For a engine on switch I re-purposed the oil pressure sending unit, it supplies ground to a relay once 7psi is reached in the oil.
For Key On position, Tap A2 on the Ignition switch (Gray/Yellow wire), need to double check that one.
How many Amps?
For a engine on switch I re-purposed the oil pressure sending unit, it supplies ground to a relay once 7psi is reached in the oil.
It's up to 30 amps under a load. That's interesting about the oil pressure sending unit. I may have to do something like that.
The ECU I have uses grounds to trigger a relay to power units, but it isn't simple to do that in my case.
It's for an electric power steering pump. Here's how the relay is wired with a switched 12V trigger.
Can't you just use the ECU to trigger a relay and use that to switch always-on 12v for the 12V Ignition on the drawing?
RwP
I believe this car no longer has the eec.
CMac89 said:The ECU I have uses grounds to trigger a relay to power units, but it isn't simple to do that in my case.
RalphP said:Can't you just use the ECU to trigger a relay and use that to switch always-on 12v for the 12V Ignition on the drawing?
Fuel Pump only runs continously when the ECU sees a running engine. There is the 3 second prime and then it will run when cranking. You may not want that additional 50 amp load during crank time.
Will the ECU signal to the fuel pump relay handle the additional load of a second relay coil? Use the 12V feed from the fuel pump relay to drive the coil of the relay for the PS pump. Just looked and typical coil load on a 50 Amp automotive relay is .25 of an amp. An additional .25 amp on the fuel pump circuit should have minimal effect on voltage drop to the fuel pump.
But isn't that what happens on a stock vehicle? If the engine ain't spinnin either is the PS pump.Only thing about the oil pressure switch...what if the car dies/loses oil pressure for some reason....you also lose power steering.
But isn't that what happens on a stock vehicle? If the engine ain't spinnin either is the PS pump.
Truuuue..... at least with the motor dying...loss of oil pressure due to a mechanical failure (assuming the motor keeps running) on a belt-driven pump would still give you assist while you got it off the road/track in the rare case of that happening.
I had pictured the wheels being even harder to turn w/the electric pump...I might be totally off-base though. I don't know much about the electric PS pump systems really.
The fuel pump relay is controlled by the factory EEC, which I am assuming is totally gone from K-C's car, since he has an aftermarket ECU. Maybe the aftermarket unit has this function though?
I had considered the fuel pump circuitry earlier, but with the HP and fuel demand levels he will surely be at, I wouldn't want ANY voltage drop to the fuel pump - especially if it could vary over time. Triggering the fuel pump RELAY (might be what you were trying to say in the first place!) might be okay, as long as the ECU can handle the extra load of the PS pump relay coil. This would not affect the fuel pump supply voltage.