MyE28.com

Longtime lurker here. '88 535i, 93,000 miles. I am about at the end of my rope with this car. I will walk you through the timeline of what has been happening so someone can help me pinpoint the problem:

Early December of last year: Stalled on a highway offramp. Able to throw it back into gear and get restarted. Made it home. When I looked around the engine bay I noticed that the crankshaft position sensor plugs were disintegrating and falling out. Ordered two new sensors. Replaced with Facet brand sensors and car started right up.

December 17: Car died while idling in my driveway. Tach would randomly bounce up to 3,000 while trying to restart. Figured new Crank Pos Sensors were defective. Ordered two FAE brand ones. Plugged them in and car still did not start. Replaced main and fuel pump relays. (Replaced both fuel pumps as well for good measure). Car started right up.

December 21: Car died while idling at a stoplight. Nice man helped me push it out of traffic. Close enough to home so I could assemble a rescue mission. Towed car home with my truck. I then read up on how the 059 ECU solder joints can crack and cause intermittent stalling. So, Christmas Eve I took apart the ECU and resoldered the trouble-prone joints. Plugged it in and the car started right up. I had no more issues until last weekend. 

Last weekend: Drove to gas station near my house. Car would not restart after refueling. Plugged in remanufactured ECU I got from online. Nothing. Towed it home (again with my truck since I was close enough to home). Tired bypassing the OBC relay. Nothing. Cranks and cranks but no start. 

This weekend: cleaned C101 connector and relay terminals. Try to start. Still cranks but no start. I then tried cranking it again and jerked the wheel to the right--Car fires right up and idles smoothly! I let it warm up and then cut it off. Car will not restart--just cranks. Replace ignition switch. No change. Replace coil--no change.

Where does this leave me? I don't possibly know what else could be causing this!

Commenting to get you a bump. Good work so far, interesting that the work you did "fixed" the issue temporarily. I wonder if these could have been separate issues that coincidently happened around the same time. Surprised the experts haven't chimed in. Maybe the thermo-time switch and coolant temp switch? 

I've got an answer for everything, or close to it, but I'm not seeing anything obvious here.

Several things do come to mind though. Change out the main relay. It's a unique relay in the car and known to be problematic. Cheap. But it usually manifests itself as a no or hard to start, not cutting out while running.

Check for spark and or fuel. Gotta have both, go back to basics, if you have spark shoot some gas or carb cleaner or something in the intake and try to start it. If it fires, at all after that, it suggests you have spark, so look to fueling.

AFMs can be bad and or cranky. Not often, but can.

Check all that stuff and report back.

I solved it. 

I pulled a plug and cranked it and saw that I was getting spark. So it must be a fuel issue. I looked very closely at the fuel pump fuse (not the relay) and saw that one of the brackets on the fuse had apparently melted the plastic housing around it causing it to warp and lose connection, resulting in now power to the fuel pump.

Holy Grail Labs, here we come.