DME Relay Issues

[Chade7320]

I have a 325e, it will start no problem if I jump 30 to both 87s but when I put the relay back in it won't start. I replaced the relay but it still won't start unless I jump it. It turns over but won't fire, it get spark but no fuel without jumping it.

[jlevie]

Did you get the correct relay? It should have 5 pins.

[Chade7320]

Yes this one has the same pins and matches the locations of the old one.

[jlevie]

The only things I can think of is that the replacement relay is bad or that pin 87a isn't making a good connection to the relay socket. If I recall correctly, 87a supplies power to the fuel pump relay. You can check that in the wiring diagrams at http://wedophones.com/BMWManualsLead.htm

[Chade7320]

Maybe so, will have to buy another one and see I guess

[Chade7320]

Is that the only thing it could be? There's nothing else that jumping the relay bypasses that could be keeping the fuel pump from activating?

[jlevie]

Given the fact that the engine will run if you apply power to pins 87 & 87a of the main relay from pin 30 and that you have spark but no fuel with the relay in place, I can't think of anything else it could be.

[Chade7320]

I tried another relay, and no luck. However, If I jump just the 30 to the top 87 and put the relay in it will run. I am stumped.

[jlevie]

All I can think of is a bad relay socket.

[RobDog]

Does your main relay click when you turn on the ignition? If so have someone crank the engine while you listen and feel the main relay. If the main relay wildly clicks on and off while cranking then your engine speed sensor is bad. The engine speed sensor is the sensor in the trans. bell housing. Of the 2 sensor in the bell housing it is the one closes to the engine and the highest. This sensor is responsible for seeing a rotating engine and keeping the main relay closed.

Also if you have a 13 button OBC try bypassing the OBC relay

[jlevie]

The DME relay has no relationship to the engine timing sensors. When the DME sees the "Start" signal from the ignition it turns on the main relay.

In this case it sounds like the main relay is operating, but no power is getting from the relay socket to the fuel pump relay with the relay in place.