1950 Buick stalling/dying at idle

[Guest Joshhirst13]

Hey guys. It's been awhile since I've posted. Sorry. Got a quick question to see if anyone can help. I can't figure it out. I've got a 1950 Buick & after I drive it for about 15 min. It's starts to stall or act like it's gonna die while sitting at a stop light or a drive thru. I parked it in the driveway, opened the hood & watched the carb. Every time it would try to stall gas would shoot out of a hole in the side of the carb. I took the carb apart & blew it out & checked the needle & seat, which is the new flat style with a rubber pad on it that seats. I rebuilt the carb a few months back. Attached is a you tube video link of what is happening. Any help would be great. Thanks. 

 

 

 

 

[JohnD1956]

Oh man, that's an odd one!  Does your manual show if that's the vent hole for the bowl?  Or is that passage above the needle valve?

[SpecialEducation]

Makes me think that something is transferring heat to the fuel. When the fuel flow is lower (stop lights / drive thru) the fuel has more time to warm up & vaporize. It's not necessicarily boiling in the bowl, that's just the only place for the vapor pressure to find relief. 

[Joseph P. Indusi]

Strange indeed.  Did you change the fuel pump recently?  Could be excessive pump pressure or the float could be defective or the needle and seat are not sealing when the fuel gets to the top of the bowl.  Try to eliminate one at a time.

Joe

[Guest Joshhirst13]

I just had the carb apart before I made the video. I believe that the hole is above the bowl & not the needle valve. I checked the float. No leaks.  I did replace the fuel pump with a rebuilt mechanical pump from Kantar a few months ago. It does seem like it could be a heat issue. It only happens after the car has been driven a few miles. Maybe I need to work on the cooling system. I'm stumped. 

[Guest Joshhirst13]

Thanks for all of your replies guys. 

[buick5563]

I'm gonna take a wild swing at this one. It appears to happen when the carb is filling with fuel. Is it possible the fuel inlet filter gasket (big red one) is missing?

 

[Alfre]

Most carb problems are electrical check coil and condenser

Al  

[buick5563]

That isn't electrical.

 

[JohnD1956]

The video seems to show a lot of fuel in that momentary burst.  So much that I would be looking for a plug that missing on the top of that carb.  But I can't think of anything other than the needle valve which would cause a sudden change in pressure to account for this.

 

If it was excessive pressure from the fuel pump why would the flow stop?  If there was an electric pump in the system I'd be looking there initially.  Otherwise the  only other thing moving in the system is the float and needle.  Perhaps the float is hanging up while the bowl is filling and then pops to the top pushing the gas along with it?  Or perhaps the needle valve is out of round and not seating correctly till it snaps shut?  Anything else would seem to lead to a constant leak, not this momentary burst.

 

Better keep the fire extinguisher on the seat next to you. 

[old-tank]

13 hours ago, SpecialEducation said:

Makes me think that something is transferring heat to the fuel. When the fuel flow is lower (stop lights / drive thru) the fuel has more time to warm up & vaporize. It's not necessicarily boiling in the bowl, that's just the only place for the vapor pressure to find relief. 

What Matt said and the real blame is the highly volatile available fuel (winter blend that boils as low as 100* F).  Summer blend should be available in most places by May.

Around here it is getting into the 90's and with the winter blend I can't drive any of mine more that 5 miles before experiencing vapor lock (corrected by electric fuel pump), carburetor percolation after stopping or even driving slowly after warmed up.

[SpecialEducation]

1 hour ago, old-tank said:

 

Around here it is getting into the 90's and with the winter blend I can't drive any of mine more that 5 miles before experiencing vapor lock (corrected by electric fuel pump), carburetor percolation after stopping or even driving slowly after warmed up.

 

Thanks for the déjà vu...

 

 

[Guest Joshhirst13]

Hey guys. Thanks for all the great info. I thought that possibly the heat riser might be stuck.  Doesn't seem to be the heat riser. I lubricated it & made sure it was moving freely. Ran the car & still did the same thing. Where would I get an aluminum heat shield to put between the carb & manifold. I already have a thicker fibrous one in place, which may or may not be working. I still need to try insulating the fuel lines & I wouldn't say the fuel lines are not that close to the manifold. Maybe 8-10 inches away. I'm going to also try checking the thermostat to see if the motor isn't cooling properly. Could that cause percolation?

[Guest Joshhirst13]

Also how would an electric fuel pump solve this issue????

[carbking]

Just wondering out loud.

 

Not really certain this is carburetor related.

 

Timing too far advanced, or possibly a sticking or burned intake valve MIGHT be allowing cylinder pressure to blow back through the carb when the engine stalls, blowing fuel from the bowl out of a vent.

 

And while the volatility of modern fuel is awful, the seemingly heat related issue could also be electrical. Older coils can break down when hot causing too little high voltage, thus causing the initial stall. Electronic conversions can do the same thing, especially at idle.

 

Since you stated you recently rebuilt the carb; before doing additional work to the carb (you may need to later), I would suggest a compression test, followed by an ignition test. The ignition test should be conducted when the engine is hot, to attempt to duplicate the issues causing the stall.

 

Jon. 

[trp3141592]

Hi,

 

How about a float that doesn't float?  I had to replace one of mine because it would sink, leaving the needle valve open.

 

--Tom

 

[Guest Joshhirst13]

Ok. Thanks again to all involved trying to help me out. So today I lubricated the heat riser butterfly. The spring seemed to be keeping the butterfly too open so I disconnected the spring & it allowed the butterfly to close completely. This seemed to help some but the carb still ended up spurting fuel. Here's something I came up with today, but I'm gonna have to pull the carb & open it up again to check. When I rebuilt the carb it came with a new type of needle valve called a "Daytona Float Valve". Instead of the tapered needle it's flat with a rubber seal on bottom (see attached pics). I don't remember the needle on this Daytona type having a spot to attach the little metal clip to the float. If it does I don't think I put it on.  I'm gonna have to check. The last pic is just to show the metal clip I'm talking about used to attach it to the float.  If the Daytona style doesn't have the hole to attach the clip I think I'll be going back to the old style needle valve. I'll let you guys know if that is the issue & if it solves the issue. Anybody have any experience with this type of needle valve?

Thanks,

Josh

[carbking]

The valve pictured by Daytona appears to be the old Parker Brothers valve:

 

http://www.thecarburetorshop.com/Fuel_valves.htm

 

The clip to which you refer was used to prevent the valve from sticking in the seat, and preventing fuel from entering the carburetor; not to prevent the carburetor from flooding. The Parker valve did not use the clip. We have not used the valve sold by Daytona, so do not know.

 

Jon.

[JohnD1956]

I have a Daytona Valve in my 56. Works great, but I can't remember if it has that clip or not.

[SpecialEducation]

On March 25, 2016 at 5:53 PM, Joshhirst13 said:

Also how would an electric fuel pump solve this issue????

 

 Just found that I typed this but never hit the post button...

 

Same way the pressure cap on your radiator keeps your water from boiling.   Higher pressure = higher vapor point. 

 

We we do the same thing in airplanes. High altitude = low pressure, and mechanical fuel pumps don't pressurize vapors. At higher altitudes, you turn on an electric boot pump that's aft of the firewall (in a hopper tank or wing tank, where it's cooler).  Providing positive pressure to the main pump prevents vaporizing, and if it does vaporize, the pressure from the aft pushes the vapor through.  We also like return systems because it keeps the fuel moving and back to cooler places. 

[Guest Joshhirst13]

Hey guys. So I think I'm 95% sure I've got it figured out. I pulled the Daytona needle valve & put the old style needle valve back in. Put everything back together & ran car for 30 min. I couldn't get the car to reproduce the fuel spitting issue with the old style needle valve. Knock on wood. I'm gonna have to give it another In N Out drive thru test on a hot day to really know for sure. That being said I think I must have had the float adjusted wrong with the new style Daytona needle valve.   I never adjusted the float when I rebuilt the carb. I just assumed they both used the same float adjustment. Ughhhhhhh!!!!  I'm a little confused on why this would fix the problem though. i would really like to put the daytona valve back in because it seems like a better design, but I'm unsure how to adjust the float properly to make it work. 

Thanks again for all of your suggestions & help guys. You all really help with getting the creative juices flowing. 

[JohnD1956]

The Daytona valve needs less float drop because it seals around the throat of the valve artery.  A needle valve seals within the artery of the valve.  When the Daytona Valve begins to open there is no restriction in the artery. So when it opens a little, it's fully open.  The needle valve needs additional float drop because as it opens the needle point is still in the artery of the valve, restricting flow.

 

Now in theory, you may say it doesn't matter about the drop of the float because if the Daytona valve is fully open when it is any part activated,  then the float should never drop. All that matters is where the float stops.  However, with the increased flow provided by the Daytona valve it just seems to make a lot of sense to keep the valve closer to it's seat.

 

Here's a possible hypothesis.

Willie once said that fuel under pressure will not vaporize, and Matt explained the same with airplane mechanics.  But what if, at idle, the fuel pump does not spin fast enough to keep constant pressure on the line to the Carb?  The pump itself gets at least as hot as the engine, maybe hotter in the airflow of the fan pushing  the heat from the radiator directly onto it without any of the scavenging effects since the car is sitting in one spot.  In this case, as the pressure in the line between the pump and carb ebbs, the gas may be vaporizing.  This could lead to pulses filling the carb bowl.  The bowl may empty more and then your float is dropping, opening the Daytona valve much further than anticipated in engineering.  The low bowl capacity would also make that fuel there subject to greater  heat from the exhaust, with the possibility of boiling.  So what you are seeing at the expulsion point could be a boil over inside the carb meeting a pulse of gas in the fuel line, and the Daytona valve can't close fast enough to contain the pressure?   

 

Or, maybe there was something preventing the Daytona valve from closing all the way?

[60FlatTop]

You are in a good spot. You can make it happen and you can make it stop. Along with ALL the routine tests of a major tune-up you can put a fuel pressure gauge on it under both conditions.

 

The muddy part is buying a rebuilt fuel pump and rebuilding the carb at the same time. It's not good to fix two or more broken things concurrently.

At this point you really need to check the pump to be sure it is regulating internally. Someone could have fat fingered the diaphragm link or used the wrong one.

Compression and ignition shouldn't be ruled out. What if the air flow through the aircleaner is good going into the engine but for some reason blocks a reverse flow if the engine hiccups o burps back for some reason. The manifold and carb could pressurized and blow out the vent hole. It could do that going slightly lean. And if your old needle valve really did leak, putting it back in could richen the mixture enough to mask it.

 

I don't think the fat lady sang yet. It's still in the symptoms symphony section.

Bernie

[Guest buickkuhn]

On 3/26/2016 at 2:54 PM, carbking said:

Just wondering out loud.

 

Not really certain this is carburetor related.

 

Timing too far advanced, or possibly a sticking or burned intake valve MIGHT be allowing cylinder pressure to blow back through the carb when the engine stalls, blowing fuel from the bowl out of a vent.

 

And while the volatility of modern fuel is awful, the seemingly heat related issue could also be electrical. Older coils can break down when hot causing too little high voltage, thus causing the initial stall. Electronic conversions can do the same thing, especially at idle.

 

Since you stated you recently rebuilt the carb; before doing additional work to the carb (you may need to later), I would suggest a compression test, followed by an ignition test. The ignition test should be conducted when the engine is hot, to attempt to duplicate the issues causing the stall.

 

Jon. 

I also had the vacuum advance going bad doing the same thing (spitting gas from vent on top of carb ) . I disconnected the vacuum line from carb then suck on it to watch the inside guts in the distributor or even while it's running to see the difference . Good luck .