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  1. #1
    ///ARI
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    HELP... 745i , fuel pump relay doesnt Turn on.

    I dont understand whats wrong. The fuel pump relay itself is good, but it gets no power. The main relay is fine and turns on. when i jump the #87 terminal with B+ the fuel flows BUT the car still doen't start. WHAT"S GOING ON. Someone Please help. I'm in Bayside Queens New York, Mabey someone close by is nice enough to come over and give me a hand. Thanks Guys.


  2. #2
    ///ARI
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    SOMEONE PLEASE LOOK AND HELP!!!

    I really want to get this car moving again<p><i><br>I dont understand whats wrong. The fuel pump relay itself is good, but it gets no power. The main relay is fine and turns on. when i jump the #87 terminal with B+ the fuel flows BUT the car still doen't start. WHAT"S GOING ON. Someone Please help. I'm in Bayside Queens New York, Mabey someone close by is nice enough to come over and give me a hand. Thanks Guys.<p></i><br>

  3. #3
    Callan
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    Re: SOMEONE PLEASE LOOK AND HELP!!!

    Normally BMW wires their fuel pump circuiton the older Sevens like this. The Main relay feeds the fuel pump relay.<br>The Control unit grounds the fuel pump relay to run the pump. If you have power to the fuel pump relay on the 2 power pins, #30 and probably #86, then you need to check the ground pin, usually pin #85. The wire color usually should be a brown wire with a color tracing around it. This is the wire that is grounded by the DME, which in your case should be the monster unit that has both the trans and the Fuel injection all in one. larger unit than usual.<p>The output pin out of the fuel pump relay should be a green/purple wire[pin #87] If you have all the inputs, main power,control power, and switched ground, then it sounds like just the relay is bad if you can jump the relay and make the car run.

  4. #4
    Callan
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    Re: More things to check, like spark

    OK, things as I understand them, you can jump the fuel pump relay and hear the pump, but did you take a inlet hose off and see if you have any fuel coming out of the line when you jump the relay.<p>Next, if the fuel is getting to the injectors,do you have any spark out of the distr. cap or at the coil wire. Lift the boot up a bit , hold it with something that doesn't conduct electricity, and have a friend crank the car over.<br>If you see and hear a strong spark at the ign.coil, then you just eliminated the 2 flywheel sensors as a possible source of not starting.<p>If you DON'T have any spark, then you have to check the following items that all tie into that side of the engine controls.<br>Both flywheel sensors, should have about 1000ohms of resistance at their 3pin connectors[only 2 of the 3 pins will give you a reading, one is a shielded ground] usually at the back of the intake manifold on a silver bracket, next to each other.]<p>Pick-up point on the flywheel, most BMW autos have a little "arm" welded to the face of the flywheel to act as a trigger point for the rear mounted sensor which is the reference sensor.<br>These arms fall off, the weld breaks etc. Slowly spin the trans torque converter around with a screwdriver after taking the plastic screen on the bottom of the trans bell housing off[they just pop out] to see if that arm is still there.<p>Possible bad ign. coil, use an ohm meter to check it. or, swap with a new one.<p>Bad coil wire going from the coil to the distr. cap. a open wire here can cause the DME[Motronic] control unit to fry part of its circuit board.<p>If you still have the factory OBC alarm board/relay unit installed in the car, it provides the control power to the main relay via a relay inside the OBc relay box. This relay can act up on its points, which prevents ign. switch power from going to the main relay when you crank the car. Normally the relay is at "rest". so power should always flow with the key on , and no "Code" set in the OBC.<br>Check the green or green/red wire at the main relay with the ign. key on to see if you're getting power. If you've got power, then the OBC relay/box should be OK and you've got to look elsewhere. Let me know, maybe we can narrow it down with some more info after testing.<p>Last question, does the engine have the cold start injector at the bottom of the intake manifold? Most 745i's that I've worked on have about the same layout as US spec cars for the same years of production, just more parts that do more things like work with the turbo control or they have a different idle system set-up.<p>Is the cold start injector working when you crank the engine over?

  5. #5
    ///ARI
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    no spark ,,, coil , sensors good...ECU ???

    I checked everything. Still no spark and no ground signal to fuel pump relay.<br>i check all resistances and voltage on the coil. Checks out fine.<br>I checked the resistance of the 2 sensors. they are good too. I looked for a little arm on the fly wheel that there too.<br>Main relay is good and is getting power from both the big red wire and thinner green wire.<br>Whats left...<br>I thinks it's the ECU **OR** I remeber when i had a similar problem on my e30 and it turned out to be the Fused Link. do E23 have this? but since the main relay and fuel pump relay are both getting power i think it's the DME

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    did u find out why the fuel relay wasnt being grounded
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