b****i
发帖数: 108 | 1 Spark
If the cranking circuit has passed the appropriate tests, it's time to conce
ntrate on why the engine won't run. There are four areas of concern-spark, f
uel, compression and timing. The easiest test to start with is usually the o
ne for the ignition system. On older systems, it's convenient to remove a co
il wire, then use a spark tester to test for proper spark. An adjustable spa
rk tester is preferable to a fixed design because it allows you to adjust th
e tool to a smaller gap, which w | b****i
发帖数: 108 | 2 Fuel
Fuel system diagnosis can be broken into two parts-the fuel delivery system
and the injector electrical circuit. Just as the ignition system has primary
and secondary components, the fuel system has command and fuel delivery.
Command, or the injector electrical circuit, is usually diagnosed with a sca
n tool and a DSO. A noid light, which is plugged into the wiring harness in
place of one of the injectors, is not a good test. While convenient, this to
ol does not put the proper load on the | b****i
发帖数: 108 | 3 Compression
You can test engine integrity with a compression gauge, but the starter's cr
anking speed will give a trained ear an indication of low cylinder compressi
on. If you hear a fast-cranking engine, test the compression to see where th
e problem is. Low compression does not always indicate an internal engine pr
oblem.
After identifying low compression, a leakdown test is a good follow-up step.
On some engines, it may be convenient to check cam timing before engine com
pression. This depen |
|
