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Thread: Murder Mystery LS Done

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    Not Certified Slow SDSUsnowboards's Avatar
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    Default Murder Mystery LS Done

    The villainous grim reapo has struck again. The culprit is known, but what was the murder weapon? The facts are still preliminary.

    The Victim:
    LS1 with 96,000 miles and no modifications, sitting in a 2002 Corvette with no modifications.

    The Setting:
    Button Willow, between the esses and sunset.

    Autopsy:
    The oil filter was removed and cut by Tom at 7's Only. A low amount of bearing material was discovered inside.

    The Witness:
    "I was accelerating out of the esses. It was at that time I noticed the cluster said "low oil pressure." The analogue dial read 0 oil psi. I immediately entered the pit and decelerated. Once I reached parking lot speed I attempted to maintain speed, but noticed the throttle was conceptually 'dead,' the engine had stalled. I disengaged the clutch and the engine speed dropped to zero, and I free-rolled to a stop. I attempted to start the car. The crank turned, but no ignition. I observed a small amount of white smoke from the engine bay. There is no obvious sign of anything out of the ordinary in the engine bay."

    What dunnit?
    The presence of only a small amount of bearing material in the filter is comforting. With a little luck I need only replace the bearing(s) affected, but I am puzzled as to what happened, and why my spark/fuel is no longer working. As far as I can see, these motors don't have any common oiling issues.
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    Senior Member Silversprint's Avatar
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    Sorry to hear that.

    Maybe oil pump or oil pump bypass spring failure?

    Or something else died first then metal shavings killed the pump.

    If you have metal in the filter I think the whole motor needs to be gone through.
    Last edited by Silversprint; 01-28-2018 at 08:27 PM.
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    BMW Master bawareca's Avatar
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    But worn bearings will not cause the engine to not start except if it has seized already, which it is not.
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    Not Certified Slow SDSUsnowboards's Avatar
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    Quote Originally Posted by Silversprint View Post
    Sorry to hear that.

    Maybe oil pump or oil pump bypass spring failure?

    Or something else died first then metal shavings killed the pump.

    If you have metal in the filter I think the whole motor needs to be gone through.
    I hadn't thought of that--you're right though, everything the oil touches must be inspected and cleaned. Bummer.


    Quote Originally Posted by bawareca View Post
    But worn bearings will not cause the engine to not start except if it has seized already, which it is not.
    Exactly. That's what makes this a murder mystery.
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    Tough break. I think you have worse luck around cars than I do.

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    Also, I'm sure you can pick up a nice used LS6 for less than the price of a junkyard motor for that Mister Too you have.
    This is always a plus, right?

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    Not Certified Slow SDSUsnowboards's Avatar
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    I have a theory for the engine stall. Too bad I am not near the Corvette to test it.
    The fuel pump derives power from two sources. One circuit gives it power when the ECU tells it to have power, i.e. when the key is in the 'on' position. This is controlled by a relay. The second circuit from through the oil pressure sending unit. It is a backup power source that powers the pump should the relay fail.

    If the relay fails, then you accidentally have an oil-pressure cut off safeguard. Meaning, when you have less than ~7 psi the contacts in the oil pressure sending unit do not close, and the fuel pump gets no power through that circuit. I suspect my fuel pump has been powered solely through the oil sending unit. It would explain why my engine stalled when I lost pressure. It would be a mere coincidence that this coincided with me lifting off the throttle at around the same time, hiding the fact from me until I reduced speed.

    I don't think we'll have any indication of what caused the catastrophic loss of oil pressure until the engine is opened. I'm going to ask the mechanic to test the oil pressure sending unit before doing anything else. Maybe the sending unit simply went out, the bearings were on their way out due to the previously existing moisture problem, and the little puff of white smoke was just something transient, like my optimistic hope this is just an electrical issue.


    Quote Originally Posted by Schmoe Money View Post
    Tough break. I think you have worse luck around cars than I do. Also, I'm sure you can pick up a nice used LS6 for less than the price of a junkyard motor for that Mister Too you have.
    This is always a plus, right?
    That is the truth. Two times in a row now. My last track day was in 2014, when the Mr Two died from still unknown causes. One thing is for certain now, I have to stop this sport. The Mr Two is for sale (now running).
    Last edited by SDSUsnowboards; 01-29-2018 at 08:41 AM.
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    Chest hair required Olitho's Avatar
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    You should talk to Chris Beliovsky about what happened. Ping me for his contact info if interested.
    To the right of The Sheriff. Isn't everyone?

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    The trouble with your theory is if the pump needs enough power for it to be supplied through a relay, then the oil pressure sending unit would need a relay in its circuit too for it to power the pump.

    Also, wouldn't you want the fuel to cut at 0 oil psi? Although you'd never get the car started if that were true.

    Getting the oil pan off from below is somewhat of a pain, but doable. I wonder if you can replace an oil pump from below...

    Try draining your oil through a rag and see how much more metal shows up.

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    Not Certified Slow SDSUsnowboards's Avatar
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    The oil pressure sending unit only sends power if PSI >=7. i.e if the engine is being cranked, or is already running. The theory is that my relay had already failed before yesterday. The description of the circuits is (as far as I know) fact.
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    Senior Member Silversprint's Avatar
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    If only that was true. 2zz low mileage engines are $1000. Way cheaper than any LS engine. LS engine are expensive compared to these little 4 bangers. Best bet is another LS1 for $2500

    You can try to take off the valve cover and see if there is any shiny stuff floating in the oil. If there is then motor probably needs a rebuild..
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    As Robburgoon mentioned the pressure switch would probably activate a relay also.

    Although I work on a lot of old cars I don't work on new ones very often so I may be way off base, however. Having installed electric pumps on a bunch of various vehicles that didn't have factory ones I do have some experience.

    The oil pressure switch is typically used to protect the engine from killing itself due to loss of oil pressure AND reducing the risk of pumping fuel onto a fire if there's an accident or other issue by stopping the fuel pump from running if the engine stops. I suspect the ECU probably only provides a signal to provide fuel when the key is in the "start" position, and once ignition occurs the oil pressure switch provides signal for continued operation when key is in the "run" position. If it wasn't like this it might be possible to have a fuel line severed in an accident and the pump would pump fuel until the key was turned off even if the engine ran out of fuel.

    I wouldn't start tearing the engine apart right away till you determine cause of failure. Might have been due to temp loss of oil pressure which might have been caused by sucking air in the oil pump or something simple like that and the pressure switch just did it's job and shut the engine down. Oil pressure switch shutting off fuel pump would be just like running out of gas.
    Last edited by NOT A TA; 01-29-2018 at 10:44 AM.

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    Administrator ucfbrett's Avatar
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    My guess is it was starved for oil in either the Sweeper or the Esses, which dropped the pressure far enough to shut off the fuel pump.

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    Senior Member robburgoon's Avatar
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    If it starved for oil and scared the ECU, it should have refired when he tried to start it.

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    I agree with Rob. Unless the ECU needs to be reset, the car should have started. The existence of this reset should have become apparent in my research, but instead I found examples of people able to start their motor with no oil pressure.

    I doubt I experienced G-induced oil starvation at any point. I was driving like 5/10ths. It felt like being out the first time again and I only got about 4 laps in, one of which was a warm up.
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    Right, then. Carry on.

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    Not Certified Slow SDSUsnowboards's Avatar
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    A shop in Bakersfield wants something in the vicinity of $4k for a rebuild of the top and bottom, or $1,800 for a diagnostic.
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    Senior Member Silversprint's Avatar
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    You still have a car trailer? Why not bring it back down to a local mechanic?
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    Senior Member robburgoon's Avatar
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    Quote Originally Posted by SDSUsnowboards View Post
    A shop in Bakersfield wants something in the vicinity of $4k for a rebuild of the top and bottom, or $1,800 for a diagnostic.
    You should really talk to Oli's guy.

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    Quote Originally Posted by Silversprint View Post
    You still have a car trailer? Why not bring it back down to a local mechanic?
    That's the plan.

    Quote Originally Posted by robburgoon View Post
    You should really talk to Oli's guy.
    I have. If I am to rebuilding it, I'd want a specialist like Chris. If I'm just swapping in a motor, my regular mechanic should manage. So I suppose it comes down to which route I go. Labor for the swap is looking to be $1,200, which is about what I expected. LS1 motors going from $2,500 to 4,000. They aren't inexpensive.
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