Alright, well so today the culmination of all of my hours of labor came together and...nothing. No start at least.

It turns over, and you can hear the compression, but no start. The tach doesn't bounce, I get oil pressure. I can hear the turbo coolant pump going. When we cranked it in order to test an injector harness wire, it backfired. Things I've checked:

- Put a test lamp to an injector harness - it was lit, and pulsed as I cranked.
- Checked for fuel in the rail, there was fuel there
- Put a voltmeter to the reference sensor, the needle was twitching as we tried to crank - not 2V but it was moving, I thought it was likely because it was just pulsing and I had an analog multimeter. I don't have an osciliscope to test it better.
- Pulled a spark plug and confirmed we're getting a spark on it

We also backed up the reference sensor stud in the flywheel just a tad thinking that perhaps the signal from that was weak.

Could this be caused by a vac leak? What about having the air flow meter plugged in but not installed? DME Relay? Bad ground?

Oh also, can the car start with the speed sensor unplugged?

 

The speed sensor has to be installed and plugged in. Install the AFM and can make the 3 wire jumper for the DME Relay.

Cheers,
Larry

 

When I hooked a test lamp to the injector harness, with the key in the ignition I got power on both of the wires to the injector. I also noticed that when I cranked, the bulb flashed?

So is the way that the injectors wires work is they are always on and cut out when the injector should fire?

 

Alright so today I hooked up the speed sensor, installed the AFM and jumpered the DME.

I did notice that I hear the fuel pump now, which I wasn't hearing before. So the DME relay could definitely be a problem.

The plastic housing on the plugs from my reference and speed sensor have deteriorated away, all that I have left is the three leads.

If I try one orientation of the reference/speed sensor plugs, I get a ton of backfires. If I try the other orientation (flip them upside down), I just get constant turning over no cranking at all.

 

A good sensor plug could never be installed upside down unless the connector housing is cracked. They are shaped to fit one way only. Any chance you have the speed and reference sensors reversed? If you heard the fuel pump when the relay is jumpered but it still won't start you have a sensor problem I bet.

 

I'm fairly certain I don't have the sensor reversed, I marked the cables when I had taken it apart.

The connector housing is basically non existent, which is why I can plug them in either way.

 

I would start with checking the Speed/Ref sensors and make sure the distributor cap is not 180deg off.

Check Eng Temp sensor, a short in the wiring could cause a no start.

Since you checked for a injectors pulse and it's tehre. Did you check to see if you have a spark.

 

I did check the #1 plug and I do get a spark.

How would I tell if the distributor cap is 180 deg off? The words are pointed up, and the wiring is right (as far as I can tell).

The problem I have is I can't figure out necessarily how to wire the speed/ref sensors because the plugs are gone. If I were to cut open the sleeve on the harness to see the color of the wires, would they be colored the same as the wires in the sleeve of the sensor itself?

 

Here you go:

 

Thanks for this, the only question I have is - since I can't see into the harness side plug, how will this help tell me the orientation?

 

Pull the sheathing back at the female connector (harness side) and look at the wire colors. If your male side connectors are shot you need to replace them with new sensors, the sensors for BMW E30's are the same (except longer wiring) but much cheaper than the the Porsche ones for some reason.

 

I looked around I think You mean the E30 M3? Yeah it looks the same.

Are they the same for both the speed and reference sensor?

 

Yes, they are the same. Pelican Parts.com, BMW Sensor part no. is 12-14-1-708-619-M14 and 618-M14 . 944online.com sells the sensor ends. Give them a call at 1-866-944-7883 and tell them what you need for the sensor plugs.

Cheers,
Larry

 

Yes, both sensors are the same. I sold my BMW so don't know about the M3 question. The BMW alternates are sold through Paragon. Sounds like you need the male end of the plug for the sensor and no one sells those as far as I know.

Reference/Speed sensors