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Thread: Car won't start; suspect fuel problem

  1. #1
    Join Date
    Jan 2004
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    Voorhees, NJ
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    Default Car won't start; suspect fuel problem

    Help! My 1992 525i had an overheating problem. Thermostat changed solved it. Today it would not start. Engine turns over and cranks like a mother but it won't even sputter. I suspect a fuel pump problem or possilby a relay or a fuse. The car was running fine yesterday. It now has 218,000 miles and I know I have never replaced the fuel pump. How should I diagnose this problem and if it is the pump is it a big deal to change? Any help would be appreciated.

    Al Gray (Age 62 and still kickin' ass)
    Last edited by Al Gray; 05-21-2009 at 08:49 PM.

  2. #2
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    Default

    Check voltage at the pump first. If no voltage will need to track voltage from the fuse box back.

    If good then you should hook a gauge to the end of the fuel rail and check pressure.

    The pump is in the tank accessible through a panel on the trunk floor. Sounds easy enough to me.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  3. #3
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    Default

    Check for spark too. A squirt of carb cleaner in the intake will tell you if it's a fueling problem, unless the plugs are wet.
    Most common sudden death in the fuel system would be the relay, in the ignition probably the crank position sensor.
    "The gas pedal wouldn't go to the floor if it weren't meant to be there"

  4. #4
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    Default More specific instructions....

    Quote Originally Posted by 632 Regal View Post
    Check voltage at the pump first. If no voltage will need to track voltage from the fuse box back.

    If good then you should hook a gauge to the end of the fuel rail and check pressure.

    The pump is in the tank accessible through a panel on the trunk floor. Sounds easy enough to me.
    I have a Craftsman Digital Multi-meter. I assume I would need to place the leads from the multi-meter on both sides where the wiring connects to the pump. I also assume that I would need the ignition key in the on position. If no voltage they I need to see if I fuse is blown or the relay is bad.

    Regarding checking pressure to the end of the fuel rail; what type of gauge do you recommend and which end of the fuel rail?

    Al Gray

  5. #5
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    Default Carb cleaner in the intake.....

    Quote Originally Posted by Ross View Post
    Check for spark too. A squirt of carb cleaner in the intake will tell you if it's a fueling problem, unless the plugs are wet.
    Most common sudden death in the fuel system would be the relay, in the ignition probably the crank position sensor.
    Spraying carb cleaner in the intake (specifically do you mean where the intake box is that holds the air filter); would that be like spraying ether in the intake, starting fluid. For the ignition; where is the crank sensor located and what should I look for to indicate if it is bad.

    Al Gray

  6. #6
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    Look for a vacuum port or hose connection that is easy to disconnect, spray in there. You're just trying to give the engine something to burn should it have spark.
    The crank sensor is mounted on the front of the engine at the perimeter of a toothed wheel attatched to the crank. According to Bentley the resistance should be 1280 ohms +- 10% and air gap should be 1.0mm+-.3 Sometimes a sharp rap on a dead one will bring it back, temporarily.
    "The gas pedal wouldn't go to the floor if it weren't meant to be there"

  7. #7
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    Default I sprayed some starter fluid...

    Quote Originally Posted by Ross View Post
    Look for a vacuum port or hose connection that is easy to disconnect, spray in there. You're just trying to give the engine something to burn should it have spark.
    The crank sensor is mounted on the front of the engine at the perimeter of a toothed wheel attatched to the crank. According to Bentley the resistance should be 1280 ohms +- 10% and air gap should be 1.0mm+-.3 Sometimes a sharp rap on a dead one will bring it back, temporarily.
    I sprayed some starter fluid (ether) into the intake (large hose conection after the air filter box that connects to the intake). The card made an attempt to start and ran very briefly. Therefore it is not a spark/ignition probelm. I located the computer box on the passengers side firewall and located the fuel pump relay which is a 4 prong one located as the middle relay of 3 relays and swapped it with another relay which is 4 prong. I attempted to start the car. The car turns over but does not start or catch. I have read that usually the fuel pump relay is the culprit when the car instantly gets no fuel. There was no indication of fuel pump failure (sputtering, hesitating, etc.). This litterally happened over night where the car was running perfectly to the next day where it would not start (car turning over but not catching or trying to start) at all. Seems to me that maybe I should still replace the fuel pump relay and try it ($17 ) before I spend $200 plus on a new fuel pump. By the way the car has 218,000 miles on it and to my knowledge the fuel pump has never been replaced. Any thoughts would be appreciated.

    Al Gray

  8. #8
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    Jump the relay with a piece of heavy wire. To do this, look at the relay. It'll have a diagram on the side. Using the diagram determine which contacts are closed when the relay is energized. Next install a jumper into the contacts in the relay socket (ie, instead of the relay). This should energize the pump and you should hear it run inside the tank. Run over to the driver's seat and crank the car. If it starts, the issue is definitely with the relay. If the car still fails to start, the issue is either upstream of the relay or the pump is dead. Good luck

  9. #9
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    Default Upstream of the relay or the fuel pump....

    Quote Originally Posted by Rus View Post
    Jump the relay with a piece of heavy wire. To do this, look at the relay. It'll have a diagram on the side. Using the diagram determine which contacts are closed when the relay is energized. Next install a jumper into the contacts in the relay socket (ie, instead of the relay). This should energize the pump and you should hear it run inside the tank. Run over to the driver's seat and crank the car. If it starts, the issue is definitely with the relay. If the car still fails to start, the issue is either upstream of the relay or the pump is dead. Good luck
    What would be upstream of the relay other than the fuse #23. I checked that and it is fine. I will try to jumpstart the relay but my suspicion at this point is the fuel pump since it is original as far as I know. Your thoughts?

    Al Gray

  10. #10
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    Jump the relay. I'll wager that's your problem. Relays are known to fail.
    Bellevue WA
    90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
    86 Porsche 951 - Track Toy

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