Fuel pump/starting problem for the electricians and experts

[azale]

yes, I replaced the DME with a new unit $17, fuel pump relay was $15.

I also replaced the fuse in my dad's volt meter when measuring the amps going through the relay . . . there are at least five amps moving through just fine

Bavarian BMW in Utica/Shelby Township want $114 to look at it but I have to tow it there.
The crankshaft sensor will be $95 if I need it.

[DanDombrowski]

I read somewhere a writeup on checking fuel pressure by doing that, and the guy ran the fuel into a 2 liter bottle. If you've ever sprayed a part with throttle body cleaner (or brake cleaner) and had the excess run into a plastic cup, you'll see why this makes me wary. Not saying its dangerous, but I think petroleum based products don't like plastic so much. In any event, mabye drain the gas into a glass bottle when you check for fuel?

Now, as far as your electrical problem...

When the key is turned, 86 is hot and is sending 12 volts through contact 85 which grounds out without a problem.

I don't like the way this sounds. I might be misinterpreting what you're saying, but nothing at 12V should short directly to ground.

You said you replaced the DME for $17, I assume you mean the DME relay. I've never really had a need to run a test to see if the DME had power by checking voltage, I guess if you're checking current running to it that would tell you (if you have the multimeter connected correctly). I would check for spark by pulling a spark plug. If the DME doesn't have power (or doesn't have all of its info, i.e. no cps, etc) it won't fire the plugs and injectors, right? Someone else can back me up or refute that one.

I would think that if the CPS were bad, or another sensor was keeping the DME from wanting the engine to run, you would get a check engine light. You never know though, the PO could have removed the bulb.

Have a check at the fuel flow rate, but I don't think thats it. If you look at the procedure for replacing the fuel filter, it says "pull the fuel pump fuse and let the car run till it stalls". You would think that if the system has pressure when you shut the engine off, and then go to restart it (without the fuel pump turning on), it should at least run and then die (not sure on that one either).

Also, check for spark and let us know whats up with that. Thats about the extent of my electrical expertise I can give you for now.

[azale]

The contacts I was referencing were specifically for the fuel pump relay (although the DME relay plug tests correctly as well, the only difference there is where the DME relay contacts 87 go, there are 2 87s, five prongs in all)

on the fuel pump relay, contact 86 comes from the DME relay or some type of switch (see here http://www.carsoft.ru/avtorepair/bmw....10/index.html) and 85 goes to the actual DME control unit. I just tested that contact 85 was grounded (I assume after it goes through the DME control unit.

The check engine light is definitely working but I may be reading the codes incorrectly, please see my first post. Also, when I press the reset button under the tach and trun the key and then release the button one line says "CODE.NR 0000" which I assume means no codes??

Tonight I will revert to the troubleshooting I use on my 1980 johne deere snowmobile but I fear the problem is deep inside the electronics.

[stevebuk]

Sounds like you should check the crank position sensor.

I currently have the same problem with my 520i, it was intermitent but now will not fire, cranks fine, fuel pump runs etc.

I've followed the cps cable from the sensor to up near the thermostat housing and behind the oil filter housing but then the cable disappears beneath the inlet manifold / near the alternator and so far I can't locate the connector. Perhaps it's easier from underneath the car?? Or maybe it's easier to check the signal at the ECU plug? anyone know the pin number?

[azale]

Does your fuel pump run when your turn the key? Mine doesn't.

Can you give me a clue where the CPS is? front of engine I hear. high/low? left right? Have you tested your sensor for resistance? everyone says look for 600 to 800 ohms, more than that and you need to get a new one.

Garlic, No, it doesn't ever start (for 2 weeks now, I'm afraid the battery is going to give out soon. BTW I removed the interior lighting fuse but I don't think that should affect anything.

[DanDombrowski]

The fuel pump should run for a few seconds when you turn the key on, then shut off.

I read over those diagrams, I don't think 85 goes to ground. I think its saying that when it has power (12V) from 86 AND 85, then it routes power from the battery to 87, which is the fuel pump. So 85 should not go to ground, but I could be wrong.

See if you can actually test one of the leads for the DME for voltage to see if its turning on, and do a fuel pressure/flow check.

[stevebuk]

I can't hear the pump when I turn on the ignition but I can if I bridge the relay connection - under normal conditions it runs very briefly to prime the system but then switches off until the engine fires.

CPS is about 10 o'clock at the side of the crankshaft pulley close to the teeth of the pulley, there's a picture on this forum somewhere but can't locate it at the moment. If there aren't any pulses from the CPS the car will not start so it's the logical thing to check after the fuel pump - just wish I could find the connector!!

[azale]

stevebuk, maybe we do have the same problem. http://www.carsoft.ru/avtorepair/bmw....10/index.html says that pins 78, 79 and 82 are for the crankshaft sensor and pin 52 may be important as well. But I don't know where that plug is. Is it the DME harness inside the passenger-side box? And what are we looking for resistance/votage between + and - or resistance to the ground? I'll mess around with it tonight.

Dan, I've tested leads to the DME successfully and it should be/is switching. I'll still check the pressure flow.

garlic, thanks for your help anyway.

[ryan roopnarine]

look at the front of the cylinder head. the cps sensor body is attached down near where timing marks would normally be. a wire runs up and along the front of the cylinder head. a plastic "retainer" held on with circlip type fastners is on the front of the cyl head too, the cable runs under there. follow it back under the intake manifold . the connector you are trying to get to may or may not be resting in a mounting bracket.

[stevebuk]

If you use a jumper lead to connect the fuel pump relay pins 30 & 87 (6 and 2) on the socket the pump should run continuously, if the car still doesn't star it will point to a different problem. You should hear the fuel hissing through the pressure regulator in the injector rail and near the wheel arch under the fuel filler.

I'm going to have another look under the inlet manifold tomorrow to see if I can locate the CPS connector, the CPS produces pulses around 0.5v if it's working.