Another 3.6 transplant problem question - electrics?
 

I decided to go for the initial test start last night, but after having cranked it with the DME relay removed to get oil pressure, I connected in the DME relay and quickly discovered I have an electrical problem :(

I am not sure if this is down to a faulty relay, DME or something I have connected wrong - but here is the issue...

If I turn the ignition to the run position so that all the warning lights come on etc, and then switch it back to off (ie. remove the key from the ignition), I still have a +12 feed to everything - all the warning lights stay on!

I discovered that I can kill the power by removing the DME relay and the installing it again.

After some searching, measuring and drawing up my own small diagram to help I discovered that once the DME relay is activated it remains activated even when the key is removed from the ignition.

Here is my bad (simple) diagram for the relay and where the Timmins harness is included...

http://forums.pelicanparts.com/uploa...1285830625.jpg

What I have discovered is that Pin 1 with the black Timmins wire retains +12 volts even after the ignition is switched off :confused:

I also do not hear the fuel pump getting activated when I put the ignition to the run position - should I, or does the DME not start the pump until you try to crank the car with a ground signal via Pin 2 on T16?

I am hoping this is a bad DME relay (maybe the diode is dead?), but I can not understand how the black wire can hold +12 if the other end is connected to ground? Just to clarify. If I disconnect the black wire from switched live after having turned the key to run and back to off - it still measures +12 :confused:

Anyone got some clever ideas here???

Just had another close look at the electrical diagrams, and it looks like pin 1 on the DME relay is also connected to pin 2 on T15 which goes to the Ignition coils.

Did some more testing during lunch, and did not get the problem to go away. I did the following:-
.- Completely disconnect the 14 pin connector at engine - problem still there, so reconnect and then -
.- Disconnect the other connector with engine harness - problem still there, so reconnect and then -
.- Disconnect the DME - problem still there, so reconnect and then -
.- Disconnect the DME relay - problem is not there!!!

I think my next step is to try a new DME relay. I will order one and see what results I get...

OK, spoke a bit with Timmins and he suggested I measure the voltages at the relay socket with the relay removed. This is the results I am getting:

With ignition OFF...
Pin 1 - Ground
Pin 2 - Ground
Pin 3 - Ground
Pin 4 - Nothing
Pin 5 - Ground
Pin 6 - +12

With ignition in the ON (run position)
Pin 1 - +12
Pin 2 - Ground
Pin 3 - Ground
Pin 4 - Nothing
Pin 5 - +12
Pin 6 - +12

what i recall in my case the pump was only running while cranking.

Good luck. Btw. The timmins instruction are not the best...

What does "???TBC" mean in your diagram? That pin is the output of the first stage of the DME relay and it is used to switch power to the DME. You have that one connected to something wrong (e.g. Terminal 15, switched +12V) with is the input to stage 1 of the DME relay (pin1). So once the first relay closes it supports itself even if you remove power from pin 1 by turning the ignition switch to off.

The fuel pump only runs when you crank (flywheel motion detected)

Ingo

OK, more testing and measuring!!!

I think I have managed to narrow it down to the red/white cable on connector T15 (pin 3). If I disconnect this wire then the problem is no longer there.

Looking at the electrical diagram for the 964, this wire feeds +12 from the DME relay to pin 37 on the DME. It also feeds +12 to a load of other stuff...

So either I have a faulty component somewhere connected to this wire, or the main harness that I got with the engine is bad - it was not the cleanest harness I have ever seen!!

Question: Anyone know if there maybe is a diode somewhere in the main harness that this wire is connected to that prevents it from back-feeding +12? Maybe there is a diode there that has gone bad or something?

I could not figure out where it went from the diagram, so for now I put TBC.
I hope it is not wired wrong, as it is all connected with the harness I got from Timmins. I only did the diagram to help me see what the relay should be doing....

Yo

I cant work out where you have gone wrong with this, the Timmins loom only has 4 wires, purple to tacho, green to fuel pump (makign sure you insulate the old feed to pump), red perm live (I used battery terminal) and black switched live ( I used the switched on the fuse panel, checking its still live when cranking)

Are you sure this is not to do with the 14 pin out back?

The problem is not in the Timmins loom. I did think it was in the DME relay, but not so sure any more.

The problem is in the original main loom that I got with the engine and DME or a component connected to it...

On the Timmins loom, there is a 6 pin connector that has three pins. The other side of that connector is on the main loom and has the label T15 on the electrical diagrams.

In T15 there are three wires:-
Black - switched +12 volts
Red/white - +12 from DME relay to DME and a load of other things on the engine
Green/Black - to the oil temp gage

I have narrowed it down to a problem with the Red/White wire.

When I got the main loom with the engine, this connector was broken and someone had done some bad repairs to the loom that I had to clean up. Either I have made a mistake in the cleaning or someone has messed up the loom!

Timmins suggests to try and disconnect the coils and see if the problem disappears next...

OK, here is the plan...

Disconnect everything with a plug and work backwards by connecting in one thing at a time until the problem comes back. If I have the problem with everything disconnected, then it is rather sure it is the harness that is faulty. The only thing I will keep connected at all time is the DME relay as that is fundamental in the fault appearing!

Need to get the kids off to bed first, and then I will sneak into the garage and start investigations again...

OK, went back into the garage and started to follow the electrical diagrams and started checking out all the wires and connectors. I was drawn back to T15 all the time and the strange behavior with the Red/White wire, so did some more digging and finally found that there was a short between that wire and the Black one on the same connector about 6 inches down the harness!!!

Fixed the short and the problem is now gone :)

Tomorrow I will return back to trying to start the car!

Result Norseman!

I reckon you are about to get there first.

I will not count my chickens yet - I could still have problems!?!

Yep - that makes sense. Once the white/red wire was energized it fed the power right back to the black one and thus kept everything energized.

While this condition won't allow you to turn the engine (terminal 15) off it should have allowed you to fire up the engine. So there might be more to check/correct. Good luck,

Ingo

Thank you for confirming that for me Ingo. I discovered the problem before trying to actually start the car, so could have luck - but I am expecting there to be more problems, there almost always are!