"tom" <tom@adelphia.net> wrote in message
news:fvn061l0vqme8bcfk090oqkvvja426t5sa@4ax.com...
>I have recently developed a severe hesitation problem. Cyl 1 shows
> compression of 120. Other 3 have 150. If I squirt oil into 1, it
> also shows 150. There has been no change in compression or vacuum
> (18) since before the problem, but the hesitation and missing started
> suddenly as I was
> driving last week. Prior to this, I ran smoothly at all speeds up to
> 85 mph., although the engine had been a little weak, I consume very
> little oil, except at sustained very high speeds,
>
> Now the engine idles nicely, but hesitates under load under any
> driving conditions. I removed the #1 spark plug wire and grounded it
> to the block. Car runs much smoother now on 3 cylinders at all speeds
> than it had been on 4 with one missing..
>
>
> Questions:
> Will running the car like this on a short term basis damage the
> engine?
> Could raw gas ignite in the exhaust system and damage it? (I can't
> shut off gas supply because this is a carb engine, not EFI.)
> Is there any way to tell if problem is rings rather than valves
> without pulling the cylinder head?
>
> Thanks,
>
> Tom
>
1) Don't run it with the ignition dead on one cylinder. Find and fix the
problem. Running with 25% unburned fuel entering the exhaust will toast the
exhaust system very quickly and will worsen the ring wear in the dead
cylinder as the gasoline washes the oil away. (I wonder if that is why the
compression is low in the first place... inadequate oil to seal the rings.)
2) The compression problem is almost certainly with the rings. Your oil test
is used to tell the difference: the oil temporarily seals the rings better,
and in your case that restored compression. The valves have to seal well to
do that, so your valves are good enough.

Now, that isn't a good sign, but that probably has little to do with the
hesitation. What you describe isn't what I'd call hesitation as much as it
is really ratty running, so I'll address that first, then move on to classic
hesitation.

Bad running under load makes me think of poor ignition. If you've recently
done a tune-up, I think you got a bad part. I once got a distributor cap
that lasted one hour, then one cylinder died completely. But if it's been a
while, now is the time. The distributor cap, plug and wire are all big time
suspects for this symptom.

The two things to look at for actual hesitation suddenly appearing are the
carburetor and the ignition timing - especially the advance. If the
hesitation occurs even when you floor the accelerator while travelling 30-40
mph, I'd bet on the carburetor.

With the engine off, pull the air cleaner off the carb and look down the
throat at the throttle butterfly in the primary barrel. It will be easiest
if the engine is warm so the choke is open. Open the throttle by hand and
watch for a solid stream of gasoline in the throat. If that is weak or
missing, you have found the cause - a bad accelerator pump. It's a very
common failure. The cure is a carburetor rebuild, or exchange if you are
especially wealthy.

If that looks okay, put it back together and start the engine. Remove all
vacuum hoses from the distributor and plug them. Connect a timing light and
operate the throttle by hand, slowly and rapidly. You should see the timing
advance smoothly as you open it slowly, and rapidly advance matching the
engine speed as you open it rapidly. If either of these are not true, you
have problems with the mechanical advance in the distributor. A replacement
from the wrecking yard is one approach to that. The other is to disassemble
the distributor and clean and lube the advance weights and the plate they
ride on. If there are pits in the plate where the weights are at idle or at
full advance, sand them out with fine emery paper. The distributor work is
about the same skill level as the carb rebuild... medium. Don't forget to
reconnect the hoses!

So... what model and year is this?

Mike