'64 L76 warm starting trouble

[Joep F.]

I have a '64 C2 with L76 engine and the Holley carburettor. The engine fires up fine when cold and when hot and runs great. However when warm (after sitting 15 minutes - 1 hour) she will crank but not fire up. I tried several methods: gas full depressed, half depressed, not depressed. With and without pumping. However no solution which structural works. The trial ussually ends with an empty battery!

Few other details:
1. The carburettor is not flooding;
2. There is plenty fuel in the bowls.

I searched around 500 posts in the archive but couldnt find a possible solution. Who has any idea??

Thanks,
Joep

[Dino L.]

Re: '64 L76 warm starting trouble

Just some thoughts of things to read up on and rule out before you get out into the garage.

1. Call the Holley carb experts, Kunz and Jerry Luck and ask Holleyitis
2. Choke adjustment closing off, as car heats
3. Ballast resistor changing value when hot
4. Coil failure
5. Spark plug wires
6. Ignition condensor failing under high temperature
7. Fuel pump
8. Review the 64 GM service manual, I think it has a section on this.
9. Check timing.

I own a 64 L76 and never have had a cold or hot start problem (Yet...don't worry it is just a matter of time)

[Duke W.]

Re: '64 L76 warm starting trouble

You need to do some basic diagnostics - determine if it's fuel or spark.

Using a spare loose spark plug, attach a plug wire and ground the plug. Have someone crank the engine and look for spark. If there is none you will find lots of possible causes in the archives.

Duke

[Scott K.]

Re: '64 L76 warm starting trouble

I have a 65, 327, 365hp and had same problem. Did a compression check, bad compression. Final outcome was a total rebuild of my engine. Not to say that is what your problem is, but give it a try.

[Joep F.]

Re: '64 L76 warm starting trouble

Duke,

Cant tell if its a weak or strong one, but I have a little spark. The strange thing in my case is, that all is ok with engine hot and cold, but not when warm. It does fire up though, but only after very long cranking and most of the time with help of a fresh additional battery to increase cranking speed.

Few thoughts:
1. Would the replacement of my contactpoints by a magnetic ignition (like "ignitor") improve starting performance?
2. My spark plugs (AC Delco R45S) are coloured light yellowish (beige), could this tell that the air/fuel mix is lean/rich?

Thanks for suggestions,
Joep

[Duke W.]

Re: '64 L76 warm starting trouble

It's tough to tell if a spark is "weak" or "strong". A couple of years ago a buddy called when his '87 560 SEL would not start. I grabbed a spare plug, ground wire, and multimeter to do some basic electical checks.

It had spark, and I could smell fuel in the exhaust. After running some other checks I ran out of ideas. He had the car towed to his mechanic (a good one who knows Mercs). It took him awhile, but he finally diagnosed the problem as a weak coil - replaced the coil and everything was fine.

I am NOT a fan of "electronic points conversions". One of the beauties of vintage cars is that they are simple with no "black boxes", and you can diagnose virtually any electrical problem with a ten dollar Radio Shack multimeter.

Old coils can act flaky a certain temperatures and any "black box" is suspect. A properly overhauled and blueprinted single point distributor will provide a reliable spark to 7000 revs, and they rarely fail without ample warning.

Here's what I would do:

Check all ignition wiring and connectors

Check dwell and point resistance.

Check cranking voltage at the coil

Check run voltage at the coil

Check coil resistance

Check point ground while exercising the VAC with a vacuum pump

If no obvious faults were found I would bring the multimeter along with me and check cranking voltages again if I got a crank, but no start condition.

If reasonable diagnostics did not point in any direction, I would install a new set of points and buy a ten dollar generic replacement coil to install the next time the situation arises

Duke

[Joep F.]

Re: '64 L76 warm starting trouble

Thanks Duke!

I will certainly try that. Coil, distributor cap, wires, spark plugs, points and capacitor are replaced approx 2000 miles ago.

What can you tell about colour/type of spark plugs? Are these ok for my type of engine?

Joep

[Clem Z.]

Re: '64 L76 warm starting trouble

Thanks Duke!

I will certainly try that. Coil, distributor cap, wires, spark plugs, points and capacitor are replaced approx 2000 miles ago.

What can you tell about colour/type of spark plugs? Are these ok for my type of engine?

Joep

i would try a new set of points and condenser as a cheap first move.

[Duke W.]

Re: '64 L76 warm starting trouble

Spark plug type is okay. I don't try to read too much into color, but the insulators should be free of deposits.

Intermittent problems can be difficult to nail down. You have to be able to do some diagnostics when the problem occurs.

Duke