M42club.com - Home of the BMW E30/E36 318i/iS

DISCUSSION => Engine + Driveline => Topic started by: AlecB on May 27, 2018, 11:50:35 PM

Title: Cranks But Won't Start—Fried O2 Sensor and Main Relay
Post by: AlecB on May 27, 2018, 11:50:35 PM

My '91 died on the freeway a few weeks ago, and my mechanic just gave up. Here's everything I know:

It cranks but doesn't start. According to my mechanic, the O2 sensor and main relay were both fried. He also says that it fried the DME, but I don't think he's removed it or anything, and when I took it out it the circuit board looks totally clean.

Mechanic says it's not the fuel pump or crankshaft sensor, so I've ruled those out. He says it's a short in the engine wiring, as you can hear a brief click when you plug in a good main relay. I've removed the wiring harness, wrapped a nasty bare spot on the large alternator wire, and replaced it all, but no progress. I'm lost.

Thanks,
Alec

Title: Re: Cranks But Won't Start—Fried O2 Sensor and Main Relay
Post by: Jaredmac11 on June 01, 2018, 11:08:40 PM

I would say cracked cam.  Open up the valve cover and verify.  Takes 10 mins