Fuel starvation and hot coil

[Doug&Deb]

I’ve decided to run a line to remove the mechanical pump from the system and run on the electric pump to see how it works. I’m suspecting a crack in the pump housing is causing the problem so this is an easy way to test it. DCPD1941 I sure hope the coil is the problem and the new one fixes it. I know that frustration.

[Sam Buchanan]

1 hour ago, DPCD1941 said:

I am having the same problem but without the Electric fuel pump. It is on a 1941 WC with the 230 engine. I have tried new distributor, points, condenser and rebuilt Carburetor. New Fuel lines and cleaned the pump and inline filter. I can Idle for an hour no issues. But if I drive a mile down the road I start sputtering and die. Then wait a couple mins and it will start up and drive 200-400 feet sputter and die. Over and over. After it dies I still have fuel to the carb and I can pump the gas and rev it as it dies. I can only assume it has to be a spark issue. The temperature outside doesn’t affect it either. The most frustrating part is I can’t replicate it in the driveway. so every time I try an adjustment I have to leave, break down, call the wife and get towed back home. I am at my wits end. The only thing left to replace is the coil and it should be here tomorrow. 

Remote diagnosing is always subject to error, but here are a couple of thoughts.

 

The coil; the fact the engine will idle reliably takes the coil off my list. If the coil will function in the driveway it should work going down the road.

 

Fuel flow; this seems to be a likely culprit. It doesn’t take much flow to keep an engine idling, but marginal flow will only get you a little ways down the road until the carb bowl runs dry. I would also take a close look at the float and needle valve.

 

 

[Doug&Deb]

Sam sometimes when a coil is going bad it fails when it heats up. Your suggestions are valid also. Fuel and ignition problems are so interconnected sometimes.

[Sam Buchanan]

7 minutes ago, Doug&Deb said:

Sam sometimes when a coil is going bad it fails when it heats up. Your suggestions are valid also. Fuel and ignition problems are so interconnected sometimes.

So why does the coil not overheat and fail while the engine is idling for an hour? (Referencing the post to which I responded)
 

Fuel and ignition are never interconnected, they are two totally separate systems. But misdiagnoses can spill over into each system…and create a lot of confusion.  😉

Edited July 3 by Sam Buchanan

[Sniper]

14 minutes ago, Sam Buchanan said:

So why does the coil not overheat and fail while the engine is idling for an hour?

 

Minimal load on the coil.  Minimal load on the engine.  Minimal heat generated.

 

Typically, how a coil starts failing is a break in one of the windings, a microfracture.  As the coil gets hotter the gap starts to open and the electricity will jump that gap, eroding the ends of the wires further increasing the gap.  At some point the combination of the heat increasing the gap and the action of the spark jumping that gap creates a separation of the ends large enough to stop the coil from working.  The coil cools, the gap shrinks and it works again, till it gets hot enough to not work.  Finally, the issue becomes bad enough that the coil won't work at all, regardless of temperature.  Next time it dies check for spark immediately,

[DPCD1941]

So here are my thoughts. Today when it stumbled and died I went right to the carb, removed the air cleaner and pumped the throttle. Nice solid shots of fuel. It started back up drove 2-300 feet and died. Checked and nice solid shots of fuel. This to me rules out Fuel pump/ carb because if the Bowl was run dry it would not be able to refill until I started cranking it over again? Right?   I just installed a new coil from NAPA, so we will try again tomorrow when I have someone available to drag me home. Checking for spark is a bit of a bitch by myself due to the old girl having a manual starter pedal. 

[Sniper]

51 minutes ago, DPCD1941 said:

Checking for spark is a bit of a bitch by myself due to the old girl having a manual starter pedal. 

 

I hear that.  Seems you ruled out fuel though. 

[Dave72dt]

There would still be some pressure in the fuel line.  A restriction in the inlet of the carb may seep enough fuel through to idle and /or refill while removing the air cleaner.  Accelerator pump draws it's fuel from the bottom of the carb so it doesn't have to be that full to pump a few shots of gas.  There's been talk in the past about an internal line in the tank that may have pin holes so the level of fuel in the tank may be an issue. Is the driveway level,  up hill or down and the same for your road you test on?  How about jack stands so you can test drive the car in place?