Advice to Wire Pre-Lube Oil Pump

[Joe Piro]

Question: How to wire a 12 volt pre-lube pump mounted temporarily for engine cleaning?
Info: My 94 Pathfinder V6 engine top end is full of sludge (from previous owner). I happened to have an external oil pump on hand which was originally designed for a pre-lube system that I never installed on another car. I have the valve covers off and physically brushed and vacuumed a lot of the deposits out (and cleaned the oil pan), and now I want to circulate mineral spirits to try to dissolve more sludge and clean up the engine. I can use a more aggressive solvent than often used for this because I will not be running the engine while circulating cleaning fluid (as I read a lot of people do).
I have put together a rig (See photo) with the pump, a knife switch to carry the current, and a remote oil filter adapter with a large WIX spin-on filter with no bypass. I have an adapter to **** oil from the oil pan, through the pump and through the filter and back into the 1/8" bspt port where the oil pressure sensor goes.
I was just gonna throw on some jumper cables from a battery to power this thing up, but decided that was sloppy and hazardous.
I need advice on a switch to wire it. I thought the knife witch was a good idea but now I don't think so... for one thing it sparks!
The instruction book specifies 30 fused amps at 12 vdc and to use 10 AWG wire. The pump is rated 1.5 rpm at 70 degrees F with 30 weight oil. I'm sure the pump is not designed for continuous duty as the factory encapsulated circuit module that came with it is set for 15 seconds at start up and 30 seconds at shut down if you're running a turbo. (Both times are adjustable.)
... Seems to me I should interupt both the positive and negative wires since the system is not grounded to the chassis.
So would that be a DPST Switch? I started looking at switch configurations and that's when I got really confused.

Thanks in advance for suggestions on how to switch and fuse this rig.

 

[Stuart in MN]

Yes, a double pole single throw switch will interrupt both wires at the same time. I think switching the positive leg is all that's really necessary but switching both won't hurt.

 

[nadogail]

Stuart covered it.

 

[Joe Piro]

Thanks for your prompt reply. DPST is what I thought but I just wasn't sure.

 

[BillK]

Joe,

I guess you got your actual question answered even though you really only need to switch the 12volt hot wire.

But I just want to add that every time I have seen somebody do what you want to do it has not ended well for the engine. If it had decent oil pressure before you started the project I would say put it back together and run it. Use some decent oil and do a couple of low interval oil changes and it will probably go another 100K miles. Those engines are pretty bulletproof as it is.

All it takes is one little piece of carbon or heavy sludge to get broken loose and end up in one of the really small crankshaft oil passages and you are done for.

If you insist on going ahead with your plan try using diesel fuel instead of mineral spirits which really will not do much of anything.

Just my worthless opinion

 

[walta]

The part of this plan that scares me is the “aggressive solvent “that sounds to me like something more flammable than the pump was designed for.

If you are going to have fumes around the last thing you want is a switch with open contacts like a knife switch inches away from the pump and filter.



Walta

 

[Joe Piro]

All it takes is one little piece of carbon or heavy sludge to get broken loose and end up in one of the really small crankshaft oil passages and you are done for.

You are absolutely correct, and I knew this. I let a friend (who didn't know better) shame me into doing this.
Now its too late with lots of sludge stuff already loose. So the best I can do is filter all the recirculation with a filter that has no bypass
and also permanently add the remote mounting filter adapters with this oversized filter (it's probably three times the size of the factory filter) and eliminate the small filter on the engine that has a bypass built in. If you look at the before and after oil filter pickup photos above you can see how effective the PB Blaster was at dissolving the sludge.... surprised the heck out of me! The pick-up was so restricted that I am surprised the engine had not already failed, but as you said these VG30 engines are pretty bulletproof.

The part of this plan that scares me is the “aggressive solvent

Note taken... It is possible to get more aggressive and not get very flammable. When I saw the knife switch in my spare parts bin I was excited because the contacts are so massive, but in retrospect I see it was not a good idea.

I am fairly confident I can pull this off. I put the oil pan on with just a few fasteners and I expect to have it off to empty and inspect a few times before I'm done. The engine is immobilized because I'm changing the timing belt, so I can get pretty aggressive with cleaner because it doesn't have to lubricate anything and of course now I can pre-lube with oil before I start the engine again. I think BillK was right and there isn't any advantage to this, but it's too late to turn back now.

Thanks for the input ...