Vapor lock woes

[JayGoss]

Have been through 2 Solex's, 2 Proline repro fuel pumps and am on my first new style genuine fuel pump. She ran great for a few days and today the sputtering began again (today was the longest series of rides- engine block was probably hotter than previous days). I spliced into the fuel line and installed a clear plastic fuel filter so I could see what was happening. After a long ride (2-3hrs) the sputtering began. I pulled over and watched bubbles periodically rising into the fuel filter and the fuel level slowly declined until the Rover just about stalled. I poured some cold water onto the fuel pump and the fuel level in the filter glass rose back up to a normal level. I think these are textbook symptoms of vapor lock. I've done everything I can think of with stock series parts to mitigate vapor lock (lowered timing advance, used plastic fuel lines routed in the air current of the cooling fan, vented fuel cap, etc) and I'm out of ideas. I live at 7000 feet and have been using regular unleaded fuel. All of the fuel around here (Evergreen, CO) has ethanol. I'm thinking that the engine block gets hot enough to heat the metal fuel pump and it's vaporizing as it leaves the pump. This is frustrating as I know there are plenty of Series Rovers in the CO area and around the world at my altitude using the same fuel, etc- am I missing something? Does anyone know if the boiling/vaporization point increases with higher octane fuel? I've got the appropriate jet (117.5 I believe) installed for a Solex at 7000 to 9000ft- wondering if switching to the next size up (120- for 5000 to 7000 ft) might decrease pressure in the system and raise the vaporization point? I really don't want to install an electric fuel pump if I can avoid it- my rover is a recent restoration and I like the stock configuration.

[gudjeon]

I regularly venture into the high country around 6000-7000ft level in my corner of the woods. I have had my share of duff pumps so went to electric and a bypass filter to keep fuel in constant circulation. No problems with vapour lock ever again. Perhaps a mechenical pump that can be relied upon for good volume could use this system?

In hot weather, modern gasolines are not what they used to be when originally formulated/refined to work in carbs, especially in hot weather and its not to do with the lack of lead. If anyone needs further convincing, ask someone who drives a carburetted truck pulling a trailer or hauling a heavy load in the heat. When it gets really warm out and the operating temps climbed, the engine seems really gutless compared to what it usually runs. I reinstalled the fan shroud which has helped a lot with keeping the temp from climbing while climbing at elevation.

[kevkon]

Though it does sound like vapor lock, have you done a pressure test on the fuel pump when cold? Have you checked for any restrictions in the line from the tank to the pump?
Checked the pick-up in the task? Any restrictions along with a line getting hot and the increased volatility of todays fuels will be a recipe for premature fuel vaporization. I'd definately start with a pump test first, though.

[JimCT]

vapor lock

These trucks are so simple, and have run in the hottest places imaginable, and at altitude too. Can not help but think the problem is something else.

[kevkon]

It doesn't take much with the current fuels to create a vapor lock problem. A slight restriction in the line such as a kink or an obstruction in the pick-up coupled with a heat source will do it. The pump reduces the pressure and fuel vaporizes in the line. Once you determine the pump is working correctly when cool follow the line back to the tank and look for any restrictions in the line and locations where it may be in contact or proximity to a heat source.

[ArlowCT]

Had the same problem with two different trucks. Solved both by switching to a low pressure electric pump and never looked back. One truck was running around CT the other with high in the mountains in South America (14,000ft). In South America we went through two carbs and two mechanical pumps trying to fix the problem. Give it a try and see if it works.

cheers

[JayGoss]

thanks everyone- leaning towards an electric pump. Forgot to mention the Rover has brand new tank, pickup tube, lines from tank to pump and pump to carb. No kinks that I can see- each line is in great shape. Fuel lines are routed so that there is a constant incline to the carb. Will search here for posts on electric fuel pump conversion to see what I'm getting into.

[LaneRover]

Did you use stock 'hard plastic' fuel lines? I have found that those sometimes can lead to a bit of vapour lock on long hot drives.

Any chance the exhaust pipe runs too close to the fuel tank or fuel line and it could pick up heat from that? (not sure if you stayed stock with that in the rebuild)

Good luck!

Brent

[badvibes]

I run about the simplest fuel delivery system possible. Rubber fuel line, an inline filter before the low volume electric pump, another see-thru inline filter before the Rochester carb and that's it. I live in NM and have done a bunch of highway and off highway driving with this set up. Summer time temperatures at 5000 to 7500 feet, sometimes up to 10,000' elevation and have no vapor lock issues. I went electric because it has been much more reliable. YMMV. Wear on the cam lobe for the mechanical pump gets mentioned as an issue, just a thought.

[Bertha]

thanks everyone- leaning towards an electric pump. Forgot to mention the Rover has brand new tank, pickup tube, lines from tank to pump and pump to carb. No kinks that I can see- each line is in great shape. Fuel lines are routed so that there is a constant incline to the carb. Will search here for posts on electric fuel pump conversion to see what I'm getting into.

Do you have an in line fuel filter? I have noticed many people mount it right over the exhaust manifold. If yours is this way, it could be creating the problem.

[JayGoss]

Do you have an in line fuel filter? I have noticed many people mount it right over the exhaust manifold. If yours is this way, it could be creating the problem.

Just mounted an in-line fuel filter...but it's on the opposite side of the exhaust manifold. I was leery of mounting it right over the hot exhaust for the reason you mentioned- and potential leaks dripping on the hot exhaust. The filter is right in the space between the cylinder head cover and the tail end of the radiator shroud for max cooling.

[JayGoss]

Though it does sound like vapor lock, have you done a pressure test on the fuel pump when cold? Have you checked for any restrictions in the line from the tank to the pump?
Checked the pick-up in the task? Any restrictions along with a line getting hot and the increased volatility of todays fuels will be a recipe for premature fuel vaporization. I'd definately start with a pump test first, though.

Thanks Kevcon- happen to have a fuel pressure gauge handy. Will look into that. Someone else here mentions worn cam lobes at the pump- which could be a possibility and reduce pump pressure. Good idea.

[kevkon]

thanks everyone- leaning towards an electric pump. Forgot to mention the Rover has brand new tank, pickup tube, lines from tank to pump and pump to carb. No kinks that I can see- each line is in great shape. Fuel lines are routed so that there is a constant incline to the carb. Will search here for posts on electric fuel pump conversion to see what I'm getting into.

New doesn't always mean better and it certainly doesn't always mean there's no problem.
If you want to avoid an electric pump ( which you certainly should be able to) check the current fuel delivery for pressure and volume while the engine is cold. If it's ok, then look for areas where the line is in proximity to heat and insulate it. Try running the engine till it's hot, then feel the fuel line along it's length looking for a hot spot.

[BackInA88]

What temp thermostat are you running?
I have the lower temp one in mine with an electric fan.
If I set my fan turn on temp to high I will start to get some vapor lock.
Turning it down to come on sooner takes care of the problem.
In the winter I turn it back up to get more heat.

Have you tried run a cooler thermostat to get the under hood temps down?

Steve

[JayGoss]

What temp thermostat are you running?
I have the lower temp one in mine with an electric fan.
If I set my fan turn on temp to high I will start to get some vapor lock.
Turning it down to come on sooner takes care of the problem.
In the winter I turn it back up to get more heat.

Have you tried run a cooler thermostat to get the under hood temps down?

Steve

I've got the 180 degree thermostat in now- could switch that out but I installed an electric fuel pump today which should have solved the temp issue.....see next post. Thanks for the idea- it's a good one and makes sense for my previous situation.