Car not starting, seems to be fuel related.

[Makaveli2k]

Powerplant: Non Vanos M50

Symptoms:
Car won't run. It will crank and then catch but won't run. Even when pedal is pressed down, it will just die like immediately, nano seconds after it catchs. It would stay alive for a second or two if we sprayed some quick-start into the afm but after that it would die.

Before this the car would run fine on initial start up and run fine for a little while maybe a couple of minutes and then it would start to missfire bad

Tried remedies and thought processes:

First thought it was the fuel relay - Changed, same problem

Then moved on to the fuel pump thought it was bad, changed it. Same thing.
(Tested the fuel pump, in position two it would not turn on, it would only start to spin or hum while cranking)

http://www.realoem.com/bmw/diagrams/k/t/22.png

Checked over the intake manifold for vacuum leaks, I know number 9 seems to cause people problems a bit but it was connected and in quite snuggly.

There is also a hose that connects to the intake boot underneath it, I also checked that to make sure it was in. Still nothing.

[Bo525i]

Fuel filter, battery charge, idle valve?

[Makaveli2k]

Battery is good, Fuel filter will get done on Monday that was one of my thoughts as well.

Idle control valve, I think with that not working it should at least be able to run with me giving it gas no?

[whiskychaser]

Lets assume you are not parked on a hill and have low fuel level;). The pump only runs when you are cranking or if the engine is running. Jumper the relay and check your fuel pressure. Easiest place to T in would be at item 15:
http://www.realoem.com/bmw/showparts.do?model=HD68&mospid=47405&btnr=13_0347&hg=13&fg=15
Put a rag underneath when you put the T in as the rail will empty itself. Pressure should be about 50psi. Pull the jumper and check the gauge doesnt drop too

[Makaveli2k]

Thanks Whiskychaser. I'll try that. So pretty much I would assume that negates the crank position sensor as I am getting the fuel pump coming on at the proper times.

Suppose I'm not getting enough pressure, what would likely be the cause of that and what would be some remedies to the situation?

[632 Regal]

Even with low pressure it should start, I would venture CPS first in this situation.


Thanks Whiskychaser. I'll try that. So pretty much I would assume that negates the crank position sensor as I am getting the fuel pump coming on at the proper times.

Suppose I'm not getting enough pressure, what would likely be the cause of that and what would be some remedies to the situation?

[genphreak]

I thought the FP only comes on when the ECU says so, which is only at cranking position or when the engine is turning (ie the lower of the two front sensors, the CPS). Not sure if the Cam sensor has any hand in causing this trouble, but if causing trouble the ECU would not co-ordinate 12V feed to the FP - or give no spark.

I think they use an 'activity check' to govern the FP mainly to ensure the FP shuts off after an accident...

Have you also checked that you have spark and that the FPR vacuum line is OK? It is right up the back of the inlet manifold and only a small person's hand can really get to both ends- one on the inner side of the manifold and the other on the FPR. I managed it but my hands hardly a gorilla's and it was painful. Inspect and perhaps replace, air leak in there causes the wrong, or no FP.

The other end of the ICV line to number 9 (yea number 9 is a freak. Mine gives me little confidence of a seal either, have replaced 3 times already).

[Tiger]

Crank Position Sensor!!!

[Makaveli2k]

I thought the FP only comes on when the ECU says so, which is only at cranking position or when the engine is turning (ie the lower of the two front sensors, the CPS). Not sure if the Cam sensor has any hand in causing this trouble, but if causing trouble the ECU would not co-ordinate 12V feed to the FP - or give no spark.

This is what I thought, if it was a bad crank position, than I would have no power at the fuel pump, or no spark. But I clearly have both of those because the car isn't just Cranking. It's cranking and then runs/catchs, but instantly dies with like no pause in between.

I can't hold the gas to keep it running it will still die instantly.

??????

[Tiger]

What car do you have?

Fuel pressure regulator is possible too.

[Makaveli2k]

92 525iTm

Also I don't know if this helps but also while hotwiring the fuel pump and trying to crank the motor it wouldn't start.

[whiskychaser]

92 525iTm

Also I don't know if this helps but also while hotwiring the fuel pump and trying to crank the motor it wouldn't start.
That really only proves the relay isnt the problem. While it seems to be trying to start, its probably best to confirm the basics:
Remove a coil pack but leave it connected. Stick a plug in the end and ground the plug's threads. See if you get a consistent spark when cranking.
(This isnt infallible as a plug will spark more easily in free air but its a good guide)
With the relay pins jumpered, you should be able to hear fuel coursing round the pipes. But you need to check the pressure. And that it doesnt drop away.
I dont know if you can do the stomp test, but if so are there any codes?
HTH

[Tiger]

I still have to say it is the CPS. Change this first and see what happens.

[Makaveli2k]

Threw in another ECU and it started up.

[Tiger]

That's really rare for computer to go bad... 2% chance...

[whiskychaser]

Threw in another ECU and it started up.

Great you got it sorted:) How did you decide the old ECU was duff?

[Makaveli2k]

Just a hunch, something I thought I'd try.

was thinking back and all these problems started after I swapped used battery's.

didn't even change the crank or cam sensor.

I'd say mostly by fluke actually.

[genphreak]

sweeet, a thread witha happy ending... :) keep it up!