Oil pressure switch to run the relay off of for the fuel cell?

[Eddie_in_Maine]

I have seem some running the relay just off the ignition hot lines, but I am worried about leaving the car in the accessory position, then booooom. Has anyone found an oil pressure sensor to tie off of? Then you would know that the engine is definitely running and it is safe to make hho?
Just a thought...

[HHODave]

On many vehicles the oil pressure switch will only go to ground when there is no pressure, this completes the circuit and turns on the light.

This means the cell will not run when there is oil pressure.

You need to look at wires that are controlled by the power control module. It usually supplies power to the ignition coil, O2 heater, and injectors only when the sensors detect rotation of the crank and cam.

Go to a wire diagram and look the automatic shut down relay to find these wires.

[Phantom240]

Or find your fuel pump relay. It will only turn on in the 'run' position.

[FuzzyTomCat]

I have seem some running the relay just off the ignition hot lines, but I am worried about leaving the car in the accessory position, then booooom. Has anyone found an oil pressure sensor to tie off of? Then you would know that the engine is definitely running and it is safe to make hho?
Just a thought...

Hey Eddie,

You Can always purchase a "Cole Hersee" Electric Fuel Pump Switch PN-8647 at a auto parts store and insert a 1/8" NFPT tee into existing oil pressure connection to add the fuel pump switch to control the relay.

www.colehersee.com

http://i276.photobucket.com/albums/kk15/fuzzytomcat/FuelPressureSwitch.jpg

I always try to use the factory electric fuel pump circuit "crash relay" to control the HHO relay. It has a red button on it that pops out in a bad crash turning the fuel pump off they have been on cars since the 1980's usually located passenger side floor panel, trunk or ??

Good Luck,
Fuzzy
:D

[Phantom240]

lol my car has no crash relay.

[Eddie_in_Maine]

You Can always purchase a "Cole Hersee" Electric Fuel Pump Switch PN-8647 at a auto parts store and insert a 1/8" NFPT tee into existing oil pressure connection to add the fuel pump switch to control the relay.
:D

I like that idea, would work fine and get the results I want. My original concern with the fuel pump type connection is that in order to roll down the windows with the engine off, the ign switch must be in the RUN setting, which will turn on your fuel pump and therefore your fuel cell.

[Phantom240]

Yeah my car is the same way... but I would like to know how long after you shut the car off do you have oil pressure?

[waterworld]

Turning the ignition to the run position with the engine not running only energizes the fuel pump circuit for 2 seconds and then switches off. Only if the crank sensor 'sees' a signal (which means the engine is running) will the fuel pump circuit stay alive.
I install all of my units through the fuel pump relay.

[Phantom240]

Not on all cars. On mine it does what you said, except it will kick on if the fuel pressure drops, up to 5 cycles (if I remember correctly). If it still drops, you get a check engine light.

[waterworld]

Can you give the year make and model of the vehicle that has a running fuel pump circuit without the engine running? If it does then someone has altered the wiring from stock to feed power to it. Of course we are not talking about pre-fuel injected vehicles like older MG's and the like.

[Phantom240]

my friend's 91 nissan 240sx did it while we were torubleshooting his fuel injector leak. It wasn't 5 cycles, it was 3. The car's fuel system is stock.

EDIT: On second thought, it may have been pressurizing just once, cause he may have moved the crank angle sensor while we were troubleshooting. I can't honestly remember, but if he did, the computer would have seen crank movement, causing the fuel pump to come back on.