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Can An Engine Start Too Quickly?

Discussion in 'Early CJ5 and CJ6 Tech' started by boopiejones, May 9, 2022.

  1. May 9, 2022
    boopiejones

    boopiejones I can’t drive 55

    California east bay
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    I may be totally overthinking this…

    I know people talk about priming the oil on new engines builds before the first start up, but what about an engine that has been sitting for a while? I have two “fun” vehicles that don’t get driven much - 56 CJ and a 68 MGB. Both of them turn over very quickly even if they’ve been sitting for weeks or months, but I’m wondering if that is actually doing more harm than good?

    If they’ve been sitting for a while am I better off not choking the carb so I can crank the engine for a bit and get some oil flowing, and after that engaging the choke and fire it up?
     
    Last edited: May 9, 2022
  2. May 9, 2022
    Norcal69

    Norcal69 Out of the box thinker 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    An engine can definitely start too quickly! I prefer my engines to build oil pressure before firing if they have sat until cool. Perhaps pull the coil wire off before starting if the vehicle has been sitting for more than a few days. It makes me grit my teeth when I see someone's cold start video and they pump the gas a couple times before even turning the engine over. All of our race engines have an oil heater pad epoxied to the side of the oil pan. Standard procedure is to plug the heater in for 1 hour or so before starting and crank with ignition off until full oil pressure was built. These were 13:1 compression full roller SBC. While those extremes aren't necessary for our street engines, building oil pressure prevents dry starts with today's low zinc oil.
     
    Last edited: May 9, 2022
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  3. May 9, 2022
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    For fanatics there are electric pump systems to pre-pressurize the oil system before cranking, but the cost makes it a moot point, IMHO.


    That was proper procedure to "set" the automatic choke in the days of carburetors. Right in the owner's manual.
     
  4. May 9, 2022
    Norcal69

    Norcal69 Out of the box thinker 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    That is true on those type of carburetors.
    Many pull type chokes and electric chokes don't need that gas pedal input to set them. The classic Edelbrock 4bbl that is popular on hotrods today does not need any pre starting throttle input if the choke is adjusted properly.
     
  5. May 9, 2022
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Understood. But the habit may have formed at their mother's knee. At least, she was the one who taught me to do it...
     
  6. May 9, 2022
    boopiejones

    boopiejones I can’t drive 55

    California east bay
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    Both the CJ and MGB have manual chokes. My normal starting procedure is to simply pull the choke all the way out (which does require briefly and gently resting my foot on the gas pedal - but not pushing it to the floor - to make pulling the choke easier). Then I turn the key and they fire right up. After that, the choke gets pushed in about half way so the air is no longer choked but the fast idle cam is still engaged. Then I drive off. Once I’ve driven a bit, the choke goes in the rest of the way.

    So it sounds like if the CJ and MGB have been sitting for a few days, I should adjust my procedure a bit? Crank the engine for a while before pulling the choke and firing it up? Is 5-10 seconds of cranking enough?
     
  7. May 9, 2022
    Norcal69

    Norcal69 Out of the box thinker 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    If it were mine, I would crank for 10 seconds or so before lighting the fire. Every engine design is different when it comes to how fast they build oil pressure.
    Maybe its superstition..... but I feel better after I do it. Even with the fuel injection on my dauntless, if I don't allow the system to prime before cranking, I get a good 7 seconds of rotation before the engine starts. That is usually about the time the oil pressure gauge needle starts to bounce. YMMV
     
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  8. May 9, 2022
    Jw60

    Jw60 WRPD855 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    In flight school we were told to turn the engine every other weekend. (By hand with ignitions off)

    They never sat still that long but the goal was to keep a fluid film on the bearings but this is for 390ci horizontally opposed 4 cylinder that have long slow warm ups before getting to takeoff.

    Pumping the gas also risks washing the oil off the cylinder walls.

    From what I've read on the side, a warm engine won't be a concern (like the stop light deal on the new cars) there isn't oil pressure but there is oil between parts and minimum load before pressure is there. What also bothers me is starting in gear since it's loading the bearings without pressure.
     
    Last edited: May 9, 2022
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  9. May 9, 2022
    duffer

    duffer Rodent Power

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    And I was going to say it depends on how much ether you used-------

    I use the disconnect the coil method but on modern engines, that is a lot of fussing around.
     
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  10. May 10, 2022
    Rick Whitson

    Rick Whitson Detroit Area 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I have an engine kill switch on my coil, I crank it until the oil light goes out before I flip the kill switch. I is also an anti theft device.
     
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  11. May 10, 2022
    jeepdaddy2000

    jeepdaddy2000 Member

    Eagle Point oregon
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    Personally, unless it is sitting for a year or more, I would drop a can of STP or some Power Punch in the oil and call it good. The additive will help keep the oil from draining out of the bearings by creating a film on them.
     
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  12. May 10, 2022
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    If you're super concerned about it, Canton Racing makes a product called an Accusump. https://www.cantonracingproducts.com/accusump

    [​IMG]

    It's an electrically actuated accumulator added to the pressurized part of the oil system. The valve is open while the engine is running and it fills with pressurized oil. The valve closes when the engine is shut off reserving a supply of pressurized oil to be released to the engine next time the key is turned on.

    They have low feed rate ones for normal engines that fill the accumulator slowly and only work for startup. The feed rate is slow so it doesn't reduce the engine's oil pressure while filling.

    They also have high feed rate ones for race engines with high volume oil pumps. The high feed rate ones can keep oil supplied to the bearings in cases where the oil pickup becomes uncovered in the pan. Road racers often use them to prevent oil starvation in high G corners. Seems like it would be good for rock crawling too.

    They are not cheap.
     
  13. May 10, 2022
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    AS I was saying earlier.

    The question would be the cost/benefit return... how many extra miles would you get from an engine over it's lifetime? What fractional proportional cost of replacement or rebuild would you be avoiding?

    I doubt many of us would even notice.
     
  14. May 10, 2022
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

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    Uless the engine has been sitting a LONG time I don't worry about it, there will be a film left on the bearing surfaces & there's no hard load on the engine at start.
     
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  15. May 10, 2022
    scoutpilot

    scoutpilot Member

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    If the motor was of an eight-cylinder, very high compression, and very tight specs, I might worry about it. Maybe.
     
  16. May 10, 2022
    amboynut

    amboynut Member

    Chelatchie, WA
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    Right. Pressing the clutch pedal creates an axial load on the crankshaft thrust bearings. So if you're concerned about bearing wear at startup put the transmission in neutral and sit on your left foot. Yes, the battery and starter have to work a little harder because they're also turning the transmission. Pick your poison.
     
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  17. May 10, 2022
    Norcal69

    Norcal69 Out of the box thinker 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    The general consensus among many mechanics and oil manufacturers is that 75-90% of engine wear takes place during startup and warm up. Ever heard a lifter tick that goes away 10 seconds or so after cold startup then is quiet for restarts thought the day? That lifter stopped making noise once oil pressure got to it. If the lifter ran without oil then so did the rocker arm as well as lots of other engine parts.
     
  18. May 10, 2022
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Say that were true. Then with a pre-oiler a 300,000 mile engine would last 500,000 miles?

    In that case I would expect to see a pre-oiler on every vehicle owned by a mechanic or oil manufacturer. If not every car coming off the assembly line.

    And to your point about lifters, they depend upon oil pressure, not an oil film like a rocker arm or bearing.
     
  19. May 10, 2022
    Jw60

    Jw60 WRPD855 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I don't believe cylinder count is as important as cylinder displacement. I'm very curious though if a 215 starts easier than a 225 and if a 225 is easier than a 300? This would need to be measured in amps at the starter.
     
  20. May 10, 2022
    nickmil

    nickmil In mothballs.

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    Ohhh thank goodness. Another knuckle pudding and flat towing thread.
     
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