It's my guess that you have a very serious problem--probably bad rings in
at least one of the cylinders. In most cases, if the rings in one cylinder
are bad--the rest of them will need to be replaced very soon. In other
words, a mechanic or yourself will have to replace all of the rings. In
some cases, it's cheaper to buy a rebuilt engine. Prior to selling rebuilt
engines--all of the rings are replaced regardless of the condition of the
old rings. If other people respond, there advice may be better then my
advice since I am NOT a certified mechanic--just a back yard mechanic that
in the past has done only minor work on various types of automobiles. I
should note--in case you don't know--replaced rings involves taking the
engine apart.




In article <Q9CdncJMF7Tk9v3fRVn-qA@sedona.net>, "Michael Pardee"
<michaeltnull@cybertrails.com> wrote:

> "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

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