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1990 BMW 735i Question: My car starts cold. after warming up, it stops, and will not restart till cool.

 

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bob_yodan, Copiague, NY, October 02, 2011, 05:53
 Rookie

If I drive, it will run until I stop for a light. as soon as I stop for a light, it will stall, and not restart.
It is an automatic. I cannot us the car at all without risk of getting stuck.

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  • Answer #1

    patrick mannion from Greg Solow's Engine Room, October 02, 2011, 09:12
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     Master

    It could be many things, unfortunately and without experiencing the problem first hand or being able to do some basic diagnostic tests its hard to say.
    Fortunately your car is old enough to be relatively simple.When it fails you need to determine if you have lost fuel or spark. The computer in your car takes in readings from sensors on the engine (like crank shaft position, camshaft position, engine coolant temperature, air temperature, volume of air being drawn into the engine, ect...) based on these inputs the computer in your car determines how much fuel to squirt into the engine and when to send spark to set fire to the fuel. If any engine sensor is giving an erroneous reading the computer does not make proper calculations and drvability issues occur. In most cases theses sensor values are needed to "turn on" the fuel pump.
    Remove the spark plug wire and check for spark at the spark plug wire when a friend cranks over the engine to see if the engine has spark.

    Check for fuel pressure (you will need a fuel pressure gauge and look up the specified fuel pressure for your vehicle). Remove the fuel hose that goes to the fuel rail and get a friend to crank over the engine to see you have adequate fuel volume (you should have approximately 1 pint of gasoline in ten seconds of cranking). Off course take proper precautions as gasoline is highly flamable. Next "listen" to the fuel injector. Using a mechanic's stethoscope (or use a long screw driver placing the handle end up to your ear place the metal tip end of the screwdriver against the body of the fuel injector), get a friend to crank over the engine while you "listen" to the fuel injector listen to each injector at the same point of the injector body. You should hear "click, click, click" as the injector is electrically opened and closed by the computer. If the injector is not being triggered you will not have fuel getting into the engine's cylinders. Disconnect the electrical connector at the fuel injector with the ignition key in the "on" position, (next position after the accessory position) you should have 12 volts at one of the two wires at the injector. This true for most vehicles but you need to consult a workshop manual for your vehicle to see that this is true for your vehicle. When the engine is running the second wire at the injector gets (triggered) grounded by the computer in your vehicle many times a second controlling exactly when and how much fuel gets injected into the engine.
    On your car I have seen fuel pumps fail, crank signal to the computer fail, some computer failure. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online

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    LUBE LANE AUTO, October 03, 2011, 06:49
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     Enthusiast

    Call us for an appointment. Free testing with repair. Thanks, Rob Lube Lane Auto. 631-225-2653

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