ECU still 'live' when ignition key turned off !

[CHRIS CLARK]

Just thought you'd all like to know.

Having completed the 1800 'K' eng. change etc I've had a problem with the engine 'running-on' when the i/key is turned off. The eng. dies due to lack of fuel as the fuel pump cuts off ok.

Mick Smith & I played with various ideas of why, & to cut the story short it turns out that the 'Vecta' alarm retains about 1.5 volts through it which is enough to still power up the Emerald ecu!

 

I am in the process of removing said alarm (as I only have one 'key' anyway). We have proved system will work properly if alarm is 'isolated'.

 

question.gif It has been tricky to start from cold since the change of eng/ecu. Does anyone know (think they know) if the alarm system can say, 'rob' maybe 1.5 volts from the start up voltage too? Car starts fine if a second battery is jump-leaded across the fitted one.

By the way, the fitted one is a brand new 'Banner' unit.

It's fine once the eng. has been run for a very short while. Charging the batt overnight has no effect on this start up procedure.

Bl%dy inconvenient thumbsdown.gif

[Mick Day]

Interesting this one. Before my engine change (standard MEMS) the engine used to "run-on". Now with new engine & GEMS ECU it dies the moment I turn the key. It also starts 1st time even after 4 weeks. I also have a Vecta Shadow. Could this be a symptom of a dying Vecta??!! Let us know how you get on after removing the Vecta. It would also be nice if you could post step-by-step info on how to remove said item.

Mick

[jp7]

Hi Chris, cheers for the email. My 1400k used to do that sometimes as well, i thought it had something to do with the fan? Not knowing much about wiggly amps, is it not possible to fit some sort of voltage sensing device in the line between the two that cuts the line when the voltage drops below a certain value, say 6 volts. That way you could keep you vecta.

Still look on the bright side, even without the vecta, nobodies going to nick it cos its got flared wings.smile.gif What are we going to do when the world wakes up and realizes that flares rulethumbsdown.gif

Cheers

Andy

[jp7]

should have been a thumbs up at the end, stupid computer or is it the operator!

[Johnty Lyons]

Stick a diode in the fan cct the back EMF from the fan running on creates enough energy to hold the ECU on and the ECU switches its own current the ign feed is only a start up device.

Been there Done that Got the T-Shirt.

 

jj

[CHRIS CLARK]

Sorry Johnty.

Close, but no coconut or second t-shirt! It is not the cooling fan spooling down creating the back EMF generator effect. That is all well known, but is not 'my' problem. The Vecta is the cause; full stop.As stated, when this alarm is isolated it stops on the key just as it should. I might add that the key is just for the purpose of turning the ignition on & off (& freeing the steering lock!).

The actual start is by the 'big red button'.I can say that I NEVER had a problem with this set up with the MEMS fitted, & yes, it could be left for weeks with no start problems.

 

Mick D. As to the Vecta now giving problems, well, maybe. I've certainly heard of starting problems being associated with a 'duff' Vecta. It may be that it has just picked this time to give the grief and it happens to co-incide with the engine change. Murphy's law in action (no offence intended Johnty!)

 

Vecta. A brief description of it as I have found so far in my Caterham.

Others may of course be different!

 

The Vecta unit itself is mounted under the dash cable cable tied to the existing loom. Access to it is best with the heater/blanking plate removed.

It looks a bit like an ignition coil spewing black wires.

The system has 16 (all!) black wires running around various parts of the car loom. From what I can guess, it probably had paper identification tags mounted on the leads that have been removed after the fitting.

Two of the leads are:- 1)An earth &, 2)A permanent fused feed (from the lighting circuit). That leaves 7 pairs of wires to connect to the various functions. The fuel pump is one such function that has its supply split by the Vecta. Basically this means the loom is cut and the wires are soldered/heatshrunk to the alarm 'in & out' pair.They are then bound back with the ubiquitous black PVC tape and 'lost' in the system. In theory this leaves another six functions to interupt. On my car this fuel pump wire has two 'ins' & two 'outs' soldered into the cut ends.

This is either to, a)Halve the operating current, b) Give a degree of redundancy in case of failure or, c) My favourite; that to operate at all, all 'pairs' have to be connected to something and therefore with the Caterhams relative simplicity/lack of electrical bits its easier to double up on the wires!!

There are the others, but for security I won't go into which ones are cut/joined. I'm sure you get the idea though!

I'll let you know how the removal goes when I finally finish it/the weather warms up !!!