Ignition Key and Start Problem

I've read a few posts about stuck ignition keys, and some of them hint
that this may relate to starting problems. I don't understand enough
about what goes on in the ignition switch to figure this out, so I
would be grateful if someone could explain it to me.

Here's the problem. The truck is a 1994 Suburban K1500 4WD with
213,000 miles. When the engine is running, it runs very well, but just
recently it has failed to start sometimes. The engine turns over, but
I get no sounds like ignition is occurring.

When it won't start, here's what I can tell you:
1) When the key is in the start position, I can hear something what
sounds like a fuel pump.
2) The key got stuck in the ignition last night. It wouldn't come out
of the start position. So I could crank it, it wouldn't start, and it
would only back off to the run position.
3) As for the stuck key, I tried moving the steering wheel, shifting
the transmission (automatic, on the column). This didn't work.
4) This morning, I pulled one of the spark plug wires and turned the
engine over, and I have spark. (When I did this test, the engine
started, so lack of spark might still be the problem.)

The stuck key problem started a few month ago, but I haven't had the
problem for quite awhile, so I assumed it was a badly cut key. When
the engine wouldn't start a couple of days ago, the key was not
sticking. Then last night when the engine wouldn't start, the key was
stuck. I had it towed home.

I disconnected the battery last night and gave it a full charge. This
morning I hooked it back up. I could hear the fuel pump running.I
tested for spark (#4 above), and could see the spark. While doing
this, the engine started. I shut it down and the key came out easily.

Is the key and ignition switch the problem? If so, how?

Thanks,
Jim

>> Is the key and ignition switch the problem?
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> Do not confuse the ignition switch which is mounted on the top of the
> steering column at its base, with the key and lock assembly located below
> the steering wheel.
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I think I understand you. So i my case, the key is stuck in the lock
cylinder for some reason. My have something to do with no start, maybe
not.


One other thing that might be worth mentioning:

For several months, when the ignition key is inserted and turned to
the start position , I hear a very loud tapping sound coming from
somewhere in front of the firewall on the passenger side. The tapping
(about 4 per second) continues for about 15 to 20 seconds after the
engine starts. When turn the key to off, the tapping occurs again for
the about the same amount of time, even when the key is removed. I
pulled each fuse in the fuse panel by the brake release, and couldn't
get the tapping to stop. I disconnected the battery (when the engine
is off), and the tapping stops. I considered this to be just an
annoying noise that I couldn't figure out, but now I'm wondering if
it's related.

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