Vapor lock.....

**albersj51** · 07-22-2011, 01:20 AM

Julian,

Been there and it sucks! someone on here recommended a low pressure e-pump and pre carb fuel filter with a bypass so you can run a return line to the tank. It wasn't recommended that you run the e-pump through the mech pump due to the risk of a mech pump issue allowing fuel into the oil.

a british mechanic also recommended I make sure the carb float is adjusted propely.

PM me if you need details on the e-pump/bypass filter.

**LaneRover** · 07-22-2011, 06:58 AM

Your fuel line placement sounds almost correct. Is it held in place by a clip that is on the first valve cover nut?

An old trick to get you home is to slice a potato in half and tie that around the fuel line - for future use since you are already home. On one drive through Sonoma Valley on a REALLY hot day with lots of road construction I wedged a 2x4 under the hood to keep the hood open a bit and create more room for the heat to escape. BUT that is a bit drastic . . .

If it continues to be a problem I would even look at a bit of pipe insulation around the fuel line where it gets the warmest.

**smukai** · 07-22-2011, 10:26 AM

I live in Colorado as well. I used to have the same problem.

I now run an electric fuel pump (no return line though...twin tanks so I'm not sure how I could handle a return line).

I also do my best to run gas without ethanol. To me, it seems like ethanol lowers the boiling point of fuel and gets me into vapor lock trouble.

This link has been helpful in finding clear gas: http://pure-gas.org/

If you are ever in Golden, lemme know!

**knac1234** · 07-22-2011, 10:28 AM

Jason & LaneRover-
Thanks.

I am surprised to hear that this is the proper routing (no clip holding it to the valve cover.....zip tied to the air intake hose!!). I would have thought that perhaps closer to the radiator (grille side) with air flow coming through directly over it?

Fuel pump--I will have to explore that more. I had not heard about the fuel in oil issue. I had thought that if the mechanical pump failed completely, I could simply flip a switch to activate the electrical. In the event of vapor lock, I thought the same thing.....flip it on for a few moments to get it started and then shut it off.

Float--Good tip, however I know mine is good from setting up for altitude a short while back.

Cheers,
Julian

**albersj51** · 07-22-2011, 01:30 PM

IIRC, the issue with fuel in the oil is if the the diaphragm in the mechanical pump ruptures/fails, it could allow fuel to be pumped into the block diluting the oil and could result in a spun bearing. That was enough for me to avoid it. if you have a new pump or a recently rebuilt one, the probability of it happening is probably low. Also, your plan is to switch it on and only use it to start during VL issues (push the vapor out), its probably a none issue. In fact, I like this idea!

For the return line I took the blanking plate on the tank, tapped it for a fitting and and ran some cheap fuel hose to it.

**knac1234** · 07-22-2011, 02:26 PM

Jason,

Glad you like the idea!

Again, the electric pump would also serve as a backup to get me home if the mechanical died, and then I would immediately replace the mech pump to reduce the chance of the issues you mention. In the center of my gauges on the S3 there is a blanking plate where I believe a diesel related light went. Was thinking of installing a lighted round push button switch for the pump there. Right in front of my face and lit up to remind me it is on....and not have to cut or drill any extra dash holes!

Can you elaborate on the return line? Currently I have an emissions controlled Series III that is no longer emissions controlled! I think the line runs from the tank to the pump to the Weber. There is a line that vents the tank under the truck (which if you overfill the tank, the fuel comes out of). PO change.....never messed with it.

Julian

**rickv100** · 07-22-2011, 02:45 PM

Why not insulate the line with some reflective foil covering? Seems like the simple solutions is the best.

Ad hoc solutions I have heard include spraying the fuel pump with a fire extinguisher to cool it down.

Rick

**daveb** · 07-22-2011, 10:05 PM

This thread contains false information. The factory fuel line routing goes in front of the valve cover and thermostat housing. It gets held down by a metal p-clip and one of the three thermostat housing bolts. Routed over the valve cover in the way suggested here is what I call the "Vapor Lock Special"

**knac1234** · 07-23-2011, 09:39 AM

daveb--thanks for the insight. Do you or anyone else have a pic of exactly how that is routed then?

Julian

**meatblanket** · 07-23-2011, 09:47 AM

Originally posted by knac1234

Jason,

Glad you like the idea!

Again, the electric pump would also serve as a backup to get me home if the mechanical died, and then I would immediately replace the mech pump to reduce the chance of the issues you mention.

Vapor lock is brutal in CO. The only really effective way to deal with it is to fit an electric pump. I had a setup just like this on my IIa.

However, if you plumb them in a series, I don't think the mechanical pump is strong enough to pull the fuel out of the tank and through the electric pump. So to use the electric pump as an auxiliary, you have a line that goes around the electric pump that includes a one way valve. Carter makes a setup to accomplish exactly what you want to do, and it works well. I posted part numbers on the old GnR site.

Having said that, if I were doing it again, I probably wouldn't bother keeping the mechanical pump.

**artpeck** · 07-23-2011, 10:20 AM

I can post a photo later today of my routing with is stock factory if that is still helpful.

**tmckeon88** · 07-23-2011, 11:16 AM

I had a vapor lock on hot days issue a few years ago and what I ended up doing was drilling two or three small holes in the inside of the gas tank filler cap. Not all the way through, but just through the inner sheet metal, to allow air to pass more easily into the fuel tank as it emptied. For whatever reason, it was not vented enough. It ran fine after that. If you get stuck again, you might just try opening the gas cap for a moment to allow air in, then starting it. If you hear some hissing as if you're releasing vacuum, that might well be part of the problem. I am not sure about how the high altitude affects the whole situation. For what it's worth, my fuel line runs in front of the valve cover too, rather than on the top of it.

Good luck!

Tom

**meatblanket** · 07-23-2011, 11:48 AM

Originally posted by tmckeon88

I am not sure about how the high altitude affects the whole situation.

Higher altitude = lower atmospheric pressure which lowers the boiling point of your fuel. So the higher you are, the less heat it takes to cause a problem. I could drive my truck around Denver with no problems, but then vapor lock at 10,000 ft (prior to installing the electric pump).

**knac1234** · 07-23-2011, 01:04 PM

All-

Thanks for the comments.

Tom-Good idea.....actually when at a stop at Walmart, the mechanic suggested that one....slight pressure release, but the vent on the tank is an overflow line (like my Hillman Imp)....might help.

Meat-Electric is sounding better, especially as I have a new pump lying about.....I live at 9100 feet, but between there and Co Springs it's a 3000 ft drop....still high though.

Artpeck-Please do post a photo....that will be the first try.....just buy a longer bit of fuel line and run it as yours shows.

Carb shield.....any thoughts......was there one stock an a S3....fits my Weber.....any use?

You know the more thought I've given to this.......the only other car I've experienced this with up here is my Imp. Coincidentally, it is the only other car I have with a mechanical fuel pump. Hmmm.....

Cheers,
Julian

Vapor lock.....

Vapor lock.....

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