Technical 500F: Car suddenly dies when hot

[dangfiat]

Hey All,

Ran into an interesting problem yesterday: We had the hottest day so far here in California (80F --> ~26 C).

Drove my 67 500F with 650 (126p) motor ~3miles to the market. When I got there the car stalled.

This is when the weird started....
1. Starter wouldn't start: nothing, nadda
2. No lights (Gen & Oil) on the binnacle
3. Wipers and headlights still working...

After waiting for ~5 minutes, the starter and everything came back to life... Never happened before, not sure what's going on

What could get hot enough to shut down, then work when cooled? Volatage regulator (it's origional)? Coil (it's on the dynamo side of the engine)? Points/Condenser?

Final clue: Idle seems to go from 1000 when warm (no choke) to 800 (or it just cuts out) when the engine get's hot......

Hope the Mechanical Sleuth Department of this forum has some suggestions.....

Thanks
Daniel

 

[Bounding Bambino]

Is your starter the original mechanical cable start, or has it been upgraded to electric key start?

If its still mechanical cable. You more then likely have a bad electrical connection at either the battery or terminal at the starter. Or a bad ground between battery and chassis.

Typically the 67 F would pull its source + voltage for the harness of the car right at the terminal at the starter. The fact you still had some power is odd. Because there is only one feed source into the cars harness, and its right at the + terminal at the starter. If the mechanical starter doesnt work, nothing would technically. In case its multiple intermittent issues going on.

Im currently doing all the wiring on my gen 1 67-F so ive learned the entire harness diagram inside and out right now lol.

 

[smart51]

It sounds like you're saying it idles when cool but the revs drop as it gets hot until it eventually stalls. When it does that, it won't restart until it cools down, after which it is fine again.

When the revs start to drop, does it recover if you start to open the choke, or does it die quicker? That might suggest fuel starvation with heat, or an air leak when something expands due to heat.

 

[dangfiat]

Thanks all for the suggestions:

@Bounding Bambino :
I hadn't thought of a grounding issue.. good suggestion. I did just replace the starter (a pull starter). Although NOT FUN, I'll have to go and dig around back there an see if the connections are still good.

Where is the chassis ground strap? Is there one on the motor?

Also, I'm eventually going to do a new wiring loom too. Will just keep the patchwork going till them

@smart51 :
You're correct, in general the thing drops revs as it warms up. Eventually getting to an extremely low idle. When cold or just kind of warm, it will die off the choke (usually takes about 5min or so until I can drop the choke entirely). Also it hesitates (dies) on hard throttle for the first few minutes

I've replace all the gaskets & the carb mount. Cleaned the carb & new jet. I'm starting to think along the same lines as you: the old fuel lines and fuel filter might be starving the motor. I might convert over to a new electric pump and replace all the lines/filters

Finally, when I shut down I get a "pop" out of the exhaust... maybe unburnt fuel due to lean out?

As for the "dies when hot", it just conked out and wouldn't get power to the starter. After it cooled, everything went back to normal

Thanks again all!! Having a ball figuring out and learning!

Daniel

 

[smart51]

If you think there may be an air leak around the carb, spray some WD40 where you think the air is getting in while the engine is running (and still cold!). The extra 'fuel' in the WD40 spray will cause the engine to pick up briefly. I once started and ran an engine by squirting WD40 down the carb intake just to prove that it would run. A million and one uses.

 

[Goldnrust]

As for the "dies when hot", it just conked out and wouldn't get power to the starter. After it cooled, everything went back to normal

This is a flag to me that you're not dealing with the 'usual' issues around running hot, like a coil/condenser that doesn't like getting hot or an air leak at the carb base.

Is this starter motor failing and ignition lights going out element of the issue repeatable? Or was it a one off? An earthing issue sounds like a sensible thing to investigate.

On the general running poorly when hot, it would be also worth checking your valve clearances. if they've closed up a bit that can cause issues as the engine warms up.

 

[dangfiat]

Thanks @Goldnrust .

The starter motor is brand new. I haven't been able to repeat this yet, even today on a 87F day. Went for a ~6mile ride and didn't get the issue. I'll just check grounds/etc and see if it crops up again

 

[Etsab]

Check cables between plugs and distributor, and distributor and coil. Had similar issues, and replacing the cable between coil and distributor solved the problem. There was a well hidden crack in the cable that became progressively worse, and in the end the car would start, and stop again a few minutes later.