The Stovebolt Site Forums The Shop Area Engine Shop Vapor lock??

My '59 with a stock 235 setup except for Fenton dual exhaust headers will NOT do a hot start. No combination of throttle and/or choke knob settings will get it to fire, but the situation improves with time. The shorter the time since I shut it off, the worse the problem. Then yesterday, while stuck in construction traffic, it stumbled and almost died. Only blipping the throttle kept it going.

The fuel line is a new replacement, routed in the factory configuration. And temps here in western OR have been mid-60's.

Whaddaya think? Does that sound like vapor lock to you? And if so, what are available fixes? I thought about slitting some rubber line lengthwise and putting it over the fuel line, but would that provide enough insulation to make a difference? I doubt there's room for header insulation. Maybe the best fix is to bend/re-route the fuel line over the top of the valve cover so it doesn't run along the left side back to the carb.

Or is there another common cause for this problem I'm missing??

Do you have heat under the intake?

Does it smell rich once it fires up?

Was it hot out? What temp is the motor? What percent of ethanol are you using?

Temps in the mid 60's, the OR standard ethanol content (20% I think), and the Dakota gauge shows 150 degrees. No noticeable rich smell.

Anything else changed or worked on .My 54 after installing engine ran great would not start when warm turned out to be ground strap had paint on the engine were the ground strap was bolted to.Would only start when rolled and put into gearwhen warm.

Ignition coil?

Nothing else worked on that should affect this, tho it's been a nut-and-bolt restoration. So I guess everything has been worked on. Only on the road one week. I'll check ground strap, but the coil is new.

Three common things that can break down when hot then begin working after they cool. Coil, condenser and fuel system. Today's condensers absolutely suck. Sometimes takes two or three times changing it to get one that works right. Your idea of splitting hose to cover the steel fuel lines has worked for some in the past. Making sure you have heat to the intake helps.
When it dies pop the hood and pull the air cleaner. Work the accelerator while looking down the carb. If you see fuel spray then your problem might be in the ignition system. Good luck.

Ballast resistor per chance?

I'm going with "all of the above." I'm putting rubber tubing around the fuel line and replacing both the coil and the condenser. The ballast resistor is new and *shouldn't* fail. It's a piece of ceramic; what's to go wrong??

I'll let you know the outcomes once the parts are in and replaced on Monday.

I don't believe that rubber tubing on the fuel lines is worth the effort. You need to find the root cause of the problem. No need in putting Band-aids on while the Hash Slinging Slasher (see Spongbob Squarepants for clarification) is still cutting you to pieces.
The ballast resistor is more than a piece of ceramic. It has a coil of wires in it which converts voltage to heat, thus reducing voltage. I doubt that's the problem either, since they usually fail completely rather than causing an intermittent issue.
Carl

It's not vapor lock. Fuel delivery or electrical break down as mentioned. Best way to figure out is not to replace parts, but do a test or two when it won't start. Like spark test and fuel squirt observation. If it was vapor lock, it would start if you put gas down carb throat. If it does not, it's electrics. Not to be sinister but without tests it can be anywhere from a loose wire connection to vacuum lock in gas tank to motor semi-seizing. I assume it starts right up in the morning? Without heavy choking or pumping or long turnover?

Commentary, not aimed at anyone:
To have and own an old truck is fun, rewarding and educational. We need to "grow" with our trucks. We need to use these troubles as a learning opportunity for the long future of ownership. Being able to diagnose it can only be learned by testing and finding the problem. If a bunch of are parts are replaced, nothing will be learned. The post will not teach anything. The results could be satisfactory, however. If it's a hobby of sorts, learn all you can and solve it yourself with suggestions as to what it could be. Suggestions as to what it could be are used by some people to start buying and some to focus testing. Testing results are then analyzed and thought out. A person will never learn to do that by replacement of several parts at once. That's how the Guru's on here got to be Guru's. We can all do what they do with their help. There is no OBD, they are our OBD.
Drive it with gas cap off for a day.

It starts instantly when cold. Choke out (closed) and throttle out some. As soon as it starts I take off some choke and most throttle and continue to decrease each as it comes up to temp.
It runs perfectly and idles well whether cold or up to temp. It is ONLY a hot start issue, and that's what made me think vapor lock. Also, that it almost died when I was stuck in construction traffic suggested that with no air moving over the engine it could be vapor lock.

This is not a hobby vehicle, it's my daily driver. And having trouble while it's parked at home is a whole different thing than a truck that won't start when I'm out somewhere, or sitting at the gas station pump having just filled up and with a line of people waiting behind me. So while I agree that patiently working each potential cause is the preferred approach, sometimes the need for a reliable vehicle that won't leave me stuck is the higher priority.

Vapor lock will cause the fuel bowl to be empty.
1) The next time it dies on you, remove the air cleaner, climb in the engine bay so that you can look down the carburetor and work the the throttle lever swiftly and watch for a squirt of gas. If no squirt, you have a fuel delivery issue.
2) If you have determined that you have a fuel delivery issue from the no-squirt test above, put your hands on the fuel line. If you can hold it without any discomfort, your fuel delivery issue is not vapor lock. The fuel temperature needs to be approaching the boiling point for vapor lock to occur.
That's enough for now.
Get back to us after you have performed these tests.
BTW, the only way one of these old trucks can become a reliable daily driver for you, is for you to become a Stovebolt guru. They are not highly complex, but they do require regularly scheduled maintenance, and you will need to learn how to troubleshoot problems as they arise.
I remember when I dove into this game many years ago. The thought of traveling far from home made me as nervous as a long-tailed cat in a room full of rocking chairs filled with Texans looking to gauge the size of the draft under the door to see if a cat could be throwed through it.
Now, when I have any issues with the truck, I can find it and fix it pretty quick. There is a learning curve, but it will put a smile on your face when you become able to handle anything she throws at you.
Carl

Test the fuel pump for output volume, vacuum, and pressure. True vapor lock, particularly on a stovebolt engine, is about as rare as finding the wicked witch of the west's flying monkeys hitching a ride on a unicorn.

The pump should deliver at least a pint of fuel in 30 seconds with the engine idling at normal speed. If it won't idle for 30 seconds on the fuel in the float bowl, fix the carburetor. Pressure at idle speed with the fuel line at the carb disconnected and deadheaded into a pressure gauge should be 3-5 PSI and the pressure should stay there for several seconds after engine shutdown. Vacuum at the pump inlet should be 10-12 inches of mercury and stay for several seconds after shutdown also. If the pump is low on volume but passes the pressure and vacuum tests, find the air leak or restriction between the pump and the tank.

If the fuel system checks out, look for a no spark situation with the engine hot.
Jerry

I see your point Rev. Also I've seen posts by you and know that you know what you are doing. Sometimes I buy new parts in lieu of testing also. I should have said that in my "treatise". It IS a viable method for a DD if parts are cheap and easy to install and you don't live out in the woods.
Fuel delivery issues may the problem. Also condenser or coil or points (the spring not closing), new or not as others have mentioned. Jerry's flow test is how to test a pump. I prefer to see if it starts when HOT by putting gas down throat. I quickly know if it's gas delivery or not. Carry a little bottle of gas around your neck, when driving, for this purpose. Jerry's test is too messy and not safe.

I know all this stuff is hard to do out on the road. Try to catch it as you get home or leave it run in the driveway. You really need to pin it down to vacuum lock, fuel blockage/filter/pump or electrical/spark. As Carl says: seeing gas squirt from pumping throttle tells you if bowl is dry or not. Pouring small amount of gas down carb and it starts is good news.
Please let us know after you replace some parts.

The guru's that have responded are spot on with their test requests. You need to isolate to the subsystem that is causing the problem. Then test individual related components.
That said, these old 6 bangers can be notorious to restart after a good run. Alot has to do with how well the intake is heated or the lack there of and condition of all the sub systems.

A tried and true procedure is thus:
While cranking, slowly fully depress the throttle then slowly lift up. What you are doing is varying the fuel/air mixture while cranking to find the happy spot. I have to use this procedure on my 49 216 regularly and it works 100% of the time.
Do NOT apply choke once it's warmed up. You'll flood it and that causes a whole new set pf starting issues.....

Likes been said, theres an art to owning/operating/wrenching these old manually fabulous machines of yesterday. You are the CPU with them.

Here is what I suspect is your problem. You are running Fenton exhaust manifolds that are not heating the bottom of the intake manifold. You have not mentioned water heat for the intake, so can we assume you are not using it?

Without heat under the manifold, the excess fuel in the runners drops out of suspension and pools in the bottom of the intake once the engine is shut down. Without the heated floors, the fuel just sets and makes for a hard start up. High heat vaporizes the excess fuel. Mine did the same thing till I heated the manifold.

60 degrees out side and 150 degree engine temp is not hot enough to vapor lock a fuel system. If the weather was damp, your blimp of the throttle in the traffic jam could have been from icing, and again, heating the manifold will cure this.

I have a heat tube from the Fenton header to the underside of the intake manifold, so I *should* be getting sufficient heat to prevent icing. FWIW