Main battery disconnect

[Jon]

Couple comments Wayno.
The alternator wire is always hot the way it is drawn, I would take it to the heavy pole on the starter so it is cut on isolate.

The fuel pump will run all the time the isolate switch is turned on as drawn, needs a manual switch in series with the inetria switch to control the relay that mike mentioned.

Do you want the interia switch to cut the ignition as well as the fuel pump?

Do you want separate fuel pump & ignition switches or a combined switch for both?

jon

[jacksoni]

By the way, the battery shut off switch does not have to be on the back of the car. Can be on the front. As someone noted, long distance running wires not necessarily good and not all of us have the battery(s) in the trunk.  Though of course is not SCTA, couple years ago running at Maxton (ECTA and they use same rules) inspector wanted the engine running and pull the battery switch to prove that it shut off the motor. Never had that done to me on the salt but it shows what they are looking for. As has been pointed out a lot on this forum, different inspectors may have different interpretations of the book.

[BHR301]

Just a thought..how about a relay in the alternator wiring circut with power to operate the relay from the master cutoff? Cut the power at the master and power to operate the relay is shut off, no alternator, no engine running...

Bill

[Rick Byrnes]

Just a thought..how about a relay in the alternator wiring circuit with power to operate the relay from the master cutoff? Cut the power at the master and power to operate the relay is shut off, no alternator, no engine running...

Bill

BINGO

But, the way the new SCTA/BNI rule book is changed, there is NO interpreting what the rule says.  If the book doesn't say the engine needs to be running and shut off when the switch is pulled, then it can't be required even if it make sense.  The wording in the book will eliminate an inspector including His personal requirements into the "book" and causing confusion.  There can be many "intent of the rule" opinions, but in my mind SCTA is now saying there is no"intent"  of the rule.  It must be written exactly as intended.
Many of us forget that the rules are minimum and for our own protection we May go way beyond the written requirements.

Of course it makes good sense that the engine should shut off when electrical switch is in the OFF position.  I'll bet the book will change quickly on that one.

I am in complete agreement though that the book should not allow for interpretation. 

[Elmo Rodge]

OK. Here's the new one. I picked up a Bosch style relay for the fuel pump. The big wire to the starter is hard wired and the little one from the switch makes it work, right? Question; If I wanted to make the ignition and the fuel pump kick out with the inertia switch (which they gave me for free at the wrecking yard. I like it here.  ) would I just move the inertia switchbetween the fuse block and the 2 switches? If I can help it I really don't want to get much more confusing than this.    Wayno

[Jon]

Yep Wayno, running the power from the fusebox to the inertia switch, teeing into the ign & fuel pump switched will cut both of them when the inertia switch trips.
This will have your ignition & fuel pump running from the one fuse.
You could have the fuel pump & ignition teeing off after the switch and have one toggle switch & a press to start switch.
I used to run speedway cars this way, start procedure was ignition on for 2 seconds to charge the fuel pressure, ignition off, hit starter for about a second then ignition on.
Let the motor turn over a little & build up some inertia before firing.

The way you have it drawn the motor will stop if the external switch is turned off.
There is still a spark risk from the main (heavy) starter wire and the alternator wire.
Depends on what you are trying to achieve with the external switch, stop the motor or make the whole wiring loom cold and have no spark risk.

[Plmkrze]

What happens to a modern hot rod (Stang, Camaro, Challenger or any modern car) when you "cut" power to the ECM, TCM, NAV, Blue Tooth (my radio presets!) etc,etc,etc when the car is running just to satisfy the tech guy. I don't think the "modern" electronics would like it much. Also, would this hurt a custom ECM tune?

All modern cars are federally mandated to have an inertia fuel cut off switch. Crash the car, put some G's on and the pump is deenergized.

To check the master (battery) cut switch all that is needed is a multimeter or a test light. 

Please, leave my eletronics alone. I can mess them up on my own thank you very much. 

[hotrod]

Most Electronic Engine Management systems will "reset" to default settings if they lose all power. Some have enough built in capacitance to keep their programing if the power interruption is "very brief". A system can be rigged up to "keep alive" by having a method to provide low current 12v power to the ECU when the system power is cut for tech but this is definitely something you would want to plan and test for.

Save your tuning changes and have a method to "reload" the maps as a minimum.

Larry

[Buickguy3]

   Back in the "olden days" when I ran a shop, the tech's had a little decice that had a 9 volt battery that plugged into the power plug and kept all this from happening.

        Doug 

[Ron Gibson]

I ran my MSD and the fuel pump through separate 50 amp relays controlled by the inertia switch. Inertia is controled from the ignition switch. Less amperage load on the ignition switch. Wouldn't be that hard for separate switches. If anything happens, I want the ignition dead too.

Ron

[Elmo Rodge]

I want to thank all of you for your help in figuring this mess out.  While the wiring isn't 100% complete, I fired the engine today for the first time and everything worked like a champ. (Sounds good, too) I've learned a lot in the last few weeks thanks to you.  I've still got to tidy things up but now I've got a handle on it. Thanx again. Wayno

[Stan Back]

We're thinking of tying the battery to the chute lines and jettisoning it at the end of a run just to be safe.

[grumm441]

We have two cut offs

We cut the earth with one of those big red key switches that is on the out side of the tank

and the positive is cut off with a 200 amp cole hersy continuous duty relay
The cole hersy relay is turned off by a switch on the steering wheel, the inertia switch, or the fire system being activated
So any of those situations will pull the positive and because the relay is close to the battery, we don't have huge voltage loss
G