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Starting Issue

This is a discussion on Starting Issue within the General Help forums, part of the LSx Technical Help Section category; I hope this is the correct forum to post ? anyway I have a 73 Datsun with a 2000 LS1 ...

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    1973 240z LS1/t56

    Starting Issue

    I hope this is the correct forum to post ? anyway I have a 73 Datsun with a 2000 LS1 and its been running fine until yesterday . I go to start it and it only cranks over .I don't hear the fuel pump come on so I put 12v to the pump and it works . Next I replaced the 5170 relay but still no pump when I turn the key . Can anyone suggest what I should try next ?
    Thanks in advance
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    Veteran 0rion's Avatar
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    I'm assuming you disabled vats when you did the swap? Do you have 12v at the relay? With a swap it could be a wire or grounding issue. Where did you get your harness from? Was it a plug and play harness or did you build it yourself?

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    Electrical Engineer KMdef9's Avatar
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    I'd check fuel pressure at the rails.

    Then I'd make sure I was getting a spark at the coils.

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    1973 240z LS1/t56

    The car has ran fine for 7 years and I have 12 volts at the relay ,all so if I manually activate the fuel pump it still won't start

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    Test the connection back at the pump when the relay is energized. If jumping it there makes it work, then the problem has to be between the relay and that connection, so long as the relay is functioning properly.

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    Senior Member JayTA98's Avatar
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    Had you checked to see if you have 12v from the ignition switch to the relay? Remember you are going to have 12v on one terminal of the relay at all time. So if you but a bypass at the relay is going to work because you are not using the relay at all. The other two terminals are the ones that work the small coil inside the relay that make the relay work. One of those terminals is ground and the other is 12v signal from the ignition switch. Use a multimeter or test light and check for voltage at one of those terminals when you turn the ignition switch all the way to "start". If you don't have signal voltage you could have a bad ignition switch or bad wiring. If you have voltage check the ground wire.

    I had this similar situation with my old 88 crown vic. It turned out to be the ignition switch.

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    1973 240z LS1/t56

    I have 12 volts at the relay but its not getting a signal from the PCM

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    Veteran 0rion's Avatar
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    pinouts for a 99+ pcm....
    99 pin PCM WIRE COLOR CONNECTOR Circuit No

    looks like that is 37 on the blue connector. Check that connector too for corrosion. Wouldn't be the first time I've heard of those pcm connectors getting corrosion in them. My gut tells me you probably have a bad connection somewhere if it's worked for 7 years and suddenly just stopped working. Going to have to chase that back until you find 12v. It could be on the ignition switch side too as someone said.

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    1973 240z LS1/t56

    I don't have juice at 19- pink Ignition Pos. Volt. When I jump it the pump comes on for a second

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    that should be hot in run and hot while cranking.....

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    1973 240z LS1/t56

    so I jumped the pink wire making it hot with the key on ,the fuel pump runs like it should but no start

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    Did you check fuel pressure at the rail?

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    yes 60 lbs at the rails

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    Veteran 0rion's Avatar
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    you check for spark too? I'm still curious as to if/how you got around the vats issue. If vats is still enabled you could be chasing your tail here. Normally vats will kill fuel and the starter but on a transplant I wouldn't even know where to begin figuring out how vats was dealt with. Did you use a stock body control module?

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    Vats is disabled I will check for spark tomorrow

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    1973 240z LS1/t56

    is there a way to see if the Crank Position Sensor is getting a signal ?

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