1997 Wagon R: No. 3 plug burns black

1997 formula Suzuki wagon R model: E-CV21S engine model: F6A turbo

An engine that only the plug of No. 3 cylinder burns black

Although it got stocked at the car inspection, if you check the plug, only plug 3 is burning black. If burning is done normally, plaque should burn a little brown without burning black. Therefore, the following inspection was carried out.

1. When compression is measured, 9 kg / cm 2
2. Sparks are flying strongly from the plug cord for all the cylinders.
3. The state of the plugs of all the cylinders is normal (except for plug No. 3)
4. Engine · Diagnosis · code is normal

From the above inspection results, compression and sparks are normal among the three elements of combustion (compression, spark, air-fuel mixture). Therefore, although the mixture becomes abnormal, when the plug is wrapped (fuel adheres) or it is burnt black, the amount of fuel in the air-fuel mixture is large, that is, the mixture is too dense .

If you suspect that there is an abnormality in the injector of No. 3 cylinder, it is conceivable that fuel leakage of the injector itself or long energization time is long.

 

Injector Inspection

Remove the coupler of the third cylinder injector and turn the fuel pump to check. Then the third plug was not wet so we judged there was no fuel leakage from the injector.

Next, using the fault diagnosis machine, the energizing time of the injector was measured and the following waveforms were shown.

 

上図の電圧CH1が第3気筒、電圧CH2が第2気筒の噴射波形である。CH1の波形がCH2の波形と比べて異常であることがわかる。

ここで、計測ブローフの差し込みを確認するためにインジェクタのワイヤーハーネスを触ったところ、波形が変化したので、ワイヤーハーネスを点検（第三シリンダのインジェクタ〜コントロールユニット間）していくと、エンジン内のプレッシャレギュレータと接触した跡があり、配線がむき出しになっていた。

したがって、今回のトラブルは、第3シリンダのインジェクタ・アースがハーネスの途中にあるプレッシャレギュレータと振動により接触することで、噴射時間を制御する信号に狂いが生じ、燃料噴射量を通常よりも増やしていたことが、プラグが黒き焼ける原因であるということがわかった。

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