Ignition/Starting - wiring advice

Bevan-L · 21 Sep 2007, 01:10 (Ref:2019401)

Can someone give me some advice regarding wiring up my car for ignition and starting etc.
It doesnt have the keylock anymore so I have to wire up some switches
I've got a 6 pole batterry cut out switch but i was wondering how should I wire the rest up? would
i have another master toggle switch? one for ignition etc?

Essentially whats the best way to go about it..

Cheers!

1200Datto27 · 21 Sep 2007, 04:45 (Ref:2019450)

I use a momentary push button wired to the starter solenoid, and two toggle switchs (one's power to the injection and ignition circuits, the other does my ECU, data logger and dash) this allows me to kill the engine but leave the electronics on so that I can download the run data after a session.

Al Weyman · 21 Sep 2007, 07:26 (Ref:2019497)

One master ignition switch, two fuel pump switches and a push button starter straight to solenoid as outlined by Mos, simple and works. Oh I have no computer or nothing on my cars.

**dtype38** · 21 Sep 2007, 07:40 (Ref:2019509)

FWIW I route the battery straight to the main battery cutout so when that's off absolutely everything goes off. From the cutout I run to the starter and the fuse box. I run the fan/horn/hazzards direct but the ignition/lights relays/fuel pump relays/instruments go via a simple dash mounted key switch. From that I use a push button for the starter solenoid. Simple and effective.

trikesrule · 23 Sep 2007, 21:57 (Ref:2021311)

Yep Dtype thats exactly the way I do our cars - simple and safe. You should see the bunch of noodles I'm sorting in a customer car at present strewth how it ran is a wonder and yes it did catch on fire. Evidently they could turn the engine over with the ignition off! They wired the relay incorrectly........trikes

GORDON STREETER · 24 Sep 2007, 07:20 (Ref:2021453)

Just to put my two pence worth in, Whatever way you go about it, I would recommend putting ancillary stuff like wipers etc on a separate fused link away from the ignition switch. (just run ign and fuel pump) then if you have a short in anything (even a brake light) the car will keep going and that is more important !

JohnD · 24 Sep 2007, 08:24 (Ref:2021490)

We seem to be adding more and more switches, but I'll follow Al.
Just a 'Main' or ignition switch, fuel pump(s) wired to go off with that and a push button start. But I add switches for the fan and the water pumps, so that they can continue even after the ognition is off, to help the engine cool evenly after stopping.

John

R59 · 24 Sep 2007, 10:00 (Ref:2021570)

Those 6-pole FIA switches are a pain in the rear. Use a simple two pole battery isolator, but run the alternator direct to the battery (connected to nothing else), that will ensure that nothing can go live with the isolator off, and always ensures that the alternator has a battery (load) on it. Modern alternators are much more tolerant of running with no load than certain old ones (which used to pop their regulators if run open circuit). Hang what you like off of the switched pole of the isolator, and make sure you have things fused.

Personally, I would operate things like fuel pumps off of their own switch, with a separate fuse in each supply. Rather than use conventional fuses, use thermal trips (either aircraft style, or the simple blade fuse style ones) that you can re-set.

My system has a main on-off which switches on things like ecu, etc... but not the fuel pumps/ignition, and allows me to turn it over to build oil pressure before firing it up. The "ign" switch turns on fuel pump(s), and the ignition supply to the coils.

And when it comes to fuses, don't put fuses in the circuit that are way over the top for the current that the device will draw, or the wire can carry. I've seen 25A fuses with 1.5mm wire (6-8A max)!!! A recipe for a wiring loom fire!

zefarelly · 24 Sep 2007, 11:27 (Ref:2021628)

I run an Fia cut of switch but otherwise I put the key in the lock and turn it . . . everything works just as it did when it left Dagenham !!!

Bevan-L · 30 Jul 2008, 23:07 (Ref:2260616)

How do you wire the fuel pumps to a switch if they're switched on by the ECU usually?

coln72 · 30 Jul 2008, 23:59 (Ref:2260626)

I kept mine simple. Power on switch, ignition switch and one fuel pump switch (so I could prime the system before starting).

phoenix · 31 Jul 2008, 15:57 (Ref:2261068)

Quote:

Originally Posted by Bevan-L

How do you wire the fuel pumps to a switch if they're switched on by the ECU usually?

The ECU will probably control the fuel pump(s) via a relay; the ECU commonly grounds/earths the 'pump' pin to turn the pump on. The other side of the relay operating coil can be fed it's positive supply from the ignition switch or master cut-out switch.

You could either:

1) wire a switch to ground the same negative relay pin, i.e. wire the switch in parallel with the ECU control wire. This will enable you to turn the pumps on even if the ECU is not connected or powered up.

2) wire a switch in between the ECU pin and the relay, i.e. in series. The pump(s) will only be turned on if the switch is turned on and the ECU thinks the pump(s) should be on. Wired this way the additional switch can only be used to turn the pump off when the ECU thinks it should be on. It can't turn the pump on independently of the ECU.

I use option 1) as it allows you to prime or bleed the fuel system, empty the tank or even find fuel leaks without the engine running or the ECU powered up - much safer!

There are other ways you could configure an additional switch if you want to get more complicated!

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