1986 325 won't run!!!

When cold the engine will fire, idle, rev,and run well for approximately 20 seconds. After 20 seconds of running the idle begins to break-up and within 3 or 4 seconds the engine dies. I have checked for fuel pressure, spark, and compression, all of which seem okay. After running for 20 seconds the car will not repeat the cycle until engine has completely cooled(next day). Any ideas?
Stefan

So if I understand correctly, The car won't start back up for a day once it dies out. During this period of time you say you have spark, compression, and fuel pressure WHILE the car is dead? Does the engine die/cut out like a switch flipping on/off or does it start to bog as if it were choking/starving?If it is bogging/choking you could try disconnecting the exhaust system from the exhaust manifold. This with confirm whether or not the cat. converter is plugged. Spray the manifold bolts(and exhaust hanger fasteners) with PB BLASTER liberally and let them soak for 24 hours BEFORE you attempt removal. Trust me, you dont want to break the studs. This test maybe the most labor intensive, but least expensive.If the engine is cutting out I would also suggest another avenue which is the ignition coil or DME control unit (engine computer) These are more difficult to test without swapping donor parts. You should be checking spark with spark tester not a spark plug. This way you can moniter the spark as the engine is running/dying out. You also could have an faulty injector check resistance after the vehicle dies out. Give me some more detailed info.

I purchased the car not properly running. I have no way of contacting previous owners to get a sense of how and when and/or other symptoms that the 325 may have exibited prior to failure. The car will not run for an extended period of time. The car will start when cold. It will run well for a brief period of time ( approximately 15 seconds ) and the the engine will break-up, stumble, and die. The engine does not die like turning off a switch. I have checked both fuel pumps for fuel flow and fuel flow at the cold start injector and pressure seems okay. I replaced the spark plugs which were slightly fouled but also too cold a heat range with the proper plugs. I also checked the condition of all the distributor components and everything seems in order. I just had a thought. I had an issue with a BMW motorcycle where a fuel return line check valve was not allowing fuel back into the gas tank so fuel rail pressure would increase and too much fuel was being injected into the cylinders and consequently the engine would foul up. I will also check the cat. converter. If you have any other ideas please let me know,
Stefan

If it is a fuel issue then see if you can introduce a straw and starting fluid into the intake and perform some testing. If fuel starvation is causing the problem then the engine should run a bit longer or better on the starting fluid. I would also test for an injector problem by having someone start the car as you pull the plug on the cold start injector as soon as the engine fires up. If you have bad injector(s)etc, the engine will die immediatly as you pull the plug because it won't sustain itself without the extra fuel from the cold start injector. It's worth a try, I suppose. I know that parts are too expensive to replace without definite a failure noted. Do you have a Bentley repair manual (essential)? How about an ohm meter to check resistance on the temp sensor and injectors. I would also suggest posting a thread on 5 series about your problem because 528e is the same engine only there are just as many if not more on the road. I used to swap parts with my brothers 528e and we saved each other tons of guesswork that way.

I just removed the electrical connector for the cold sart injector and the car was difficult to start but did start. ( As I would expect) The engine then ran well with stable idle and it would also rev well too! After running for approx 15 seconds the engine died. I have checked the spary pattern of the cold start injector in the past. The spray pattern was excellent. I surmize the cold start function is working properly.
I do not have a manual. I do have meters and such.
Do you have any ideas as to what function other than the cold start system might cycle for a given period of time on cold start-up then change operating conditions? The repetitive nature of the dysfunction leads me to believe that some feedback loop is causing the ECU to limit the the length of pulse to the injectors. What do you think?

Stefan

the coolant temperature sensors are located on the thermostat housing pointing up and towards the back of the car. The lower one should have two terminals and tells the DME/ECU how cold the engine is so that it can then adjust the amount of fuel. The resistance on my cold engine right now is 1166 ohms @ 50 degrees F. Test yours and I can use the chart in my manual to see if your in the ball park. Also see if unplugging the O2 sensor changes anything.

I checked the thermostat housing and there are two sensors on the housing just behind the fuel pressure regulator. One of the sensors has loose spade connectors and the resistance between them is 1.6meg. I suspect this is a sending unit for a temp. gauge. The other sensor uses a brown plug in connector, i think that unit more than likely is for temp. feedback for the ECU. The resistance is 36.7 ohms at the sensor. I haven't had time to check the o2 sensor today but, I have disconnected the sensor in the past and it made no difference to the performance of the engine...

By the way, thanks alot for you input!

Stefan

Stefan, please go to bavauto.com and spend the fifty bucks and get a BENTLEY repair manual for e30. I have owned a bunch of e30s and this manual is essential. No other will suffice. Also, the sensor with 2 contact terminals with the white plug is for the ECU. The single wire sensor is for the guage. 1.6k ohm is exactly what mine reads but you mentioned something about loose terminals ? If so you might need a better one.
You may want to start the car, wait until the car dies, pull an accessable main injector out, plug it back into the harness and see if you can hear it clicking as your assistant cranks the engine. If it falls silent, let me know. You could try to find someone who's not afraid to let you trade ECUs or other components for testing purposes.

i have same problem,car has been at bmw for 8months and they cant fix it either! ive already changed computer,fuel pressure reg,airflow meter,temp sensors. if you work it out please let me know,il do the same.cheers

How about the idle control valve and module?
I recently bought a running 86 325e. If you are in the Chicago area I could look at it.