No switched power supply...

[Crispy Beef]

Hi All,

In short my problem is that my FD won\'t start up, it turns over just fine but doesn\'t fire. Previously to this the problem was intermittent, sometimes it wouldn\'t work at all and other times you\'d hear lots of clicks from the relay(s) - I guess it was the EGI Main Relay - and then they\'d settle down and you could turn the engine over and it would fire perfectly, and then run with no problems.  I was pretty sure that it was the main relay on it\'s way out as I have a gauge wired into the PCME on the switched feed (terminal 1B) that gets it\'s power from the main relay (therefore switched supply), if the gauge lights up then I know power from the relay is ok. But right now nothing, so I\'m definately not getting the switched power supply through.

The main relay + feed from the ignition is reading 12v as it should be, so is the + for the fuel pump relay so the wiring is ok upto that point, also the grounds running from negative terminal on the main relay box are ok too.  I\'ve had both relays out of the car and tested them with a spare battery, both click as expected and both seem to have continuity across the opposing terminals, so I think they\'re ok. Could the relays still be bad, even if they seem to check out like that?

I\'ve checked the fuel pump works by bridging F/P and GND on the data link connector and listened for it operating with the ignition switch on, I can hear it so I guess the pump is ok...haven\'t tested the actual unit but I figure I don\'t need to yet as I\'m not getting the main relay clicking when I turn the ignition on and until that happens it\'s not an issue as things like injectors and solonoids won\'t get power anyway.

I\'ve checked voltages and lots of grounds at various points and all check out ok. Other than one or both of the relays being shot I\'m running out of ideas as to what the problem is. I would just buy new relays and try them out if they weren\'t so expensive. 50 quid and 70 quid from the local Mazda dealer.  

I\'m going to take the box out now and check the connectors are ok, outside of this I\'m running out of ideas as to what the problem could be, the car has always run nicely until this issue.

Any thoughts or suggestions would be welcome.

[jon haines]

if the relays have continuity then they are probably ok, the only way to be sure is to test again under load, test them like you already have but put a headlight bulb in the switched curcuit side to draw some current. you can also link out the relay holder in the car to eliminate the relay as the fault, just link the live to the switched side, best to put a fuse in if you have one but not critical if your sure you have the correct two wires.

[Crispy Beef]

if the relays have continuity then they are probably ok, the only way to be sure is to test again under load, test them like you already have but put a headlight bulb in the switched curcuit side to draw some current. you can also link out the relay holder in the car to eliminate the relay as the fault, just link the live to the switched side, best to put a fuse in if you have one but not critical if your sure you have the correct two wires.

I tried bridging the terminals the other day but I didn\'t do it diagonally which now makes sense.  Have just bridged the gap as you suggest and everything fired up first time no problem.

I guess the relay is not good under load, will test it again later anyway as it\'s good to work out how to do stuff like that as it\'ll no doubt come in handy in the future.

Cheers, for the help.

[Crispy Beef]

Bit of an old thread but thought I\'d say that I found the real cause of the problem ... there was a dodgy wire running from the 30A EGI Fuse box to the EGI main relay box so no unswitched 12v supply was going to the main relay.  Replaced the wire and it all works just fine now.

I hate electrical problems...