R32 ECCS / IGN relay issue

[jti-Jamie]

Hi guys,

Hope you can help.

R32 gtst, spec 2 RB25 on a G4+ pnp

ECCS relay had failed, causing fuel pump to stay on with key turned to ignition and ECU looses power when cranking.

Tried a new relay, same issue. Removing the relay entirely gives the same symptoms as it being plugged in, even wiring in a 40a 4pin relay does the same.

The only way around is to bridge the pins on the relay (3 to 5, 6 to 7 and 1 to 2). Then everything works as it should, fuel pump works when cranking and running, issue being now that the ECU has permanent power.

Do I have a further issue with a relay elsewhere, or is it a wiring/ecu problem. The car had been running for a few years before this, so nothing has changed recently other than the car being in a minor crash and then it got repaired/painted.

 

Appreciate any advice!

Thanks 

[Adamw]

The skyline power circuit works like this:

The ignition switch is connected to pin 45, this pin should have 12V when the ignition switch is on.  This pin does not power the ecu, it is just an "ignition on" signal.  There is an independent circuit on the adapter board that grounds pin 16 when the Ign switch pin is live.  Pin 16 is the control for the ECCS relay.  When the ECCS relay engages, this supplies 12V to pin 49 & 59 and the ecu then powers up.  

So, one of these is missing.  3 things to confirm:

1. There is 12V on pin 45 when ign is on.  
2. The ECU is grounding pin 16 when the ignition is on.
3. There is 14V coming from the ECCS relay to pin 49&59 when pin 16 is shorted to ground. 

[jti-Jamie]

Sorry my bad, it's a GTT link 

[Adamw]

3 things to confirm:

1. There is 12V on pin 31 when ign is on.  
2. The ECU is grounding pin 4 when the ignition is on.
3. There is 14V coming from the ECCS relay to pin 67&72 when pin 4 is shorted to ground. 

[jti-Jamie]

-Pin 31 has 12v when ignition is on

-Pin 4 is ground ignition on or off

-Only seeing 9v to pin 67 & 72

Disconnecting the relay and bridging the pins gets me 14v on 67 and 72

 

Thanks again for the guidance 

 

[jti-Jamie]

1 hour ago, Adamw said:

3 things to confirm:

1. There is 12V on pin 31 when ign is on.  
2. The ECU is grounding pin 4 when the ignition is on.
3. There is 14V coming from the ECCS relay to pin 67&72 when pin 4 is shorted to ground. 

 

[Adamw]

7 hours ago, jti-Jamie said:

Pin 4 is ground ignition on or off

That doesnt sound right, but perhaps you are not testing it how I imagine.  If you manually short ecu pin 4 to ground with a piece of wire and paperclip or similar, do you then have 12V on 67/72?

 

9 hours ago, jti-Jamie said:

The only way around is to bridge the pins on the relay (3 to 5, 6 to 7 and 1 to 2)

Bridging 1 to 2 would have been a dead short so has possibly fried the FET, but the test above will help understand if this is the issue or not. 

[jti-Jamie]

13 hours ago, Adamw said:

That doesnt sound right, but perhaps you are not testing it how I imagine.  If you manually short ecu pin 4 to ground with a piece of wire and paperclip or similar, do you then have 12V on 67/72?

 

Bridging 1 to 2 would have been a dead short so has possibly fried the FET, but the test above will help understand if this is the issue or not. 

Sorry let me start again!

Pin 4 is 12v with ignition on or off

If I then ground pin 4 with ignition on using a power probe I get 13.5v on pin 67/72

 

[jti-Jamie]

This issue was evident before bridging the eccs plug. So I suspect a driver (or FET as you said) is dead from the relay failing. 

As a work around could I take a 12v ignition live from pin 31 into a relay and ground pin 4 that way?

[Adamw]

Yes, I would say the fet or one of the PCB tracks related to it has been burnt.  

Yes, you can use your own relay to ground pin 4 instead.