Main Relay

Whats it really do? And do I really need it? I'm tearing through my z6 harness pulling anything that isn't absolutely necessary to run the engine. The Ignition, Fans and Fuel pump are all gonna be hooked up to a switch. So that should just leave me needing the sensors on the intake, fuel injectors and distributor wires, correct?

Also, anyone know a way to get rid of the fuse boxes? I know there are a few things in the one under the hood I still need, but most of it is useless. Can I just get a fuse block, run a wire from the battery/alternator to it and just hook what I need up to the other side?

Sorry for the strange, and maybe dumb questions, just trying to get all of the weight I can out of this little CRX(granted there isn't much weight to begin with). In the end I might end up having to put more weight back in it, but then I can put it where I want it :)

if the pump is on a switch you don't need the main relay.. it just tells the fuel pump to prime before running the engine.

You can replace the entire fuse box under the dash w/ a single fuse block, you can get rid of the one under the hood, too.

I almost did the fuse delete on my '85, just b/c I didn't want it all there.

Basically, get a standard fuse block from any other vehicle that has the integrated big fuse holes, so you can still have the ones that you need under the hood, but mount the whole thing on the strut tower in the passenger side... or keep it under the dash.. another thing you can do is use inline fuses, and get rid of the fuse "block" altogether, which is what I'll be doing.

Not to bring back a resolved thread, but that last post was a lil misleading.. actually the main relay does a lil more than just the fuel pump, but atm, I can't remember what.. I was reading about it in my Chilton tho, I'll copy down word for word and get you what it says here soon, pry in the next day or so.

I think it had something to do with ignition system too, or maybe it was the ECU staging process... in fact, I think that was it.. it stages the ECU for startup and run conditions, and sends it the signal to turn on.

lol...too late now. Harness is down to Intake sensors, Distributor and fuel injectors and the under hood fuse box.

well, you'll need to wire in a relay of some kind for the ecu, direct application of voltage can cause a spike, and burn it up.

We will find out when I finally get the mounts made up and the fuel lines in. Right now this is what the harness is down to:

http://tssforums.com/imgs/tony/phot0152.jpg

Ill resize the pic sometime, just too busy right now.

Holy jebus, its like your trying to run it on the harness of a motorcycle lol, theres nothing THERE.

When I resize the pics, ill put up the one of the wires I have taken out...its a nice mess.

alright Tony, you just need a car

I have a car...I now have 5 again, lol. Just bought one today, should only be here about a week or so, another is getting hauled off soon too.

jeez dude, I've run cars on less than that, but that's GREAT for a FI car... I'm talking carb'd shit, only need like two wires in the whole car lol :P

Alright, to bring up an old thread, but to answer the question. The main relay isn't NEEDED, just have to get power to the fuel pump and ECM where the main relay connects to it.

The final wire harness was even smaller than the one I posted. My original plan was to use the factory wires for the ignition, but I ended up running them on the right side of the shifter, so I cut all those wires out and both fuse boxes. My 2 switches(one for ignition, one for fans) have a 30 amp fuse on them, and my main battery cable has a 175 amp fuse before it hits my master cutoff switch.

Now I just gotta figure my alternator out. Just as long as I have the white wire connected to the battery, that should keep it charged correct? or do I still need the wires going to the ECM? I wouldn't think I would need them, but the alternator isn't working, and it was when I pulled it out of the car last year, but its been sitting for awhile too.

YOU DO need those wires to the ecm. They are the alternator load switch. The alternator isnt always charging the battery. Watch next time you put jumper cables on a car, the idle will change and the load on the alternator will increase. As far as the main relay being needed, yeah your right you dont. After doing the mpfi swap I noticed that it just basically puts 12v to the injectors and other things.

I just was out there messing with it, and found out you are correct Frodo. Now I just gotta put those wires back in, lol....and then figure out what just happened. Car was running, then it quit. Now I flip one of my switches on and both LEDs come on for both switches, but nothing else does. They share the same ground, but each one is powered off the switch individually so that has me a little baffled. Ill have to mess with it more tomorrow.

the main relay isn't necessary, but it's there for a reason.

The reason would be the same as any other relay on any other circuit anywhere in the world, if you check the circuit on an ocilloscope (sp), you will notice that the voltage is a sudden spike when you turn the circuit on, then it levels out in less than a second... the relay prevents that spike, by not allowing the circuit to open until it's steady (level).