Packard Forum Index » Pre-War (1899-1942)

1941 160 runs rough when warm. If i leave the car sit for 5 minutes and restart the car it will run smooth a few minutes, then eventually it will start running rough. The other day it was warm and i shut it off. About an hour later I started it again it ran smooth. I was thinking the coil or condenser may be breaking down when hot. I don not have the oringinal coil on the car its an aftermarket do to key switch is also aftermarket. I saw in the parts cross reference that a coil number should be Ic-1 but when i went to the auto parts the guy said it was a 12 volt coil so what other number would work 6 volt positve ground ?

From Napa their premium offering in a universal 6v coil is the Echlin IC7 at around $50. Their economy brand sold under various names but often as a Mileage Plus MPE IC7SB is about half that price.

Universal coils are not polarity specific and will work either way but for best performance and hottest spark you should have the terminals on the coil match the grounding. For a positive ground the + or pos terminal on the coil should go to the distributor and the - or neg terminal would connect to the hot wire coming from the ign switch.

In addition to the coil and condenser, some modern aftermarket ignition switches could also be a source of issues. Most are designed for 12v so their current capacities are somewhat marginal when carrying the heavier demands of 6v. If the switch is overheating some intermittent connections could result.

i dont think its the switch because i put a jumper wire from the battery cable at the starter to the coil while it was running to see if it would smooth out it did not. But by doing that i eliminated the old wiring and switch.

I've had that happen on two Ford products; my '69 Galaxie convert about two years ago, and on Monday night, on my 71 F-500.

The Galaxie had about 500 miles on the tuneup, with the original coil which looked fine and tested good when the rebuilt engine went in. One summer day she just start to miss intermittently; I had stock points in it then. Replaced those with a drop in electronic ignition, sort of improved but not fully. About a month later the coil just gave up and I replaced it with a universal replacement--started and ran like a dream.

The F-500 (has a hydraulic ladder/lift on it) was running at a fast idle as I was installing Christmas lights on one of the big trees out back. As I finished up that two hour project (truck running the whole time due to the cold and high electrical loads from the lift and hydraulics), the truck stalled. Figured it was just the added demand of retracting the ladder; nope. No spark whatsoever.

That engine has about 18 years of use on the only tuneup I've ever done to it, and, ahem, untold hours on it since it's used infrequently for house painting, changing parking lot lights at church, tree trimming etc.

Tested everything; coil was the culprit and started it right up with a new unit. Then for good measure replaced points and condenser just because. At this rate, I won't have to do it again until I'm 80, which means, uh, never.

Well new plugs new wires new points and condenser new coil new cap and rotor. Same problem starts up runs like a Packard should. After a few minutes starts running rough and keeps getting worse. Engine temp is around 165 degrees warm. I checked it with a heat gun. Put my hand slightly over the carb to see if it would smooth out it did not.

Bad / Frozen Vacuum advance?

Is the hear riser value working and not stuck in the easy bake mode?

The heat riser on the exhaust manifold moves freely but thanks for the reply

Heat Riser could still not be working, maybe just pin it open.

Choke stuck on?

I might put one of those "spark plug lights" and see if a cylinder is cutting out when warm.

Have you tried a warm compression test? Maybe you need to adjust the valves? Could be they are o.k. cold but as the engine warms the valve clearance tightens up on one or more valves and now you get no compression in that cylinder.

When is shut off and you restarted it an hour later, did it start quickly or did you need to crank it over a bit? If it needed to be cranked a bit, that might indicate a gas problem.

When it stops have the air cleaner off and verify that there is gas in the carb by pumping the carb. Has the car's spark plug wire been "updated" with carbon wires? I would check the master wire from the between the distributer and the coil.

Good Luck and keep us onboard.

the choke works and it is wide open when warm. I recently replace the exhaust pipe going to the manifold and i checked the heat riser at that time. The car has hydraulic valves so they self adjust. I also tried putting a jumper wire between battery cable and coil also did the coil to distributor. Sometimes I shut the car off and restart it 5 minutes later and it runs smooth again for the first couple minutes.Also checked for fuel in carb by hitting the throttle.My brother-in-law says to replace the fuel pump but why would it run smooth for the first couple minutes if that was bad. Also it usually starts up easy when its warm