1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Fuel supply problem on TII Swap

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Old Oct 12, 2012 | 08:11 PM
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Fuel supply problem on TII Swap

This is the deal, I swaped an S4 TII engine on my 85 GSL-SE. All the wiring is done. My problem is that I have no fuel. I disconected the fuel supply hose and there is just a little bit of fuel coming out of the hose. I believe that as soon you move the key to the on position the pump should start pumping gas. Am I missing something here? Thank you fir your responses.
Hernan
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Old Oct 22, 2012 | 09:53 AM
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Moved to tech section...

I know this is true for FC's, but I believe all 84 and up Rx7's need to see trailing ignition for the fuel pump to actually run. If you simply turn the key on it shouldn't do anything. Once the engine cranks and the ECU sees this, it will turn the pump on. It might be easiest, at least initially, for you to wire up a simple relay that turns the pump on when the key is on, that way you can get it running and rule that out as a problem....
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Old Oct 22, 2012 | 09:11 PM
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On the SE and all S4's the fuel pump wiring is tied directly into the AFM, where when the engine cranks and moves the flapper door inside the AFM, the AFM closes the circuit to the fuel pump and allows it to turn on, therfore when KOEO the pump will not flow. How exactly did you mesh the S4 engine and S3 chassis harness together? There is a chance that when removing all the -SE stuff, you may have overlooked this small section of wiring and essentially cut the fuel pump circuit. If you did incorporate the wiring for this, then you can either jump the fuel pump jumper plug or physically hold the AFM door open w/ key on, and the pump should run. If you did cut the wiring for this circuit, find the 2 wires and either re-incorporate them into the AFM harness, or hard wire them in
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Old Oct 23, 2012 | 08:34 AM
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^Ah yeah, i forgot that the AFM's on those have a switch for the circuit opening relay. Thanks for the correction.
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