konradlip Posted March 31, 2014 Share Posted March 31, 2014 Hi, I'm looking into creating a fuel pump cut off switch in my l28et swapped 280z. I want to make one because I'm running megasquirt 1 v3 and often i want to upload and tune the car with it being off but with megasquirt still powered on and my problem is the fact that the fuel pump stay on. Not only does that drain my battery but also floods the engine. I'm not totally sure how to make one and I would like some help. From What I can imagine the switch would have to be between the megasquirt and the fuel pump relay. Is that correct? Thanks Quote Link to comment Share on other sites More sharing options...
mattb3562 Posted March 31, 2014 Share Posted March 31, 2014 That is correct. You want to break the ground signal that is controlling the fuel pump relay. (Assuming that's the way its wired up) I wouldn't recommend breaking a 12v supply on/off. Quote Link to comment Share on other sites More sharing options...
konradlip Posted March 31, 2014 Author Share Posted March 31, 2014 thats what i figured out. if i only cut the 12v then still some power will be send to the pump Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 31, 2014 Share Posted March 31, 2014 Seems like Megasquirt should be able to control a relay using an ignition signal. Just a thought. Here's a link that might offer something. http://www.diyautotune.com/tech_articles/common_megasquirt_modifications.htm Quote Link to comment Share on other sites More sharing options...
Metro Posted March 31, 2014 Share Posted March 31, 2014 Pin #37 on MS is a fuel pump relay ground. It will only turn the fuel pump on to prime for 1-2 seconds (depending on settings) and when the engine is running - engine RPM signal is detected. If your MS is wired correctly to use a fuel pump relay, something is wrong if the fuel pump is always on. Quote Link to comment Share on other sites More sharing options...
konradlip Posted March 31, 2014 Author Share Posted March 31, 2014 Well the wiring on my car is all f'ed up (im not the one to do it. i just bought a ca that way). for example the whole ms is grounded on the little pieces of metal that the kick panel cover screws in instead of the engine block like megasquirt suggests. I want to redo the wiring but for now i need the fuel pump off. Quote Link to comment Share on other sites More sharing options...
konradlip Posted March 31, 2014 Author Share Posted March 31, 2014 so how would i have to wire the pump in so it shuts off after that 1-2 seconds? im using ms1 v3 just fyi Quote Link to comment Share on other sites More sharing options...
Metro Posted March 31, 2014 Share Posted March 31, 2014 You'll have to dig through your wiring to figure it out, here's the general MS1 external wiring you can use as a reference http://www.msextra.com/doc/general/ms1external.html Quote Link to comment Share on other sites More sharing options...
seattlejester Posted March 31, 2014 Share Posted March 31, 2014 The megasquirt actuated pump does kick on for a second or two and then only remains on when it notices rpm signals. Perhaps your pump is running off just the ignition signal? If your engine is flooding from just the fuel pump being on, that seems like a problem. The injectors should be closed even if the pump is cycling. Perhaps your fuel pressure is too high? When my car was carb'd I had a manual switch to turn the fuel pump off that I wired to the ground of the signal wire on the fuel pump relay. You can add it somewhere inconspicuous and use it as a theft deterrent as well. Quote Link to comment Share on other sites More sharing options...
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