMW supplies: Either relay K1 and fuse 3, or relay K6 and fuse 18. Earth one side of the fan and take the live feed for the fan from the outer terminal of the fuse. Apply 12V+, from what ever switching/control arrangement you choose, to terminal 85 of the relay.
For the fuel pump, use the existing fuel pump relay and fuse 11, but it should ideally be arranged so that the pump only runs when the engine is running or cranking.

[Si316]

thanks for the reply mate, let me see if I understand you right.

If I get a live fron the ignition and connect that to terminal 85 of the relay. then take a wire from either fuse 3 or 18 to the fan positive. then a wire from the fan negative to ground?

For the fuel pump, facet recomend using an oil preasure switch so the pump stops when oil preasure is lost. is there a sensor that I can use in the stock e30 place (m10 engine)? or maybe could somehow run it off the altenator so that if the fanbelt snaps it kills the engine?

Cheers
Si

[Brianmoooore]

thanks for the reply mate, let me see if I understand you right.

If I get a live fron the ignition and connect that to terminal 85 of the relay. then take a wire from either fuse 3 or 18 to the fan positive. then a wire from the fan negative to ground?

For the fuel pump, facet recomend using an oil preasure switch so the pump stops when oil preasure is lost. is there a sensor that I can use in the stock e30 place (m10 engine)? or maybe could somehow run it off the altenator so that if the fanbelt snaps it kills the engine?

Cheers
Si

For the fan, all correct, except that the fan will run all the time the ignition is on. This will use a measurable amount of your engine power.
You need a switch of some sort (manual or automatic) between ignition live and terminal 85.
You need to wire your fuel pump relay: Pin 30 to 12V+ from battery, 87 to fuel pump fuse then fuel pump, 85 to ignition live, and 86 to the oil pressure switch.
Connect a second relay: 30 to 86 of the first relay, 87 and 86 to earth and 85 to the black/yellow starter wire.
This second relay will bypass the oil pressure switch when cranking, and allow the fuel pump to run before oil pressure is built up.
Only downside of this is, if your engine is worn, or you have oil surge, then the fuel pump may cut at an inconvenient moment.
LPG powered cars have an arrangement that monitors ignition pulses (as does the standard E30 ECU), and cuts the gas supply at the tank if they are not present.

[Si316]

Should have mentioned I have a temp switch fitted for the fan ready to sort out when the fan comes on.

So I can use the stock oil pressure switch for the dash light? just run an extra wire from that to 86 on the first relay?

The engine has been fully rebuilt so shouldnt be an issue.

Cheers
Si

[Brianmoooore]

Stock oil switch - just tap into the wire where it runs through the fusebox. All the wires/connections you need are in there.

[Si316]

Awesome, thanks very much mate your a hero!

Si

[Si316]

Ok so i think i've got a problem with the wiring of the fuel pump. Ive got round to starting the car (finaly).

The pump is going when the key is in the second position when theres no oil preasure. I thought the pump would only work when ive got oil preasure and be bypassed when the key is in position 3 while cranking? or have i got that wrong?
Could this be that when theres no oil preasure the oil light is on and supplying a live signal? therefore when I get oil preasure and the light goes off the pump might also go off?

Ive got a problem with my ignition which is just not working. There doesnt seem to be any power going to the coil. Ive checked all connections and they appear correct and fine. Any ideas?

Cheers
Si

[Brianmoooore]

Live supply to the ignition coil is a simple unfused supply straight from the ignition switch.
Small red wire goes from the battery + to a cap bolt visible in the top face of the fusebox. Another red wire goes from here to a plug and socket clipped to the steering column, and then to the ignition switch.
Now becomes a green wire, switched by the ignition switch, which goes back through the plug and socket on the column, and then to the C101 engine loom connector. Goes from there to the engine ECU and the ignition coil +.
Fuel pump relay is activated by the ECU when it sees pulses from the crank position sensor, and has an 'ignition on' signal from the green wire.

[lycara]

Rite just sorted out the ignition system. The impulse generator connector wasn't connected...whoops.

The fuel pump is the only problem now.
Its working when I turn the key to position 2 but as soon as I get oil pressure the pump turns off. This is the opposite to what should be happening. This is why I'm thinking I'm getting a positive from the oil pressure switch when it needs to be negative meaning I have oil pressure and the pump can work.

Ive got the relay wired in as follows.
87 - Fuel pump
30 - +12v
86 - Pressure switch
85 - ignition live

This is a relay I've wired in myself with the advice above.

[Si316]

Whoops posted on the wrong login. Thats me above!

[Brianmoooore]

See what you are doing now! You have a normally open relay, but you need a normally closed one.
In practice this will be a five terminal change over one, and you need to connect to pin 87A, not 87. Relay from the 'windows work with doors open' circuit is the sort you want!

[Si316]

so it'll be like this for the pump to run?
87A - Oil pressure switch, 0 as I've got oil pressure and the light is off.
30 - +12v, 1
85 - ignition live, 1 key in position 2
87 - Fuel pump = 1

[Brianmoooore]

No! As your lycara post above, but change 87 for 87b (not 87a - my mistake)

[Si316]

ok cool, I've got a 5 pin relay sat in front of me. Is 87b the pin labeled 87 in the middle and 87a in the same position as a 4 pin fuse?

[Brianmoooore]

I would expect to find 87a or b in the middle, but it doesn't matter which way around you connect the 87s, or which way around you connect 85 and 86.
Not all 5 pin relays are changeover types, by the way. You need one where there is zero resistance between the 87s when the relay is unpowered on the bench.

[Si316]

Rite mate, ive got it wired in with the correct relay now like this.
87a - Fuel pump
30 - +12v
86 - Pressure switch
85 - ignition live

Now when I put the key to position 2 the pump doesn't run. When I crank the oil pressure light goes dim but not off. When I take the relay out the light goes fully off. Is this because I've got Ignition live and the oil pressure signal on the same circuit? and the light goes dim because it has a signal coming from the ignition being live? should it be oil pressure on pin 86 and pin 85 to ground? Should the +12v on pin 30 be changed to ignition live meaning its wired in like this.

87a - Fuel pump
30 - ignition live
86 - Pressure switch
85 - ground

[Si316]

Would this work?

Relay 1

87a - Fuel pump
30 - +12v
85 - Pressure switch
86 - pin 30 of Relay 2

Relay 2
87 - Ground
30 - pin 86 of Relay 1
85 - ignition live
86 - ground

That would mean the pump would work with the oil pressure light off and with an ignition live?

[Brianmoooore]

Right, try this:
87a to fuel pump, via fuse.
30 to 12v+ ignition live. Needs to be ignition live (green), not permanent live (red), as pump would run when the car is stopped with a normally closed relay.
86 to oil pressure switch.
85 to pin 87 of unloader relay K5. This will cut the power to your fuel pump relay coil when cranking, allow the relay contacts 30 and 87a to close, and turn the fuel pump on without having to wait for oil pressure to build up.

[essexboy]

just found this thread great as i now understand how to wire my fan thanks to mr more but does anyone know where i can buy the little spade type connectors for the fuseboard from?

Thanks
Lee

[Brianmoooore]

but does anyone know where i can buy the little spade type connectors for the fuseboard from?

From BMW!