1988 BMW 535i • 16,000 miles

Has no spark, injector pulse or fuel pump operating when trying to start the car.I have put on a secondhand crank sensor (from one that was running) and replaced the ECU 9under the bonnet beside the ABS ecu) because it had got water in it abe the circuit board had green corrosion on it. The fuel pump will work if I ground the brown and green wire from the ECU. So I tracked this wire to another ECU (under the dash on the passangers side) But it is for the auto gear box (Bosch 0260002050) could it cause this fault?Thanks: NOEL.
Noel Begley
March 25, 2012.

I am thinking you may want to look at the wireing harness and the elctrical connectors at the ECU.
If they were exposed to water and another ground helped the situation, the harness may have corrosion at the connectors or maybe a little more damage as far as damaged and corroded wories. It all depends where the water got to.
Try using PB Blaster or Electrical cleaner with a toothbrush at first and some fine emery paper if you see and corrosion.
You may have to replace some ends, Radio Shack is good for auto electrical terminals, because cleaning corodeded ones is hard and makes the fit loose.
Try that.
Remmebr, you can remove each wire from a connector by using a dental pick kit, which will come in handy for this job, to push in tabs that hold each terminal. It can then be pulled on gently and the terminal replaced and put back into the connector. Make sure it, "Snaps" back into place as you may have to make sure it connects by hand each thime you connect it.

I have replaced the ECU so all those conections are good. The water that got in went to the bottom of the box and corroded the board and the things at that end of it.
I am puzeled why I don't have any fuel pump opperation when I first turn on the key. I thought it may be the power supply to the ECU but I got a pin out of it and all the powers are there when they should be. There is a posability the ECU is a faulty one but it is suposed to have been tested before it was sent.
Or the connection for the crank sensor may be not good.
Your help is appreciated.

Noel Begley
Mar 26, 2012.
Have you checked the connections for the car's harness? They might have gotten corroded and are hard to tell if they are corroded unless you pull a wire/terminal out of the connector.
That can often be an issue in your situation that can even lead to the ECU getting shorted out.
ECU tests are hard to performa if they have any voltage signal required to do so. So, I would recommend letting the vendor test any questionable ECU that you purchased. It does happen. Just like a Computer a little stic shcok can make a circuity fail.
As far as the fuel pump thre should be a relay that actually starts to prime the pump when the key is in th, "ON" position before you even reach the, "START" position. It runs a second or 2 to prime the system and bring it up to pressure.
The relay is on the fuse/relay block and I sent you a diagram with its location.

Any luck Noel?

Dr. Hagerty
Oct 21, 2012.