Ignition Kill-Switch Activated by Low Oil Pressure

[QPP]

After viewing this:

http://www.youtube.com/watch?v=xljqqrW0XRo&feature=related

Has anyone done this?  Is it viable with the stock sending unit?

Poor guy.

[martin]

Holley sells a relay to cut out the electric fuel pump using the oil pressure switch which could kill the ignition too. It might be too late but it is a good idea.

[Bruce Amacker]

Has anyone done this?  Is it viable with the stock sending unit?

Can it be done with the stock sender?  Yes, quite easily using the sender to trigger the 85/86 terminals on a relay and 87A to the ignition coil.  You might need a momentary pushbutton to override the signal while cranking.  This type of relay is common on construction equipment like compressors, generators, and water pumps where they are started and abandoned for hours on end. They do have the momentary switch to get them started.

Is it needed in a VW?  Probably not in my opinion, 99.9% of the time the driver is within view of the dummy light or gauge. Even in this video the guy probably did not have damage to the engine.

Now maybe if the regular driver had a tendency to ignore the warning lights.....!

Good Luck!

[Bruce Tweddle]

A better solution to this problem is to use proper braided steel oil lines.

[martin]

It should save a few seconds of full throttle running with no oil pressure if a valve cover comes off in a race, compared to the drivers reaction time.

[superdrag]

This is why I have a large idiot light on my dash of my drag car in addition to the gauge.  When racing you can't be staring at a gauge the whole time.  I have my brain programed that if I see red light, clutch in, engine off.

[1836vw]

I run the Hobbs pressure switch on the oil system.  You can get it a 4lbs or 10lbs.  It needs a override switch to start the motor.  It comes with 1/8" NPT male treads.  The motor will shut down at the pressure you want it to.

 http://content.honeywell.com/sensing/hss/hobbscorp/catswitch.asp

[Chip Birks]

You might need a momentary pushbutton to override the signal while cranking.

Like, the ignition(start position) switch?

[Bruce Amacker]

Like, the ignition(start position) switch?

No, it's actually a momentary push button switch to override the ignition kill feature.  Remember during cranking it may take a bit to get oil pressure up high enough to activate the relay, turning on the spark.  During this few seconds you would not have spark because there is no oil pressure. The pushbutton overrides this so you have spark immediately to get the engine started. Construction machines have a pushbutton you hold in while cranking which overrides the system. This enables spark while cranking before oil pressure enables the coil power circuit.

It's actually a pretty simple circuit, if you buy a standard Bosch 5 pin relay and a momentary switch, I'll tell you how to wire it.  Buy a relay harness, too, it will make things cleaner. You will have to run an extra wire or two from the front of the car to the engine compartment.

Good Luck!

[John P]

This is why I have a large idiot light on my dash of my drag car in addition to the gauge.  When racing you can't be staring at a gauge the whole time.  I have my brain programed that if I see red light, clutch in, engine off.

Yeah, I see that on vintage race cars all the time. My favourite was one I saw in a 356 Speedster that had a "$" painted on the face of the red light.

I used to have mildly modified '71 Super Beetle that I did a few autocrosses with. It handled really well, and one day, while taking an on ramp at high speed, the stock oil pressure light went on. It was at night, very visible, and I immediately killed the ignition.

Too late, and took out a rod bearing.

JP

[madoski]

Here's a stupid question.  I always hear about losing oil pressure and having catastrophic failures, but I've had the green light go on for more than a few seconds while driving, hard cornering, after changing oil, etc., with the engine running, and never had any problems.  Is this because it's a stock 1600 with no real load on it?  I feel like the best thing to do when the light comes on from what I know is a temporary starvation is to keep the engine running at an idle while there's still a lot of oil around the journals and let the pressure pump quickly back up.  I guess I could kill the engine and crank it, but it's never seemed to make a difference for me.  Granted, it doesn't run as smoothly as it once did, but it's got close to 100k miles on it.

[superdrag]

Hmmm, intersting stuff.  I have seen my oil psi light on before, no failures.

[Bruce Amacker]

This is one of those things in which everyone is going to have an opinion.  Mine is that you can lose oil pressure occasionally through a hard turn or something and "probably" not do damage. I've known many vehicles that lost oil pressure for a time and lived a long healthy life afterward.  The worst story is an IH DT466 diesel truck that flipped on its side and remained running for 10-15 minutes with no oil pressure. We did an oil analysis that showed fine and that truck ran over 100K more miles in its life with no internal repairs.

I bought a 327 that had way too long of a dipstick in it and would lose pressure on every turn, I wonder how many miles and years it went like that before I bought it.  On teardown there was no lube related failures inside, the crank and bearings looked fine but the walls were worn out.

[1836vw]

I think most VW people know when they lose oil pressure and can save their motor.

[superdrag]

A while back my dad started up his Ghia.  Someone pulled in his driveway, so he got to chat with the guy.  Left the car idling.  Started chatting, and he heard a snap noise from the car.  He glanced at the car, but didn't think much of it.  Like 10 minutes went by, finally he said goodbye to the guy.  Got in the car, and saw his oil light on.  I don't remember exactly what happened, but I remember something snapped in his oil pump.  Maybe it was the flat spot that engages the cam.  Obviously at idle it wouldn't hurt as bad as at full song, but still it was pretty scary!