Hey guys!

Hows it goin today?

I've got a quick question for all of you. Is there any reason why I couldn't adjust the oil pressure switch to act as an actual fuel cut off should I loose oil pressure in my truck?

Basically, as most of you know already, the switch just acts as a backup to the fuel pump relay. I want to set it up, so the ECM sends its power / ground path (whichever it uses for the relay coil, can't remember off hand) through the oil pressure switch, then over to the relay, this way, my truck will not turn the fuel pump on until it sees oil pressure (very important when it gets down to -40 F up here, my carbed truck would fire right up, and the sluggish oil would take a few seconds before it got everywhere, which caused some pretty nasty knocking in all the bearings ), and should my truck loose oil pressure on the highway for some reason, it would shut down then as well.

I personally can't think of any reason why this would be a bad idea, but I figured I should get a second opinion before I did anything

 

well the ECM primes the system for 2 seconds before starting, you'd still want that, otherwise you be cranking the engine until oil pressure was high enough to activate the oil pressure switch. I don't know what it's set at.
With temps that low, how long will it take to get the pressure up?


I'm doing a TPI swap in my 86 K10. Had planned for this summer but got distracted with the T56 swap in the Camaro.
What did you do for the fuel supply, as far what tank, sending unit pump lines? Just curious.

 

This is the schematic of the factory system:



The easiest method to accomplish what you propose would be to rewire the auxilliary oil pressure switch so that it is in series with the relay, instead of being in parallel as the factory intended.

However, as has been mentioned, there would be no 2-second prime cycle of the fuel system when the system powers up. There would be no fuel pump action until oil pressure was established at about 4-7 PSIG. This may lead to some protracted cranking times. In colder weather, that may require a LOT of battery reserve. Any cold start injector system would be useless, since the fuel rails would have no pressure. After the presumed (longer) cranking time, the cold start control would have reached its time limit, and there would be no additional fuel for starting by the time the oil pressure switch was satisfied.

If you are concerned about cold weather startup lubrication, quit dinking around with oil and use a fully synthetic (PAO base) lubricant. That would solve your cold lubrication problem, and a lot more.

I've had the Mrs.' van parked outside overnight in -45°F more than once, and even though the battery barely had the energy to light the interior lights and crank it over, it has fired off straight away and lubricated (via Mobil 1 10W30) without incident. It probably did some serious engine damage, but since it got traded in at only 188,000 miles, I never really had it long enough to find out.

 

well the ECM primes the system for 2 seconds before starting, you'd still want that, otherwise you be cranking the engine until oil pressure was high enough to activate the oil pressure switch. I don't know what it's set at.
With temps that low, how long will it take to get the pressure up?

Ah yes, I forgot about the ECM doing it's priming... I suppose that is reason enough to hook it all up like stock

When its -40F out, with my carburated engine, it typically fired up pretty much on the bump of the starter if you gave it two pumps of the gas pedal before you hit the key. When it did that, it'd almost immediately go to nearly 1200 rpm, due to the fast idle cam. At that RPM, it took the light winter grade oil about 5 - 10 seconds to build pressure. Usually it was the valve train that'd be clacking and ticking like crazy, cause the rotating assembly is the first to receive oil from the pump.

At a lower RPM (say if you didn't pump the pedal to activate the fast idle cam, and give her some gas) the truck would knock for about 5 seconds, then tick for another 15 - 20 seconds after that till the oil light went off.

Typically, I tried not to drive my vehicles when it was that cold out, unless it was for a long drive somewhere, run into the store, and go before the engine cooled off (I keep my truck in a heated shop, so I don't mind starting it there) but when it is that cold, the school could never get their diesel or propane buses to start, but still didn't cancel school, so I'd have to drive myself in, and by the time school let out, half the cars in the parking lot had frozen oil (I always plugged mine in)

I'm doing a TPI swap in my 86 K10. Had planned for this summer but got distracted with the T56 swap in the Camaro.
What did you do for the fuel supply, as far what tank, sending unit pump lines? Just curious.

For fuel, I installed a suburban fuel tank from an 87+ truck with a Camaro TPI fuel pump installed in it's place.

If I were to do it over again, I'd have gone with a Blazer tank instead. The big suburban tank barely clears my diff cover when I compress the suspension all the way down, while a Blazer tank would not have any clearance trouble like that at all.

I used the Suburban's rear bracket, and made my own front bracket, using a peice of 2" x 1" angle iron, and the old spare tire bracket.

After a guy installs it, the tank is almost perfectly level in the pickup frame, and is almost a bolt in swap (less drilling some holes, and needing some longer tank straps).

There is a great tutorial about swapping a blazer tank into a shortbed truck at

thttp://www.captkaoscustoms.com/blazertank.html

Installing it into a longbed is pretty similar.

For fuel lines, I just went to Napa, bought some 3/8 and 5/16 steel aluminized line, and ran it from front to back down my driver's side frame rail.

I mounted the tank "backwards" which put the fuel filler nozzle on the driver's side of the truck, along with the sending unit outputs.

I got some of that wicked steel braided fuel line from a 90s something TBI truck, and ran hoses from my tank to the frame, where I double flared hard end of the steel braided lines, and the hard lines I bent up.

Same thing up front, ran steel braided line from the fuel rail down to my frame (being careful to avoid the exhaust) put the filter on the end, got a small section of the factory GM hardline, then double flared it to connect it to my custom lines.

Works real well Though, double flares are a huge pain in the butt! You only really need single flares for fuel lines, and if I were to do it again, I'd go that route instead, lol

If you've got any other questions about installing the TPI in your K10, shoot me a PM, and I'll do the best to answer your questions, I can probally get you pictures too. Mine went into an 80 K25. I'm still working out the bugs with my TPI setup though. My MAF is giving me greif, among other things...

 

Yeah, synthetic probally would have been the right answer. But I never had to do oil changes on the truck before I re-sealed / rebuilt the engine, lol It leaked all the oil out fast enough that I could just change the filter every once in a while, lol

Battery power isn't a problem for me either, I run a 1500 cold cranking amp battery in my truck

Synthetic ain't cheap stuff, and I didn't want to leak it everywhere. It only gets to -40F or so 3 - 4 days a year, most of the time is about -4F -> -30F or so, which isn't nearly as hard on the engine.

 

Just put a switch on the signal wire to the relay. Crank the truck with the switch on. Give it a few seconds to build up oil pressure. Then turn off the switch. Your fuel pump is now running off the oil pressure switch, if you loose pressure the engine will die.