Q: I’m hoping you can help me with my 2001 Blazer. It has failed to start on a dozen or so occasions. It will make no sound when I turn the key. About two or three different times, someone did something down at the starter and it started. Another time, someone jiggled the battery cables and it started. My mechanic replaced the starter relay, but that didn’t help. It has 160,000 miles. I’m very frustrated with this problem as no one seems to be able to fix it.

— Michelle M.

A: An intermittent no-start condition can place you in an inconvenient or dangerous situation. Your description of no sound helps pin this down as a no-crank starting problem as opposed to a cranking no-start (run) issue. Possible culprits include the battery, battery terminals, ignition switch, park-neutral switch, starter relay, wiring to starter and starter connections, and the starter itself.

It sounds like the battery is OK, as you don’t mention needing to jump-start the Blazer. To be sure, during an unsuccessful cranking attempt, turn on the headlights. If they remain bright as the key is tried, the battery and battery cable terminals are OK.

Next are the ignition and park-neutral switches. During an unsuccessful cranking episode, try working the key start position by rotating the key less, more etc. Same goes for the park-neutral switch, try selecting neutral, wiggling the shift lever, exploring the edges of both the park and neutral shifter detents as the key is held to the crank position. If even brief cranking or noises are heard, the wiggled switch is likely the problem.

Your starter relay lives in a very convenient, accessible location within the under-hood fuse box, a 5-inch square plastic black box with a knob-attached lid, under the hood on the left-upper side. Try removing the cover and feeling the relay — a 1-inch square black cube, centered in the box — as a helper successfully cranks the engine. You’ll feel a click. Now you know what to check for next time the Blazer fails to crank.

Now we’ll close in for a solution: If during a no-crank episode the headlights do not dim and the relay clicks as the key is tried, the fault almost has to be within the starter. With 160,000 miles on the clock, the starter, if original, is on borrowed time. Its brushes are likely worn very short and may make only tentative contact with the armature.