Little help using fuel pump to trigger a relay (scavenge pump)

[nextelbuddy]

So on my E46 it's turbocharged with s54 in a non-M. On my DME I am using x60004 pin 10 for fuel pump output. That wire goes to the fuel pump relay in my car which is behind a glove box.

Of course when you turn the key on the fuel pump primes and then it shuts off and it won't turn back on until you actually start the engine which I assume is the DME controls that.. I assume that the DME sends a prime signal via pin 10 for priming and then turns off until you start the engine where it sends a constant signal. Could be wrong though.

Currently Pin 10 always has 12 volts.

I wired up my scavenge pump with a 4 pin relay and it's wired directly to the battery and grounded and I'm using the trigger wire going to pin 10.

Of course when I turn the ignition on the fuel pump and the scavenge pump both come on but they both constantly stay running if I unplug the scavenge pump trigger wire, about the scavenge pump and the fuel pump both shut off.

Trying to figure out why just adding a trigger wire to the fuel pump pin 10 signal wire is energizing the fuel pump.

Where am I supposed to get a proper fuel pump trigger signal that primes only on ignition two and shuts off and turns back on when the engine is running?

Should I instead just use the power wire coming off the relay that goes to the fuel pump instead?

[nextelbuddy]

Okay after digging around in the TIS wiring diagrams for the fuel pump relay....

It looks like pin 2 white with a blue stripe goes from the fuel pump relay directly to the fuel pump...

I used a voltmeter on that same wire at the fuel pump plug under the seat and can see it gets 12 volts on ignition to prime and then drops the 0 volts.

So that's the wire I want to use unless there's another way because that's a pain in the butt. I can't tap into the wire coming off the relay behind the glove box there's no space to splice into that wire and I really didn't want to run a wire all the way to the back under the seat.

I just don't understand where the control is who determines when to send 12 volts to prime and turn off... The relay is not an EKP relay It's a green dumb relay.. and if the ECU is outputting 12 volts from x60004 pin 10 to the relay as the trigger... Where the heck does the signal come from determines prime on ignition 2 and turn off.

[ZiMMie]

looks like a "ground" signal not [+12V]

wire the relay like this and should work.

but a diode in between scavenger pump <--- fuel pump trigger

[nextelbuddy]

looks like a "ground" signal not [+12V]

wire the relay like this and should work.

but a diode in between scavenger pump <--- fuel pump trigger

what do you mean looks like a ground? Do you mean the fuel pump signal from DME PIN 10 x60004 is a ground signal?

I think on the MSS54 DME x60002 PIN 11 which is the S54 EKP Fuel pump relay signal wire.. maybe THAT one is a negative PWM signal to the EKP relay?

the X60004 pin 10 is EURO Fuel pump and NON M Fuel pump signal to a standard relay and that is 12 volts coming from the DME as tested with my volt meter. when i tested x60002 PIN 11 for 12 volts i got nothing which led me to believe its negative PWM possibly.


so a Diode is like an electronic one way check valve right? Not really sure m understanding where exactly the diode would be going sorry.

[ZiMMie]

What i posted its a euro/normal non m fuel pump diagram.

the fuel pump is activated with a ground signal to the relay. its not a 12V. you can confirm it by ground pin 10.

I do not know how your scavenger pump is wired.

But if you wired it like the schematic i posted with a diode in between it will work.

basically take an old e30/e36/e46 fuel pump relay, and wired it exactly like the schematics i posted.

Use a diode to save your ecu if something was to go wrong.

[nextelbuddy]

What i posted its a euro/normal non m fuel pump diagram.

the fuel pump is activated with a ground signal to the relay. its not a 12V. you can confirm it by ground pin 10.

I do not know how your scavenger pump is wired.

But if you wired it like the schematic i posted with a diode in between it will work.

basically take an old e30/e36/e46 fuel pump relay, and wired it exactly like the schematics i posted.

Use a diode to save your ecu if something was to go wrong.

Currently i took a spare BMW 30 amp 4 pin orange/green relay socket and relay and used that for the scavenge pump. I wired it like this:

PIN 30 - 12 volt terminal under hood (has 30 amp fuse inline)
PIN 85 - Ground post under hood
PIN 87 - 12 volt Power wire to scavenge pump under car (has inline 20 amp fuse inline)
PIN 86 - (I thought was trigger wire) was going to use this from PIN 10 x60004


i looked at k96 Fuel pump relay pin out again this morning and can now see they have if different than i thought.

PIN 30 - Fuse 54 12v+
PIN 85 - DME x60004 PIN10
PIN 87 - Fuel pump White/blue wire
PIN 86 - Voltage supply Terminal 87


so i'm scratching my head trying to understand 3. things

1. what is the fuel pump relay doing wired that way
2. what is terminal 87 so i can wire my new relay in a similar fashion
3. where would you put the diode? PIN 30, 85, 87 or 86? I assume on 85 between relay and DME x60004 pin 10?

[nextelbuddy]

Currently i took a spare BMW 30 amp 4 pin orange/green relay socket and relay and used that for the scavenge pump. I wired it like this:

PIN 30 - 12 volt terminal under hood (has 30 amp fuse inline)
PIN 85 - Ground post under hood
PIN 87 - 12 volt Power wire to scavenge pump under car (has inline 20 amp fuse inline)
PIN 86 - (I thought was trigger wire) was going to use this from PIN 10 x60004


i looked at k96 Fuel pump relay pin out again this morning and can now see they have if different than i thought.

PIN 30 - Fuse 54 12v+
PIN 85 - DME x60004 PIN10
PIN 87 - Fuel pump White/blue wire
PIN 86 - Voltage supply Terminal 87


so i'm scratching my head trying to understand 3. things

1. what is the fuel pump relay doing wired that way
2. what is terminal 87 so i can wire my new relay in a similar fashion
3. where would you put the diode? PIN 30, 85, 87 or 86? I assume on 85 between relay and DME x60004 pin 10?

ok i understand more now.

Voltage supply Terminal 87 IS the switched 12 volt source aka trigger. so instead of grounding the relay on pin 85, they run the pin 85 ground wire to the DME and the relay is setup for negative trigger?


in any event i suppose its not too hard to emulate this now with my second relay. I will give this a try:

PIN 30 - 12 volt terminal under hood (has 30 amp fuse inline)
PIN 85 - PIN 10 x60004 DME
PIN 87 - 12 volt Power wire to scavenge pump under car (has inline 20 amp fuse inline)
PIN 86 - Ignition II 12 volt switched source (ill look for a yellow wire red stripe in DME box to tie into)

is the Diode absolutely necessary? does BMW use one in their setup? there are no hardware stores around here that sell circuits so i would have to order one and i dont even know what size i would order

[ZiMMie]

Good.

If the relay is setup properly your shouldn't need a diode.

I'd still install one if it was my car.

[S54B32]

In my opinion it‘s absolut unnecessary to use a diode in this position.

if you really want to protect the ECU output from inductive current (from de-energizing the coil in the relay) use a flyback diode or a relay with integrated flyback diode like Bosch 0 332 209 152

[gixxer]

Hello, my current application includes running E85 tunes with 1000cc injectors and upgraded fuel pump (525LPH Walbro Hellcat). After the initial install, already blown the 20A stock fuse with upgraded fuel pump once. As a temporary stop gap, replaced 20A with 40A. We are doing wiring upgrade with 10 gauges, to bypass the EKP by adding separate 40A relay for the fuel pump, with separate fuse. And go back to 20A on the EKP fuse.

Was wondering if adding a separate (Bosch) relay (driven by EKP signal) for fuel pump will add noticeable lag/delay?

And if there will be noticeable (clicking) relay sounds from the extra relay, assuming located where the EKP is?

Thanks.