The Stovebolt Site Forums The Shop Area Engine Shop 50 chevy stalling won't start

Just recently got the Rochester single barrel carb rebuilt by a very reputable mechanic for my 235 engine. The engine has ran well these past few months with a lot of pep. Today was one of the hottest days of the year and my truck stalled on me. I popped the hood and saw my glass bowl fuel filter bubbling with the level dropping. The truck wasn't not running and the glass bowl fuel pump remained full. After letting the truck sit for a while because I could not get the it started until I directly poured fuel into the carb several times. The truck started the fuel bowl filter got to top level and drove the truck for 10 minutes with a lot of pep. Let it idle several minutes then it stalled once again. Fuel filter bowl was once again low yet fuel pump bowl level was at it's maximum any ideas? Could it be a vapour lock??

any body out there to help me out?

There are only so many things that could cause this. The tank being contaminated and restriction fuel flow, a bad fuel pump, something in the carb.

This may not be the issue, but has the tank been cleaned? Is there any possibility that something could be floating around in there, getting sucked onto the fuel outlet and stopping the flow?

What is the condition of the fuel pump? You have a gravity flow from the tank to the pump and then the pump works to suck and push the fuel to the carb. The fuel in the bowl may just be flowing in from the tank.

Only asking to eliminate things.


Probably a heat issue, but a little out of my knowledge area.

Was the fuel bubbling because it was hot or was it because of air being forced into the bowl?

It is a Rochester and as talked about in another thread, they are very problematic in my opinion.

The tank is cleaned no rust no debris
the fuel bubbling was do to air entering the fuel filter bowl
Fuel pump came with the vehicle when purchased 5 yrs ago and have no idea of its history

Will start with replacing the fuel pump

Start with a pressure, vacuum, and volume check of the pump. "Wheelbarrow" troubleshooting doesn't work very well- - - -start with a wheelbarrow full of new parts and keep changing them until something fixes it!

First test- - - -disconnect the fuel line at the carburetor and direct the fuel into a 1-qt. container like an oil bottle. Start the engine and let it idle. A good pump will produce 1 pint of fuel in 30 seconds. If the volume is low, test the pressure- - - -deadhead the fuel line into a gauge, idle the engine and check the pressure. You should see 3-5 PSI, and the pressure should remain for several seconds after shutdown. Last test- - - -connect a vacuum gauge to the pump inlet and run the engine. You should see 10-15 inches of vacuum with a few seconds of residual vacuum after shutdown. If the pump passes all these tests, check the line back to the tank, including the flex line, for air leaks. You should have at least 80% of the pump vacuum at the tank outlet.
Jerry

check you vented gas cap,to make sure it is operating as it should

I had a similar problem recently and taking all of my fuel system apart and blowing it all out seemed to fix it. I could not see anything wrong with any of it though.

https://www.stovebolt.com/ubbthread...tutters_a_bit_then_stop.html#Post1168604


And hot rod Lincoln, how does one let their engine idle with the fuel line disconnected?

Any stovebolt carburetor I can imagine will run the engine for 30 seconds at idle on the gas in the float chamber. If it won't, you've got major carburetor problems!
Jerry

TEXT BOOK............It's vapor lock.........the gas is boiling ( bubbling in the filter). Any chance this is winter grade gas ??? It vapor point is much lower than summer grade. Alcohol fuel blends can make the problem worse.

The old school fix was aluminum foil wrapped around the fuel line, clothes pin on the fuel line...........any thing to keep the fuel cool. The fuel line placement on the Stovebolt is set up to be vapor lock prone.....given the pump and line locations.

https://en.m.wikipedia.org/wiki/Vapor_lock

https://www.hagerty.com/articles-vi...r-problems-and-vaporlock-blues-revisited

http://www.airtexproducts.com/news-what-is-vapor-lock.asp X

https://goo.gl/images/ipgQZp


Vapor lock "fix" picture .....

"The fuel line placement on the Stovebolt is set up to be vapor lock prone.....given the pump and line locations." (showkey).
How many millions of these trucks were made with exactly the same fuel line arrangement/location? Are you suggesting that GM would not have, at some time during this long run of trucks, altered their design to prevent "vapor lock prone" fuel line arrangement?
In my opinion, the factory line location is a very efficient design, in that the lines are elevated and in the path of the cooling fan.
If one were to have a vapor lock issue with the fuel lines in the proper factory position, I would suggest that there is another issue causing it. Clogged radiator/water jacket, incorrect timing are a few off the top of my head.
Bubbling gas in a fuel filter may be from a faulty fuel pump and/or a leaky needle and seat in the carburetor.
Carl

I agree there can be other issues or problems that contribute to vapor lock, certainly higher under hood temps will make the problem worse.

The OP Says it ran good .....but....on the hottest day this problem started. Classic vapor lock ..........in my opinion.

Sorry........ vapor lock has been an issue for 50 years ( for ever) and still present today and is made worse by the available fuel. If the winter grade fuel is used makes it far worse.
Just like carburetor icing problem exist and were not fixed for many years.

As for vapor lock happens to any engine, motorcycle are well known for the gas to boil in tank on hot days idling with low air flow over the tank.

Read all the links a lot can be learned. Jalopy Journal seems to understand the issue and the fixes or modifications.

One simple question. Why doesn't every single stock equipped Stovebolt ever built suffer from vapor lock on hot days leaving them all on the side of the road?

Given the right condtions and the right fuel vapor point they all have the potential to vapor lock. Along with any other engine...ask the flat head ford guys.

It changes with the fuel but if the fuel line or fuel filter or carb reach some where around 150-200* vapor lock can occur. Winter fuel can boil at 100*.

Is this about flat head engines or v8 engines?

Where/when on a 235/361 normally "plumbed" engine would you expect to find vapor lock to occur?

Carl asks the right question relative to the original post.

Has nothing to do this flat head vs V8 .........they are just another engine group flat heads that deals with vapor lock from time to time.

The fuel filter attached to the front of the carb or the fuel line is the most likely location for the fuel to boil. The filter bowl inches away from the manifolds is the place where boiling can be seen. That where the old school fix of aluminum foil, cloths pins and shields were applied. Others cooled the line, filter and carb by any means possible to get back on the road. Been there a few times.


As long as we are some state of denial that vapor lock can be a problem and can be related to the original design. We should add hot restart problems related flooding to the issue as it its related to the vapor point of the fuel and the temp the carb can see after engine shut down.

Hot day, hot engine, shut down, manifold heat heats the carb to above the boiling point of the fuel. (Which can be 100-200* depending ) Fuel floods over into the intake, hot restart symptoms might be long crank, acts like its flooded, misfire, black smoke on restart.

These fuel vapor point issues went when into the '80s on carburetor engine. Fuel injection fixed most of the problems.

Again hot restart problems does not happen all the time just like vapor lock, carb icing and other random issues.
If you never experienced vapor lock consider your self lucky. Fuel is the real wild card. If you want to try to experience vapor lock use winter grade fuel in the 4th of July parade in Kansas.

Restarts do require a start-up procedure that is different from the "cold" start-up procedure - somewhat related to "traditional" fuel-line/fuel-pump vapor lock, but easily avoidable via a different start-up procedure.

I have experienced vapor lock with some old engines, but never on a 216/235/261 stovebolt engine (in VA in the hot summer, at sea level and up to 1400 feet).

I've always felt the 216/235/261 was a superior design for preventing vapor lock. The fuel pump is on the opposite side of the block from the exhaust manifold. The fuel line is routed in front of the engine near the radiator. I had a 48 Dodge and it always had hot start issues after a long drive - even in mild weather. The fuel pump on that engine was right under the exhaust manifold and the gas line went right over it up to the carb.

I drove my little 52 with a 235 all over Tx, Ok, Kc, and
about 10 yrs of driving..never had it to fail but once,
had to replace a fuel pump.. but I have no idea what
might be wrong with yrs, good luck and let us know what you find

Vapor lock? In Canada? Not my first guess. Agree with Carl on that. My suggestion is the basics of troubleshooting 101: Wheelbarrow it! Just kidding. Actually it's isolation and testing. Example of isolation is: remove the glass bowl filter, replace with an inline or no filter and drive. Test example, as said: Pump flow test. Make sure you don't have some goofy pinched hose, kinked line. The Rochester is a good carb. Pretty standard design.
I think I read that even though carb was rebuilt "recently", that was months ago? It's been running for months after rebuild????
I agree with your replacing the pump, it's wheelbarrow but I do it also when it's easy, cheap, suspect and unknown age. Nothing wasted except possibly time. Let us know. Some things have to get worse/more frequent before you can find them. Why don't you just get the pump without the bowl and get rid of the filter with bowl. It's not a filter anyway, it's a sediment bowl. Too many leak paths the old way. Install a metal can filter. Nothing about the old way is good except looks. Glass pumps are 3X more money. We don't need to see the gas. You can see the gas and it's not telling you anything definitive. Just my 2 sense.
http://www.oreillyauto.com/site/c/detail/WIX0/33032.oap?pt=02515&ppt=C0024

I don't know which glass bowl filter you have, but mine definitely has a filter, With appropriate gaskets to eliminate leak paths. and the glass bowl pump also has a very fine screen in it as well. I would recommend NOT removing either of them. If you already have them, they don't cost anything. You can also get a new pump and swap the tops to retain the glass bowl. Then you can occasionally remove the bowl and clean the screen if you see it starting to gum up. Since millions of vehicles with these engines have traveled many millions of miles with no problem whatsoever, I would look elsewhere. I have driven my old truck for 35 years, in every imaginable weather scenario, cold, hot, and have never seen vapor lock, (I have never seen vapor lock in anything for that matter) You never said if the engine ran well before the carburetor rebuild and doesn't now, or ran well with the rebuilt carb for a while and doesn't now. Take the gas cap off. There for a while my truck ran horribly I did everything I could think of, changed the entire fuel system with the exception of the filler pipe in the gas tank. changed carburetors, rebuilt carburetors, I had 2 webers right out of the box I was going to use on my new fenton intake. I even tried one of those, changed plugs, wires, points, switched to pertronix, adjusted valves, new voltage regulator. NOTHING would make it run any better. The one day it started and has run fine ever since (about 3 years now) All with not one clue as to what the problem was.