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Ignition wiring 
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Part built GTM

Joined: Thu Nov 22, 2007 10:31 am
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Post Ignition wiring
Hello all,

Following a conversion from a Rover Metro 1.1 engine to a 1.8 vvc with assistance from Dudley @ Talon Sportcars 4 years ago we are back working on the car!

Picking up the project fresh he is not available (as I think Talon Sportscars has closed down?). We are struggling to get the engine firing and the wiring is a bit of a headache. A few issues below someone may be able to help with?

1) Dudley left a white and green cable running up from the pump, through the floor into the cab - The petrol pump works when a 12v is attached to this wire. We are assuming it links to purple and white wire in the metro loom at the fuse box. Can anyone confirm this?

2) Engine cranks but no spark and no petrol flow when cranked. A MEMS immobilizer interface to bypass the immobilizer (see picture attached) was installed behind the passenger seat. Three wires (black, yellow, red) appear to come from this box towards the wiring loom (cant' see exactly where they go). We can see a blue and slate wire near the ECU has been cut - which we think is from the original immobilizer and no longer required. There is however a white and green wire (which is very long in length!) coming out the same hole back into the cab. Seems like he intended for this to be connected to something in the fuse box or elsewhere in the interior of the car...

We tried connecting the two green and white wires and cracking and nothing happened. No sparks, no life as far as we can see.

Any suggestions on where to go next with this?

Many thanks

Tony G


Sat Mar 02, 2019 5:39 pm
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Post Re: Ignition wiring
See attached


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Mems.jpg
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Sat Mar 02, 2019 5:40 pm
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Post Re: Ignition wiring
Tony normally the ecu has an outut to drive a relay to switch the fuel pump which only energises when the engine is is cranking/running as a safety feature in case of an accident. Cannot comment on 1800 as mine is a V6
Ian


Sat Mar 02, 2019 7:12 pm
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Post Re: Ignition wiring
Hi Tony,

I can confirm that the fuel pump wire is normally connected to the immobiliser circuit so in your case (with the immobiliser effectively bypassed) it could go back to the white purple feed from the fuse box so that it will run when the ignition is on.

Has the 5AS immobiliser unit been stripped out of your car or is it still there? On mine the 5AS turned out to be faulty so I used the 5AS wiring and wired in a cobra immobiliser instead and got rid of the 5AS unit completely, I expect that the unit talon installed needs to be wired in and sends the ECU a signal as if an immobiliser is fitted so that it all runs correctly. If this is the case I have some wiring diagrams that might make your life easier when it comes to making sense of the connections. From memory the immobiliser works on the fuel pump and ignition to the ECU circuits so thats a good place to start.

The blue/grey wire near the ECU probably went to the immobiliser originally via connection to a yellow/red wire that ran back to the 5AS unit. Any idea where that White / green wire terminates? Make sure it isn't a grey/blue wire near the ECU as this will be a connection for the ECU to switch on the cooling fan and its often not connected and left with a short length of wire from the ECU plug.

Let me know if you want the wiring diagrams and I'll email over to you.

Cheers, Jamie


Sat Mar 02, 2019 8:32 pm
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Post Re: Ignition wiring
Thanks for the responses.

Those diagrams would be useful agerrard680@googlemail.com

Yes the 5as has been removed, will take another look at where thise wires join this morning.


Sun Mar 03, 2019 9:04 am
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Post Re: Ignition wiring
Just emailed you some info Tony.


Sun Mar 03, 2019 9:45 am
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Post Re: Ignition wiring
I reckon Jamie's info will sort you out but a couple of other things to add:
1) you don't say if you are MEMS 3.0 or 2.0 - i think there are some differences - I've not got my head around what they are but will soon (if I ever get around to my 143VVC-160VVC swap.
2) I discovered that (with my MEMS 2.0) there seemed to be three functions of the 5AS, one was the fuel pump, one was the ignition and one was a handshake/code rollover with the ECU. The first two were simply switches on the earth return so you can easily bypass the 5AS for the fuel pump and iginition circuits by wiring them straight to earth. The third function, the handshake, can't be bypassed without some external intervention, either switching it off in the ECU using remapping software (possibly only on MEMS 3?) or one of those piggy back units which it seems you have. I found that without the handshake ocurring (with that function of the 5AS still working) it wouldn't even crank so if you are cranking but not starting then the piggy back chip must be working so from my logic you just need to take the fuel pump and ignition earth returns straight to earth rather than via the 5AS circuit and you are running.

Good luck


Sun Mar 03, 2019 11:46 am
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Post Re: Ignition wiring
I think Sanz has nailed it there Tony.

That’s essentially what I did as the ECU was remapped and didn’t need the 5AS input (though it would have learned it if it were working) so I just replaced the 5AS with a cobra unit to maintain an immobiliser and wired it in from scratch after junking all the 5AS wiring, you could just hard wire the ignition and fuel pump instead.


Sun Mar 03, 2019 12:59 pm
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Post Re: Ignition wiring
For MEMS the ecu learns the rolling code from the 5AS. As people have said without it you won't get any joy out of the ecu (ignition or injectors). I have seen ECUs with the immo switched off in software. Your bypass device may work but the immo rolling code not only needs to be learned but also synchronised. This is done diagnostically using Testbook or a suitable equivalent. Obviously something like an Emerald M3D coukd be used as a plug & play replcement for the MEMS ecu. Another thing to be careful of is the different variations of engine hardware (specifically the reluctor pattern on the flywheel) vs what the ecu is setup for. There were a number of variations over the years & if incorrect the ecu will never 'lock on' to the crank trigger signal & properly recognise engjne rotation / position.

Cheers Stew.

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Tue Mar 05, 2019 10:10 pm
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Post Re: Ignition wiring
hi Tony G
i found this on the net
http://www.mgfregister.org/forum/viewto ... f=8&t=8514

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Thu Mar 07, 2019 8:59 pm
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Post Re: Ignition wiring
Thank you for all of the advise, I'll try to digest them and report back. It's a mems 2 system by the way.

As a partial update I found that there was no power to the ECU black connector from the brown and pink wires coming from the relay pack (these also feed the injectors, coil and a number of other sensors). Strange that only it had no power and all others had 12v! I can only assume a break in the wiring inside the loom which I cant get to. I tried bypassing it with 12v via a 10 amp fuse but still no spark. I wo dear if this could be related to a frazzled ECU? Any thoughts how it can be checked?


Wed Mar 27, 2019 11:27 pm
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Post Re: Ignition wiring
I spoke with Keith at Emerald a few months ago and floated the idea of a partial rewire and / or the plug n play adapter route. I'm starting to feel like I've gone far enough with the mems system. Frankly it feels like it's a bit of a mess.

Wish I'd gone mems 3 at least I'd have error codes to help me problem solve!


Wed Mar 27, 2019 11:35 pm
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Post Re: Ignition wiring
Sorry for multiple posts.

There isn't a 5as unit on the vehicle, I gave it to Dudley but he didnt install it, just installed the immobiliser interface I pictured earlier. I assumed it eliminated the need for it entirely...

I assume with an emerald k6 there wont be any immobiliser related issues as it doesn't look for a signal / code?


Wed Mar 27, 2019 11:47 pm
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Post Re: Ignition wiring
Not sure about that!!
I have an Emerald ecu on mine & it still has the 5as on as well.

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Thu Mar 28, 2019 8:16 am
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Post Re: Ignition wiring
Hi Tony,
Did the old engine have a speedo cable? If so could the white/green from the back be for the speedo?
Just need to see if you can trace it back to the sensor?
Juls


Fri Mar 29, 2019 10:49 am
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