[Mg-t] No Vacuum

[Stuart C. Keen, Jr.]

I'm at a loss! Drove from the house yesterday and the TD quit after a half
mile. It had been running just fine, then acted like it was starving for
gas. No abnormal bangs or noises. Just would not run. Got towed home.

This is a Mark II. BOTH fuel pumps are running. I disconnected the hoses and
checked the fuel flow to the bowls. Perfect. The carburetor bowls are full
of fuel. Checked the spark. Have Pertronix and a Sport Coil. Spark reads
excess of 20 KV. Removed the spark plugs and noticed they were NOT wet with
fuel after I attempted to start.

I have a fitting on the crossover member of the intake manifold. It's
normally connected to a cruise control system (shame but need the
assistance). From this port I usually read a steady 20 inches of vacuum.
Today it fluctuated wildly from 0 to 20. Basically no vacuum. Next I did a
compression test. All four cylinders are around 150 psi. Assume valves are
good. 

Apparently there is no fuel vapor being sucked into the cylinders (dry
plugs) due to a vacuum problem. What could be causing this lack of vacuum?
Where should I look next? I'm at a loss. Could the intake manifold gasket be
blown? Why? Would appreciate suggestions what the problem might be and how
to test.

This is my daily driver (74,000 miles in 9 years) so really want to get this
bugger back on the road soon. Thanks for all the help.

Stu Keen

1951 MG TD Mark II