vapor lock

[johnpaulny]

I had my '63 convertible delivered today - very happy, a true 60000 mile car. Then the fun went south. I drove for a while, stopped at a store and 10 minutes later the car cranked endlessly. It is a very hot day so I suspect vapor lock. My previous "64 did this too but not as bad. Has anyone else had this problem? What is the solution? It also seemed like an anemic crank - I suspect the battery is undersized, adding to the problem.

[simplyconnected]

Go through your fuel line and make certain that all connections are tight. Vapor lock can happen on very hot days but altitude has much to do with it as well. You are at sea level which makes me suspect the fuel line is sucking air from a joint or a rusted-through area.

Remember that from the fuel pump back to the tank, the system is under negative pressure (a vacuum). Modern cars have a fuel pump in the tank, keeping the line under positive pressure which eliminates fuel line vapor lock.

BTW, your fuel pump is supposed to have a check valve that keeps fuel from flowing back in the tank. After ten minutes, the line should have been full of fuel and your engine should have started very easily. - Dave

[johnpaulny]

Thanks Dave, very helpful. I have to have the car inspected this week and I will ask my mechanic to take a look at what you describe. John

[jopizz]

If your starter is laboring when it's hot I would check the timing. If it's too far advanced that will cause it to turn over slowly and make it seem that your battery is low.

John

[johnpaulny]

Now I'm not so sure the problem is vapor lock. I've only had the car 2 days so today was second drive. First start today it fired up immediately, runs smooth as silk. Drove it for about 20 miles, no hesitation, feels powerful. Today was cooler than yesterday and wanted to see if it would do it again. Parked in my driveway, waited 15 minutes and it wouldn't start. Tried again in 30 minutes, an hour, 2 hours, 3 hours, it won't start. That doesn't sound like vapor lock anymore. Any ideas? Again, it's so smooth when running, so i doubt it is fuel filter or fuel pump but i'm a novice with all this. Thank for any help.

[simplyconnected]

Every engine requires three elements to work; FUEL, HEAT (spark), and AIR.

These are easy to check.
Pull the air cleaner cover off. Look at the filter. Is it clean?
Pull a spark plug wire off, put a spare spark plug in the wire and lay it on your engine. Now crank it and watch for spark. (This shows better at night.)

Do you smell gas? If it is not burning raw fumes continue out the tail pipe. When you 'pump' the throttle, do you see or hear a squirt of gas going in the carb?

If you tank is full of water, you will see the squirt but not smell the gasoline fumes.

Use your senses. Look for both the presence AND the absence of these elements, then let us know what you found. - Dave

[Yadkin]

Now I'm not so sure the problem is vapor lock. I've only had the car 2 days so today was second drive. First start today it fired up immediately, runs smooth as silk. Drove it for about 20 miles, no hesitation, feels powerful. Today was cooler than yesterday and wanted to see if it would do it again. Parked in my driveway, waited 15 minutes and it wouldn't start. Tried again in 30 minutes, an hour, 2 hours, 3 hours, it won't start. That doesn't sound like vapor lock anymore. Any ideas? Again, it's so smooth when running, so i doubt it is fuel filter or fuel pump but i'm a novice with all this. Thank for any help.

The car probably has rust and crud in the tank, and it either clogged the pick-up screen (in the tank) or if the particles were small enough to pass through then clogged the filter.

A clogged screen can readily cause vapor lock because it increases the vacuum necessary to get fuel all the way down a 3/8" tube into the mechanical fuel pump. Here's a picture of my pick-up/ sending unit when I pulled it out three years ago. You have to drop the tank to get to this. If yours looks like this, throw it out and buy a new one, then have the tank professionally cleaned. Then blast a full can of carburetor cleaner through your fuel line in both directions followed with compressed air.

A clogged filter can also cause the problems that you've described. Since those are cheap and easy to change, try doing that first.

[jopizz]

I would look down the carburetor throat after you shut the engine off. Do you see gas continuing to drip. You may be flooding the engine due to worn needle valves or bad floats. It will usually take quite a while before the plugs dry out and you can start it again. That's my guess.

John

[johnpaulny]

Thanks for the suggestions. Same sequence of events today (first start no problem, restart attempt after warm no go). I noticed that when driving, after it warmed up, during stops at traffic lights, it was indeed a bit rough. It also pinged during acceleration. That seems to be leading to something timing/ignition related. I'm going to have my mechanic take a look at that during the inspection and also replace the points/condenser with electronic ignition. Thanks again - I'll let you know how this proceeds.

[simplyconnected]

Try a used coil. Sometimes heat affects them when coils fail. Borrow one from a buddy or another car, just to try.

[scumdog]

Try a used coil. Sometimes heat affects them when coils fail. Borrow one from a buddy or another car, just to try.

What Dave said, it's my bet too.

[DKheld]

After 2 tow bills on my '60 with the original tank I'm with Steve (Yadkin) on this one. Mine was very intermittent though - drive it one day and no problems - next day it might quit 3 miles from the house.
If that's a pic of the pick-up on the Bullet birds you guys are lucky - the tank filter/screen is built into the tank on the Squarebird - have to replace the tank.
Wouldn't rule out the other ideas though..... all good ones.....

Eric

[bird 60]

It could be several things, but as John mentioned it could be a possible hairline crack with the float.

Chris.....From OZ.

[johnpaulny]

I got my car back. Mechanic replaced points/condenser with Pertronix electronic ignition. He said points needed to be changed if I hadn't done that anyway. He also fixed timing. He test drove it, said it was fine. I went to pick it up and it didn't start. He got it started. He asked if I was pumping gas a lot when starting after it's already warmed up, which I had been. He said only pump it three times when it's cold (first start). On next start don't need to pump. I test drove it, tried that after shutting it off and letting it sit for 15 minutes, and although it cranked a bit, it started without pumping. Could it be as simple as having been flooding it all along? I had been giving it a lot of gas all those times when I couldn't get it started.

[simplyconnected]

Every engine requires three elements to work; FUEL, HEAT (spark), and AIR.

Do you smell gas? If it is not burning raw fumes continue out the tail pipe. When you 'pump' the throttle, do you see or hear a squirt of gas going in the carb?

So... you flooded your engine.
Would be nice if you answered our questions. The only info we can go by is what you provide. At first, you thought the engine was starved for gas, which is what vapor lock does. In fact, you were giving it too much gas which would have been very evident by the smell.

Pertronix is a good upgrade but your engine ran for many decades using points. Upkeep and scheduled maintenance is far more than your modern driver. If you don't wrench, then stay close to a good mechanic. - Dave