I need help troubleshooting and locatingthe crankshaft sensor. I know that the fuel pump will not turn on if the ECM does not sense the crank rotation. I have tested the fuel pump relay and supporting connections. If i jump the relay i get 60 psi to the fuel rail. I have an open signal from the ECM with the LED test light.
I need to know where the crank sensor is and looks like and how to test it in the auto trans.
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Re: 1998 Audi A4 1.8T fuel pump does not turn on
If you have diagnostic equipment you will be able to see the signal through serial data(if you believe it)the cranksensor is located near the rear of the engine pointing towards the radiator i think it goes to a grey plug....
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NEED HAVE VECHICLE CODE SCANNED FIRST LOOK FOR FAULT CODES MANY THINGS WILL CAUSE NO STARTING,LIKE BAD CRANKSHAFT POSITION SENSOR.FAULTY CAMSHAFT POSITION SENSOR,BAD SPARK PLUGS FOULED OUT BY FLOODING ENGINE DUE TO LEAKING FUEL INJECTORS,BAD ENGINE COOLANT TEMPERATURE SENSOR,BAD MASS AIR FLOW SENSOR.FAULTY ECM. CODE SCAN VECHICLE FIRST.IF NO FAULT CODES CAME UP YOU COULD HAVE FAULT IN FUEL SYSTEM, COULD HAVE STOPPED UP FUEL FILTER,BAD FUEL PUMP RELAY OR FUSE THE FUEL PUMP COULD BE FAULTY. TURN IGNITION SWITCH TO ON POSITION LISTEN FOR FUEL PUMP OPERATION IN FUEL TANK, YOU SHOULD HEAR FUEL PUMP RUN FOR FEW SECONDS THEN TURN OFF.IF NO FUEL PUMP BAD MORE LIKELY BUT CHECK FUSE AND RELAY FIRST BEFORE BUYING NEW FUEL PUMP.DONT BUY NEW PARTS HAVE VECHICLE CODE SCANNED FIRST USING DIAGNOSTIC SCANNER YOU COULD HAVE BAD CONTAMINATED FUEL.
The relay just turns it on and off - if the pump comes on the relay is fine. You may have a bad fuel pressure regulator. If you want to change or troubleshoot the relay you need to remove the lower dash panel below the steering column. The relay is marked with "372".
Check the Camshaft Position Sensor or the Crankshaft Position Sensor. Those are the modern day Distributor Caps of the 21st Century, if neither of them are working the ECM (Computer) does not know what position the Crankshaft is in so it will not be able to start your motor.,
If the motor is turning over, then the battery is good. You are either not getting spark or fuel. If not spark, the crankshaft position sensor is usually faulty. If no fuel, either fuel pump or fuel pump relay is bad, or clogged fuel filter, or fuel pressure regulator is faulty. You have a fuel rail that has your injectors attached to it. It should have a test port on it that looks like a tire valve. You can put a rag on top of it,, press it in and there should be lots of fuel pressure, If not, either filter is clogged or pump is not running either due to bad fuse or relay or pump is bad. For spark, there is a crankshaft position sensor that screws in engine block next to the crank. Then from here the wires go to ignition module and coil packs, then to plugs and wires. You can test any relay or sensor with an ohmmeter in the ohm position. You can test any power in an electrical unit with a voltmeter
If it will turn over but not start, it could be a fuel delivery problem ( fuel pump), clogged fuel filter, bad spark plug or wire, or it could even be something like a crankshaft position sensor. Try the cheaper fixes first. Hope this helps. Good luck
Look around the bottom of cylinder block. Or near where the flywheel is to, because the crank angle sensor works from missing teeth or magnets on the flywheel or a cog/wheel fixed to the crankshaft.Hope this helps