MTFCA Forum

Got a engine giving me nightmares. Will not run on all 4. Good compression, good spark but not getting fuel to number 2 cylinder. Any ideas?

Intake leak or cracked intake manifold for starters.

Stuck Valve?

Check your intake manifold for obstructions such as a wasp nest. This was the cause of another engine's problem here recently.

Good Luck,

I don't think it is a wasp nest or other clog in the intake manifold because 1 and 2 share the same intake port. If the intake valve were stuck, I think it would also affect #1 because instead of drawing fuel through the manifold #1 would be taking drawing compression from #2. So if it really is not getting fuel, I think you have a stuck exhaust valve on 2 so that it is drawing exhaust from the manifold instead of fuel. So check the exhaust valve on #2.
Norm

He stated that it had "good compression" - if that's the case, it couldn't be a stuck valve ?

Had a 3 cylinder T once, good compression, turned out that the adjustable tappet had backed off, if it still has solid lifters then check that the cam still has a lobe.

When did it start doing this? What did you do to the engine between the last time you remember it running good and now? Jim Patrick

A truly stuck valve will remain open and give no compression. However, a "sticky" valve may "float". It takes a nearly a second to close, which is fast enough to pass a standard compression test, but even at an idle (say about 300 rpm, four cycle motor, 600 cycles per minute), the valve must close in a fraction of a half cycle. Or roughly less than a twentieth of a second in order to have proper compression.And of course much faster at any higher speeds. So you can see how a sticky valve can in fact pass a standard compression test, yet fail in a running engine. Often, the offending valve can be heard by a trained ear at either the carburetor of the exhaust pipe depending upon whether the offending valve is an intake or an exhaust. There is also a test using a stiff piece of paper or a light cardboard held over the end of the exhaust pipe for if it is an exhaust valve. The exhaust gasses should flow out continuously, pushing the paper/cardboard out somewhat steadily. A slightly burned or sticky exhaust valve will cause a momentary "suck-back" causing the paper/cardboard to slap the end of the exhaust pipe. Intake valves are a bit tougher to test, but usually, will cause more running issues with interference with fuel flow to the neighboring cylinder, or even coughing back clear through the carburetor.

Check your firing order 1-2-4-3

Well Kerry hit it right on the nose. Intake adjustable lifter loosened and turned in to the point it was not opening the valve.

Glad you found it Jim. I was going to sugest turning the car around and see if it made number 3 cylinder not work.

Glad to be of some help Jim, I'll charge you the same as all my T work and advice, a freebe
As a rule when I do re-builds I set the push rods with just a 3/4 turn from bottoming out and set the valve lash/clearance the old way of stem grinding to avoid this from happening.
Happy T'ing

What an outstanding example of online engine diagnosis. It was fun and informative to read.