94' 530i - Hmmmmm?

[Tiger]

Alarm unit interfering? Pull one or the other harness off the alarm unit and see if the car will start.

[blackbird80k]

Hi Guys,

94 530i Canadian car, second owner.
Starter turns well, slight fuel smell, pulled plugs - wet, spark and battery good, fuses good. CPS replaced, cam position sensor replaced. Replaced DME Relay, fuel pump relay, fuel pump works, battery was disconnected for a period, no codes present other than a stomp test that seems to indicate 1,1,1,1.
Compression good. DME replaced. Damn! Still won't start. Turns over well. Mass Air Flow sensor good.

Symptoms - Car was running well, no smoke, smooth, started it one day...ran, then stopped...tried to start it, wouldn't start...came back next day and started it. Wouldn't start after that.

Wiring Diagram indicates that pin 30 of the fuel pump relay wiring should be battery hot at all times...Mine is not. Suspect wiring diagram error, but it also makes sense that the wire should be hot because that is what turns the fuel pump on when required once the relay contact is made.

This of course would not have changed from the time between the car running and the car not starting, so I do believe the wiring in the car is correct, despite what the diagram says.

Any thoughts out there Guru(s)?

Thanks

[blackbird80k]

Alarm unit interfering? Pull one or the other harness off the alarm unit and see if the car will start.

I'll try that and get back to the thread. Won't be until tomorrow though. Thank you.

[bubba966]

If the alarm is a problem it won't even turn the engine over.

I had a similar-ish problem on a '95 515iT that turned out to be a really bad vacuum leak as a large (hidden) vacuum line had come out since the retaining clip on the connector had broke off.

Make sure all of your vacuum lines are properly connected and aren't leaking. Also check the oil fill cap to make sure it's not a source of a vacuum leak as well.

[whiskychaser]

Replaced DME Relay, fuel pump relay, fuel pump works
Thanks

Are you actually getting fuel at the rail and have you got 51psi pressure?

[blackbird80k]

Are you actually getting fuel at the rail and have you got 51psi pressure?

I've got to get a guage that goes high enough. I'll recheck for px at the rail and pump output. Fuel smell is there, but I'll have to confirm px. Pump is running via a direct "power to pump" check and fuel pump relay is clicking when ign is turned to start. 12v at pin 30 of the fuel pump relay. I'll check px on Saturday and see how that goes.

[blackbird80k]

I've got to get a guage that goes high enough. I'll recheck for px at the rail and pump output. Fuel smell is there, but I'll have to confirm px. Pump is running via a direct "power to pump" check and fuel pump relay is clicking when ign is turned to start. 12v at pin 30 of the fuel pump relay. I'll check px on Saturday and see how that goes.

Did the fuel px check and found it to be 60 psi, blew out the return line finding no restrictions, indicating the fuel px regulator was defective - Replaced with new and tested system again and found it within spec at 51 psi exactly. During that process, I also put in my new Bosch 4 electrode platinum/iridium plugs. Tried to start the car, and it was the closest it had come to starting. Couple of "almost catches" but that was it.

Performed compresion check and had favourable numbers of 115 to 123 for all cylinders, despite probably all the oil having washed away with all the excessive fuel starting attempts, so the engine should be tight when it does start.

Fuel, air, and spark...That's all it takes, not a difficult equation, but one that eludes me up to this point!

[blackbird80k]

Oh my! O2 sensor probe. Didn't check it because it had been changed by the previous owner a year ago. Not at an approved shop. WOnder if the basta#**ds installed a used one?

Oh my! first time driving the car....WOW! WOW
I can't say that loud enough! Whoo Hah!

I'm a convert.