Page 263 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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Engine systems 247

Figure 2.331 Six direct ignition coils in position

1 4

3 5

6
8

2
7

Figure 2.332 Direct ignition coil features: 1, direct ignition coil; 2, spark plug connector; 3, low
voltage connection, outer; 4, laminated iron core; 5, primary winding; 6, secondary winding;
7, spark plug; 8, high-voltage connection, inner, via spring contact

determines the information by initially fi ring all of the coils. The voltage across the
plugs allows measurement of the current for each spark and will indicate which
cylinder is on its combustion stroke. This works because a burning mixture has
a lower resistance. The cylinder with the highest current at this point will be the
cylinder on the combustion stroke.
A further feature of some systems is the case when the engine is cranked over for
an excessive time making fl ooding likely. The plugs can all be fi red with multisparks
for a period of time after the ignition is left on to burn away any excess fuel. During
diffi cult starting conditions, multisparking is also used by some systems during
70° of crank rotation BTDC. This assists with starting and then once the engine is
running, the timing will return to its normal calculated position.

2.6.5 Spark plugs

The simple requirement of a spark plug is that it must allow a spark to form within
the combustion chamber, to initiate combustion ( Fig. 2.333 ). In order to do this