MembersPage/BmwMFiftyTwoMainRelayPrelling (2019-10-06 12:42:27)

Old subpage of MembersPage/BmwMFiftyTwoMainRelay ( MembersPage/BmwMFiftyTwo )

See MembersPage/BmwMFiftyTwoMainRelayTesting


This page is old, obsolete (historical):

investigation when EC36/16 (=p259/ch1) flyback was connected to EC36/25 (not EC36/23).


Maybe M52/9 fuel consumption output can cause damage to p259 chip ?


OLD: Prelling - solved by adding diode, anode=ec36/25 >| cathode = mot88/65 cam sensor 12V (BMW88/54 left open)

The strange thing:


Historical, only for the curious

(some confirmation, notes from install measurements would be nice; and would allow better cleanup).

We received a report of some relay prelling (when ignition off) that we cannot reproduce.

What should be hooked to the mot88 (which pin) to simulate the "ignition off" state ?

  • The flyback=mot88/87 (not pin54 in the xls beware, that is cam sensor +12V!) in the car also comes from the main relay but could possibly be moved to a constant 12V (pin26) instead to solve this?
  • good find: apparently the mot88/54 = mot88/49 (12V connection wire) inside the ECU is simply not needed, if the mot88/54 is supplied from the harness (weird, why is it connected back to the ECU at all ?)
  • Can a failed diode in the relay cause this?
  • possible, but more likely the mot88/54 cam12V seems to be unnecessary from the ECU if the harness feeds 12V there (via main relay) anyway

OEM wiring information here

http://www.gbnetwork.co.uk/bmw/ftp/etm_e36_1998final.zip

Page 108 shows that flyback 12V mot88/87 = mot88/54 cam12V in the harness so how that same connection can cause any problem in the ECU ?


The bold, or last 2 are suspect to cause prelling, especially if switched 12V (ECU main supply) is connected to cam12V in the harness

New Tests

No prelling at all. ECU does not power up.

If ECU forced ON with mot88/49 = 12V than ECU turns on, with minor 0.4sec delay the main relay turns on and no prelling: everything seem perfect.

Maybe the BMW has some very low resistance relay

Proposal:


Dave suggests:

The problem with the PNP relay prelling is caused by the

v3.8b

p259 diode >| mot88/87=EC36/23

not connected to EC36/25 (#15) inside the ECU.

Somehow mot88/54 is (suspected) involved in creating the path...

Actually, perhaps the main relay itself connected the #15 to injector supply, EC36/23, and possibly causes inability to turn off main relay ? (reproducing failed because of some relay differences ?)


FP relay solenoid powered from node15 ( = M52/87 = M52/54 DME relay out), see p112 and p108

NOT from node30 (VBATT), good. So the FP and DME relay are in series (the fuelpump current goes across both).


This page is obsolete