To summarize the answers to the majority of questions on my non-starting
problem:
- The valves are working. If they were stuck, there would be far less
compression, and no vacuum. I also had the valve covers off and
verified that each valve did in fact operate.
- Verified spark a few different ways. The lead is okay. Tried four
coils. Tried multiple sets of points. Tried about six new and used
condensors as well. The engine is sparking, as is verified by the
kick-back on advanced ignition timing. That is a definite. The firing
order has been verified 100 different ways and that is also definitely
correct. There definitely IS spark.
- Grounds are good
- If the damper has slipped (and thus the timing mark), it would not
make much of a difference. What I mean by this, is that even if there
was no timing mark at all, I could still verify TDC manually (which we
did) and set the plug wires accordingly. Rotating the distributor would
thus correct for any variances in perception and the car would at least
fire, which it currently doesn't.
- Point gap / spark plug gaps are correct. Verified that often.
- Brand new battery. Just replaced the one from October.
- Plugs are not fouled. Plugs are correct type (Tried Autolite A75
which is the replacement for A42, and Champion J12Y. Even cleaned a set
of original A42 Autolite plugs and found no difference.
- Starter cranks just fine. But that variable was removed when we
cranked it at 24 volts -- cranked twice as fast but still no firing.
- The 90-110 PSI compression stays consistent, and is consistent across
the cylinders.
- Oil has been changed. Pistons are carbony, but not terrible.
- The spark plug wires are new also. Also tried other wires.
- The rotor is still turning just fine. Makes a decent spark when
viewing an externally grounded plug. Rotor is not spinning or slipping
when I hold it during cranking
- I checked the line between the pump and carb; cleaned with carb
cleaner. New fuel filter too. I'm positive carb is getting enough gas,
- Tried gas down the carb. The carb is getting gas; the accelerator
pumps work fine. Should start on the ether anyway though.
John McCann, Mackey Nelson and Dave Grove all suggested something
similar (in Dave's words):
"It sounds for all the world like the cam timing is off - like the
timing chained has slipped a few notches. There is an easy way to check
the cam timing - remove the left valve cover, and watch the "valve
action" as the engine is turned over with the starter. Pay attention and
you will see that the intake valve starts to open immediately (and
sometimes even before) as the exhaust valve closes. The idea is to
"catch" the intake and exhaust valves at the exact point where they are
BOTH open the same amount. the intake will be opening, and the exhaust
will be closing, and at some point, they will (obviously) be "open" the
same amount. This is the "center" (so to speak) of "overlap". Now, at
this point in engine rotation (the center of overlap), the timing mark
(on the damper) will be (ideally) exactly on TDC. Anything within 5
degrees of TDC is OK. Considering that there are about 14 crankshaft
degrees for every link of the timing chain, it is easy to spot when the
chain has jumped even one notch, and even an engine that's off one notch
can be coaxed to life, so if this is your problem, the above test will
show that things are *way* off." Thus, with this test, the pointer
would be at 0 degrees (TDC) but 180 degrees out when the valves are in
the position described above.
So at this point, there are three possibilities as far as I see it.
1) Although we see a good spark, that spark is not good.
2) The valve timing is off
3) The compression is not high enough to start the car (is my tester
bad?)
To test #1, I can try a known-good distributor. Two test #2 I will try
the test above. To test #3 I will be using this stuff called "OMC
Carbon Guard", GM's "Upper Engine Cleaner" and/or "Yamaha Ring Free"
that are sold for outboard marine engines that are reported to do an
absolutely incredible job of freeing carbon and sludge on rings. (It's
actually the same stuff Chevron calls "Techron" and adds to their fuel,
but in concentrate form.) After the cleaning, there should be some
further increase in compression.
I will also put 90 weight oil in every other cylinder (by firing order)
and try starting then. If compression is indeed the problem, then the
engine should run at least briefly until a) the oil burns off, or b) the
plugs foul from the oil.
Other than these tests, I'm still stumped.
-Dave
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