The Ford Barn

alexiskai · 03-29-2019, 10:24 AM

Problem: '29 coupe suddenly started running very rough, not drivable

Notable symptoms:

Sounds like the cylinders are only occasionally firing, engine rotation very irregular
Sparkplugs show a lot of black residue
Exhaust seen coming from somewhere at the back of the engine compartment, maybe from the point where the manifold meets the muffler? Hard to tell.
At idle, ammeter wobbles constantly
If left at idle, engine will stall out within 30-60 seconds

What I already tried/examined:

Lights and starter work fine, so no problem with electrical grounding
Re-did the timing, checked clearance at rotor and points
With ignition on, opened points. Spark was seen at the points and a spark jumped from the coil wire to a plug terminal when held nearby. Worked every time I opened the points. (Modern distributor plates installed last month, older coil)
With engine running, grounded each plug terminal to the block with a screwdriver. Saw spark at each plug.
Using Nu-Rex "C" spark tool, saw good spark between coil and distributor up to 10K volts
Fuel line is clear
Removed and inspected carburetor, seems fine, no deposits, all parts move smoothly (balanced carb is less than a year old)
Tried various settings for GAV and spark advance, no notable change in behavior
Tried with air filter off, no change

Anyone have any ideas? I don't have any spare parts to swap in unfortunately. It's bewildering because I just drove it a couple weeks ago and it was fine. I've worked on a few components since then, but nothing in the fuel-air-engine block system. The only system I've messed with is the distributor and coil, but I feel like I've tested them thoroughly.

03-29-2019, 10:24 AM	#1
alexiskai Senior Member Join Date: Apr 2018 Location: Mebane NC Posts: 3,178	Rough running, stall on idle (mostly solved) Problem: '29 coupe suddenly started running very rough, not drivable Notable symptoms: Sounds like the cylinders are only occasionally firing, engine rotation very irregular Sparkplugs show a lot of black residue Exhaust seen coming from somewhere at the back of the engine compartment, maybe from the point where the manifold meets the muffler? Hard to tell. At idle, ammeter wobbles constantly If left at idle, engine will stall out within 30-60 seconds What I already tried/examined: Lights and starter work fine, so no problem with electrical grounding Re-did the timing, checked clearance at rotor and points With ignition on, opened points. Spark was seen at the points and a spark jumped from the coil wire to a plug terminal when held nearby. Worked every time I opened the points. (Modern distributor plates installed last month, older coil) With engine running, grounded each plug terminal to the block with a screwdriver. Saw spark at each plug. Using Nu-Rex "C" spark tool, saw good spark between coil and distributor up to 10K volts Fuel line is clear Removed and inspected carburetor, seems fine, no deposits, all parts move smoothly (balanced carb is less than a year old) Tried various settings for GAV and spark advance, no notable change in behavior Tried with air filter off, no change Anyone have any ideas? I don't have any spare parts to swap in unfortunately. It's bewildering because I just drove it a couple weeks ago and it was fine. I've worked on a few components since then, but nothing in the fuel-air-engine block system. The only system I've messed with is the distributor and coil, but I feel like I've tested them thoroughly. Last edited by alexiskai; 05-10-2019 at 09:14 AM.