jaferrio
New member
1941 Ford 9N will barely idle and will not throttle up w/o backfiring. Will sometimes run OK for a few seconds, then goes back to rough idle. Cannot throttle up at all.
Ignition System:
1. Looks like a brand new distributor+coil was installed from previous owner. Tore apart, lubricated centrifugal weights that were a little sticky. Bench adjusted timing per manual (1/4" offset from hole, using continuity meter to adjust points to open at this point). Adjustment screw was approximately half-way in the adjustment zone. When installed, verified #1 plug fires at T.D.C. by slowly turning over engine by hand crank. Determined approx. TDC using a U-tube manometer connected to #1 cyliner. Also checked w/ inductive timing light when running. Could not get engine to run much faster than idle, no spark advance observed at low speeds, but couldn't rev up to check.
2. Ignition coil is new, no markings; presume this is probably a 6v coil as it has 1 ohm internal resistance. Replaced old ballast resistor w/ a new 1 ohm ballast, planning on putting another one in series, but for now we have 1 ohm in coil + 1 ohm ballast. Previous owner installed a 12v battery, was running with that OK. Not ideal as we don't think they converted to 12v, looks like they just swapped out the 6v battery with a 12v.
3. New spark plugs. Checked each plug when running using an inline spark tester; all are firing. Pulled plugs and turned engine over, all are sparking and appear blue. Autolite 216 plugs, gapped first at 0.025", then 0.020", then back to 0.025". No change.
4. All new spark plug wires: wire core.
Valve Train:
Compression check showed #2 cylinder at 95 psi, other cylinders were between 100-115 psi. So issue with #2 perhaps, didn't dig any deeper on that yet.
Fuel:
1. Adjusted carb float to 1/4" per manual. Brand new carb. Forced fuel through all ports & orifices on bench. Fuel tank was removed, running using a small gas can w/ clean fuel (ethanol free).
2. Tried swapping new carb w/ original Marvel Schebler TSX carb. No change, still rough idle, even with adjusting idle screw.
3. Adjusted idle screw (on both old & new carb), unable to run smooth, sounds like fuel starving even w/ idle screw all the way in. No happy medium rich or lean. Adjusted main as well, no change.
4. New gasket between carb & intake manifold.
Air:
Oil bath cleaner was removed during testing to eliminate possible air restriction.
Ideas: (1) condenser looks brand new but did not check. (2) sticky valve?, (3) 6v coil, 12v battery, perhaps issues with spark?
Looking for more ideas before digging deeper into engine internals.
Ignition System:
1. Looks like a brand new distributor+coil was installed from previous owner. Tore apart, lubricated centrifugal weights that were a little sticky. Bench adjusted timing per manual (1/4" offset from hole, using continuity meter to adjust points to open at this point). Adjustment screw was approximately half-way in the adjustment zone. When installed, verified #1 plug fires at T.D.C. by slowly turning over engine by hand crank. Determined approx. TDC using a U-tube manometer connected to #1 cyliner. Also checked w/ inductive timing light when running. Could not get engine to run much faster than idle, no spark advance observed at low speeds, but couldn't rev up to check.
2. Ignition coil is new, no markings; presume this is probably a 6v coil as it has 1 ohm internal resistance. Replaced old ballast resistor w/ a new 1 ohm ballast, planning on putting another one in series, but for now we have 1 ohm in coil + 1 ohm ballast. Previous owner installed a 12v battery, was running with that OK. Not ideal as we don't think they converted to 12v, looks like they just swapped out the 6v battery with a 12v.
3. New spark plugs. Checked each plug when running using an inline spark tester; all are firing. Pulled plugs and turned engine over, all are sparking and appear blue. Autolite 216 plugs, gapped first at 0.025", then 0.020", then back to 0.025". No change.
4. All new spark plug wires: wire core.
Valve Train:
Compression check showed #2 cylinder at 95 psi, other cylinders were between 100-115 psi. So issue with #2 perhaps, didn't dig any deeper on that yet.
Fuel:
1. Adjusted carb float to 1/4" per manual. Brand new carb. Forced fuel through all ports & orifices on bench. Fuel tank was removed, running using a small gas can w/ clean fuel (ethanol free).
2. Tried swapping new carb w/ original Marvel Schebler TSX carb. No change, still rough idle, even with adjusting idle screw.
3. Adjusted idle screw (on both old & new carb), unable to run smooth, sounds like fuel starving even w/ idle screw all the way in. No happy medium rich or lean. Adjusted main as well, no change.
4. New gasket between carb & intake manifold.
Air:
Oil bath cleaner was removed during testing to eliminate possible air restriction.
Ideas: (1) condenser looks brand new but did not check. (2) sticky valve?, (3) 6v coil, 12v battery, perhaps issues with spark?
Looking for more ideas before digging deeper into engine internals.
