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Old 05-12-2013, 07:37 AM
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540iman 540iman is offline
resident, old fart
Location: N.W. Indiana
Join Date: Sep 2008
Posts: 1,873
Mein Auto: 2002 540i sport
Just for kicks (I'm an electronics tech) I removed relay completely on my 2002 and 2000 540s. As anyone can see, the wire from fuse #107 is solid red-not red with black or yellow or anything but SOLID RED. It leads from fuse #107 to terminal 30 on the socket and terminal 30 on the relay, btw. Terminal #30 has a large red wire leading to it and has 12VDC with lots of current handling capacity. Cn90s schematic and my car are exactly alike. Terminal 30 of the relay is not the center of the SPDT relay, but nonetheless has 12 VDC at ALL times. Terminal 87 is the lead to the pump and when 12 volts is applied to the relay coil through terminals 85 and 86, the relay energizes which puts terminal 87 to terminal 30 and energizes the pump. When the DME says "enough" the coil drops out and terminal 87a is the NC contact and grounds the pump. Terminal 87 in the NO contact and gets 12 volts from terminal 30 which is always hot because it is fed from fuse 107. My relay and my relay base and the schematic CN posted all agree on my cars. Do not run a jumper between terminal 30 and terminal 87 as you will blow fuse #107 as the pump power lead is grounded because it is still connected to ground through pin 87a. If you want to force the pump to run, take the connector off the pump. then ground the appropriate terminal of pump and run a lead from pin 30 to the pump. My cars agree entirely in all respects to the relay, the relay base, and the schematic. I would let car sit in garage overnight and then have multimeter connected to pump connector and see if pump is getting 12 volts. I would then go from there.

I have had to replace 2 saps, valves, hoses, fuse and relay and one car took PowerChips software to over-ride CBU issue in M5 heads.

Last edited by 540iman; 05-12-2013 at 08:28 AM.
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