Challenger Posted August 24, 2010 Share Posted August 24, 2010 (edited) Car is a 78 280z. Will be running MS2 with EDIS so all of the coil wiring and ignition module isnt in use anymore, although I did use the switched power going to the ignition module to power EDIS.. I didnt use the relay board and I have modified the original engine harness for all my sensor, power to megasquirt, etc. Ive been looking through the wiring diagram and using the multimeter on the car to no success. Id like to wire up the stock relays to be triggered by megasquirt. This means the fuel pump control relay has to be grounded through the oil pressure sending unit and I assume another wire which Id have to trace down and connect to megasquirt. Am I just wasting my time trying to get this to work? Im considering just bypassing the original relays all together and just installing my own relay with a holley oil pressure switch (Holley part 12-810) http://www.holley.com/data/Products/Technical/199R9680-1rev.pdf It seems like this might just be the easiest to do.. But in this case would I be able to just unplug all the relays in the engine bay relay box? Im not running AC anymore so I dont need that relay, both the fuel pump relay and fuel pump control relay wouldnt be needed but would the electronic fuel injection relay be needed? As of now I dont think even the electronic fuel injection relay is needed. Ill continue to read through my FSM and trace wires... Edited August 24, 2010 by Challenger Quote Link to comment Share on other sites More sharing options...
Challenger Posted August 24, 2010 Author Share Posted August 24, 2010 Other option is to just not use the signal from megasquirt. 6. Connect the fuel pump (RED lead) to the terminal marked “Câ€. In this line, add an in-line fuse holder and a 7.5 amp fuse.7. Connect the terminal marked “NO†on the ON terminal of the ignition switch. 8. Connect the terminal marked “N†to the starter motor circuit (should have power only while cranking). 9. To complete the installation, connect the ground cable to the battery. I could just wire it up like this with a switch going from the ignition switch to the "NO" terminal. Then Id have a switch inside as a safety and anti-theft device as well as an automatic cut off if the engine stalls (crash, etc). Sorry if Ive just answered my own question but any information is appreciated. Maybe information in here will help someone else. haha Quote Link to comment Share on other sites More sharing options...
MikeyZee Posted August 24, 2010 Share Posted August 24, 2010 (edited) I am not familiar with the Megasquirt but I know there are threads out there specific to that. I used the factory 78 ECU working in my son's 72. The fuel pump control relay and fuel pump relay should act the same. I know allot of people go with the outboard relays instead. The 78 relays are specific to the 78 and seems like they are not readily available. I have a bad fuel pump control relay and have not been able to find a working one so I will have to construct my own. The fuel pump control in mine is wired up like this: (If you have the harness that plugs into the relay for the color codes) Fuel Pump Control WB to Fuel Pump Relay (powers the fuel pump relay) L to the Alternator S Terminal (Engine Run??) BY to Starter Connection (Ignition Start) WB to Umbilical WB (signal to ECU) YB to Oil Pressure Sending Unit (shuts off with no Oil Pressure and not in start) Fuel Pump Relay WB to Fuel Pump Control Relay GL to Fused Battery/Starter Constant 12v (same as the Fusible Link would be) GL to Fuel Pump (+) (supplies power to the fuel pump) Just looked at the wiring for the Holley and truthfully that looks easier than the factory but same concept. I'm not sure if that will help you or if that's what you are looking for. The thing I had a problem with is sending the injection pulse to the ECU. Edited August 24, 2010 by MikeyZee Quote Link to comment Share on other sites More sharing options...
Challenger Posted August 24, 2010 Author Share Posted August 24, 2010 Haha, yeah I spent a couple hours just figuring out where each of those wires went.. Well as you said, its alot simpler to use the holley setup. I have the oil fuel pump relay off of my 81 turbo so I might be able to use that for the new system, save a few bucks. But Im still left with what to do with the originals. I dont mind having the box there but if possible it would be great to just get rid of it all together. Quote Link to comment Share on other sites More sharing options...
MikeyZee Posted August 24, 2010 Share Posted August 24, 2010 I'm not sure if you will need to keep the originals installed. I mean allot of the connections go to the factory ECU but are sometimes terminated to the harness in other places like to feed the gauges and things like that. I know the Fuel Pump Control only sends power to the ECU and then Powers the Fuel Pump relay. So, not sure if those would be needed. The EFI relay also sends signal to the factory ECU so not sure if that would have to be kept in tact to make the car run. Now, you are using EDIS right? So anything connected to the factory ignition may not have to be connected either I would imagine. I know allot of guys have used MS. It seems to be the preferred aftermarket ECU. I have seen a huge amount of post for it. Have you looked in the specific "Megasquirt" section of the forums? http://forums.hybridz.org/index.php/forum/34-megasquirt/ I wish I would have gone with MS after dealing with so many issues getting mine retrofitted. The guys in the MS know their stuff. It's been done before and I'm sure they can help more than I could. Quote Link to comment Share on other sites More sharing options...
Challenger Posted August 24, 2010 Author Share Posted August 24, 2010 Yeah Ive got a handle on the wiring for megasquirt, my questions are more specific to Zs wiring in general. Quote Link to comment Share on other sites More sharing options...
MikeyZee Posted August 24, 2010 Share Posted August 24, 2010 ahhhh.....gottcha. Just making sure you have everything you need connected to make the "car" run and disconnecting that is not needed. Sorry I can't be more help but I feel your pain...... Quote Link to comment Share on other sites More sharing options...
Challenger Posted August 27, 2010 Author Share Posted August 27, 2010 (edited) Another question... I ended up just using the stock fuel pump relay with a toggle switch ran to power all the time. So I can run my fuel pump as long as the battery is plugged in. I still want to hook up the oil pressure cut off switch which is simply a ground when their is oil pressure. How I have it now. Picture attached. So any ideas on I can incorporate the stock oil pressure sender and utilize its ground to cut power to the fuel pump in the event of lost oil pressure/crash? This would work fine with the holley unit but I dont want to spend the money for it. So is there a different datsun relay that would perform this task in a similar of manner? Ill check my ZX when I get home to see how each of them work. Thanks Fuel Pump Wiring.bmp Edited August 27, 2010 by Challenger Quote Link to comment Share on other sites More sharing options...
MikeyZee Posted August 29, 2010 Share Posted August 29, 2010 I think you would have to get another relay and put it in series to break the ground if no pressure making the ground. The way the factory one works is that if you are starting it will also complete the circuit. I don't think having the switch to battery power will work. It's like you would need a defeat in the event of no oil pressure and you still need to make sure you are making fuel pressure on start as well. That is what I am dealing with right now since my fuel pump runs constantly, key on, crank, no oil pressure. My fuel pump control relay is faulty and I have not been able to find a replacement. I'll let you know if I can come up with any specifics. Quote Link to comment Share on other sites More sharing options...
Challenger Posted August 29, 2010 Author Share Posted August 29, 2010 (edited) Ended up just using another switch that Ill flip as I crank the car. I figured I could use a second relay which would ground the original fuel pump relay triggered by a crank signal but now my car will be impossible to steal. haha Anyways heres the new wiring. Fuel_Pump_Wiring.bmp Edited August 29, 2010 by Challenger Quote Link to comment Share on other sites More sharing options...
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