LMM Fuse Box

[DieselUser]

I'm trying to find a point in the fuse block that I can tie-in a wire so it only has voltage when the engine is running. It has to have no voltage when the key is only turned to "On" but the engine is not running.

So far, I have been unable to find such a point. What's more, a mechanic I had looking at it pulled the Fuel Pump Relay while the engine was running and the engine kept running as if nothing had happened. Is that Normal? The mechanic expected the engine to die when he pulled the relay.

Thanks for any help you can give.

>> Jan <<

[JohnC]

Get a normally open oil pressure switch. NAPA 701-1575

[DieselUser]

Get a normally open oil pressure switch. NAPA 701-1575

Thanks John. I could get one, but $30 for something to carry around in my pocket is a little steep. I could get a pet rock for free! :D Seriously, when it says "Newbie" under my user name, it means it. I may be an old fart, but the only auto work I have done is to change oil and I did mess with my VW Bugs; setting valves, etc.

I have no idea what getting the oil pressure switch would gain me. More info?

>> Jan <<

[jbplock]

I have no idea what getting the oil pressure switch would gain me. More info?

>> Jan <<

Wire one side of the OPS (oil pressure switch) to 12 volts from the battery and then when the engine is running (oil pressure) the switch closes yielding 12v to your circuit. If the engine is not running 12 volts is not present (switch open = no oil pressure). I have an OPS wired to my add-on lift pump as safety feature to prevent feeding fuel in the event of an wreck (this is an OEM feature on the GM6.5 which has a stock Lift Pump) .. see the circuit here (http://rides.webshots.com/photo/1143154393033933568zVJoLp)

:)

[DieselUser]

Wire one side of the OPS (oil pressure switch) to 12 volts from the battery and then when the engine is running (oil pressure) the switch closes yielding 12v to your circuit. If the engine is not running 12 volts is not present (switch open = no oil pressure). I have an OPS wired to my add-on lift pump as safety feature to prevent feeding fuel in the event of an wreck (this is an OEM feature on the GM6.5 which has a stock Lift Pump) .. see the circuit here (http://rides.webshots.com/photo/1143154393033933568zVJoLp)

:)

So JB, (if I can get this picture uploaded) I can just wire the switch in without having to have anything to do with the oil pressure sending unit etc.?? Does this picture seem OK?? (sorry, can't seem to get it small enough).:confused:


Basically I wire Batt + to one terminal of the OPS and the wire (that needs 12V to operate) from my CCPWM to the other terminal of the OPS and just mount it somewhere in my engine compartment?

Thanks for your help,

>> Jan <<

[Jerry Redtruck]

this might give you an idea, using a single pole grounding n/o oil switch, in conjuction with a relay

[DmaxMaverick]

What, exactly, are you trying to supply power to? It may be very important, or there may be a much more simple way to do it.

[DieselUser]

What, exactly, are you trying to supply power to? It may be very important, or there may be a much more simple way to do it.

It's for a Constant Current Pulse Width Modulator. It needs to only have voltage to it when the engine is actually running, but not when the key is turned to the accessory or on position.

[cowboywildbill]

The fuse box under the hood on the drivers side should have a fuse that is only hot when ignition is on. If it is the same as my LML I found one with a test light and then tied it to a relay to power my CB.

[DieselUser]

The fuse box under the hood on the drivers side should have a fuse that is only hot when ignition is on. If it is the same as my LML I found one with a test light and then tied it to a relay to power my CB.

That's what the mechanic thought that looked at it with me. I went home and tested EVERY fuse and EVERY kind of open slot (for relays and fuses that weren't filled). The ones that were hot with the engine running were also hot with the key in the "on" position.

There was NOT ONE point that was only hot while the engine was running.

[DmaxMaverick]

Assuming this is for HHO......

You have 3 options:

Oil Pressure Switch, as suggested. The relay is essential, as the current will be too great for the OPS to carry alone (80A+). Use Jerry's excellent diagram.

Alternator generator preload circuit. I don't have a diagram of your alternator, but it may have an output control pin available with this, if it has a 4 or 6 pole connector. A relay is essential for consistent supply voltage from the battery. This may not be the best method, as a bad battery will interfere with alternator output control.

PCM logic. The engine harness connector should have an output for this. I don't have the diagram for your truck, but it should have an output signal pin. Again, the relay is essential.

I think the OPS/relay method would be best, all things considered. www.kennedydiesel.com sells a complete kit that's intended for a fuel lift pump addition that would works well for your application. Look for it in the Duramax lift pump section.

[DieselUser]

Assuming this is for HHO......

You have 3 options:

Oil Pressure Switch, as suggested. The relay is essential, as the current will be too great for the OPS to carry alone (80A+). Use Jerry's excellent diagram.

Alternator generator preload circuit. I don't have a diagram of your alternator, but it may have an output control pin available with this, if it has a 4 or 6 pole connector. A relay is essential for consistent supply voltage from the battery. This may not be the best method, as a bad battery will interfere with alternator output control.

PCM logic. The engine harness connector should have an output for this. I don't have the diagram for your truck, but it should have an output signal pin. Again, the relay is essential.

I think the OPS/relay method would be best, all things considered. www.kennedydiesel.com (http://www.kennedydiesel.com) sells a complete kit that's intended for a fuel lift pump addition that would works well for your application. Look for it in the Duramax lift pump section.

Thanks DmaxMav. Looking at Jerry's drawing, would I then hook up the CCPWM (you're right, it's for hho) to the 87 terminal of the relay? The OPS has 2 connections on it, would I only use one? Like I said before, this is all NEWBIE to me. :D

Also, looking at jbplock's setup, I guess I could use that if I wanted to also wire in a manual on/off switch in the cab; only minus the lift pump and the timer thingy. Am I correct in that assumption? If so, why the jumper from terminal 30 to 85? Is that because of the timer thingy?

Thanks for your help,

>> Jan <<

[jbplock]

Also, looking at jbplock's setup, I guess I could use that if I wanted to also wire in a manual on/off switch in the cab; only minus the lift pump and the timer thingy. Am I correct in that assumption? If so, why the jumper from terminal 30 to 85? Is that because of the timer thingy?

Thanks for your help,

>> Jan <<
DU,
I'm not sure what the HHO is but if you want to switch on a high current load only when the engine is running, you could use the circuit I posted (http://rides.webshots.com/photo/1143154393033933568zVJoLp) as follows:

1. The jumper puts 12V one one side of the coil .. when the OPS turns on it grounds the other side of the relay coil and energizes the relay which closes the switch and applies power to the load.
2. substitute the lift pump for the HHO high current load - also increase the value of the fuse to the max load of the HHO.
2 delete the timer (this is a one shot timer (http://rides.webshots.com/photo/1143154350033933568CzJEWK)to run my lift pump during the glow cycle - primes the fuel system before starting)
3. Keep the momentary switch to turn on the HHO at any time - I use this in my system to bleed the fuel system through the schrader valve (http://rides.webshots.com/photo/1095466160033933568coWkql) after a filter change - switch is mounted under the hood. (http://rides.webshots.com/photo/1078007431033933568FZIwJH)

:)

[DieselUser]

DU,
I'm not sure what the HHO is but if you want to switch on a high current load only when the engine is running, you could use the circuit I posted (http://rides.webshots.com/photo/1143154393033933568zVJoLp) as follows:

1. The jumper puts 12V one one side of the coil .. when the OPS turns on it grounds the other side of the relay coil and energizes the relay which closes the switch and applies power to the load.
2. substitute the lift pump for the HHO high current load - also increase the value of the fuse to the max load of the HHO.
2 delete the timer (this is a one shot timer (http://rides.webshots.com/photo/1143154350033933568CzJEWK)to run my lift pump during the glow cycle - primes the fuel system before starting)
3. Keep the momentary switch to turn on the HHO at any time - I use this in my system to bleed the fuel system through the schrader valve (http://rides.webshots.com/photo/1095466160033933568coWkql) after a filter change - switch is mounted under the hood. (http://rides.webshots.com/photo/1078007431033933568FZIwJH)

:)
JB,
1. Got it.
2. Actually, the load on that terminal is minimal, it just needs to get 12V to the Pulse Width Modulator to turn it on (only needs 18AWG wire). Then the PWM handles the heavier current.

Thanks for the clarification. :) I think once I get the OPS tomorrow, (had to send it up here from Atlanta) I should be good to go. :cool:

BTW, hho is Hydroxy Gas to be inserted into the air stream to increase combustion efficiency, almost eliminate emissions, clean the engine, give better mileage/performance and make a cooler running engine.

>> Jan <<

[JohnC]

Be aware that the oil pressure switch will turn on when oil pressure builds. This could be while the engine is still cranking, or it could be not for several seconds after the engine starts. Also, the engine can maintain oil pressure for some time after the engine stops, up to 10-15 seconds with cold oil.

The Hobbs (NAPA) switch can handle 1/2 amp or so without a relay, which may be plenty for your application.

[DieselUser]

I said I should be good to go, but where would be the best place to install this thing? :confused:

[DieselUser]

Wire one side of the OPS (oil pressure switch) to 12 volts from the battery and then when the engine is running (oil pressure) the switch closes yielding 12v to your circuit. If the engine is not running 12 volts is not present (switch open = no oil pressure). I have an OPS wired to my add-on lift pump as safety feature to prevent feeding fuel in the event of an wreck (this is an OEM feature on the GM6.5 which has a stock Lift Pump) .. see the circuit here (http://rides.webshots.com/photo/1143154393033933568zVJoLp)

:)

Where would be the best place to install the OPS. Remember, I have almost no experience working on vehicles. :o

[jbplock]

Here's two places where there is oil pressure ..

1923

1924

If I remember correctly there are also oil gallery plugs on the side of the block that could be used .. Or you could add your OPS to the OE oil pressure sender location with a tee .. it's on the lower front driver side of the engine block.

:)

[DieselUser]

DU,
I'm not sure what the HHO is but if you want to switch on a high current load only when the engine is running, you could use the circuit I posted (http://rides.webshots.com/photo/1143154393033933568zVJoLp) as follows:

1. The jumper puts 12V one one side of the coil .. when the OPS turns on it grounds the other side of the relay coil and energizes the relay which closes the switch and applies power to the load.
2. substitute the lift pump for the HHO high current load - also increase the value of the fuse to the max load of the HHO.
2 delete the timer (this is a one shot timer (http://rides.webshots.com/photo/1143154350033933568CzJEWK)to run my lift pump during the glow cycle - primes the fuel system before starting)
3. Keep the momentary switch to turn on the HHO at any time - I use this in my system to bleed the fuel system through the schrader valve (http://rides.webshots.com/photo/1095466160033933568coWkql) after a filter change - switch is mounted under the hood. (http://rides.webshots.com/photo/1078007431033933568FZIwJH)

:)


Here's two places where there is oil pressure ..

1923

1924

If I remember correctly there are also oil gallery plugs on the side of the block that could be used .. Or you could add your OPS to the OE oil pressure sender location with a tee .. it's on the lower front driver side of the engine block.

:)

Thanks for your help, Bill.

Do you think it would be easier to put it in a gallery plug or do the "T" at the OE sender location?

>> Jan <<

[jbplock]

Jan,

I have experience with the 3/8 NPTF plug on the bottom of the oil filter adapter (second pic above) which is where I tapped the feed for my Oilguard Bypass filter. This plug is relatively east to get to but it can be difficult to remove (appeared to have red permanent loctite on it when removed). I also found I had to use a steel hydraulic NPTF dryseal (http://www.cutting-tool-supply.com/TechTips/Tapping/NPTvsNPTF/NPTVsNPTF.htm)fitting. My first attempt with a common 3/8 NPT brass fitting leaked.

Assuming it's accessible a Tee on the OE oil pressure sender may be the best option for your application. You could remove the driver side wheel and fender liner to see if you can get access.

:)

[DieselUser]

Jan,

I have experience with the 3/8 NPTF plug on the bottom of the oil filter adapter (second pic above) which is where I tapped the feed for my Oilguard Bypass filter. This plug is relatively east to get to but it can be difficult to remove (appeared to have red permanent loctite on it when removed). I also found I had to use a steel hydraulic NPTF dryseal (http://www.cutting-tool-supply.com/TechTips/Tapping/NPTvsNPTF/NPTVsNPTF.htm)fitting. My first attempt with a common 3/8 NPT brass fitting leaked.

Assuming it's accessible a Tee on the OE oil pressure sender may be the best option for your application. You could remove the driver side wheel and fender liner to see if you can get access.

:)

Thanks Bill. I'll pull the fender liner and see what I can see. Thanks for the info on the NPT/NPTF, too. Vedddddy Interesting. :D

They say you learn something new every day, but since starting this project, I'm learning bunches.;)

>> Jan <<

[DieselUser]

Jan,

I have experience with the 3/8 NPTF plug on the bottom of the oil filter adapter (second pic above) which is where I tapped the feed for my Oilguard Bypass filter. This plug is relatively east to get to but it can be difficult to remove (appeared to have red permanent loctite on it when removed). I also found I had to use a steel hydraulic NPTF dryseal (http://www.cutting-tool-supply.com/TechTips/Tapping/NPTvsNPTF/NPTVsNPTF.htm)fitting. My first attempt with a common 3/8 NPT brass fitting leaked.

Assuming it's accessible a Tee on the OE oil pressure sender may be the best option for your application. You could remove the driver side wheel and fender liner to see if you can get access.

:)

Looks like it should be, but wanted your "Expert" opinion. :D

The Driver's side with the fender liner removed.

1925