90 525i Won't start - Where to go from here?

[RotarySam]

Hello everyone. I am trying to help my brother get his 1990 BMW 525i (manual transmission) running, but we are kind of at a stand still. I was hoping to get some help. I went to school for electrical engineering and have been working in the mobile audio/security industry for 7 years, so I know my way around electrical things, I just need to know what to test.

Here's how the story goes. The car ran fine and then sat for two days. When he went to go use it, it wouldn't start. The car then sat for about 7 months or so because he had other transportation. I started looking at it with him a few days ago.

Here's a summary of the car. The car cranks. The battery is good. The fusible link was blown for a while before this happened, but it is fixed now. We couldn't do the "stomp test" because the check engine light wasn't coming on even though the bulb was good. I tracked that down to the main electronics relay (the white one) which was bad, so it was replaced. We did the stomp test now, but it reads no faults (1444). Occasionally, the oil pressure sensor/switch light message comes up on the dash, so he replaced that because it was cheap, but it still comes up. The wire doesn't look too healthy, but I can change that later. I don't think that would cause the car not to start.. but tell me if I'm wrong.

The fuel pump relay is not being turned on. If I manually energize the relay, it will turn on, but the car still doesn't start. We can hear the fuel pump working in the back when I power up the relay too. It is just not getting signal from the computer or something to turn it on normally.

I tried testing the coil, but I don't know what it is supposed to read. The coil has the wire that goes to the distributor, a wire labeled +, and one labeled -. I assumed the + would be 12v ignition and the - would be ground. When I meter them, I get 12v on both wires when the ignition is turned on. I pulled the wires off and the + and - terminals read continuity with each other inside the coil. Is that normal? Is it pulling a ground from somewhere else to turn it on? I didn't do the test where I take a spark plug out and test for spark that way yet.

Even if it wasn't getting spark though, the fuel pump relay still isn't turning on.

A mechanic who used to own this car did look at it and said the crank sensor was good, but I don't really trust him. I'm positive he has zero electrical skills, but he may have switched the sensor out with a new one temporarily to try it. I don't know for sure. It would throw a code if the sensor was bad right?

So I am wondering where I should go from here. I'm hoping it's not a computer problem. He doesn't have a lot of money to be swapping parts out to see if they work. Thanks for any help!!

[TouringDan]

Check your fuel pressure by energizing the pump. could be a bad filter, pump, regulator or all 3. In my car, the pump won't turn on until the car actually starts - it relies on residual pressure to get the car going. I thought that my relay was bad too, but to my knowledge - that's how they go. Just thinking outside the box here, perhaps you could energize the pump to get it going, then try to start the car? The car also won't start if the clutch isn't engaged so check the switch at the clutch arm. The crank sensor can easily be tested by hooking a meter up to it and comparing the results against the proper, known values.

[urai4m]

I am the owner of this car. As my brother said...I don't have a lot of money, and I need to get this car running. Enough with my sob story. Regarding the suggestion about the fuel pressure, filter, etc... The mechanic did not test to see if it was getting fuel, but he specifically said that it was not getting spark. However, he did seem to be rather incompetent. I didn't know if this might give you more ideas. Any additional suggestions would be appreciated.

[TouringDan]

If it's not getting spark, then you should start looking at your DME or coils.

[slocar]

Download the Bentley manual from the following link; it's probably the most help any of us can provide without physically being there.

http://www.mediafire.com/?eyz2ydoe3dz

[urai4m]

For one...what exactly is the DME and where is it located? Also, my car only has one coil and he ran into the problem he mentioned above.

"I tried testing the coil, but I don't know what it is supposed to read. The coil has the wire that goes to the distributor, a wire labeled +, and one labeled -. I assumed the + would be 12v ignition and the - would be ground. When I meter them, I get 12v on both wires when the ignition is turned on. I pulled the wires off and the + and - terminals read continuity with each other inside the coil. Is that normal? Is it pulling a ground from somewhere else to turn it on? I didn't do the test where I take a spark plug out and test for spark that way yet."

[slocar]

DME = ECU. It's under the black cover on the passenger side (right next to the windshield/behind the battery.

And yes, your car has just one coil; you have a m20 engine; m50 that he is referring to has individual coils.

[RotarySam]

Thanks for the manual. I will give it a look.