have a 76 midget that starts and runs fine for about a half hour but on hot days it will begin to stumble stall and eventually quit. Theg if it sits for a few minutes it will start right up and run strom for 5 to 15 minutes and then dtumble and die again and again. Only does this on hot days and the engine temp is fine. Could this be vapor lock. If so do you have any recommendations how to solve it ???? Or is it possibly something else.

Is there a "woosh" when you open the gas cap after it has died?

Have you checked the spark after it has died?

What kind of ignition system do you have? Could be a faulty condenser.

I also have a 1500 that died on me. It stalled on the highway after a few hours driving. My first thought was vapor lock but I have a new theory that might apply to you as well. Spark plugs.

Check what plugs you are using. When I changed my plugs a couple of weeks ago I went to my local supplier and asked for a new set of plugs. My book says that Champion N9Y was the original plugs. That translates to BP6E in the NKG brand. He asked me if I wanted BPR or actually BP plugs. I asked what the difference was and thats when he told me that the NGK "R" or resistor spark plugs use a 5k ohm ceramic resistor in the spark plug to suppress ignition noise generated during sparking.
I then asked if it mattered which I used and he said that some older cars could actually stall from overheated ignition coil when using the newer "R" plugs. The symptom he described exactly what I experienced on a long highway drive last year and guess what spark plugs were in the engine! BPR6ES!

The engine would stall, just as if I had turned off the ignition, and then run fine again after a 15-30 minutes cooling. The engine itself was not overheated, temp was ok on gauge and the readiator fluid was nice and warm but not hot. I never really understood what the problem was and since I didn't go for any really long drives (and the Swedish weather is rarely really hot) I didn't experience the problem again. Now I guess I have to do some long driving to check that it doesn't happen again.

//Erik

Makes snese to me, I think.

Intresting that, stay away from resister plugs, good idea.

A hairline crack in the rotor button could also cause the problem as it became warm and opened up.

Did you remove emission equipment from the engine/car?

Not sure if the question was for me but I'll answer it anyway. No, my midget is a UK spec. car. No US emission control stuff.

//Erik

FWIW.
My 1500 was susceptible to vapor loss.
I fabricated a heat shield to fit between carb and exhaust. Also, removed that coolant recovery bottle (didn't seem to be doing anything) to increase air flow around the carb.
Cheers, Adrian

I too,made a heat sheild after suffering this particular problem. And the whole thing was caused by a severe kink in the fuel hose to the pump.Straitened it up a little,put on the sheild,and so far so good.
I have a 1500 with a mechanical pump.


Stuart.

Does it have points? In that case I would suspect the condenser. If not then it might be the coil getting hot and breaking down. I have had this problem before. I would change out the coil with another just to try it.

Vapor lock was my first guess also but then someone told me that vapor lock was most commonly experienced when going slow or getting stuck in traffic as this would cause cooling to be virtually non-existing. My problem was when cruising at 50-60 mph for more than 2 hours.

I was planning to get a heat shield (and probably still will get one) but the descriotion of the problem with "R" plugs fit my experience exactly and moved the vapor lock idea to second place.

Please share detailed description of the conditions when vapor lock can occur with the community if you know a bit about it.

//Erik

I've seen it more in cars that were shut off hot and allowed to sit for a while. The air stops moving under the hood and the hot parts continue to radiate heat with not way to remove it. The under hood temps go way up. this can lead to the fuel in the lines turning to vapor (hence the term vapor lock). The fuel pump can't put the vapor as it is designed to pump liquid. High pressure systems aren't nearly as vulnerable to this condition. I have never seen "vapor lock" affect a motor that was running and the gas was flowing... But I've also never seen a lot of things that probably happen.
JC