Fuel Pump Switch

I'm trying to wire in a switch to turn on and off the fuel pump in my 2004 Hymotion L5 PHEV Prius. I know the power runs through one of the wires in the bundle by the driver's left foot, but I don't know which one. Does anyone know how to identify the proper wire?

Just curious, any particular reason?

Index of /Documents_2006/

the files present on this site have many many connectors and tell what the wires do in them... just have to look and see which one

Oddest_raindrop,

Thanks for the site that you posted. There's all kinds of info there, well beyond
wiring stuff.

Although the material there is in English, I note that it is a European site,
Italian I think. There are some really obvious differences between EU and US
Prii -- rear disc brakes as an example -- and some quite subtle -- reverse
beeper can't be disabled IIRC -- so it would be best to go slowly and verify
what they're showing against what's in your car.

I installed one a while back, simple toggle switch on the kick
panel. The connection is basically the lowest, rightmost wire
in the whole group under the drivers-side kick panel, as you look
at the mess from beside the drivers seat -- in my car, the wire
changes color between red and black as it goes through the connector,
and I think I recall that the red side is toward the firewall.
If you dropped something on the footwell floor under the brake
pedal, it's the connection closest to that point.
.
I have pictures of all this and how the switch was installed and
wired up but never had time to turn it into a webpage yet. Someday,
maybe, although it seemed like a pretty simple hack. But I've
used the switch for good effect to kill excessive engine-running
under certain circumstances; downside is that it takes a while for
the engine to actually empty the remaining pressure in the fuel rail
and for the engine to cough and die.
.
_H*

Again, why would this mod be desirable? Does it allow for EV at high speeds? Otherwise, why would it be preferable to the EV button mod?

The fuel pump modification along with the Hymotion upgrade allows you to travel at a maximum speed of 52 MPH without the engine coming on. In fact, once you engage the feature you must shut off the car before the engine can be activated. It is a great feature for in town driving when you know you will not be going on the Interstate and do not need to drive over 52 MPH. Basically, you have a pure EV machine and not a hybrid.

---Kent

Kent,
It Sounds like the switch simulates an out of gas condition, therefore allowing full EV mode. What happens if going down a hill you exceed 52MPH will this hurt the components ? Does this also set off alarm displays in the dash ?
Thanks
Chris

Yes, it makes the dash light up like a Christmas Tree, red triangle, tire pressure and vsc. I don't know about going over 52 MPH. I think my max speed has been 49 MPH and I would simply not exceed 52 when in that mode.

The nice part is that if you clear the error code using Scangauge the car is normal upon the next start up. I can't wait until warmer weather to see how it does, but I love the results now. I turn on my heated seat, since I don't have any heat in this mode and I'm in Ohio.

---Kent

This is great. I'm wanting to know more. I knew it was possible, but didn't know how it was accomplished. I'd surmised that it was something to do with the fuel pump or fuel sender for the fuel gauge.

I teach in town two days a week. I can get there on surface roads without taking the freeway so this would be ideal.

Nikki.

Do be aware that the transaxle oil pump is driven from the engine - there's an 'oil pump drive shaft' which engages with the other side of the planet carrier, through MG2's shaft all the way out to the oil pump on the far side of MG2.

From the site linked to above: Hybrid Vehicle Transaxle Unit [PDF].

If you run through Art's Automotive's Rebuilding a Toyota Prius Transaxle, where they replace MG2, you can see that MG2's driveshaft is a tube, not a solid shaft. The oil pump drive shaft runs through the centre of this.

It probably isn't great, for the transaxle, for the oil not to be circulating for long periods of time.

Hobbit,

I briefly met you at the very first Hybridfest in 2006. I had the Prius with the trailer and working trailer taillights. The system included a standard trailer connector with standard 12 volts and enough watts to power old fashioned incandescent taillights (LED wattage just wasn’t enough and had to be boosted).

I read the above post about a Fuel Pump Cutoff Switch and was thinking of the problems with the stuck accelerators Toyota is having. Sure, if the problem was just the floor mats or a physical binding of parts in the gas pedal mechanism, then pushing the transmission joystick to Neutral will work or you could even hold the Power button down for over 3 seconds to turn the engine off. (See Youtube videos at [ame="http://www.youtube.com/watch?v=II_03lbr-Jw"]http://www.youtube.com/watch?v=II_03lbr-Jw[/ame] )

If the problem really is in the electronics, I believe that some routines in the ECU programming may be locking up (like a PC program locking up), therefore any inputs such as pushing the joystick to Neutral or holding down the power button will not have any effect. At that point a Fuel Pump Cutoff Switch could come in handy.

The question I have about your fuel pump cutoff switch is if the wire under the kickboard sends direct power to the fuel pump or if it goes thru other electronics that may be frozen with the same bug that causes the engine to race.

Any ideas you or anyone else have on the subject would be appreciated.

Thanks,
Tommy Kahn