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Need help with designing a simple12 volt timer for an automotive application Answered

Hello all,

I have an idea to make a pre-oiler system for my car's engine.  The idea is to hook up a 12 volt oil pump  to bring oil from the pan up to the head to pre lube everything before I start the engine.  This is to hopefully help prevent unnecessary wear on the engine.  I want to have a timer to control the electric pump so that when the key is turned to the position just before "start" that it triggers the pump to start for  approximately 30-60 seconds.  The question is really, where do I start to look  for information and parts to build this simple circuit?  Also, would it need to be hooked up to constant power to store the timing program, or can it be just a simple mechanical/electrical trigger from the ignition to start the countdown?

Thank you for your time in advance,


I'll agree with you that some wear occurs when an engine first starts. There is however some oil left on internal components (unless the vehicle sits for months without being driven), therefore under normal use, this wear is considered minimal. The other aspect to consider is when you turn off the engine, and the oil stops circulating, and hot internal parts continue to cook the residual oil before it fully drains or cools. Just as much 'damage' can occur at this time, and its why some turbochargers have what's called a "turbo timer".

In theory, what you're proposing isn't bad, per se, its just not considered feasible or practical for the average automobile. It was tried in the past on a Mercedes (AFAIR) and they were forced to "fix" the problems caused by the fact the vehicle was street-legal, but also a high speed racing auto. The dry sump did its job for the demands of racing, but for normal use the oil ran too cool. 

Also, AFAIR, a dry sump scenario, typically uses an additional external oil reservoir, and will utilize a dry sump for each crankcase section. It's due to the extra parts, extra oil, extra lines and extra maintenance costs, that the risk of leaks and repairs tend to outweigh the benefits in normal driving conditions. 

If you still intend to develop this idea, ensure that you familiarize yourself with the concept of a dry sump, and ensure that you maintain adequate oil pressure, oil levels, and can run the pump without compromising your vehicle as it is now. Therefore getting a repair manual (such as Haynes) is a good idea to fully understand your engine and all the specs.

I hope that helps.

There are many ways to implement a time delay. 

Speaking generally, the way this works is you start a process that you know will take a certain amount of time to finish.  Also you have some way of watching/sensing the process, so that your circuit can see/sense when it is done.

The actual time-consuming process can be whatever, as long as that something is "simple", from your perspective, since you are the one who has to build it.

If you like working with microcontrollers, you know, these little programmable ICs with names like Arduino(Atmel), PIC(Microchip), etc, then that would probably be the most simple way to do it.  Such a time delay is implemented by just having the program running on the microcontroller count to a large number.

If you are mechanically inclined, then maybe the process could be a motor geared down to turn a slow moving cam, so that the cam has to turn over once before it can close your switch or whatever. 

A delay of 30-60 seconds might, just barely, be in the range of time it takes to charge a capacitor through a resistor, which is approximately 1or 2 times R*C.
E.g. a 10 microfarad (10e-6) capacitor, and a 1 megaohm (1e6) resistor give R*C=10 seconds.  

Also you can build a circuit that produces pulses periodically, and then use a digital counter IC to count a small number of these pulses. 
For the kind of ICs I am thinking of, the highest number is usually just a small number, in binary.  E.g. if it is a 12-bit counter, the highest number you can count to is 2^12 = 4096

BTW, the circuit that gives you pulses periodically (e.g one pulse every second, or one every 1/1000 of a second, or whatever) is commonly called a "clock" or "timer", but these words when used in the electronic sense, denote the most simple kind of clock or timer; i.e. a clock without "hands", or an "alarm", or coffee machine, or any other peripheral hardware.  It is clock that produces nothing but "tick". Its only output is just that periodic signal.

Final note:  It might be fun to have some kind of output signal, so that the user who is waiting for the cycle to complete, has something to occupy his or her attention.  For the digital counter, this would naturally be some blinking LEDs.  Or maybe even a LED "progress bar" using the old CD4017 decade counter.  For a motor driven cam, you could mount it on the dash somewhere, so the user could actually watch the little wheel(s?) turn.

What kind of engine is it that needs pre-lube ? A modern automotive engine can run 200,000 miles before it "wears" enough to need servicing - and its not failing in areas your lubrication pump can reach, unless the engine is turning at rated speed. MANY areas of the fired engine are dynamically lubricated, and simply pumping oil around won't help anything towards reducing wear.