Misfiring during driving - '73 CS

[124spiderman]

Hi all.
The other evening my car started to develop a mysterious sputter at speed - similar to a miss, lack of power and slighty jerky. It's very frustrating because it's intermitten.
Has been running great for about month. (I only drive it rarely). Fuel is still the same sample from a refuel when car was still running good.
I'm suspecting it could be the fuel pump? or a dodgy coil? Any other suggestions? As i'm tempted to keep driving it until it gives up, then I'll know for sure. But I'm planning a big weekend trip (wedding anniversary) and that might not go too well with my beloved other half.......
BTW - It happened while driving home in the rain, but my car also has the underbelly tray, so water couldn't splash up.
points/condensor new, timing is perfect, plugs are new, leads also. Coil is an old Bosch GT40R unit.

[mdrburchette]

It could very well be the fuel pump. Are you still running the mechanical one? My 72 acted the same way. It was intermittent and actually held on for a few days until it finally died. One way you can usually eliminate an ignition problem is to watch the tach. If it's erratic when the car is acting up, it's usually an ignition problem.

[124spiderman]

Thanks. Yes. It's a mechanically unit (pump). Will change both pump & coil.
Speaking on coils, does yours have a ballast resistor?

[chrisg]

..and, fuel filter is usually worth a check, and - dumb as it may sound - all the wiring at the distributor is a good check for frayed or shorting wires. I suppose if you have any questionable fuel line routing you could be getting some sort of vapor lock deal going....maybe...??? Oh..one more check for an early "C"...there is a cluster of heavy gauge wires leading to the starter & on my '74 (built 9/73) those wires had an internal short that would basically act as a randomly activated kill switch...if all else fails, look for a three wire connector leading to the starter & make sure there's no melting, no excessive corrosion, etc. Good luck. Don't break down on purpose on your anniversary trip! (if you need to schedule a breakdown, at least you'll be driving a car where such a thing is completely plausible )

[mdrburchette]

Both my early cars have been changed over to electronic ignition but I don't recall a ballast resistor on the original setup.

[124spiderman]

Here's the lowdown.
reset points - new points pitted a bit, clean them up reset to 0.017" - new dizzy cap throw in a new fuel pump for good measure.
Starts fine, runs Ok for a little while then runs like sh*ite!
Check & Reset ignition timing. Starts up great, idles beaut. Hop in take for a test run, drives great for about a mile then.....
starts to fart and miss and run like a pig!
I'm over it!!
Any takers?

[So Cal Mark]

you're giving it away? That's like getting a divorce because your wife left a light on

[ventura ace]

. . . and did you swap out the fuel filter?? Symptoms could very well be from a clogged up fuel filter.

Alvon

[124spiderman]

Fuel filter was replaced.

[So Cal Mark]

did you replace the coil? If the points started to pit that quickly, I'd add a ballast resistor to cut the voltage to them.

[mdrburchette]

Don't give up so easily! Is it spitting through the carb when it farts or through the exhaust? You could have a carb problem like the choke sticking, bad pump diaphragm or clogged jet. When it acts up, does the tach stay constant or does it bounce? You may have a bad coil or connector at the coil or ignition switch. Replace the condenser. I'd also check to make sure you're getting constant voltage from the charging system....
Or you could bring that poor baby home to Mama. I promise to take care of it.

[124spiderman]

Spent all day on "the lady" today.
Firstly, stone-cold retorqued the head bolts.
Pressure tested the cooling system to check for leaks within engine none.
Pulled dizzy out replaced points and put back the old condensor.
Guess what?
Seems to run OK now.
But another problem seems to have emerged.
Cooling fan won't come on now
Switch is new. Tested the relay - fine. Checked the fuse - good (shared with horns)
Fan motor tests OK.
There doesn't seem to be any current at the switch?
By joining the two wires from the thermo switch together, shouldn't the fan come on?

[So Cal Mark]

the switch is on the ground side, and connecting the two leads together should make the fan come on. The fan motor should have constant power, with the ground side switched

[mdrburchette]

You might want to check to make sure the thermostat is opening by seeing if the lower radiator hose is hot when up to temperature. You can also jack the front end high, run the engine with the cap off and see if there's any air in the system by squeezing the upper hoses. Make sure the heater valve is open.

[perthling]

I'm not sure is Spiderman fixed his problem, but I had similar problems a while back, and a friend in the FLCWA had the same symptoms on the weekend. Problem was a worn out rotor button - the spring was just too soft to maintain a constant pressure when under load. I think the fix was about $15 from http://www.turinimports.com.au .