constant ignition live

[wildo105e]

Whilst solving my fuel pump probs i noticed my ECU is shutting down on cranking. This is down to the ignition live i am using. Running a live from the battery solves this but i was wondering if anyone knew of a suitable ign live on a MK1 escort which wont shut off on cranking. This would save me a load of hassle:thumb:

Cheers

[seventynine]

the one that supplied the coil originally. green on the mk2 escort

[Dave]

the one that supplied the coil originally. green on the mk2 escort
That gives 12volts only while cranking though doesn't it?

[seventynine]

it powers the coil.......i.e its live when the coil needs to be live, under cranking and when the engines running.

if it were live just while under cranking, what would power the coil when the engine is running?

[Dave]

If running the points ignition the feed to the coil goes 12 volts only when cranking, then 9 volts when running. The coil is fed through a ballast resistor when running.

[Zetec_Escorts]

Just go straight to the battery, no nonsense!!

[Miniliteman]

Just go straight to the battery, no nonsense!!

Agree, but fit a switch plus a fuse in the line.

[wildo105e]

Cheers gents. Running from the battery is my last option (i think my only option):D.

I have a good heavy 12v supply from the battery fuesd and to a relay when given an ignition live it supplies a fuse box to feed everything else. I was just a bit uneasy about the same live making the relay switch on albeit with a switch. I don't suppose it is any different than running in another 12v live from the battery as i have tried a temp one and that works fine.

I do like the look of those aircraft style switches though they would make me feel really racey:D

Working this weekend or it could have been the lighting ceremony:stu:

[boombang]

Use the ignition live you did before to activate a relay, and run from battery to fuse to relay to ECU.

Turn on ignition, ECU comes on and has proper feed!

[seventynine]

i was about to put the exact same thing as above ^^^

thanks for that dave, i genuinly didnt know that.

ah things you think are so easy all of a sudden prove otherwise!

[Dave]

That's how it works on a Mk1, modern cars like yours might be different :D

(Mk2's still run a ballast resistor somewhere)

[wildo105e]

Mmmm I think i see what you are saying will have a think.

Cheers again:thumb:

[andrewr]

That's how it works on a Mk1, modern cars like yours might be different :D

(Mk2's still run a ballast resistor somewhere)

If you are running some form of spark control it is likely you either don't need or don't have the ballast.

For example in my Mk2 I don't, I have a modern 12V coil so I have the ecu switched off the coil feed, which always gives 12V.

[wildo105e]

I think that hits the nail on the head. I may have forgot to mention that i will be using a coil pack. Does that mean that the coil feed gives a constant 12v during cranking. If so i can just trace that back and use that to kick in the relay that allows power to verything else.

I will try and test this weekend.

Cheers:thumb:

[Dave]

The 12 volt feed during cranking comes from the green and black wire that connects to the coil. That is fed from the solenoid. When you crank the engine the green and black wire goes live, when you release the key the solenoid disengages and the feed to the coil reverts back to the pinkish red and white wire to the coil (9v ballasted) The green and black wire has no feed at that point.
What I am trying to say is that as long as you are using the original solenoid and the green and black wire connected to it, you will indeed get 12 volts at cranking. It will not run on that feed though, as it is turned off by releasing the key and reverts back to the 9volt feed from the pinkish red/white wire. (they are connected at the coil feed wire)
Hope that makes sense :)

[wildo105e]

100% Back to the drawing board:thumb:

Might just throw a switch in for now.

Surely anyone running an ECU in an old car must have this problem. I think cossie ECU's have a live and an ignition live connected to them:confused:

[andrewr]

releasing the key and reverts back to the 9volt feed from the pinkish red/white wire. (they are connected at the coil feed wire)
Hope that makes sense :)

does a mk1 have a ballast? If so all you do is remove the ballast and connect the cranking ignition wire to the running ignition wire.

If a mk1 doesn't have a ballast then from memory the pinkish red/white wire has an internal resistance. So all you need to do is replace the wire with normal wire. Then join the cranking and running ignition wires.

Either way use a multimeter to check the resistance of the part you're removing to confirm it is whats dropping the voltage...

andrew