SG Shenanigans
 

OK, so it's likely not the SG's fault - probably something with the ECU...

I have the SG set to hybrid so it stays on when the engine is off. Here's the list of events as I don't have a kill switch.

Pulse up to speed
Ignition Off
Ignition Back on (engine off)
wait for SG to shut down
Restart SG
SG starts displaying data

But, the GPH meter says .3 - just as if it were at idle, but TPS is 1 (idle is normally 3).

I tried this again, while stopped. Engine off, car not moving. GPH=.3 -- I have not yet reset the SG, but I will when I refuel (currently at a quarter tank). That might take awhile as my goal is not to refuel until the middle of next month (I've been cycling everywhere trying to meet this goal).

:confused: Anyone else experience this?

This is a Mark4 VW Jetta - 2.0 engine.

I kill my engine with fuel cut off. I would say about 5% of the time the fuel consumption will stay at about .3 gph even though the engine is off. If I want to stop this I need to run the engine about 5-10 seconds before shutting off again. A brief start and stop will not get out of this loop.

My scangauge will most often not start automatically either. I need to hit a button to get it going when I first start up.

I like it but there are a couple glitches.

So you're restarting the engine for 5-10 seconds then killing it again? Out of curiosity, how are you cutting fuel?

Mine also doesn't restart automatically.

As long as I'm not the only one :p I guess we are kinda pushing the concept of the SG pretty far.

trebuchet03 -

I do this :

- Pulse up to speed
- Put stick in Neutral
- Ignition Off
- Wait > 2 seconds (otherwise engine may restart in next step)
- Ignition Back on to "run" position (engine off)
- SG turns on
- EOC coast for X seconds
- Bump start

During the EOC, I always see 0.1 GPH even though there is no fuel being used. My MPG becomes 10 times my MPH (30 MPH => 300 MPG) even though I am at 0 RPMs. The MPG should be the "divide by zero" maximum 9999 MPG that is representative of fuel cutoff.

CarloSW2

That's probably a closer representation to what I was doing.... Except my SG didn't automatically turn back on (perhaps waiting for a signal from the ECU?).

Perhaps I'll send an eMail over to LinearLogic to get input from them - and perhaps work on an interim solution? OR, maybe I'll just make a kill switch and be done :p

trebuchet03 -

The kill switch is the best way to go. It's on my todo list but I am lazy.

CarloSW2

Story of my life :p

I bet it has to do with the ECU's programmed enrichment on startup since the car goes on and off. The proportions seem correct anyway...

Sometimes I start for short bursts. The ten second point was just to demonstrate it needs to run for a while so that at the next shut down it will go to zero fuel.

I was lazy. I soldered wires to fuse lugs and installed an inline fuse and switch in place of the fuel pump fuse. It is not instant off and I was cautioned about running the injectors without fuel. If I cut the fuel under load it dies quickly but if at idle it will run for quite a while.

On an extreme hot day with fresh fuel the vapor pressure of the fuel kept the car running but lean. I let it run that way for a longer than I should have and the computer retrimmed richer. It took about 10 miles before I got really good gas mileage again. Like I said I took an easy way. The proper way is to interrupt the electrical signal to the injectors. For me it was a choice between something quick and dirty or not at all.

The fuel pump fuse was right beside the console in my Saturn.

usedgeo and skewbe -

Is this the skewbe mod? I thought skewbe interrupted the fuel injector fuse (for my SW2) :

Attachment 888

If I do the fuel cutoff mod, I would rather do it here.

..... [reconnecting brain fuse] ...... Ohhhhh, I get it, the fuel pump fuse is in the fusebox in the cabin of the car, so it is easier to implement. Got it. Duhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh.

CarloSW2

Pikachu, have you taken the engine compartment box out to see what the mess of wires looks like under it? I'd rather connect the Inj Enable switch leads to the wires which go to the back of the fuse than pull the fuse and poke leads into the fuse socket.

For the kill switch, I wired up a blown fuse actually to plug into the fuse carlosw2 indicated, then cut a little of the fuse box covers edge so the leads could escape unharmed.

https://www.gassavers.org/attachment....1&d=1188559611

more info:
If the inline fuse burns out, just unplug the whole kill switch circuit and plug in a fuse till you can fix it. No kill switch till then, but the car will run :)

I didn't have a burnt out fuse, so I popped one on the battery with a jumper. whee.

This technique is sure to work on a lot of different cars.

Jim -

You don't have to go under the fuse box. I will publish my manual fan radiator switch in another thread to show you how I modded that relay (thank you saturnfans.com!!!!!!!!!!!!!).

CarloSW2

skewbe -

THANKS!!!!!!!!!!!!!!!!!!!!!!! Meat and potatoes right there.

One reason I haven't done the kill switch is that I want to use either the cruise control button (I would lose cruise control, but that's ok) or the horn button (stealthy!!!) on my steering wheel to activate the fuel cutoff.

I don't want it on the shifter because I don't trust myself when it comes to accidentally tripping it.

CarloSW2

For the record skewbe's way is much better than mine. When I looked at that fuse I thought it meant it was shutting down a part of the ECM. I take it that is not happening or in any case it works well.

Thanks to whomever fixed the title - you rock :)

I have repented. I redid the kill switch wiring today. It kills the engine immediately of course. Probably better, but at first it left the fuel consumption number at .3 gallons per hour almost every time. Maybe I need to play with the scan rate.