Possible vapor lock???

[warhorse65]

Start off with my truck is a 65 f100 inline 6. When I got the truck from my dads to get it running it was still cool weather. Now that summer is going the truck is acting like it is vapor locking. After I take it for a drive and make some different stops it doesn't want to run. If I get it to crank every time I try to take off it cuts off. I have tried the clothes pin on the fuel line it didn't do anything to help. Any more suggestions would be great. I hate for the truck to sits till it gets cold again.

[LM14]

I had a car that vapor locked really bad. We tried everything. Insulated fuel lines, wrapping in tin foil, clothes pins, covering steel lines with rubber hose, replacing steel line with rubber hose, new fuel pump, different pressure new fuel pump, moving the fuel filter, bigger lines, spraying water on the fuel lines to cool them before trying to re-start it, etc.

Nothing worked. This went on for over a year. Drive until it dies, try to let it cool down before starting again and go until it died again.

Then one day my car simply would not start and ended up at a garage for diagnostics (pre computer days) and they found a badly worn bushing in the distributor. We replaced the distributor with a new one and it fired right up (faster than waiting on parts for a rebuild and I needed the car so in went a new part). It never vapor locked again. I started removing all the band-aids and it was still fine. After the distributor was fixed, it never died again and I never had a hot start problem again. Looking back, it was happening more frequently until the day it refused to start at all.

Not saying its the distributor but take a close look at it and the coil. Check for excessive play in the distributor shaft, it fixed mine. Also look for weeping of the coil or swelling of the coil body. If it's an original coil, I would replace it as a cheat thing to try, they are affected by heat.

SPark

[bobenhotep]

What he said. If the coil gets hot it will do a lot of "vapor lock" type symptoms.

Do you have any pictures of the offending engine?

Dan

[Oregoon]

I had the same problem, and I live in Western Oregon, where it's perpetually between 50 and 80 degrees.

First, check the exhaust-flapper under the intake manifold. It heats up the intake when the truck is cold, then once it's at operating temperature, it's supposed to flip back out of the way. After 50 years, these can stick in the closed (heating) position. I ended up turning the heat-spring around in mine, so it's permanently open. LIke I said, 99% of my driving is in a temperate environment, and my intake gets warm wnough without any help. Even on a trip to the mountains, I had little trouble with icing.

Your environment may be different. Many people need the manifold heater to work properly, and if that's so, try replacing the sping and ensuring the mechanism moves freely.

If that doesn't work, go to the classic inlines site and order a phenolic spacer and new gaskets. Depending on your carb, you'll need to space your throttle spring-return plate and throttle-cable locator up in a similar height. Don't forget longer studs, too. And be sure to get the right gasket. The Carter YF has a declivity in the base that some 1 bbl gaskets won't seal, and some spacers have holes machined in them. With an Autolite, this isn't a problem. With a Carter, you'll have a vacuum leak unless you can find a spacer with no holes in it, and a gasket to match.

Anyway, as far as I can tell, the culprit appears to be the ethanol gas we get these days. The fuel bubbles away in the float-bowl at low temperatures and seems to cause all sorts of issues.

[Toyz]

I don't believe you can blame it on the ethanol, since it's boiling point is considerably higher than gasoline.
You seldom hear of vapor lock anymore, but that's probably due to the preponderance of injected vehicles with higher pressures and return fuel lines. Just as others have mentioned, it is my opinion problems attributed to "vapor lock" seldom prove to be such.
Paul

[warhorse65]

here is a couple pics of the motor that was asked for.

[Oregoon]

I had no idea ethanol boiled higher!

That said, my gurgled away and the truck started very hard when hot before I fixed my stuck manifold heater.

Now, I have new problems related to fuel delivery, but too much heat isn't one of them.

[mtb2liv]

Has this issue been resolved?

I am very interested as I am experiencing the same issue.

Starts, idles and runs fine; then after 20 mins or so of driving, starts the stalling/starving for gas thing.

Carb does not leak nor do I hear any percolation -

Starts really hard then dies immediately when attempting to drive.

Let it cool, starts right up and all is well; AAA of Oregon flatbed to the rescue yet again.

I read through all the threads/posts I could find on this and went into the shop to look into exhaust flapper.

Checked my exhaust flapper; seems to work freely but I am not 100% sure (I didn't think to check it last stalling episode) if it was set to open/close correctly. It is now fixed in the "warm" or closed position by virtue of my setting the spring so it remains closed so heat does not rise into the carb.

I will more than likely, rarely or even maybe never, drive the truck when it's cold (sub 40 degrees) as my heater box was removed from the truck when I bought it and I have not yet replaced the missing blower motor to reinstall it; admittedly not a huge priority at the moment being summertime.

I have a "new" rebuilt 1100 with SCV (from Summit Racing), Pertronix w/ Coil and Load-o-matic (seems to function freely without tons of play and returns freely), new fuel pump, clear inline filter, new hard line from pump to carb and soft lines where applicable, new vacuum line from carb to dist., new plugs/wires/cap, alternator...list goes on.

I have not yet driven it since springing the flapper shut, but I did let it idle for about 45 mins with my vary-ing the idle speed - got the water temp to about 190...revved up and down to idle - ran fine.

I know I should drive it now with the flapper fixed shut, but a little gun shy as my last AAA ride home was just yesterday - so I went on to Classic Inlines and ordered up 2 x phenolic spacers - will take her out once I install them and see how it goes.

Any updates on this trucks' issue would be helpful and I'll do the same.

Thanks, Slick60's for being the place that it is...awesome.

[Oregoon]

Just to be sure: When the weight is rocked back against the manifold (vertical) the flapper is open, and letting exhaust freely out of the manifold. When it's closed, the oppostite is true, the weight is level, and exhaust is deflected up against the base of the intake. I spun my spring so it remains wide-open, and it certainly helped the heating and the hard starts. Intake remains cool enough to be touched.

I'm going to install my EFI exhaust manifolds soon, so it'll be a moot point. Future plans are for a water-heated 4bbl intake, and until then, I'll live with the occasional cold-start grumpiness that comes from an unheated intake.

If indeed you're having vapor lock, or suffering from evaporation in the float-bowl, there's a few considerations: First, try a phenolic spacer. If it's still being a pain, consider the factory fuel lines, which run right over the valve cover, or between the valve cover and water-neck. Obviously this is a place where a lot of heat builds up, so insulating your fuel line might be a good place to start. Try the clothes-peg trick first: Clamp several pegs on the line to create heat-sinks. If it works, consider buying some line-insulation, since the pegs are a stop-gap at best.

Back in high school, my friend's 250-cid Maverick had all sorts of trouble with vapor lock, and since he was delivering pizzas, he needed to solve it badly. He tried rebuilding his carb, playing with float levels, running a rubber fuel line, clothes-pegging the stock line, and god-knows-what-else before his drag-racer dad entered the picture and the Mav' ended up with an electric fuel pump mounted near the tank, fuel line insulation, a phenolic spacer, and header-wrap.

After that, the car ran like a UPS truck. Not the easiest solution, but it worked really well.

[mtb2liv]

Oregoon; thanks for the clarification - I set it up based on posts I saw you make in the past - I configured the spring to keep the weight back against the manifold, understanding that this was the way to keep heat out of/off of the intake/carb - The spring holds it in this position and when heats up, try's to push it even further against the manifold. I think I did it correctly. Flapper cannot move the weight to top position.

I ordered phenolic spacers from Classic Inlines but now assume I also need new carb studs; any ideas as to the correct size I need?

I hope that the flapper fixed in the "heat off the carb" position and the phenolic spacer, my probs will be solved...I really just want to drive this cool old truck and not need to sit and wait for a tow truck or a cool down period.

[ICEMAN6166]

studs are 1\4 20 on the coarse end that goes into the manifold and 1\4 28 on the carb end. the carb end is the end you want longer , take an old one out and add the thickness of the spacers you will be using or measure whats above the top of the manifold now and add.
pretty sure the coarse end is 1\2" length of threads.

[Oregoon]

Oregoon; thanks for the clarification - I set it up based on posts I saw you make in the past - I configured the spring to keep the weight back against the manifold, understanding that this was the way to keep heat out of/off of the intake/carb - The spring holds it in this position and when heats up, try's to push it even further against the manifold. I think I did it correctly. Flapper cannot move the weight to top position.

I ordered phenolic spacers from Classic Inlines but now assume I also need new carb studs; any ideas as to the correct size I need?

I hope that the flapper fixed in the "heat off the carb" position and the phenolic spacer, my probs will be solved...I really just want to drive this cool old truck and not need to sit and wait for a tow truck or a cool down period.

Sounds like you're on the right track! Classic offers the right studs, but as Iceman pointed out, you can take one out and any decent parts store or hardware shop will have exactly what you need. I'm a huge fan of Winks Hardware, down on 2nd and Stark, since they carry every fastener known to man. Parkrose Hardware are really good, too.

Let us know how it works out!

[mtb2liv]

Thanks, fellas - once the spacers arrive I'll get them installed and go for a drive (I'll hit up the hardware stores for studs this weekend) and report back!