fuel pump relay / fuel cutoff

[schuss]

hoping to install a simple hidden fuel pump cutoff in my friend's new 91, as one of several lines of theft defense.

i ordered an FSM on CD today but won't have it for several days.

can someone with a wiring diagram and/or FSM help me out? where is the fuel pump relay located, or rather where can i easily tap into it's wiring and create a cutoff circuit? what are the color codes of the wires?

i couldn't find anything about it in the forum or faq... although i did find lots of other good stuff

thanx!

 

[D'Ecosse]

I already supplied this to someone else - may still have the schematic, let me look. Pretty easy proposition - main relay is behind the panel behind the seats - quite easily accessible. The trick is where you hide the hidden switch

 

[EIFFEL]

Pulling the fuse for the fuel pump circuit is much easier, and most thieves will not spend the time to troubleshoot.

 

[D'Ecosse]

Pulling the fuse for the fuel pump circuit is much easier, and most thieves will not spend the time to troubleshoot.

Kind of a pain to pull fuse & re-install every time surely? a switch much more convenient

 

[schuss]

EIFFEL - it's something i want to install with a hidden switch, so it can be done anytime the car is parked. pulling a fuse wouldn't really be feasible that often, plus you want it to be discreet so someone doesn't see you doing it when you park.

D'Ecosse - excellent, thanx! i installed one in my car, and even with a timing circuit to make it turbo timer-safe it was still pretty easy. but i have the full factory wiring diagram for my car, and the FSM clearly documents the component locations. i'm flying blind on this NSX!

 

[D'Ecosse]

... i'm flying blind on this NSX!

This will help!

 

[schuss]

holy crap, that rules! thanx!

 

[D'Ecosse]

At the output of the fuse 7 (7.5A) on the dash fuebox (driver's kickpanel) break the black/white wire & put switch in series - this will break power to the ECM & Fuel circuits.
Should be pretty accessible to tap into down there with ability to hide a switch within easy driver access.

.

 

[schuss]

you're quicker than me... i'm trying to maintain the illusion that i'm still doing some work when really i'm looking at wiring diagrams.

thanx! we'll take some pics, maybe put together something nice enough for the FAQ. i think this should be every exotic car owner's first DIY mod

 

[D'Ecosse]

... we'll take some pics, maybe put together something nice enough for the FAQ. i think this should be every exotic car owner's first DIY mod

except we don't reallly want to take any pics or secret switch locations!

 

[schuss]

right... no. i was thinking more of drawing up the wiring diagram and explaining why and how in general terms. maybe taking pics of how to wire up the relay, etc. but we'll see how ambitious we get... haven't even installed the thing yet.

 

[DrVolkl]

Thanks Schuss...didn't realize you were gathering all this info!!

(It's my car he's working this out on...I suck at electronics)

 

[schuss]

np - i need something interesting to do at work, right?

 

[AdvansCPAP]

D'ecosse,

Do I need to unbolt the entire fuse box in order to get access to that black/white wire? And since it's fused for 7.5 amps is running a 10-20 amp toggle switch more than adequate? If I was going to do it from the main relay which wire did I need to tap into? Thanks.

 

[nsxman2001]

At the output of the fuse 7 (7.5A) on the dash fuebox (driver's kickpanel) break the black/white wire & put switch in series - this will break power to the ECM & Fuel circuits.
Should be pretty accessible to tap into down there with ability to hide a switch within easy driver access.

.

Do u have to use a relay when u ADD the switch to this?

 

[schuss]

Do u have to use a relay when u ADD the switch to this?

yes, yes, a thousand times, yes!

get a good quality one, too:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=330-070

 

[schuss]

D'ecosse,

Do I need to unbolt the entire fuse box in order to get access to that black/white wire? And since it's fused for 7.5 amps is running a 10-20 amp toggle switch more than adequate? If I was going to do it from the main relay which wire did I need to tap into? Thanks.

use a relay, then it doesn't matter how beefy your switch is.

and no, you shouldn't have to unbolt the box - i was able to find the wires from the top.

 

[AdvansCPAP]

Thanks for the info!

 

[NSX2398]

Do u have to use a relay when u ADD the switch to this? ....yes, yes, a thousand times, yes!

It's not at all clear to me why you'd want the extra complexity of wiring in a relay when a switch will work fine. Please enlighten us.

 

[Malibu Rapper]

It's not at all clear to me why you'd want the extra complexity of wiring in a relay when a switch will work fine. Please enlighten us.

You are correct, the relay is not necessary. However, if you want to do an ultra stealth kill on a momentary device, a relay is your best friend. Like say you want to make it so the car can only crank the starter when the parking lamps are on, or when the mirror adjustment is on the driver side, etc. For something that requires constant power/ground like a fuel pump, I would go for a switch. But I prefer an alarm because I'd forget the kill otherwise.

 

[schuss]

The kind of tiny switches you want for this sort of application - that can be hidden anywhere, or chosen to blend in with your interior - are usually not going to be rated for the current involved. Rather than risk a melted switch or a short circuit, use a relay and then you're free to use any switch, located nearly anywhere you want.

In this case, considering the importance of the circuit involved and the ultimate goal (stealth), I think the extra complexity is worthwhile, especially if folks are new to wiring and don't feel comfortable with ratings on various switches.

 

[NSX2398]

...I think the extra complexity is worthwhile, especially if folks are new to wiring and don't feel comfortable with ratings on various switches.

You're kidding, right? If people can't understand what the ratings on a switch mean, they probably shouldn't be tackling this as a "new to wiring" project. A relay will involve at least twice as many connections; will involve symbols and concepts more complex than a switch (which is nearly impossible to screw up); and needs a mounting strategy (socket; tab; etc) in addition to wiring the switch.

The last time I looked, Radio Shack (or whatever it's become) had lots of micro switches that could handle up to 15 volts and 7.5 amps. I will admit though that the pure switch approach will also require suitable sized wire (which will be heavier than the relay approach) which could easily get overlooked by a novice.