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I know that someone has made a relay that shuts off the power to the fuel injectors for a FAS switch and as I considered this I found I had a fuse for the fuel pump. I figured that since that was its only source of fuel pressure that I know of it would die relatively quickly (wrong) but while I was in the UHFB I found that lo and behold I have a Fuel Injector fuse. Pulling it results in instant engine shutoff with *no* visible side effects (tach smoothly drops to nothing, oil press and alt. light come on like they would. Engine restarts without a hitch and no CEL., not even the CEL that's on before you start the car the first time). What I'm wondering is ... this seems to good to be true, any long term bad effects of doing this? FWIW this is a 2004 Saturn Vue 5 Spd Manual with a 2.2L GM Ecotec gas engine.

Thx in advance!
--Ryan

I know that someone has made a relay that shuts off the power to the fuel injectors for a FAS switch and as I considered this I found I had a fuse for the fuel pump. I figured that since that was its only source of fuel pressure that I know of it would die relatively quickly (wrong) but while I was in the UHFB I found that lo and behold I have a Fuel Injector fuse. Pulling it results in instant engine shutoff with *no* visible side effects (tach smoothly drops to nothing, oil press and alt. light come on like they would. Engine restarts without a hitch and no CEL., not even the CEL that's on before you start the car the first time). What I'm wondering is ... this seems to good to be true, any long term bad effects of doing this? FWIW this is a 2004 Saturn Vue 5 Spd Manual with a 2.2L GM Ecotec gas engine.

Thx in advance!
--Ryan
It does appear that this would have the same effect as the relay setup you mentioned. One minor thing to keep in mind is this method would require a switch and wiring to handle the full current draw of the fuel injectors vs. current requirements of operating the relay. It doesn't seem like there would be any long term negative effects. I would, however, avoid using the fuel pump to kill the engine. The reason is that the fuel injectors will continue to cycle for awhile and it can be hard on the injector to operate without the lubrication that the fuel provides.

I'm using a 20 A relay on the closed side to make the connection and fusing between the relay and the fuse box with the original 10A fuse, drawing current off the 12V acc supply and fusing it with a very small fuse to operate the relay only when the switch is pressed.

Even though I have a lot of confidence in the relay method I don't want to mess with the OEM wiring so I'd like to just make the connection break at the fuse box. is there such a thing as a mini fuse that will go into the fuse slot and let me solder on wiring? I thought about taking a blown fuse and soldering on and putting heatshrink tubing around it but it doesn't seem as elegant.

Well. I installed the mod today. It works well for killing the engine but there's a few iffy things...

I went on a long trip after I installed it tripped a check engine light twice. The codes were related to the injectors which makes sense, but it doesn't trip consistently. The other huge annoyance is that when the engine dies the scangauge hangs for a few seconds before resuming updating. This happens when the engine actually dies. You can toy with the cutoff and rev it back up before it dies all day long but when the RPM hits 0 the scanguage hangs. No idea why. The other really odd thing is the electric power assist on the non-hybrid gas vehicle doesn't actually turn off when the engine dies until the car comes to a complete stop. I don't know if this is by design or omission but i sure don't want the battery to die but maybe I'm overestimating how much current draw the electric P/S uses.

So my wonder is any ideas on how to solve the

A) Injector Check Engine tripping (codes are P0202, P0203, P0204, and P0000 ... no idea about the last one) -- Mainly why is it intermittently (like one in twenty kills) coming on?

B) ScanGauge dropout when the engine hits 0 --- it comes back on after about 7 seconds but this is almost the entire reason I performed the mod was to have the scangauge have the real gas mileage with FAS recorded.

C) Power Steering -- At first I thought it was terrible, now I kind of like it because it feels sort of like driving a hybrid. :-P Should I worry about battery draw?

Thanks everyone and regards

Good info! I think for C - program the scanguage to look at battery power, and if you need to you can always bumpstart (alternator should be enough to power the restart) - just make sure you don't come to a complete stop when the battery is low and you should be all set.

As for the engine code: of course it throws a code! You're turning the injectors off! My guess to the intermittantness is that sometimes the engine will continue to pump just a little too long causing the ecu to think something is wrong (engine pumping, no injectors).

PS - this is the breakthrough I've been looking for on my car, I'm gonna have to look into that fuse.

P0000 is essentially end of list (EOL).

-mr. bill

Try playing with the timing when you shut it off. Does the code pop up when you kill it at high rpm, or after it settles down into idle?

As for the ScanGuage dropout, try setting the engine type to HYBRID.

Randall

I have done such, but the Scanguage stays lit, it just stops receiving information for a time right as the engine dies.

As for the Cel, i think switch bounce is making the relay flop back and forth some times which trips out the engine computer. I'll try putting a capacitor in series with the switch and see if it helps.

About 80% of the time the CEL gets tripped the first or second time I hit the fas switch after a cold start though, if I clear it after that it stays gone.

If you did not 'debounce' your switch, it is surely bouncing on and off probably dozens to hundreds of times in the few milliseconds it takes you to shut it off, probably wreaking havoc on your ECU.

You need to debounce (http://www.bioinspired.com/users/ajg112/electronics/debounce.shtml) your switch.

So how do you debounce a switch??