1986 535i No Spark Issues

[gbo]

Well I have had a weird sort of problems just happen and I am stumped on what to do next. First I ran out of gas, put a few gallons in and then went and filled the car up and drove on to work. When I came out that evening the car would just turn over but not start. I thought well the fuel filter is clogged so I replaced it with a new one. Nothing. Next I figured the fuel pump must have burned out - I couldnt hear anything at the fuel pump when cranking the car. I changed the fuel pump out twice with 2 pumps I picked up at the salvage yard but still I dont hear anything BUT I am getting fuel up thru the fuel rail in the engine bay. I unhooked a hose at the fuel pressure regulator and lots of fuel came out when I cranked the motor. I also checked the main fuel line at the other end of the fuel rail and plenty of gas so fuel is getting to the front of the car. I swapped out the main relay and the fuel relay for good measure and still nothing. Next I took out a spark plug and connected it to the wire and laid it on the motor and cranked over the engine and I did not see anything. No spark, nothing. What could it be or what should I check next to try and fix this. I am close to a salvage yard and they have several same models in decent shape I can pull from so any suggestions is appreciated. Im broke and need this fixed quick and hopefully cheap. - Cheers

[jimoreno]

Since you have done some troubleshooting already, I feel that you are left with 2 options: either a bad reference sensor or bad ECU solder joints. For the first one, there are 2 of them installed on the bellhousing and their plugs are at the end of the cylinder head in a metal bracket. One of them reads the flywheel teeth and the other one reads a locating pin on the flywheel. If the signal from the pin is missing the car won't start. There is a testing proceudre in bentley's manual using a VOM (there have been known ocurrences of this pin falling from the flywheel!). For the second one, an easy was to test for it is to give your ECU a good whack! You do know where it is located, do you? (open the glovebox and is under the black plastic cover). I would get a new main and fuel pump relay just in case and also make sure that when you changed them they are in their proper locations (I think one has 4 pins and the other one has 5 so they are different).

Good Luck!