Vapour Lock

[willincalgary]

Last summer when I was doodling around the US (cambrianadventures.blogspot.ca) I had some issues with vapour lock, particularly when temperatures got into the hundreds. I installed an electric fuel pump closer to my fuel tank selector valve and bypassed the mechanical fuel pump at the block. This mostly alleviated my problem of vapour lock but now I had to listen to the whine of a cheapo electric fuel pump when I drive around town.
Most of the time my truck does not have any issues with vapour lock as I live in relatively northern climes and the temperature is rarely hot enough. What I want to do is run the mechanical fuel pump again and have the electric plumbed in with a switch to activate it in case issues arise. Does anybody see any issue with running the electric fuel pump through the mechanical one, or vice versa? My ony concern is the mechanical fuel pump will now be constantly pressurized when the electric fuel pump is active. Thoughts?

[albersj51]

Make sure the mechanical pump is in good shape. If the diaphragm is bad, I am told you could push fuel into the engine and dilute your oil. Someone will correct me if I'm wrong. You could try a carter 4070 vane pump, which is quieter than the cheap Napa pulse pumps.

[mearstrae]

I use the Carter pump and hardly notice any noise. These pumps work best when closest to the tank, as they are pusher pumps. If you have a good elec. pump you hardly need a mech. one (although I've seen them being run in tandem). This would eliminate any problems with the diaphram failure on the mech. pump, and causing gas to get into your engine and kill the bearings or worse.

'95 R.R.C. Lwb
'76 Series III Hybrid 109
'70 Rover 3500S

[bugeye88]

I use a Facet solid state pump just after the mechanical one. I use it to fill float the float bowl after sitting for a time, to reduce the cranking needed to do this. Also good for hot days and vapor lock situations. On/off switch inside the cabin so usually I only use it for brief periods of time. No problem for the mechanical to push through this pump. It's a nice back up for the mechanical one also.

Rob

[SafeAirOne]

There are no problems running an appropriate fuel boost pump ahead of the mechanical pump--2.6l 109s have done this since the dawn of time.

[jeff kropp]

This is sort of off the mark, but in summer I carry a mister bottle of water. When hot weather VL prevents starting, I spray from fuel pump to the carb, wait 5 min., and start. Someday will try electric pump.

[SafeAirOne]

I wonder if you'd get the same result without the spraying; Just open the hood?

[crankin]

I will back up that running both is not a problem. But like others have said, if the diaphragm is old in the mechanical pump you could push fuel into your oil...which could be bad.

I also run the carter and do not notice it running around town.

[jeff kropp]

Spraying hastens the recovery process compared with just opening hood. All depends on how hot the day is.

[SafeAirOne]

Spraying hastens the recovery process compared with just opening hood. All depends on how hot the day is.

Why not just pour water on it like lotsa folks do?

[ArlowCT]

I would disconnect the fuel line at the carb and turn the motor over until fuel came out the line. By placing the line in a catch can you can just dump the fuel back in the tank. Used this method to get back up and running in a min or so a whole bunch if times!

My dad blew some fuses one time with the bucket of water trick, so be careful with that one!

[SafeAirOne]

My dad blew some fuses one time with the bucket of water trick, so be careful with that one!

I imagine you want to keep it away from the stuff that can crack when shock-cooled too.

[JimCT]

Hot climates

LR's have spent much of their life in hot hot climates. I think what you are seeing as vapor lock is worn fuel pumps, not just the internals but the arm that rides on the cam. I think they only need an electric pump if there is something else amiss.

I imagine you want to keep it away from the stuff that can crack when shock-cooled too.

[ArlowCT]

Our fuels today are much different then they were back when these trucks were made. They are specially formulated to be used in sealed/pressurized systems and our rovers do not have that. The suction placed on the fuel line causes the fuel to turn to vapor at a lower temp helping raise the occurrence of vapor lock. Google vapor lock, Rovers are not the only old vehicle having this problem and the most common fix is removing the mechanical fuel pump and replacing with a electric.

[SafeAirOne]

Our fuels today are much different then they were back when these trucks were made.

They're getting worse too--The Supreme Court just refused to hear an appeal from automotive organizations who were trying to prevent the EPA from forcing 15% ethanol onto the market.

Stand by for even MORE vapor lock, diminished fuel economy and engine destruction than the current E10 (10% ethanol) gasoline is causing.