Bmw wiring

[timmy325is]

Thanks I'll try that

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[grom_e30]

that should cause the dme relay to power on with the key so you should get 12v to the injectors the icv fuel pump relay and so on. you should also get 12v on pin 54 that's the 12v supply you want to power the ms from, not the green wire on 56

[timmy325is]

I tried that. The relay clicks but still no fp. I read that Fidle does the same thing as that transistor combo I just tried. I get 12v to the injectors

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[grom_e30]

so are you getting 12v on the red + white wire on the fuel pump relay now?

[timmy325is]

No I'm getting 1.8v on the red& white of the fp. And the brown relay wire has 12v

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[grom_e30]

on the fuel pump relay:

pin 30 on the relay should be a red wire constant 12v
pin 87 power to the pump green and violet
pin 86 red and white switch live powered by the dme relay
pin 85 brown and green signal wire pin 1 on motronic connector.

if you remove the relay you should have 12v on pin 30, and an ignition 12v on pin 85. if that checks out put the relay back in and with your megasquirt disconnected try grounding the brown and green wire to see if the pump runs.

[timmy325is]

The pump runs when I jump the relay

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[grom_e30]

what do mean by jumping the relay? connecting pins 30+87 together?

[timmy325is]

Grounding pin 85

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[grom_e30]

ah ok so sounds like the wiring it there maybe look at the ecu next

[timmy325is]

ah ok so sounds like the wiring it there maybe look at the ecu next

I've got continuity between pins on Q2. That's never good... that could be my problem

on the fuel pump relay:

pin 30 on the relay should be a red wire constant 12v
pin 87 power to the pump green and violet
pin 86 red and white switch live powered by the dme relay
pin 85 brown and green signal wire pin 1 on motronic connector.

if you remove the relay you should have 12v on pin 30, and an ignition 12v on pin 85. if that checks out put the relay back in and with your megasquirt disconnected try grounding the brown and green wire to see if the pump runs.

so are you getting 12v on the red + white wire on the fuel pump relay now?

No I'm getting 1.8v on the red& white of the fp. And the brown relay wire has 12v

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[93supercoupe]

Grom is doing a great job here, but there is a much easier way to get the main relay to switch.

Hook pin 54 from the car side to your 12v on your MS

Take a normal relay, and take pin 56 on the dme and hook it pin 85 of the relay.
Pin 86 of the relay goes to ground
Take pin 27 of the dme goes to relay pin 30
Relay pin 87 also goes to ground.


Once you switch the main relay, the FP and O2 relay will switch with it. At that point, your coils, injectors, vanos should have 12v.

First tooth agle is 84 on all US 24v engines (for the most part, except the non vanos early 92's)

Ive attached a little document ive done for these cars. Intead of the tranisotr setup you will see pictured, i use a relay. Ive done about 10 of these so far like this and they work fine.


Again, not taking anything away from Grom as he has given very good info in here.

[grom_e30]

funnily enough i originally used a relay to provide ground to turn the dme relay on..... but i found that on a low battery during cranking the voltage droop would sometimes cause the relay to turn off cutting power to the ecu and injectors ect and made starting the car difficult. the transistor requires less voltage and solved that issue.

[93supercoupe]

funnily enough i originally used a relay to provide ground to turn the dme relay on..... but i found that on a low battery during cranking the voltage droop would sometimes cause the relay to turn off cutting power to the ecu and injectors ect and made starting the car difficult. the transistor requires less voltage and solved that issue.

Ive heard that before but have never seen it myself. Even in New England winters

[timmy325is]

Thanks to both of u for all the great info! I'll try that tonight. This m50 is non vanos pretty sure it's the same 1st tooth angle.

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[timmy325is]

Didn't see the attached document tho

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[93supercoupe]

it wouldnt allow me to attach. Shoot me a PM with your email and ill send it over.

[timmy325is]

Huge Props- 93supercoupe and Grom for being stand up guys and sharing your knowledge. I appreciate everything... merry Christmas!!! That's what these pages are about.

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[93supercoupe]

Just pay it forward man!

Good luck and merry Xmas