toupee

Hi all,

I was wondering if someone can tell me if there is a fuse/something I can tap into that only runs it's accessory whenever the engine is running.
Thanks

AggieJustin

Are you trying to limit to only when the engine is running? Or anytime the key is on?

If you want only with engine running, you'll probably have to do something like rig up a pressure switch to be activated by oil pressure so that you have power whenever you have oil pressure.

toupee

The pressure switch should work. I only want it when the engine is running. I have a 7 psi hobbs switch setting around here. I never thought about oil pressure. I would do boost, but I don't think my switch goes down below 3 psi. Any ideas on how to make that (oil pressure + switch) work?

Tree DR

Use the cigaret lighter fuse it only comes on when on acc or the ignition is on or truck is running. You have to make sure you hook into the correct side of the fuse.

AggieJustin

Just run a tap directly to your battery for power. Route this through a relay that is triggered by the output from your Hobbs switch. Then power your accessory from the relay output.

Just curious, what are you wiring in?

toupee

Propane injection. On my 7.3's I just put a pressure switch in-line with the map sensor, but on the dodge can't do that. I had thought of the relay idea. Probably the best. Where do I need to look on the engine to find a place to put the switch for the oil pressure?

AggieJustin

Interesting. Do you have a seperate trigger wire for the propane system, or are you going to be injecting anytime the engine is running? If you have a seperate trigger wire, then you could just power the system using any accessory circuit so it's powered when the key is on, since it won't be injecting till it's triggered. If you were using a pressure switch on the MAP in the Ford, it must have been only kicking it when it saw some amount of boost.

toupee

Yep. On the fords it's set to 3 psi. I manage a propane delivery business so I like to use propane anytime I can. I have a professionally built system called "red rooster" on a 2001 kenworth t300. The system saw an increase in mpg from about 6 to about 9. Pretty good I think. I decided to engineer my own system for my 7.3's. It works off boost pressure, but to be honest it should just be set to run all the time. The 7.3's don't see above 3 psi too often so the benefits are not what they could be. I also just have a little impco negative pressure regulator on there. I think I'm going to take it off and replace it with an adjustable positive pressure regulator. I don't think the impco goes over 2 pounds of supply pressure. It doesn't really even affect egt's with a stock intake and exhaust. I'm pretty sure I could shoot quite a bit more in there and maybe see some benefits.
Anyways, anyone know where I need to look on the 5.9 to put my switch on there to be activated by oil pressure?

jrussell

No offense intended man!! I just got this visual when I read your post.

AggieJustin

You should be able to tap into the extra plug on top of the oil filter for your Hobbs switch. I didn't run outside and look at mine, but I remember people tapping in there for their mechanical oil pressure gauges.

toupee

Thanks for the info. And yeah, Hank's just like me..... only I'm a heck of a lot younger with black hair and skinny