RonJ
Banned
A very common cause for no-start engine problems is a lack of spark at the spark plugs. I created this thread to describe a relatively simple yet effective method to...
Check for spark
1) Unplug all four fuel injector clips to avoid flooding the cylinders with gas during the procedure. (Thanks goes to Sonia's Driver at H-T for this tip.)
2) Buy a spare NGK spark plug for your engine (inexpensive $2-3) and gap it properly.
3) Remove the plug wire from one spark plug and insert the spare plug into the end.
4) While firmly grounding the threads of the spark plug against a clean metallic area of the valve cover, have a buddy crank the engine. If you are concerned about getting shocked, you can wear a rubber glove on the hand holding the spark plug, though this is really unnecessary if you take care to keep fingers or other body parts away from the spark plug tip.
5) With the engine cranking, you should see bright white spark (with only a faint bluish tinge) rather than weak orange/yellow or deep blue spark at the tip of the plug.
6) Repeat procedure above for the remaining three spark plugs.
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Outcomes and troubleshooting
A) Weak orange/yellow or deep blue spark
Check whether the coil in the distributor is bad. The service manual (see links in my signature) describes resistance measurements to test the coil or, alternatively, find out whether your local autoparts stores (e.g., AutoZone) will test it for you (some will not).
B) All plugs lack spark
Do these steps in order:
a) Check whether the timing belt snapped or stripped. This is most easily done by removing the oil filler cap and, while a buddy cranks the engine, by peering into the hole with a flashlight to look for evidence that the camshaft is turning (e.g., movement of the rocker arms). If the belt snapped (=no rocker arm movement), install a new timing belt, tension it properly, and then compression test the cylinders. The latter step is essential as major engine damage may have occurred when the timing belt snapped/stripped.
b) Check whether the important G101 ground wire on the thermostat housing is loose or corroded. If so, clean it thoroughly with steel wool and tighten. By the way, if G101 is disconnected or loose, the engine will lack both spark and fuel.
c) Check whether the CEL remains ON when the key is turned to ON(II). If so, pull the code(s) (see CEL sticky). If a code for one of the distributor sensors (codes 4, 8, or 9) or the igniter/ICM (code 15) is retrieved, then the distributor subassembly or igniter/ICM, respectively, is possibly bad. Further troubleshooting here would be:
d) Check whether battery voltage is reaching the coil and igniter wire on the Blk/Yel wire in the distributor when the key is turned to ON(II). If not, there may be a bad wire from the ignition switch (or for 98-00 Civics, a blown fuse 9 in the under-hood fuse/relay box). A bad ignition switch is another possibility but, in this case, the engine will lack both spark and fuel.
e) Check whether the coil or igniter/ICM in the distributor is bad. Again, there are resistance tests for the coil (see FAQs sticky), but you may have to take the igniter/ICM to an auto parts store (e.g., AutoZone) for testing.
f) In some cases, lack of spark is due to a bad ECU. This is usually only considered if all tests described above yield negative results.
C) Some but not all plugs have weak spark or lack spark
Check the plug wires, distributor cap, and rotor.
Check for spark
1) Unplug all four fuel injector clips to avoid flooding the cylinders with gas during the procedure. (Thanks goes to Sonia's Driver at H-T for this tip.)
2) Buy a spare NGK spark plug for your engine (inexpensive $2-3) and gap it properly.
3) Remove the plug wire from one spark plug and insert the spare plug into the end.
4) While firmly grounding the threads of the spark plug against a clean metallic area of the valve cover, have a buddy crank the engine. If you are concerned about getting shocked, you can wear a rubber glove on the hand holding the spark plug, though this is really unnecessary if you take care to keep fingers or other body parts away from the spark plug tip.
5) With the engine cranking, you should see bright white spark (with only a faint bluish tinge) rather than weak orange/yellow or deep blue spark at the tip of the plug.
6) Repeat procedure above for the remaining three spark plugs.
------------------------------------------------------------------------------------------------------------------------------
Outcomes and troubleshooting
A) Weak orange/yellow or deep blue spark
Check whether the coil in the distributor is bad. The service manual (see links in my signature) describes resistance measurements to test the coil or, alternatively, find out whether your local autoparts stores (e.g., AutoZone) will test it for you (some will not).
B) All plugs lack spark
Do these steps in order:
a) Check whether the timing belt snapped or stripped. This is most easily done by removing the oil filler cap and, while a buddy cranks the engine, by peering into the hole with a flashlight to look for evidence that the camshaft is turning (e.g., movement of the rocker arms). If the belt snapped (=no rocker arm movement), install a new timing belt, tension it properly, and then compression test the cylinders. The latter step is essential as major engine damage may have occurred when the timing belt snapped/stripped.
b) Check whether the important G101 ground wire on the thermostat housing is loose or corroded. If so, clean it thoroughly with steel wool and tighten. By the way, if G101 is disconnected or loose, the engine will lack both spark and fuel.
c) Check whether the CEL remains ON when the key is turned to ON(II). If so, pull the code(s) (see CEL sticky). If a code for one of the distributor sensors (codes 4, 8, or 9) or the igniter/ICM (code 15) is retrieved, then the distributor subassembly or igniter/ICM, respectively, is possibly bad. Further troubleshooting here would be:
--->(for sensor codes) to measure the resistance of the sensors (spec = 350-700 Ohms) and their corresponding wires for a short or open.
--->(for code 15) (i) to have an auto parts store test the igniter/ICM, (ii) to test the Blk/Yel wire attached to the coil and igniter/ICM for battery voltage with the key in ON(II), and (iii) to test the Yel/Grn wire running between the igniter/ICM and the ECU for a short or open.
--->(for code 15) (i) to have an auto parts store test the igniter/ICM, (ii) to test the Blk/Yel wire attached to the coil and igniter/ICM for battery voltage with the key in ON(II), and (iii) to test the Yel/Grn wire running between the igniter/ICM and the ECU for a short or open.
d) Check whether battery voltage is reaching the coil and igniter wire on the Blk/Yel wire in the distributor when the key is turned to ON(II). If not, there may be a bad wire from the ignition switch (or for 98-00 Civics, a blown fuse 9 in the under-hood fuse/relay box). A bad ignition switch is another possibility but, in this case, the engine will lack both spark and fuel.
e) Check whether the coil or igniter/ICM in the distributor is bad. Again, there are resistance tests for the coil (see FAQs sticky), but you may have to take the igniter/ICM to an auto parts store (e.g., AutoZone) for testing.
f) In some cases, lack of spark is due to a bad ECU. This is usually only considered if all tests described above yield negative results.
C) Some but not all plugs have weak spark or lack spark
Check the plug wires, distributor cap, and rotor.