QuestionLast night the car was working great, we woke up this morning and had no spark. We scanned the vehicle and got no trouble codes. I tested the resistance of 2 plug wires and with one Ohm-meter (digital) I got infinite resistance and with the other (analog) Ohm-meter I got 18 and 20 ohms. I don't know what the typical resistance is but I tested spark at the coil and got zero spark there too. I was told I should replace the Crankshaft position sensor and I did, the car still won't start. The fuel pump is working fine I can hear with when I turn the key on. The battery is brand new, the spark plugs are about 3 weeks old. I've heard that a bad ground in the Engine Control Module can cause no spark, Is the ECM located on the fender behind the battery? Is this more likely the coil pack? what else would you recommend I check?
AnswerHi Jon,
Here is an answer I gave to another owner of a '97 LH car:
Probably there is something wrong with the ignition control system and the best way to determine that would be to read out the memory of the engine contol module for the presence of any fault codes. '97 was the first year of an updated code system that modified the codes and how to access them. It may be possible to do it yourself, if not then a code reader needs to be plugged in under the dash to a socket near the steering column. On a chance that it might allow for self readout: turn the ignition key "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch for whether the numbers change in the odometer window which replaces the mileage with 4-digit numbers OR the check engine light to begin to flash, pause, flash, etc, in which case you count the number of flashes before each pause, then repeat for accuracy, and group the numbers in pairs to form the codes. None of the above may happen however so without a code reader you have to do other tests.
Because you changed the plugs, if you saved one I would suggest that you remove the plug cap off one of the spark plugs, insert an old plug in the cap, then holding the combo by the rubber cap touch the threaded part of the plug against the engine head while a helper cranks the engine for about 5 seconds. Watch to see if you have no spark, sparks for about 1 second or sparks for the whole 5 seconds. Then if you have a voltmeter go to the alterator and find the dark green/orange wire and measure the voltage to the post where it is attached when a helper turns on the ignition to the run position. It should show 12V for about a second. Then have the helper crank the engine and observe the voltage to return for either 1 second only, or for the full 5 seconds of cranking. All these observations will point us toward what might be the matter. The most usual reason is that one of the spark timing sensors has gone bad, and these tests are diagnostic of that possibility.
Write back with the results and we'll go from there. On the fuel issue, the main question is whether the fuel pump runs for 1 second when you turn the key to run position, then does it run again when you start a 5 second crank. The only problem is to hear it while the engine is cranking is difficult. It is located in the fuel tank and so you can hear it for the initial key to "run" position, but then it is difficult to tell if it starts pumping again. Actually the measurement of the dark green/orange wire's voltage is the same test because that same engine control action is responsible for both the 12V and the fuel pump activation. But in any case listen near the rear of the car from underneath when you turn the key to run; it should last for about 1 second. The pressure is probably there if it runs.
The primary resistance of the spark coils should be 0.45 to 0.65 ohms. And the resistance between the paired high tension posts should be 7,000 to 15,800 ohms.
I believe there should be a fault code that should come out with a reader or via the ignition key:on-off-on-off-on and leave on, doing that in 5 seconds or less elapsed time. Then watch the check engine light which remains on to see if it begins to flash, pause, flash, etc. Count the flashes, then repeat for accuracy. Let me know. Also watch the odometer to see if the mileage changes to show any 4-digit fault code numbers. If neither happens then a fault code reader would be very helpful to plug into the multi-pin socket under the dash by the steering column.
You can also check the cam and crank sensors for pulsing, with the ignition in the run position and the crank turned by hand using a socket and handle on the crank pulley bolt. Measure between the black/light blue and tan/yellow on the cam and between the black/light blue and the gray/black wires on the crank sensor. The voltage should pulse between 5 and 0.3V several times per revolution if the sensor is good.
Roland
Roland
