need "run" power source to tap on LSx vehicle
 

I need to figure out a way to run a pump from a power source that only has voltage when the engine is running.

Are there any sources that I could tap and use a relay to do what I need?

Last resort I think would be to make a circuit that get power from an IGN source then uses a pulse activation relay that will turn on when key hits "run" and stays on until IGN is turned off.

You don't want power during start?

My guess is this is for the electric oil scavenge pump which prob doesn't like being run dry

yes it is for that. however it can be run dry indefinitely without any damage. id just rather have it only running while the engine is running. and i don't want to get into too complex of controls since the wiring must be reliable. i did get a warning system to alert me if the pump stops.

Why not do something off of the alternator like how a remote start/computer controlled cranking works?

Can you piggy back off the fuel pump hot or trigger line to engage the relay for the oil pump?

I was originally going to suggest that but the fuel pump primes when you turn the key on. That's why I suggested off of the alternator.

I'm gonna check the leads off the Alt, but I could also use the fuel pump relay I think. Are there any negative aspects to tapping power off that relay? I would only run the tap right to a 30A relay so its not like there would be any extra draw on the circuit.


I got this wiring diagram... It seems I should be able to tap the signal coming from the ECM. Any thoughts?

http://i32.photobucket.com/albums/d5...V/4570b091.png

That's how most any autostart works as far as I know. Once it sees a signal from the alternator, it stops cranking. Don't see a reason why you couldn't use the lead to energize a relay.

I would run a relay off of the fuel pump relay system. That is the best solution. You want the pump running when the engine is running. The alternator could die and the engine would continue to run and you would be screwed because your electric oil scavenge pump would stop running. GM has put a lot of research to make sure the fuel pump is only running when the engine is running (except for pre-start priming).