steaditim

Greeting all:

Yesterday As I left for work, my 1990 GT took quite a bit of turning over before it would start. This is unusual for my car, but it did start and seemed fine. Then after about an hour in stop and go traffic, I fet the engine cut out for just a beat. This happened a few times. Then ten minutes later, She dies. I started it again, was fine for several minutes, then she dies.

I could hear some clicking from the fuse panel everytime she died so I'm thinking it's the Fuel pump relay. Ah I've read about this. I swap the horn relay for the fuel pump relay and off I go. Afew minutes later, she dies. Yikes!

At this point I start the engine again and sit face to face with the fuse panel and wait. CLick CLik and she dies. It sounded like it came from the left side of the panel but I'm not sure. I start poking around the other relays and I come to the one labeled relay X and this thing is burning up. I mean damn hot. I switch out relay X with another one of the same rating. After some driving, it too gets really hot and the engine cuts out. I looked up relay X and it's listed as the ignition relay.
So what's going on here? Any thoughts?

As always, the help I get from you guys is greatly appreciated.

Tim M

Alan

Tim,
I think this should be called the 'Supply Relay' (as in the FWMs)- don't know why it would be called the 'Ignition Relay' anywhere??

This relay is similar to the X-Bus relay on earlier years - although it is no longer active in the accessory position. It is on only with the ignition when NOT starting.

The Supply Relay feeds only the HVAC/Cooling Fan Control Units/Fog Lights

None of these should be critical to start/keep the car running (at least for a while - due to temp issues). If the relay is burning up - it is sinking a huge current - maybe that is the issue thats killing the engine.

You could remove the relay - start the car (should be OK) monitor engine temp and see how it runs - for a while? Otherwise - I'd try disabling those circuits one by one with the Supply Relay on - remove fuses/modules...

I'd also look at the teminals for the relay - are the corroded - can you see the pins inside the relay socket - do they look OK?

Did you work on any of these systems recently?

Alan

steaditim

Alan, thanks for your post.

I looked the relay up on https://www.928gt.com/t-90fuse.aspx under their fuse and relay diagram.

But it's interesting that you mention the HVAC. As I replaced the 2A mini relay on the AC switch a few months ago. Thinking that might have something to do with the problem, I remove the fan/ac slider controler unit before I drove home this morning. Same thing happened. I will try removing fuses as you suggested and chase this down.

Thanks again.

Tim

Alan

Tim - OK so I think that 928Specialists document should be updated (Wally you out there...) to say Supply Relay. The Ignition Relay-X (X-Bus) note is in some ways a good pointer but also little confusing as although similar - it actually works a bit differently from the old X-Bus Repeater Relay.

"Supply Relay" is the correct term from the Workshop Manuals / Wiring Diagrams.

Good luck in the hunt - try running without that relay and see if its stable- just carefully monitor eng temps as you do it...

Alan