Re: [AMC-List] Weird non-running issue on '82 Jeep CJ

[Tom Jennings <tomj@xxxxxxx>]

On Thu, 16 Nov 2006, Nick Lenarz wrote:

>    The symptoms: Engine won't stay running. It starts fine, but dies
> off instantly. I can keep it running if I 'blip' the throttle, but if I
> hold it constant, it runs for a few seconds, then dies off quickly.
> This occurs at any throttle position/RPM, almost as if it's running out
> of gas, but it's as sudden as turning the key off. Changing plug gap
> has no effect.

So what thin happened to start this problem? Did it progressively
get worse, or happen all of a sudden? Carb or ignition rebuild?

If it stays running indefinitely blipping the throttle, it's
almost certainly a carb issue.

If it won't idle, it will be hard to verify the ignition timing,
but if you can blip it to keep it running long enough to see
spark timing with a timing light, with the vacuum hose off you
should see 6-8 BTDC (idle) up to around 25 BTDC (plus or minus
10, depending on your distrib, etc) but mainly it should not
be hopping wildly, just varying with RPM.

But it sure sounds like you have no gas to the idle, low and high
speed circuits in the carb -- all fed by the float bowl. The
accellerator pump gets fed from the very bottom of the bowl,
so it works when the rest of the carb is totally FU.

It's not dying from grossly rich, right? I know "blipping"
the throttle indicates the opposite, but the revs might be
clearing it.  No stinky smoke? Plugs wet and smelly, or white?
Sounds like it's not this, but it's an easy check.

I'd triple-check the float setting. Sticking needle and
seat? Spring/pin/tab falling in the way when you assemble it?
Float rubbing on something, preventing it from dropping?
If float-drop setting is not right, it could bind.

>    On the occasions I can get it to idle, it will not run without the
> idle mix screws backed out at least 4 turns and the choke mostly
> closed. When tuning, it will run at 6-8* BTDC, but acts like it's way
> retarded (snapping back into the exhaust manifold). If I tune for best
> idle/vac, it runs better, but the timing is off the rack (24*+) and it
> dies as soon as I go off-idle.

All of these things indicate wildly too lean. Super lean mixtures
need lots of advance to make any power.

My money is on the carb.
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