Vapor lock?

I went for about a 50 mile drive today. The ambient temperature is around 87 degrees. The car ran fine, with the water temperature hovering between approx. 180 to 195. As I got back into traffic approaching home, I noticed that the car seemed to be losing power slightly, and the engine note was "off". Then I had to stop at a traffic light for about two minutes. At this point, the temperature gauge indicated slightly higher than 195. For the next mile or so, in traffic at about 40 mph, the car steadily lost power (and sounded sick) until it died completely. I'd say that it definitely felt like a fuel delivery issue, and I did notice a somewhat strong gasoline smell. I turned on the flashers and was able to coast onto a side street and switch off the ignition. After less than a minute, I turned the key and it started right up. I drove the rest of the way home (about another mile and a half at low speed) with the car seeming normal.

My first thought was vapor lock, but I guess it could be the fuel pump also.

 

Dino dan,
I had a similar situation with a 1976 Rolls. There is a good chance that it is vapor lock. Where I live, we have oxygenated fuels for the winter months. the oxygenated fuels vaporize more easily than the Summer fuels. Every spring, the Rolls would behave exactly as you describd until I ran the tank low and filled up with Summer fuel.

Tony

 

Thanks for reinforcing my suspicions, Tony.

I've experienced vapor lock in a number of older vehicles (most recently a severe case in an Alfa spyder during a Lemons race), and that's definitely what this felt like. Interesting about the fuels, though I doubt that's the culprit in this case as I live in a mild climate and had just filled up prior to the drive. I do wonder what suddenly caused it to happen, as I have driven the car in hotter weather than this without any issues, though this is probably the warmest in a while. Hmmm, would ethanol added to the gas increase its volatility?

Well, well, well... A quick Internet "study" indicates that ethanol as an additive does indeed significantly increase the volatility of gasoline. Here's one tidbit:

"Oxygenates, primarily ethanol and methanol-cosolvent mixtures, have excellent octane blending values. However, alcohols complicate volatility blending. The seriousness of the situation is verified by trends that show a steady rise in the volatility of gasoline reaching the market place. As discussed previously, EPA has focused on gasoline volatility from the standpoint of readily available hydrocarbon emissions reductions."

So, this could be the warmest day that the car has been driven with the latest, higher ethanol content gasoline.

 

Could be electrical rather than fuel delivery. Are you still using the Dinoplex? Fuel smell might result from unburnt fuel exiting the exhaust, a result of CD ignition failure.

Jim S.

 

Thanks. Nope, the Dinoplex was replaced by another unit roughly 20 years ago, and then an MSD unit about a year and a half ago. Anyway, it felt like fuel, not ignition. I suppose it could be ignition. That would explain the quick restart, which does not jibe with vapor lock.

 

I had the carburetors tuned up in 7580 last year and the car has never run so well. However, on warm days, when I come to a stop sign after a jaunt through the countryside, the car loses power and dies and won't restart for several minutes. After several minutes it starts and runs fine again. I had similar problems with one of my two 330 GTC's but not the other. It certainly seems like vapor lock, but I never had the problem in the Dino until I had the carbs serviced. Any ideas on how to cure the problem?

 

That's interesting, Jim. It sounds almost exactly like my issue, except that my car started back up after less than a minute. Like you, I've never had the problem until now. I didn't get a chance to drive the car this past weekend as the weather was rainy.

I have done some more checking, and it's generally acknowledged that the ethanol being added to gasoline exacerbates the problem by increasing volatility.

 

Thanks for the suggestion regarding the ethanol content. I haven't being paying attention to that when buying gasoline until lately. A group of original AC Cobra owners has been discussing the potential harm that can be caused to older engines by ethanol containing fuel, so I will avoid it in my older cars in the future, if possible.
I look forward to getting 7580 back on the road in the next few months. It is in the paint booth this week getting primed and perhaps it will be painted by the end of the month. I can hardly wait!

 

Tough to find ethanol free fuel these days, I'd bet.

My understanding is that is has increased detergent properties too. It'll scrub all the crud off your carbs, gas tank, etc, and that can cause additional problems. (This from my Ferrari mechanic.)

And that yes, it can exacerbate vapor lock.

DM

 

Funny you mentioned that Dave -

We have started our "Summer gasoline blend" here in AZ and the Dino had developed a low RPM missfire... After clening the points, blasting the plugs, I resorted to spraying 2 cans of carb cleaner into thw webers. After a spririted run, all seems good. I think your theory holds. The fuel probably dislodged some crud in the carbs ..

Pietro

 

This is really weird. Yesterday, I had almost exactly the same thing happen again, not quite one year later. Not only that, but the car died on the same stretch of road and I had to pull off onto the same cross street. Five minutes later, it started and drove normally.

 

Mark that location in your GPS and steer clear of it! Sorta like the Bermuda Triangle.
Coop

 

Yes, my 1974 GPS which consists of a folded-up map in the door pocket!

 

Do you still use points and condensor with the MSD?
They behave very odly and will shut you down in a likewise manner.
I had a nightmarish trip once when the thing would stop every hour or so and not start gain for as many. wet plugs no spark, drove me nuts. Eventually an old farmer in a tractor rolled by and asked what was up. Told him and he said probably a bad condensor.....it was!! I went to optical pick up and never looked back.