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causes are seldom obvious. For example, the fuel pump
may produce adequate pressure and volume, but a fuel
line can have a "flapper" - a loose piece of
lining or a deteriorated hose - that shuts off the flow
of gasoline intermittently. A fitting may have been
installed improperly, creating a restriction in the
line. The hose on the suction side of the fuel pump can
collapse and cut off the gas supply just when the engine
needs maximum flow. We all have shiny braided-steel
lines on our race cars - but do we really know whether
the rubber underneath the braids is in good condition
unless we inspect it regularly?
A carburetor that has been idle (pardon the pun) over
the winter may have passages that are clogged with gum
and deposits. Alcohol is especially tough on carbs; I've
seen metering blocks with passages that were eaten out
or blocked entirely by methanol corrosion. If the damage
isn't visible, you could waste weeks trying to find the
problem. Any debris in the fuel system will
eventually end up in the carburetor. Usually you'll find
junk in the needles and seats, but occasionally it can
work its way into the circuits. I've found pieces of
fuel cell foam in jet blocks - how on earth did it get
there? I don't know, but it sure did mess up the fuel
curve!
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We strain every drop of gasoline that goes into our Pro
Stock through a fine screen. I also recommend using a
filter to keep contaminants out of the fuel system. But
just because you have a filter, don't automatically
assume that it's in good condition. A filter element
that's been exposed to moisture or excessive humidity
can starve an engine for fuel.
Electrical problems can be tricky to diagnose. Attention
to detail is essential. In a previous column, I pointed
out the pitfalls of assuming that things are as they
seem. Don't assume that the terminals and connections
are good - check their resistance with an ohmmeter. Did
you paint your car this winter? If so, does the post for
the ground strap have paint on it? Get out your stiff
wire brush and scrub every electrical connection until
it sparkles!
Crank trigger ignitions are wonderfully accurate, but
they can also be extremely temperamental. It is
absolutely crucial to shield and isolate the crank
trigger sensor wires. These systems are highly
susceptible to interference from other electrical
devices. I've seen engine misfires cured by turning off
an electric water pump or fan; that's a clear case of
electronic interference. Never bundle the crank trigger
wires with the wires for other circuits; the |
