Electric Fuel Pump

[plbs1234]

I have a 1985 Caterham with the Kent 1700 Super Sprint engine. While driving on hot (100+) days this summer the car would vapor lock and shut down. I'd have to wait for everything to cool down before it would restart. Running it hard after it had restarted would lead to it vapor locking again.

 

I'd like to remove the engine driven fuel pump and cover the opening in the block with a blank plate, and then install an electric fuel pump back near where the fuel line exits from the tank.

 

Has anyone else done this on their car and did it help?

 

I have Weber 40 DCOE's. What pressure and flow will I need with the electric fuel pump I install?

 

Thank you for any help you can offer.

 

Paul

[Nick OTeen]

The Webers will be happy with a pressure of 4psi. Take a look at this Carter fuel pump. It puts out all the volume you'll need and doesn't require a separate pressure regulator.

 

http://www.racetep.com/webfuelspark.html

[ihckb2]

I agree, I have had several electric pumps in my car and now with the Carter I would not have anything else. Works great with my twin 45 DCOEs. I mounted it at the rear near the gas tank on top of the lower frame. Just needed to make up a bracket to mount it to. I kept one old electric in line pump as a spare or to help someone else out if needed.

Makes a little clik clik at idle, but when up and running the car sounds drown it out.

[coffee break]

My xflow has a solid state electric fuel pump and a pressure regulator set @ 2psi. I'm the 4th owner, so I do not know if this is the original set-up, but it is doing the job.

I don't know if this works at 100F ambient, that's above my operating temp.

[JohnK]

Anybody got a formal definition of "vapor lock"? I've heard people use this term over the years and, y'know it SOUNDS good, but exactly what is it?

[oilteq]

I know the fluid side. Ethanol increases vapor pressure, so avoid E10 if it is possible in your state.

 

In northern states, the EPA allows higher vapor pressure in the winter for easier starting. That is one of the reasons your fuel mileage drops in winter. Higher vapor pressure winter fuel and warm weather are more likely to produce vapor lock. Worst case scenario is a warm day early in the spring when you still have winter fuel in the tank.

 

I think avgas is generally a narrower cut with lower vapor pressure, and therefore less prone to vapor lock.

[xcarguy]

In short, vapor lock occurs when fuel (in the fuel line, as per this discussion) is heated to such a temperature that the fuel actually begins to vaporize in the line. When this happens, the 'in line' fuel becomes uncontrollable by the fuel pump, injectors (FI) or a combination thereof.

 

plbs1233, another consideration; do you have fuel line routed anywhere close to a heat source (header, etc)? If so, rerouting (if possible) and/or heat shielding the fuel line may help.

[dhubbard422]

+1 on xcarguy's "other considerations". I would suspect a heating problem as much or more than a pressure problem.

[lancylad]

I agree, I have had several electric pumps in my car and now with the Carter I would not have anything else. Works great with my twin 45 DCOEs. I mounted it at the rear near the gas tank on top of the lower frame. Just needed to make up a bracket to mount it to. I kept one old electric in line pump as a spare or to help someone else out if needed.

Makes a little clik clik at idle, but when up and running the car sounds drown it out.

 

Did you buy yours in the US or from somewhere in Canada? Was it the 4070?

[oilteq]

In short, vapor lock occurs when fuel (in the fuel line, as per this discussion) is heated to such a temperature that the fuel actually begins to vaporize in the line. When this happens, the 'in line' fuel becomes uncontrollable by the fuel pump, injectors (FI) or a combination thereof.

 

I agree with this definition, but I have only heard of the problem with carbureted systems. I do not see vapor pressure exceeding the 50 psi, or whatever, of typical injection systems.

[plbs1234]

Thanks for all the replies. They are very helpful.

 

I bought my car this past summer off the LONY site from a fellow in Fredrick, MD. When the car is run in temps less than 100 degrees and I'm not pushing the car hard it runs fine.

 

The engine is a cross flow so the carbs are on the opposite side of the engine from the exhaust manifold and pipes. I think the engine bay just gets so hot at the high temps we get here in the summer that the fuel is vaporizing in the line and the engine driven pump just can't pull fuel because of the vapor.

 

When it quits it acts like fuel starvation and not like an electrical problem caused by heat. My theory is that a pump pushing fuel to the engine will be better in hot weather than an engine driven pump trying to pull fuel with vapor in the lines.

 

I'll give the electric pump a try.

 

Thanks again.

 

Paul

[The Stig]

Absolutely go with the electric pump. I also have an '85 1700 crossflow and the Facet pump at the tank with regulator close to the carbs is ideal. You will need a blanking plate with an oil baffle (Burton Power in the UK or let me know as I have a spare one). The baffle stops the cam throwing oil into the vent which is directly above.

 

The problems you have may also not be heat related. If the carbs are fixed too firmly and not allowed to flex on the manifold it will cause similar symptoms - the fuel gets stirred up, froths and you need to stop and let it settle (I am sure there is a term for this, just can't remember).

 

Let me know if you need pics or further info.

[ihckb2]

Did you buy yours in the US or from somewhere in Canada? Was it the 4070?

Lancylad

 

Off the top of my head I don't remember if 4070 or not. All I can remember is it runs at 4psi no no regulator required. In Edmonton right now so will check when I return home.

[xcarguy]

In short, vapor lock occurs when fuel (in the fuel line, as per this discussion) is heated to such a temperature that the fuel actually begins to vaporize in the line. When this happens, the 'in line' fuel becomes uncontrollable by the fuel pump, injectors (FI) or a combination thereof.

 

I agree with this definition, but I have only heard of the problem with carbureted systems. I do not see vapor pressure exceeding the 50 psi, or whatever, of typical injection systems.

 

oilteg,

 

The EFI vapor lock I refer to is mainly from the indirect experience I have with the MSD Atomic EFI (after market EFI system). I installed this system on an ERA 289 FIA Cobra I used to own and had excellent results. I say 'indirect experience' because I personally never experienced vapor lock with the system, but know of others that did; the vapor lock was always the result of an improper install of the system. Because of my knowledge of vapor lock having happened with 'after market' EFI installation, I simply felt it worth mentioning here. I don't mean to get off on a tangent, but again, for what it's worth, here is an excerpt from the MSD Atomic EFI installation manual regarding proper setup with respect to preventing vapor lock in the system:

 

Selecting a Return or Returnless Fuel System

 

The Atomic EFI has the option of working as either a return or returnless style fuel system. While many users will have the option to choose whether or not to install a return line, there are a number of factors that need to be considered in making this decision. NOTE: If you are planning to use metal tubing for your fuel system, then a fuel system with a return to the tank is recommended. Using the chart below, consider the conditions under which the vehicle with the Atomic EFI will be used on a regular basis. For best results, always plan for the worst case scenario (in this case, the hottest daytime temperatures where you will drive the vehicle using the lowest grade gasoline you will purchase). After taking all sections into consideration, at least five points should be accumulated to ensure reliable drivability with a returnless style fuel system.

 

Condition Your Points Points

 

Daytime Temperatures

 

81˚F or greater  +0

 

71 - 80˚F  +2

 

61 – 70˚F  +3

 

60˚F or lower  +4

 

Quality of Fuel

 

Low (less than 89 octane)  +0

 

Medium (89 – 90 octane)  +1

 

High (91 octane or greater)  +2

 

Fuel Pump Installation

 

Greater than 2 feet from tank  +0

 

Less than 2 feet from tank  +2

 

In-tank  +5

 

A minimum of 5 points is recommended to use a returnless fuel system

 

Total: _____________

 

The Atomic EFI with a returnless fuel system is NOT meant to be a solution to fuel vapor lock issues that already exist on a carbureted engine. The Atomic EFI with a returnless fuel system is equally as susceptible to vapor locking as a carbureted system would be. Therefore, if vapor lock has been an issue on your vehicle in the past, it is not recommended to use a returnless fuel system with the Atomic EFI. Instead, use a fuel regulator with a return line to correct the issue.

 

MSD

 

 

Using the above points system (sorry, it didn't copy and paste well), I scored less than five which resulted in my needing either an in-tank pump install or a return-line fuel system. Because of the shallow depth of the fuel tank on the Cobra, an in-tank pump wasn't possible so I plumbed a return-line system and positioned my fuel pump as close as possible to the tank outlet so as to allow the pump to push fuel to the fuel rail rather than pull it from the tank thus keeping as much fuel as possible (between the tank and the fuel rail) pressurized.

 

Unless one is running the pump in-tank, positioning the fuel pump as close as possible to the tank outlet is paramount to aid in preventing vapor lock. With an external (outside of the fuel tank) pump system, any fuel line positioned between the tank outlet and the fuel pump is not pressurized and subject to vapor lock given the right conditions regarding heat and fuel grade. When you factor in placing the EFI pump in the tank (such as factory installations), all the fuel is being pushed to the fuel rail, and all that fuel being pushed is pressurized, therefore, pretty much eliminating any possibility of vapor lock in the system.

 

If plbs1234 switches to an electric pump (and positions the pump as close as possible to the fuel tank outlet as stated in his original post) this, in theory, should eliminate or, at the very least, severely lesson the possibility of vapor lock in the fuel line.

 

There is also another area in a fuel system where vapor lock can occur; in the float bowl of a carburetor (the result of engine heat tranfer, low fuel grade or a combination of both). But having said that, I not familiar with the design and operating characteristics of the Weber 40 DCOE's.

 

Here's a photo of the MSD excerpt:

Edited December 29, 2013 by xcarguy

[oilteq]

xcarguy

 

I agree with your evaluation, and I think the discussion may be useful. I do not agree with MSD when they correlate vapor lock and octane. 120 octane avgas is likely to have a lower vapor pressure than 87 octane gasoline at your local gas station. Vapor lock was a fairly common problem 25 years ago. At that time refiners would blend in as much benzene as the vapor pressure regs would allow to increase octane for premium grades. So, at least back then, premium octane gas was likely to be (but not necessarily) more prone to vapor lock than regular grades.

[xcarguy]

outlet,

 

With MSD having been involved in after market performance products for many years, I have to wonder (after reading your comments about octane) if MSD is 'blending' (pardon the pun) old school philosophy (octane and vapor lock correlation) with new technology (the Atomic EFI system). Just a thought.

 

Anyway, didn't mean to hijack the thread; back to Kents and pumps.