Warm start problems: 72 carbed

[njoconnor]

Folks: I did first search on "warm start problems", and saw a lot of issues with the FI models, and none quite like mine.

Quick cold starts, run for about 30-45 minutes, shut down.....no restart. Gas smell with choke all the way *in*. Tried the "pedal to the metal" twice, and it worked (memories of the old 71 coupe!), but today at the body shop, no luck after 30 minutes of trying. While I cranked, the owner (a friend) held first the coil wire, then a plug wire, against a ground, and he reported no spark.

Details: 72 124, 1 year on engine rebuild by prior owner, 49.4K on the whole car. Electronic ignition system fitted, and coil looks very recent. White module on coil's side looks aged. All conections tight. Idles at spec and runs smooth on the road. Any trouble shooting suggestions or fixes?

At the shop for an estimate on the boggy driver pan. Owner says it's the only bad place on the car, and he's never seen one so old and so solid. New pan, labor, and a paint buff out/touchup for about a grand. I've seen his prior work....it's immaculate.

And, yeah, pix when I can whittle them down to the required size.....

Thanks

[So Cal Mark]

if you hold the coil against a ground, you won't see a spark. You must hold it about a 1/4" away from ground to allow the spark to jump

[njoconnor]

Thanks, Mark. I couldn't see the coil lead (I was in the seat), but he did hold the spark cable a good 1/4-1/2 inch from a ground.....no spark. I'll keep this in mind when I go back.

Benn mulling this over, and wondering what's the liklihood of the coil side control module being bad" As I mentioned, it looked "aged", certainly older/original than the newer looking coil or the newer electronic ignition (sorry...no brand info on this...done before I bought the car). I can't determine if there are any other devices between the startewr motor and the coil except for the module...or am I off base here?

Thanks...

[majicwrench]

Since you asked.....you're off base. Not sure what a "Coil side control module" is. Usually white unit on side of coil is ballast resistor. If you don't know what the parts are, don't go changing them.
That said, a car that doesn't run is easy to ficks ( sorry bout the spelling my ecks key won't work ) while it is dead. Verify again no spark. Check for power on + side of coil key on. Put test light on - side of coil, crank engine, test light should flash.
Check those things get back to us.

[baltobernie]

Perhaps exhaust heat is getting to the aftermarket electronic ignition system he installed. On early cars, the coil is only inches from the manifold, and the dizzy is right above it. So plenty of opportunity for heat soak to temporarily disable you.

There's also the possibility that it's fuel-related. Expanding fuel flooding carburetted cars is not uncommon. Try opening the hood after arriving at your next destination. And a twist of the key should be all you need to start a warm engine; foot off the pedal, sir.

[majicwrench]

It would be nice if a hot carbed car fired up foot off, but I know mine doesn't. Not unusual after a good hot soak on a hot day to have to hold pedal down most the way and crank for 5 seconds or so.
But back to the subject at hand, test test test. Don't assume anything. Get back to us.

[njoconnor]

Thanks, all, for the responses. As for changing parts w/o testing, have no fear....the multi-meter is first out of the box when I go back to the car!

The heat soak idea has merit. The coil on this car is on the intake side of the bay (the distributor is over on the exhaust side). The two prior hard start events both seemed to respond to a cool down; this last time, however, it had been sitting in an a/c'd shop for about 5 minutes while we inspected the unibody and structure.

I'll be getting back to it in about two weeks; shop owner on vacation, and the car is getting a long rest.

Updates as they happen!

Neil

[njoconnor]

Uh....make that "45 minutes". For some it's the x key.....my 4 key is a PITA......

Neil

[njoconnor]

About a week after the last post, the restorer called to say the car was starting at every attempt; no issues! Went back, picked it up. Spent the intervening 2 weeks stripping out the interior carpets (old and bad), insulation (likewise) in prep for the driver floor pan replacement. Discovered that the seat brackets also needed replacing, ordered a set from Wolf Steel. Returned the car to the restorer on 16 AUG, picked it up last Friday all newly welded and solid, paint buffed and touched up....looks fantastic! (pix when I figure out the upload process).

Through it all, no start problems, including after the 30 mile trip home. So, as recommended, I'll be taking test unit under the hood and check everything (connections and circuit) in starter/distrib path. Thanks, all, for the suggestions, and I'm sure I'll be back (I already note the R turn signal cuts out when the brakes are applied...I suspect a bulb, so going there first). This IS a Marelli system, after all......