The Stovebolt Site Forums The Shop Area Engine Shop Boiling fuel.

Short story.
Rebuilt 230ci in my 1965 C10.
2/14/19 she left me on the side of the road. Sputtered and stalled out. Couldn’t get her started.
Started up just fine the next day with some starter fluid.
Runs and drives fine for short trips.
Fast forward 3/13/19 it did same thing. Sputtered and stalled. Would crank and try to start. I poured a little gas down the carb and it boiled.
So, my intake manifold is getting too hot I guess.
Now I don’t think my engine is actually getting too hot. My temp gauge reads 180 at the water neck BEFORE the thermostat. Aluminum radiator is newish and oversized. Electric fan comes on at 195. Thermostat is a 195*. Timing is at 9* BTDC with an HEI and was set at 12* back in February. Runs about the same.
I think I’ll put my mechanical fan back on and see if that cures the problem. It will move air past the manifold at all times. I’ll also make sure the heat riser flap is closed.
Ideas?

Same thing happened to me just a few weeks ago. Turned out to be a bad fuel pump. Be sure to check yours to make sure it’s getting gas.

Once the manifold cooled down, it started and ran fine again. I had a bad fuel pump in another truck and it would drive fine at 35 MPH but sputter and stall if I maintained 60 MPH. Electric fuel pump solved that bad mechanical pump problem. This has no problem running at 65 for extended periods of time, but if I’m at the traffic light or stop and go traffic, that’s when it seems to get too hot. Just needs more air flow under the hood and across the manifold.

Aw, someone is running ethanol contaminated gas. Methinks you’re experiencing what was commonly called vaporlock back in the day. Make sure all gas lines are as far from th engine and radiator as possible and consider insulation around the fuel filter. You might try an insulator between the carb and intake as well.

Made sure your heat riser isn't in the wrong position and keeping the heat directed at the bottom of the carb. If that's OK I'd wager a cup of coffee on a weak fuel pump.

It idles just fine when cold and only does this once the engine is HOT! I'm beginning to doubt the accuracy of my temp gauge. If the fuel pump was weak, wouldn't it want to stall when the engine is cold too?

I was considering getting a carb spacer, but would that require modification of my mechanical throttle linkage?

If the spacer solves the problem, then I wouldn't have to install the mechanical fan. I spent considerable time installing the electric fan and all that effort would have been wasted. Shucks. Any idea where I could buy a carb spacer for a Rochester B?

Try shooting an infrared thermometer at the various parts of the engine and get some readings so you can verify temp vs your gauge, etc. Double checking the heat riser is a good idea too.

SimS

Nope. Think about it. When it's hot the fuel will have a tendency to vaporize. A weak pump can't pump enough to compensate. Not an issue with a cold engine, no vaporizing fuel.

I’m going to offer two suggestions. 1. As Tiny and others have said... weak fuel pump. 2. HEI breaking down when warmed up causing an open circuit.

I for sure agree that fuel inside the carb bowl is vaporizing or building pressure or something causing fuel starvation. However, it is strange that it doesn’t seem to have a problem at highway speeds. Looks like Jim Carter sells insulators to go between the carb and manifold.
Oh, and I’m pretty sure my heat riser stays open all the time (bad).

"I for sure agree that fuel inside the carb bowl is vaporizing or building pressure or something causing fuel starvation."

If non-ethanol fuel is available in your area, as an experiment try a tank full. I'll wager the problem disappears. Now the question... is the slightly extra cost (in my location at least) worth the benefits.

Good Luck,

RonR

That is likely the root cause of your problem. If it's stuck in the heat on position you are directing all that heat to the bottom of your carburetor even when the engine is hot. If that is the issue anything else you do is simply putting lipstick on a pig. If you want to fix the problem that needs to be addressed.

I plan to travel with this truck. Searching high and low for non-ethanol fuel while traveling wont be practical.

If your running a little hot and no carb insulator..............then winter grade fuel is going to boil in the carb.

It’s more about the vapor point but the symptom is fuel boiling. Some areas are in change over now. But if you had winter grade fuel from the fall ride.........that fuel on spring 80* day will behavior different than a summer grade Purchased in July.

http://haneperformance.com/techtips5.html

https://auto.howstuffworks.com/fuel-efficiency/fuel-consumption/summer-fuel1.htm


Motorcycle or ATV it is common for the gas to boil in the tank as the fuel is heated by the engine heat.

It sounds like your fuel pump could be vapor locking. Modern gasolines have low boiling points which work fine with EFI. For carbureted vehicles, if the fuel pump becomes hot enough, boiling fuel will prevent the fuel pump from moving liquid fuel to the carburetor. Percolation in the carburetor will cause the engine to run rough from the added richness of boiling fuel and could cause it to stall from flooding. I would consider adding a solenoid-type electric pump at the fuel tank that you can run when necessary. See Vapor Lock.

I would also add an insulating carb spacer to keep the carburetor cooler and make sure that the manifold heat control valve is lubed and working properly. The heat control valve replaces the heat absorbed by vaporizing gasoline in the intake manifold and helps the engine run better even in hot weather. See Intake Manifold Heat.

Carry a gallon of water with you. If it stalls next time, try pouring cold water over the fuel pump.

YouTube: Fuel Boiling at Hot Pump

Great info on a problem that's only going to get worse I suspect. It looks like the percentage of ethanol may well increase in the near future from the current 10% to as much as 20% article here.

I use this app when I travel in the '51 to find non-ethanol gas. With the Google Earth component in the app it's easy to route to service stations that carry pure gasoline.

Adding an electric fuel pump is a great solution, except when one has a 6V truck like the '51, then other steps are called for. To date I've moved the fuel filter (which acted as a huge heat sink) that was between the fuel pump and the carb to the fuel tank, about a foot away. that and using insulation on the fuel line from the fuel pump to the carb cured vapor lock on hot days when running ethanol fuel. Despite the best of efforts sometimes you get caught on the road had have to run whatever's available.

I have never experienced what you guys are talking about, but I have done the following.

1. Fuel filter is 6” from fuel tank.
2. I wrapped the fuel line with heat resistant cloth where it is next to the engine.
3. I do not have anything but a straight line from fuel pump to carb. I figured less places fuel can leak onto the engine from.
4. Original style mechanical fuel pump.

I have driven 2,000 miles in western Texas and no issues. 800 miles were hot summer heat. If it can handle Texas, it can handle summer heat and I run 86 octane unleaded.

Chris

overheating manifold for sure, just shut the heat riser, its only to get some efficiency driving in cold weather, or fix it with a new riser spring.

I’ve fixed the heat riser issue. I’ll try one thing at a time and see what works. An electric fuel pump is an easy swap but may not be necessary.

that should fix it if not it could be a issue with a pump, aside from that idk where else heat reaches fuel components, aside from the line feeding from the pump to the carb.or the insulator separating the carb from the intake manifold, and yes that needs to be there, very important, it basically prevents the throttle body from getting hot, which is rather thick steel or iron..