Broke it then fixed it

The E28 has been running just fine lately, so I was tinkering around with some smaller projects this weekend.

Short version - the can ran just fine in the morning, disconnected the O2 sensor to check readings, and then it would crank but not start.

Long version
I was cleaning the car from underneath on Saturday (primarily near the steering box), trying to remove a bunch of grime and find a slow weep of power steering fluid. Then I got it back on the ground and went for a 10 minute drive. Came back and tested power to the auxiliary fan (it doesn’t come on with the AC on at all) with the car running, no power to the fan, so turned the car back off.


Then I was going to test the O2 sensor since it didn’t look great when I checked it earlier, so I disconnected it at the top of the engine near the firewall.

Set up the multimeter to test, and when I went to start the car and I got crank but no start. Ugh.

S what i started with troubleshooting with no change in result:

-Replaced both main and fuel relays with new ones (this is a common E28 failure point)
-Pulled the DME and put in my other one (known good and running when I pulled it out less than two months ago)
-Checked the fuel pump (put my hand on it while my wife tried starting; though cranking kind of shakes the entire car, pretty sure it was on)
-Checked fuel relay - #30 had 12V with the car off, got voltage on #85 when my wife tried to start


Also - both fuel pumps, filter, plugs, and distributor rotor are less than 6 months old. They were installed at the shop I purchased the car from.

So next step was to check for spark at the plugs. Had to wait a couple of days as life happened, so didn’t get back to it until last night.


Hooked up the spark checker and had my wife crank, no light so no spark.

Then a took a step back and just stared at it for a bit to think.

I was trying to check the O2 sensor readings when it wouldn’t start. What is that near the O2 sensor connector on top of the engine covered in tape?


Crank and speed sensor connectors (thanks Bentley!).

And is that how they are supposed to look?

Now, you might think that that was just a protective layer of electrical tape over perfectly good crank and speed sensor connectors, but you would be wrong. (No one thought that.)


This is what they looked like underneath...after I reconnected the sensor wires into the connector.


It started right up. Clearly I moved them in the wrong direction when disconnecting the O2 sensor.

I didn’t let it run long since I clearly need to protect those wires.

Ideas on how to do it the right way? I certainly don’t want to replace a good sensor just for the connector, but at the moment can’t think of a better solution than tape.


Can you use sugru in an engine compartment?  Never used it before but the website says it is good to 180C.

Then back to the small projects, which includes aforementioned O2 sensor checking and clutch slave cylinder replacement.

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