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what exactly does a main relay do?

Discussion in 'HYBRID -> EG-EK / DC' started by civiclxb16, Mar 2, 2005.

  1. civiclxb16

    civiclxb16 Senior Member

    i was wondering if someone can help me out here. my civic is not starting and i have had some people tell me that it sounds like the main relay. i was wondering if someone could please inform me what exactly the relay does. if it is bad the car will not start right?
  2. CRX-YEM

    CRX-YEM Super Moderator Moderator

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    A realy is a switch in a way. There is a low voltage coil that is connected in series with a switch(your ignition switch in this case) when the switch is closed it energizes the coil and the coil acts like magnet which closes a second set of contacts (that act like a switch) that can handle a much high load and current.

    On a relay a few things can fail, the coil can fry and cause a short and the cooil does work anymore which won't let the secondard contacts function, The second set of contacts can tack weld together and and cease to function. there could also be a cold solder joint and an intermittent connection to the coil is observed.

    How Stuff works (About Relays)

    And to confirm your thoughts if hte main relay fails the car won't start.
    Turn your radio off, put the key in the ignition, turn it to the on position, if you listen carefully you can hear the feul pump prime the fuel rail, if you don't hear this noise most likely the main relay has failed.
  3. erikespo

    erikespo Senior Member

    EDIT: Ahh you beat me too it!


    Yes if your main relay is bad you car will not start.. but usually they start to go bad.. as in your car stall randomly (actually when the main relay heats up the solder connection are broken) when that happens the fuel pump looses power..

    to tell if yours is bad put the key in your car and turn it to run... I don't remember what it is called 2nd click so everything powers up.. you should here the fuel pump whirr for a moment.. if not = bad main relay.. or bad fuel pump or shorted wire..

    you should really start by checking if you have the 3 essentials, fuel spark and air..
  4. civiclxb16

    civiclxb16 Senior Member

    well to top that i will tell you what i did i took the fuel line off the rail and i turned the key and fuel was spilling out.
  5. civiclxb16

    civiclxb16 Senior Member

    yeah you said it starts to go bad well the car one day started acting like it was running on three cylinders and then it went back to normal. then it started acting like it was running out of gas. once the car got home it died it didn't want to start now it seems like it is only running on two cylinders when i spray starter fluid in the IM but it turns on the 2 and the 3 spark plugs come out with the fluid on it and the 1 and 4 don't what could that be?
  6. erikespo

    erikespo Senior Member

    dizzy.. gotta spare cap?

    Edit: second thought it runs fine with the starter fluid being ssprayed in?
  7. civiclxb16

    civiclxb16 Senior Member

    well it runs but doesn't run fine i have tried two different dizzys with two different cap and rotors
  8. erikespo

    erikespo Senior Member

    plugs and wires?
  9. civiclxb16

    civiclxb16 Senior Member

    brand new two different sets
  10. erikespo

    erikespo Senior Member

    clogged fuel injectors maybe.. also has the ignition timing changed at all that you know of?
  11. civiclxb16

    civiclxb16 Senior Member

    well before i took off the old dizzy i put a mark on it and on the place where it bolts on to and i put the new dizzy right on that mark so the dizzy timing should be fine but i can't check it with out the engine being on. i took the injectors out one day matter of fact the next day after it died on me and placed them on the head and turned the key and all four of them are spraying
  12. erikespo

    erikespo Senior Member

    when does it run like poo?





    yes.. poo
  13. civiclxb16

    civiclxb16 Senior Member

    no it runs like ish
  14. erikespo

    erikespo Senior Member

    does it turn over? if so, does it almost start or sputter?
    if it doesn't might be a short somewhere else.. ignition switch maybe
  15. civiclxb16

    civiclxb16 Senior Member

    when i turn the key it sputters and runs for a half second but when it has starter fluid it runs but not great what and where can i have a short at?
  16. erikespo

    erikespo Senior Member

    well if it sputters and run for a bit and with starter fluid it runs but not great - it is probably fuel related.. bad gas? last fuel filter change?
    easy to change too.

    the short was if it didn't turn overand just clicked
  17. civiclxb16

    civiclxb16 Senior Member

    when the swap went it i put a new fuel filter in as well also the gas has to be good because i just filled it up well half way up with fresh 93
  18. 88bluehf

    88bluehf Senior Member

    im thinking the place you got gas from sucks and you have water in your ish. drain it off purge the whole system. Refill with reliable gas and make sure all injectors are spraying.
  19. 88bluehf

    88bluehf Senior Member

    have you tried replacing the main relay yet?> i dont remember from the old post..if not they are easily fixable.....just open them up and resolder the joints and there good for another 100,000. Main relay located on drivers side kickpanel under dash
  20. civiclxb16

    civiclxb16 Senior Member

    well the place where i get my gas from is the same place i get my prelude from and it is running just fine so i don't think it is bad gas, my dad gets gas there for his q45 and for his 4runner so the place is good in my eyes. what else could i look at i am going to change out the injectors and see what happens with that!

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