2eighTZ4me Posted July 10, 2013 Share Posted July 10, 2013 OK - actually it's a Bosch 044, but regardless, I'm getting no power to the fuel pump while cranking - period. I know the 78's fuel pump is controlled by the oil pressure switch. No pressure = no fuel. I have oil pressure, but no fuel pump. Is there something I need to bypass/jumper when using the MS II v.3.0 on the fuel pump relay? I'll do some more studying tonight - didn't know if someone had the method off the top of their head... Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted July 11, 2013 Share Posted July 11, 2013 Pin 37 sends ground to the fuel pump relay. See if MS is seeing rpm. If ms isn't see rpm it won't switch on the fuel pump. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted July 11, 2013 Author Share Posted July 11, 2013 OK - so are you saying I can't get fuel pump signal without using the MS's pin 37? I 'thought' I could get the stock 78 system - which is triggered by oil pressure - to kick on once I got oil pressure from cranking it over. Apparently not... What am I missing here. I don't 'think' I should need to use MS's fuel pump relay circuit - but I have lots to learn about wiring - so if I need to employ the MS's fuel pump relay circuit - I'd really appreciate a 'lesson'.... Thanks! Quote Link to comment Share on other sites More sharing options...
Metro Posted July 12, 2013 Share Posted July 12, 2013 OK - so are you saying I can't get fuel pump signal without using the MS's pin 37? I 'thought' I could get the stock 78 system - which is triggered by oil pressure - to kick on once I got oil pressure from cranking it over. Apparently not... What am I missing here. I don't 'think' I should need to use MS's fuel pump relay circuit - but I have lots to learn about wiring - so if I need to employ the MS's fuel pump relay circuit - I'd really appreciate a 'lesson'.... Thanks! Are you positive the 78's efi works that way? It doesn't make any sense to me and I've never heard of an oil pressure switch cut off in Z cars (75-76, and '81 280zx). If anything, if there is an oil pressure switch it would kill the relay's ground so so the relay would turn off. The ECU should control when the fuel pump turns on and off. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted July 12, 2013 Author Share Posted July 12, 2013 Yes - the 75-76 had the fuel pump cutoff in the AFM - hence 2 extra pins in the AFM in 75-76, as opposed to a 77-78 which completes the circuit via oil pressure through the switch - which is 2 wires in 77-78, and only a single wire from 70-76. Also 2 less pins on the AFM, as they were relocated to the oil pressure circuit. Oil pressure signal doesn't go through the EFI harness, which is why it shouldn't matter that I'm running the MS and no 'stock' engine EFI harness. Oil pressure signal goes through the lower body/engine harness on the passenger side and comes right in to the cabin. Doesn't even touch the EFI harness..... I should have fuel pump because I have oil pressure.... I need to do my research. Really appreciate you bouncing some ideas - .Im kinda lost at this point and certainly would not rule out a bad relay - this car's wiring is fooked.....the fun has yet begun.... Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 12, 2013 Share Posted July 12, 2013 EF-7 has a diagram. You might find that relay and check it for power. Quote Link to comment Share on other sites More sharing options...
AkRev Posted July 24, 2013 Share Posted July 24, 2013 I might be too late with this, but if you are still scratching your head this might help. http://atlanticz.ca/zclub/techtips/fuelpump/moreinfo.htm its not just the oil pressure switch that runs the fuel pump. Good luck Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted July 24, 2013 Author Share Posted July 24, 2013 AkRev - GREAT information and good find. So - since my EFI relay is gone - along with all the other EFI related components - is there anything I need to jumper on that 4 prong plug under the driver side dash to get the pump to kick on? I have been having a nightmare of a time with wiring on this car... Quote Link to comment Share on other sites More sharing options...
AkRev Posted July 25, 2013 Share Posted July 25, 2013 Yes, I had to run a jumper power wire to the upper left when looking at it with your head by the peddles (I think, I have rewired everything and can not check and tell you for sure). I had the same problem, finally went out with a live wire and just started putting it in different places until pump kicked on. In hindsight, it is not smart to work on electrical systems when you are mad and hanging upside down. I would suggest using a new relay and letting MS run the Fuel pump. I ditched the oil sensor relay in favor of the ms due to slightly faster starts from the prime cycle. I was paranoid at first because I liked the idea of the car not able run with no oil in there. However, I just wired the hand brake light to my oil sensor relay so now I do not need to watch the center gauge in fear (my lazy attempt at a idiot light). Good Luck, Quote Link to comment Share on other sites More sharing options...
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