Tuesday, July 04, 2006

1996 BMW 328i 2.8L engine has no spark and no fuel, is it the ecm?

Car wiring question:

I own a 1996 328i BMW with 2.8L engine, which I bought from an auction lot and a week later quit on me. There is no spark and no injector signals, which to me points to a engine computer failure. The computer is over a thousand dollars and before I spend this kind of money, I want to get a second opinion from you. Thank you.

Vehicle wiring advice:

Before condemning your computer (ecm), I would like to explain to you how this engine ecm control works. This system has a power distribution box, which houses the ecm relay and fuel relay. The ecm supplies 12 volts to both ecm and fuel relays thru pins 6 and 8 of the power distribution box shown by the red wire. This red wire comes from B+ terminal of the ecm shown as pin 26. This ecm relay also gets a ground signal from the ecm at pin 73 of the ecm which comes from pin 4 of the relay. This pin 4 is the brown wire. Once you turn the key on, your ecm activates both relays.

If the ecm does not supplies 12 volts at pins 6 and 8 and also not supply ground voltage at pin 4 then you can say the ecm is no good.

These are what your engine electronic system also does:

The fuel pump relay powers all the injectors thru the red wire after being activated by the ecm when you turn the key on.

The ecm relay powers all the ignition coils thru the red wire coming ecm relay after being activated by the ecm.


This computer is known to fail cause by water damage after the cowl drain above it gets clogged with debris. To check, open the top cover of the ecm and check for presence of heat burns or corrosion.

Always disconnect the battery negative terminal when working with electrical components.


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