There is a sequence of basic tests to do to repair a
non-starting vehicle or any gas piston engine. You do them in order and do them
thoroughly, so that you are sure you've eliminated each cause as you go. The
mnemonic is "fire, fuel, compression."
Fire means spark. You remove a spark plug
from a cylinder, lay it somewhere metal on the engine where you can see it and
you're sure it's grounded, crank briefly with the help of a friend if your arms
are short, and hope to see a spark. If there isn't a spark, try very hard to
check that it was grounded just to be sure.
Still no? Problem is "fire." You
then need to troubleshoot the ignition system. There are too many possibilities
under the category of "bad ignition" to go into over FB, but with high miler
cars it's often the spark plugs that are so worn that the spark gap is too
large. The gap should be around 30 thousands of an inch, which is about the
thickness of thin cardboard. No spark and a large gap, change the plugs.
If
there is spark, move to "fuel." The easiest test is to spray starter fluid in
the intake manifold, replacing the gas experimentally. If the car fires, you
know by logical elimination that it was fuel, so troubleshoot the fuel system.
For compression you need a compression tester and the knowledge to use it, but
most mechanics can tell if an engine has very bad compression in one cylinder by
turning the engine over by hand with a wrench on the crankshaft pulley or by
using the belt, comparing the compression resistance between cylinders.
Don't be
tempted to jump to random causes. It's necessary to use a logical
troubleshooting scheme to fix the problem.
No comments:
Post a Comment