DGV carb fuel boiling after shutoff

[mightyohm]

Has anyone else seen this? After shutting the car off, I can hear the fuel boiling in the carb, and if I take off the air filter housing I can see some of it percolating into the intake.

It's well documented on the Opel GT and BMW 2002 forums but I haven't seen anyone on the Sunbeam forums talking about it. Apparently the ethanol in the gas makes the problem worse. It's pretty much impossible to find ethanol-free gas up here.

I think our car has had this issue for a long time but I never paid much attention to it. It may be worse on the new motor, which has an intake without a water passage (though I suspect folks will disagree, and it's not clear to me in the hot water would primarily heat the intake or primarily cool it from the hot headers below).

Some of the boiling fuel winds up in the intake, which seems like a "bad thing" for the rings.

 

[Barry]

Depending on the blend / additives / altitude, some components of gasoline can start to boil as low as 100 degrees F., so "percolating" in the carburetor is not a surprise. At sea level, ethanol boils at 173 degrees F., so .....

The carburetor(s) on a Series Alpine engine is directly above the exhaust manifold, so fresh / cool air flow and radiant heat shields are probably a good idea.

 

[Ashfried]

I use to have a gas boiling problem. I did a couple things:
1. put in an electronic fuel pump
2. Changed the plastic fuel line from fuel pump to carbs with a stanless steel line that stays much further away from the manafold. See pic below.
I'm not sure which fixed it, but it has not happened again and it has been a couple years.

 

[alpine_64]

John

If you are running the DGV the factory had a pholenic spacer ( insulator) between the carb amd manifold to prevent heat soak. If the fuel is vaporizing in the carb bowls that will be the issue.

If in the fuel line, check its routing near exausts or other hot spots and insulate.

 

[mightyohm]

Barry,

I'm going to try fabricating a heat shield out of stainless or aluminum and see what that does.

Ash - the pic is helpful. Looks like your line crosses in front of the engine block. How was the stainless line to work with? Easy to bend? Is there a good source for stainless line & fittings?

Michael -

I've got the carb spacer/insulator but it looks to be made of plastic, not phenolic. I ordered a phenolic one which should be a better insulator. (I may stack two of them together if I can fit them.)

I ordered some insulation for the fuel line and I'm going to try to change the fuel line routing. Right now I have a rubber hose that wraps around the back of the valve cover and crosses over the intake manifold. Probably not the best setup.

 

[Ashfried]

I do not remember where I got the Stainless line, but I used a small pipe bender and it was easy. I did not uses fittings. I went from hose to steel pipe and from pipe to hose at the carb T. Have you worked out where the gas is boiling? For me it was in the mechanical fuel pump. I could see it boiling in the glass jar. That is why I went to an electric pump installed nowhere near anything hot.

 

[mightyohm]

I do not remember where I got the Stainless line, but I used a small pipe bender and it was easy. I did not uses fittings. I went from hose to steal pipe and from pipe to hose at the carb T. Have you worked out where the gas is boiling? For me it was in the mechanical fuel pump. I could see it boiling in the glass jar. That is why I went to an electric pump installed nowhere near anything hot.

I've seen the gas in the pump boil on a really hot day (and had to wait a few minutes for things to cool down), but the current issue is that the gas is boiling in the carb itself. On the DGV you can look down into the float bowl with the aircleaner off and see the fuel boiling. You can hear it with the hood up. Vapor lock is bad but fuel boiling in the carb is worse since it winds up spilling into the intake and washing down the cylinders.

 

[65beam]

Michael said it best. If you have an original series 3 or 4 intake there was a spacer between the carb and intake . This was used to isolate the carb from the heat of the manifold. Keep in mind that the intake and exhaust manifolds are bolted together to the head so the heat from the exhaust will pass to the intake manifold. The use of this spacer with an original intake also eliminates mods to the intake to allow the use of a 32/36 Weber. I don't have access to my photos at this time so I can't show you the spacer.

 

[Tim R]

We have had this issue with cars in the UK and it gets worse when we tour on the continent (higher ethanol content).

In addition to the ideas suggested here we have wrapped the rubber pipes with heat reflective material to lower the temperature and on some cars we have fitted electric pumps and then routed the fuel pipe all around the back of the engine bay and to the carb. This keeps it well away from everything hot and ends the problem completely.

 

[Blue Ribbon]

Relatively new member here. I have a 1965 Alpine with a 1725 engine and 3236 weber carb. I am experiencing the exact problem discussed here. When the air temp gets above 80 F the car temp goes from. 170 to 200 in stop and go city traffic. Then when leaving city and accelerating, vapor lock occurs and car will miss or shut off completely. When it cools after 20 minutes it will start and runs. Runs fine in country driving or in cooler weather. I have relocated the fuel line and will try others solutions recommended here. Anyone have any suggestions. Thanks

 

[mxp01]

I live in Tennessee and we have hot humid summers. I experienced vapor lock the first hand full of years owning my alpine. At the time I was running the stock fuel pump with a glass bowl. When I experienced vapor lock in traffic or after I turned the car off and tried to restart it after a few minutes later I would pour some ambient temperature water on the fuel pump an actually see the fuel fill back up in the bowl. That will get you out of a pinch, but beware of idling too long because it will happen again. I would keep a high idle to prevent this but that also comes with higher engine temperatures.

I finally got tired of this and installed an electric fuel pump and never had the problem again. I also removed the stock pump and fabricated a plate to put over the hole in the block.

 

[volvoguys]

Relatively new member here. I have a 1965 Alpine with a 1725 engine and 3236 weber carb. I am experiencing the exact problem discussed here. When the air temp gets above 80 F the car temp goes from. 170 to 200 in stop and go city traffic. Then when leaving city and accelerating, vapor lock occurs and car will miss or shut off completely. When it cools after 20 minutes it will start and runs. Runs fine in country driving or in cooler weather. I have relocated the fuel line and will try others solutions recommended here. Anyone have any suggestions. Thanks

My problem was solved by using a pholenic spacer, as Michael suggested above. It's about 1/4" thick and as I recall I got it from The Bug Hut years ago ($15ish).

Mountville? Heck, you're practically a neighbor!

Mark (Harrisburg)

 

[Bill Blue]

Jeff, it ain't Stainless but just as good. Copper/Nickle brake line I believe comes is sizes up 5/16", maybe larger. This stuff should be your "go to" anytime you need tubing.
Bill

Barry,

I'm going to try fabricating a heat shield out of stainless or aluminum and see what that does.

Ash - the pic is helpful. Looks like your line crosses in front of the engine block. How was the stainless line to work with? Easy to bend? Is there a good source for stainless line & fittings?

Michael -

I've got the carb spacer/insulator but it looks to be made of plastic, not phenolic. I ordered a phenolic one which should be a better insulator. (I may stack two of them together if I can fit them.)

I ordered some insulation for the fuel line and I'm going to try to change the fuel line routing. Right now I have a rubber hose that wraps around the back of the valve cover and crosses over the intake manifold. Probably not the best setup.

eff

 

[Scotty]

Are there additives that can be added to the gas that's safe for the Alpine engines that'll help counter the effects of Ethanol?

 

[husky drvr]

Are there additives that can be added to the gas that's safe for the Alpine engines that'll help counter the effects of Ethanol?

Scotty,

Here's a selection of videos. Think your question is only answered indirectly.

Hope these help.

 

[husky drvr]

Relatively new member here. I have a 1965 Alpine with a 1725 engine and 3236 weber carb. I am experiencing the exact problem discussed here. When the air temp gets above 80 F the car temp goes from 170 to 200 in stop and go city traffic. Then when leaving city and accelerating, vapor lock occurs and car will miss or shut off completely. When it cools after 20 minutes it will start and runs. Runs fine in country driving or in cooler weather. I have relocated the fuel line and will try others solutions recommended here. Anyone have any suggestions. Thanks

B-R,

Welcome to the Forum.

Just an observation, your description of your problem is a classic example of reduced air flow through the radiator at low speeds, reduced coolant flow at low speeds, or a combination of both to some degree.

You say your Alpine is a 1965. Is that a sIV? . . . with a 1725?

Does your engine have a functional oil cooler in operation?

Is your radiator in good - not clogged - shape? When you are driving in town, have you tried running with the heater on to see if the engine temp stays lower? Tried to keep the engine above an idle while stopped? Popped the bonnet so it's not snapped all the way down flush to the body to see if letting hot air out that way helps with engine temps in town?

If the fuel is boiling in the fuel pump, then the excess pressure will vent through the fuel line to the carb and display what you describe as boiling in the carb.

You might find relief treating symptoms, but I suspect you'll have to ensure some improved cooling performance before you find an engine temp spike cure.

Just a few thoughts,

 

[Mike O'D]

All summer or just spring/early summer? Many areas of the country (northern - don't know how far south it goes) use winter blend gasoline from fall to spring. It should be switching in Ohio about now, Winter blend vaporizes at a lower temp to help with winter starting, but boils easily in hot weather. I have had some really bad boiling in my glass bowl fuel pump in warm weather spring/early summer if I still had winter blend in the tanks. Never had it happen on the hottest days in the summer with summer blend.

 

[Blue Ribbon]

Amazing. Thanks to everyone for your responses. Looks like I need to start by trying to improve engine cooling and installing pholenic spacer. Then maybe an electric fuel pump. Yes, 1965, SIV, 1725, Weber 32 36. Do most of you have an oil cooler. If so, what brand and supplier.

 

[Acollin]

Sorry here, but just got to ask: what the heck is a “pholenic“ Spacer. I know what a spacer is. Is it a material and if so, what are it principles?

 

[Scotty]

Sorry here, but just got to ask: what the heck is a “pholenic“ Spacer. I know what a spacer is. Is it a material and if so, what are it principles?

It's a spacer/gasket that goes below the Carb and above the manifold. It helps with stuff like what's being mentioned on the thread and supposedly also vapor lock. I have one and it made those problems go away.

Link: https://www.pegasusautoracing.com/productdetails.asp?RecID=3585