cygnusx1 Posted September 2, 2011 Share Posted September 2, 2011 So I have the swap complete and the engine running well. 1982 L28ET into a 1977 280Z. The fuel pump module from the ZX is something I wanted to try to retain. However, the 77 fuel pumps are +12v controlled and the ZXT control module is designed to switch on the negative lead. To avoid re-wiring the fuel pump, I used the ZXT Module, to ground a control relay, which inturn, sends +12v to the fuel pump. In theory, it should work, and it seems to. However, there is no actual modulation of the fuel pump anymore, as expected. What I did not expect is that the fuel pump simply turns on with the key, and stays on. It does't prime and then stop like it should. It also does not shut off if the motor stalls. This is not what I intended. I know I can simply re-wire the fuel pump with sheilded pair and give the ground wire to the Control Module and it should work just like in the ZX. But WHY is the module not priming the pump and acting like a safety shut-off if the engine is not running? Is it because it is not seeing the fuel pump current and is only seeing the control side of the relay I installed? Electrical wizards might understand. Quote Link to comment Share on other sites More sharing options...
DCZ Posted September 2, 2011 Share Posted September 2, 2011 Hi Cygnus, I don't know for certain, but here are my thoughts: As I understand it, the ZXT fuel pump control module doesn't completely ground the fuel pump lead except maybe during periods of maximal fuel demand. It acts more like a variable resistor to ground, so that the fuel pump "sees" less than 12 volts most of the time. My guess is that when the fuel pump is supposed to be "off" there is still enough of a path to ground through the control module that your relay can stay latched. I do know that when I had the stock ECCS in my '73, I did not use the control module and just used the pin 16 output of the ECCS as the positive control of a generic relay. Priming pulse worked as it should and the pump would cut off if the engine stalled so I never had a problem. Get out the volt meter and let us know what voltages you are seeing on the various pins and we might be able to figure out what is going on. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted September 2, 2011 Author Share Posted September 2, 2011 (edited) I kind of figured that the relay might "ride-over" the module's control method, by just remaining latched. I will check the voltages. I will also trace pin 16 on the wiring diagrams, and may go that route as well. No real need to modulate a pump, on a car that will see very little use anyhow. Thanks!! Edited September 2, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
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