M20B25 - fuel doesnt start

[DennisJ]

Hi,

I need some help.

My fuel pump doesnt start when turning the key. I got the pump startet by using a wire between 30 and 87 at the fuel relay, so i asumed the relay was done. I have replaced the relay, but still no fuel when i turn the Key.

Help - what to do?

Regards
Dennis - Denmark


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[E30-325iS]

The ECU needs to see pulses comming from the CPS before it will turn the fuel pump on. Check the CPS, the specs are in the Bentley or swap it with a known working one.

[DennisJ]

Sorry - but what is CPS? :) Im Danish - so i do not know all the technical words. :)


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[dnguyen1963]

Crank Position Sensor. On the passenger side, bottom of the engine, toward the front of the car, you should see a tooth wheel. On top of the wheel you should see a little sensor...that is the CPS. Google CPS and E30 and you'll spend days reading about this topic.

[DennisJ]

Maybe i am not that smart, but i cant find the sensor. The "tooth wheel" is not a thooth wheel, but with a blank outer


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[DennisJ]

I found this that was laying on top of the valve cover. What is that?


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[dnguyen1963]

[DennisJ]

I dont have it. But i have this one, which wasnt mounted at the flywheel. I have mounted in a clip where it fits. But it still doesnt start.


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[e30onBBSs]

Hey this thread got me thinking that maybe I have a cps problem too. In the Bentely the instructions to test it are unclear, which of the terminals should we test resistance for?

[DennisJ]

M20B25 - fuel doesnt start

I found them at the gearbox. I have tested and cleaned the both of them and mounted them again. The fuel pump still doesnt start when turning the Key.

What to do?


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[MisterMiniS]

Hey this thread got me thinking that maybe I have a cps problem too. In the Bentely the instructions to test it are unclear, which of the terminals should we test resistance for?

Hey, just checked this the other day. I cannot remember the orientation, but it is the middle one and one of the outsides. I got that from the Bentley, so look at it again. It does specify indirectly. I can check when I get home. Also, the Ohm range specified in the Bentley is pretty accurate, so anything outside the range is likely bad.

[e30onBBSs]

Hey, just checked this the other day. I cannot remember the orientation, but it is the middle one and one of the outsides. I got that from the Bentley, so look at it again. It does specify indirectly. I can check when I get home. Also, the Ohm range specified in the Bentley is pretty accurate, so anything outside the range is likely bad.

Thanks man I will check again and see if I can figure it out. Get back to us if you find it again!
Ben

[101]

DennisJ:

It looks like you might have an "eta" engine in your car, or at least your engine management system appears to be the Motronic 1.0 version. I'm not sure of the engine versions that were available in Europe, but all 325i cars in the good old US of A have the later Motronic system with the single crankshaft position sensor at the front of the engine like dnguyen1963's picture shows it.

Motronic 1.0 (which it appears that you have) has the small front sensor that clips into a bracket above the crankshaft on the front of the engine. That wire leads to the diagnostic connector and nowhere else. Instead, there are two crank position sensors on the driver's side of the transmission bell housing. One of those is a "reference" sensor that senses a pin on the flywheel to identify top dead center of the crankshaft. The other sensor detects the speed of the crankshaft. A failure of either can cause a no-start condition. The pin can also come off the flywheel and cause a "no'start" as well.

I'd recommend the following:

1) remove one of those bell housing sensors and have someone else slowly turn the engine by hand so you can see if the reference pin is still installed on the flywheel.

2) If the pin on the flywheel is present, and both reference sensors test OK, check if you have spark while the engine is cranking. If you have spark, the engine control computer is getting the crankshaft position information.

3) Run the diagnostic checks at the engine computer connector as specified in the Bentley manual.

Keep us posted as to what you find!

[DennisJ]

No spark and sensors test 99x ohms. I really dont know what happens here. All i have done after i parked it was to install a radio and a set of speakers. The battery went dead the day i did it. I didnt try to start the car that day, i tried to start it a week or so later, and then i wouldnt start.


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[ahrensNW]

So, how many fuses did you blow when you put your stereo in. I'm assuming you already checked those???