*SOLVED:?* Car has been running for 2 years. Now, Cranks, no start.

[SkorcherX]

1987 325 with a M50 non-vanos swap. Car has been great for last two years. No problems, hell it even fired and ran first try after the swap.

I ran the tank very low on gas. Went to start it up and it wouldn't fire. I assumed it really just needed more gas. I went to the station got 5 gallons and filled it up. Still cranks and doesn't start.
I turn the key to run a few times to prime the fuel... I notice that I do NOT hear the fuel pump running.
I jump the fuel pump relay and I hear the pumps running.
I attempt to start the car with the fuel pump relay jumped. No start.
I spray some starting fluid into the throttle body. It then attempts to run and fires a bit then runs out of starting fluid and returns to cranking. So I know I have spark.
I check the resistance of the Crank Position Sensor. 511 Ohms. I plug the CPS back in and try to start it. It tries to fire.
I then see I didn't put the intake boot back on. I do this, and it starts. It runs. Like nothing had ever happened.
I drive it around the block. Everything appears normal.
I pull it back in the driveway and turn it off.... Moment of truth... will it turn back on? No dice. We are back to square one.
I check the resistance of the Cam Position Sensor. 1310 Ohms. I wiggle the Crank Position Sensor connector some and attempt to start it again. No start.

Something intermittently is dying. I am leaning towards the Crank Position Sensor but would like some sort of tell-tale sign that its the cause of the failure.

Any more tests I can perform before I just start replacing shit and potentially throwing money away?

Thanks guys.

[amcink]

CPS as mention or fuel pump in the tank sounds ok after jumping and how about the secondary fuel pump the one one the driver side in the rear

[SkorcherX]

how about the secondary fuel pump the one one the driver side in the rear

I am under the notion that when jumping the relay they both run. I can hear buzzing under the car.

I even went so far as to disconnect the fuel line from the rail and jumped the relay. Gas squirted out of the line. I feel that the fuel pumps work. The fuel pump relay? I don't know. I cant seem to figure out how to test it. Something about putting power to the spades... Youtube is fucking me on this one.

[amcink]

maybe this might help

http://forums.bimmerforums.com/forum/showthread.php?1783698-Testing-Fuel-Pump-Relay

[SkorcherX]

Replaced the Crank Position Sensor today. The car now starts every other time I turn the key.

I must have tested this 20 times in a row. Any thoughts?

[SkorcherX]

So just for shits and giggles. I pulled the Fuel pump relay and jumped it with a wire. I hear the pumps turn on and I start the car.

First attempt it starts right up.
Second attempt it starts right up.
Third attempt it DOESN'T start.
Fourth attempt it starts right up.

So Fuel pump relay works just fine. The fuel pumps hummed away while jumped and it displayed the same symptoms. I feel the fuel pumps are not to blame. I also bought a new fuel filter. And looking at whats in there... it looks original. So maybe just maybe its a fuel pressure issue and It take a bit to get the pressure it needs.

I will put that in later this week.

If anyone has any other troubleshooting steps I am all ears.

[Bimmian89]

Maybe check your ignition wire under the wheel. Sometimes the power wire looses connection to the dme failing to send power to dme.

[SkorcherX]

Installed the new fuel filter. The one I pulled out was 13 years old. Sheesh.
I also replaced the fuel pump relay cause i had one lying around.

The car when cold will start pretty consistently. Like 4 out of 5 attempts. If I drive the car around and get it up to temp. Then it wont start. You kind of have to sit around and wait a bit. And try a few times every 5 minutes until it starts back up.

Any other thoughts?

[SkorcherX]

Got a fuel pressure gauge. Car makes like 51psi while cranking. Once running it make about 45-ish. Then when I turn the car off it sits at 41 psi. Its been sitting for about half hour now and the needle hasn't moved. So I think I am quickly ruling out fuel. Very bizarre.

Need to check to see if I have an intermittent spark issue. Awaiting an extra set of hands to turn the key while I ground out a plug.

[SkorcherX]

Ok, I have intermittent no spark. So this is either no timing data... or bad ignition wiring? Possibly a ground? The issue is definitely exacerbated when the car is warm. When its cold it starts pretty frequently. So metal expands when its hot... so maybe something is not touching after it expands... or its grounding itself out?

I will have to check the ignition wiring under the wheel like Bimmian89 stated. Any other things to look and test?

I couldn't find a helper so I had to improvise.

[SkorcherX]

So... I unplugged the DME. Then made sure I had 12v from ignition. I did. Then I was gonna test some continuity to CKP sensor and CMP sensor, along with temp sensor.

Well I plug the harness back into the DME. Start the car. It starts. I turn it on and off again like... 10 more times. It starts every single time now.

I drove it around the block got it warmed up. Turned it off in the garage. Start it back up.. It just fires right back up. So I have a loose wire somewhere or somehow the DME plug had rattled and backed itself off ever so slightly.

I don't know what else to do, since I can no longer reproduce the issue.

[amcink]

Great! need it a reset I guess!!!