1989 bmw 325i no Injector pulse

10

Asked by Oct 04, 2013 at 10:00 PM about the 1989 BMW 3 Series 325i Sedan RWD

Question type: Maintenance & Repair

Car will run good all day on ether but will not start without .Obcc gives fault code 1252 - Fuel Injector #2 (single or group). Crank sensor was replaced, main relay seems ok, feul presure good, just no pulse going to the injectors. Any ideas ? I'm at a lose, mechanic couldn't figure it out either..

7 Answers

118,635

Recheck all of the ECM powers and grounds, remember that the injectors are triggered by a negative pulse, so one side is battery voltage and the other side is the trigger signal negative pulse, so usually if you loose the injector pulse then it is most likely the computer but make sure you have all of the necessary power and ground pathways, a service manual with wiring diagrams will really help with this.

10

all the grounds have been checked, they are good. Mechanic said he checked the computer it seems to be ok, only thing I can think is maybe the chip blew, I don't think he pulled the computer.

118,635

He needs to check for the injector pulse at the ECM, if it is there and not at the injectors then a wiring problem needs to be sorted out, if it is not at the ECM then the problem is in the ECM.

1 people found this helpful.
10

can you tell me the procedure for checking injector pulse at the ECM?

1 people found this helpful.
118,635

You need to find the injector driver wires coming out of the ECM, a wiring diagram should help with the color and location, once you locate the wires then using a low draw test light, led is preferable or a "noid light" this will prevent and injector driver damage due to high current draw, tap into the driver wire with one end of the light and put the other on a positive power source, crank the engine, the light should flash rapidly, if it doesn't then the usually the ECM needs replaced or rebuilt. If it does then you need to trace out the wiring until you find the broken circuits. Of course all of this is assuming that all of the power and ground pathways and sensors have been check and found to be good.

10

thanks for the info I'll besure to check

10

I found another ECM, confirmed good, and installed it .. still nothing. Any other ideas?

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