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  1. #1

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    Fuel Pump Wire and Engine Detonation

    These four valve pent roof style combustion chambers resist detonation very well because of the fastburn design they have in them. But when at high rpms and with induced induction, these engines high rpm can experience detonation and you will not know that detonation is going on in a lean condition. It is very difficult to hear the sound from under the thick insulated seats of these skis. Detonation will cause a piston to scuff on the "four corners of the cylinder wall"( machine shop term ) and this snowballs into loss of compression broken rings and ring ledges breaking, pitted pistons and this can happen within seconds at 9,200 rpms.
    The engine at part throttle the mixture is okay, then the engine running at full throttle WOT with lean air/fuel ratio and detonation may now occur and fast . Then a piston overheats and scuffs, the engine fails. .


    This can be a cause of the problem, the fuel pump wiring over heating after the installation of a high pressure fuel pump. The wire may not show any signs either but that thin wire needs to be able to carry 20 amps and if it doesn’t, the fuel pump may slow ( caused by a over loaded fuel pump wire) and drop fuel pressure could drop down during extended heavy loads and at high rpms. One way to solve it, is to run another wire from the bat, to a relay then to the fuel pump . A dedicated ground should also be considered too.


    Hope this can prevent any problems you all could have.
    Happy Thanksgiving to all you and your families.

    I did give copyrights to Larry Carley for using some of his article in my post. See below


    Take Care,
    C J


    PS :
    Detonation by Larry Carley copyright 2019 AA1Car.com
    Lean fuel mixtures can cause detonation.Lean fuel mixtures can also be caused by dirty fuel injectors, carburetor jets clogged with fuel deposits or dirt, a restricted fuel filter or a weak fuel pump. If the fuel mixture becomes too lean, "lean misfire" may also occur as the load on the engine increases.










    Last edited by cjk6119; 11-30-2019 at 08:56 AM. Reason: update info and copy rights


  2. #2
    SplishSplash's Avatar
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    Going to have to think about the fuel pump statement. I think the fuel pump runs the same speed all the time. Does not increase with RPM or load. The fuel pressure regulator controls the Fuel flow. At low RPM, dumps most back to tank, at high rpm, to engine. The Fuel pump just pumps the same amount of fuel all the time.

    Yes/no?

    Hope someone else can chime in on that.

  3. #3

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    Quote Originally Posted by SplishSplash View Post
    Going to have to think about the fuel pump statement. I think the fuel pump runs the same speed all the time. Does not increase with RPM or load. The fuel pressure regulator controls the Fuel flow. At low RPM, dumps most back to tank, at high rpm, to engine. The Fuel pump just pumps the same amount of fuel all the time.

    Yes/no?

    Hope someone else can chime in on that.
    You are right,I was not clear in my statement :"Under a load" additional pressure from adjustable fuel regulators and the larger fuel pump being used, the wire is over heating causing high resistance and voltage drops see Ohm`s Law and that causes the fuel pump to slow down.

    Take Care and thanks SplishSplash
    C J
    Last edited by cjk6119; 11-27-2019 at 01:49 PM. Reason: sp

  4. #4

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    This is called hot wiring your fuel pump they have many kits available for modern cars.

    Robert

  5. #5

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    On GM cars there is a yellow pigtail near the battery for the tech to test the fuel pump when using a fuel pressure gauge while under the hood
    Last edited by cjk6119; 11-27-2019 at 08:00 AM. Reason: sp

  6. #6
    TimeBandit's Avatar
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    Agreed…. fuel pump runs continuously against a constant regulated back-pressure (aka bypass valve), which establishes how hard the pump will continuously work. So I can certainly see that increasing the operational fuel rail pressure, to also include higher-duty aftermarket pump would indeed put electrical strain on the OEM wires. However, I would not run parallel wires, rather install a new dedicated circuit & wiring directly to the battery + & - and include a new heavy-duty relay on the positive wire. Now take the OEM positive pump wire & re-route it to energize the new relay.

    Detonation – First, I’m guessing the OEM knock sensor is rendered useless beyond those upper RPMs.
    I think when you are talking a combination of higher RPMs & higher cylinder PSI (via more forced air), spontaneous combustion (occurring before spark) is not so much an “ah-ha” moment, than a “no-duh” moment - basically “dieseling” the gas at that point. Lean -vs- rich AFRs via fuel rail pressure adjustments can only get one so far under these extreme conditions, the problem remains with the volatility nature of petrol - octane, yet how high is one willing to practically go and trust.

    Honestly, once again, we are talking about maintaining an engine in it’s upper-most extreme RPM end for the sole sake of turning the impeller faster. I don’t mean to minimalize the notions or the respectable people here, but the OP destruction-explanation above sounds a lot like any engine that destroys itself by spinning faster and running higher compression ratios than engineered mechanical design limits - AND engineered limits of petrol.

  7. #7
    simple way tp test this theory and watch is to install an afr gauge.

  8. #8

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    Hot wire kits come off the alternator for highest voltage. This is an easy mod to the ski if desired. The old fuel pump wire runs a relay to the new "hot wire".

    Robert

  9. #9

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    After thinking about what TimeBandit had to say about the wiring, I will recant my idea to run another wire parallel in circuit with the existing wire.
    I would do is this,
    TimeBandit " I
    nstall a new dedicated circuit & wiring directly to the battery + & - and include a new heavy-duty relay on the positive wire. Now take the OEM positive pump wire & re-route it to energize the new relay."

    That to me, is a better way,

    Thank you TimeBandit for your help.
    Take Care
    C J
    Last edited by cjk6119; 12-01-2019 at 06:33 AM.

  10. #10
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by cjk6119 View Post
    ... the wire is over heating causing high resistance and voltage drop ...
    Heat is caused by (too) high resistance in the wire (or connector) when carrying too much current (amps).

    Resistance causes a voltage drop during high amp flow, which becomes heat in the wire (or connector).

    Once a wire or connector becomes heat damaged, the resistance can increase, which causes more heat the next time it is run.

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