Vapor Lock

Nevada Hudson

Both my Hudson 6's and v8's get vapor lock when the temp gets over 90 degrees in both freeway driving and stop and go. ( Even with a backup electric fuel pump!) Never used to have this problem with the old gas. This new formula gas that's been out the last 6-7 years has it happening all the time. Any remedys? Would octane booster help? The highest octane available here now is 91.

cpr3333

How about the old clothes pin trick?



I've never had to try it and have no idea of the science behind it, but some people swear it works.

Geoff

Best way is to fit a by-pass line that continuously feeds fuel back in to the tank, which keeps the fuel in the pump cool. Also ensure that you have the insulating sleeves around the pump mounting bolts, and fiber washers under the heads. Make sure that the fuel line is not positioned where it is exposed to exhaust heat. You can fit an extended heat shield under the carburettor to deflect manifold heat away, easily made from sheet steel. Good luck.

onerare39

Marvel Mystery Oil helps a bit, I think it's 2oz. per ten gallons of gas. It has the mixture rate on the bottle.



John

Park_W

The problem's being there even with the electric pump ON suggests it might be fuel boiling in the carb bowl rather than vapor lock in the lines. To determine that, you could try to bring carb bowl temperature down by fashioning a better carb heat shield than the original, using a 160 thermostat if you're not already, or rigging a fresh air tube to blow air on the carb.

RonS

Nevada, what kind of electric pump do you have? Is it in line? I will assume you have an in line solenoid type produced by Airtex. The same thing happened to me with one of these. For years I would have to turn on the elec pump when the temp went over 90 in traffic, then OK. Last year the elec tric didn't help. After disconecting the fuel line and turning on the elec the pump ran as usual, but no fuel came through. As it was the insulating material in the pump swelled and created a blockage restricting fuel and actually making things worse. These pumps IMO are not long term reliable. There is much discussion on this if you put in search for vapor lock over the past 12 months, right Park?

RonS

Park, I forgot, did you say that the Rotary vane pump on your 47(?) will permit fuel to pass through when inline, or must the pump always be on for fuel to pass?Ron

TOM-WA-

nevada hudson wrote:

both my hudson 6's and v8's get vapor lock when the temp gets over 90 degrees in both freeway driving and stop and go. ( even with a backup electric fuel pump!) never used to have this problem with the old gas. This new formula gas that's been out the last 6-7 years has it happening all the time. Any remedys? Would octane booster help? The highest octane available here now is 91.

you might also want to make sure that the heat riser is working

properly...the one on my 54 wasp was not working correctly and

it heated the fuel in the carb and caused it to vaporize.



Tom

Park_W

Excellent point, Tom. I guess I didn't think of that since I've never had a heat riser "clank up."



Ron, the Carter rotary vane pump will not allow full flow of fuel when it's turned off, so one has to rig a bypass path with a check valve in it. See that thread here somewhere, or drop me an e-mail for photos.



Nevada, I also didn't think about failure of your electric pump ... the very widely used Walbro pumps (also branded and sold as AC) have a serious flaw in that the internal bellow-diaphragm turns to mush with age, even if not in the presence of modern fuels. These are the ones with a cast housing about 2" in diameter and 6" tall ... the "click-click" type. If you've got one of those on the car, trash it and get a new one of different type. I believe it's NAPA's EP-11 that's a good 6v pump and easy to install ... goes in the line like a filter; no need to fasten it to the body or frame.

RonS

Thanks Park, I thought that's what you said I have a carator(gear driven) one on my 53 so far so good. No mech pump. However that E-11 is the pump that I refered to in the above reply, although Carter makes one and I can't speak for its performance.

Nevada Hudson

RonS wrote:

Nevada, what kind of electric pump do you have? Is it in line? I will assume you have an in line solenoid type produced by Airtex. The same thing happened to me with one of these. For years I would have to turn on the elec pump when the temp went over 90 in traffic, then OK. Last year the elec tric didn't help. After disconecting the fuel line and turning on the elec the pump ran as usual, but no fuel came through. As it was the insulating material in the pump swelled and created a blockage restricting fuel and actually making things worse. These pumps IMO are not long term reliable. There is much discussion on this if you put in search for vapor lock over the past 12 months, right Park?

Thanks everyone for the great ideas! Had one of those electric fuel pumps and it failed exactly as you described. Lasted 3 years. Had it just above the fuel tank. This was on the v8 12 volt with Packard v8. Not running any electric pump on it now.Originally, it had a factory 2 barrel carb on it, and it had a ruturn line to the gas tank. That carb is very small ( about the size of one Twin -H carb) and inadequate for that large engine. Guess Packard did not want it to be faster than their cars, as it's much lighter. Bolted on a 4 barrel Rochester from a Packard 400, and it performs beautifully, but it has no fitting for a return line to the gas tank.

Nevada Hudson

TOM-WA- wrote:

you might also want to make sure that the heat riser is working

properly...the one on my 54 wasp was not working correctly and

it heated the fuel in the carb and caused it to vaporize.



Tom

On my 51 Twin-H Hornet the heat riser is working fine.

We have a dry heat here, no humidity.

duncan

put 1/2 quart of 2 cycle engine oil in gas tank every other fill up. It worked great in my 36 Dodge. The further South I drove the hotter the weather became the more I had to use electric fuel pump untill I put in the oil .After that no more electric fuel pump. Make sure that the electric fuel pump is placed as close to gas tank as posible. Keeps cooler. Ray:D

Nevada Hudson

Park W wrote:

Excellent point, Tom. I guess I didn't think of that since I've never had a heat riser "clank up."



Ron, the Carter rotary vane pump will not allow full flow of fuel when it's turned off, so one has to rig a bypass path with a check valve in it. See that thread here somewhere, or drop me an e-mail for photos.



Nevada, I also didn't think about failure of your electric pump ... the very widely used Walbro pumps (also branded and sold as AC) have a serious flaw in that the internal bellow-diaphragm turns to mush with age, even if not in the presence of modern fuels. These are the ones with a cast housing about 2" in diameter and 6" tall ... the "click-click" type. If you've got one of those on the car, trash it and get a new one of different type. I believe it's NAPA's EP-11 that's a good 6v pump and easy to install ... goes in the line like a filter; no need to fasten it to the body or frame.

Thanks! Yeah, they were clicking very LOUD ! The hotter it got, the louder the click! Need a 12 volt one also.

Park_W

NAPA has a real nice 12v one that, like the 6v one I mentioned, just inserts into the line like a fuel filter. Had one on my Hornet now for 6 years.



I'd put one of the rotary vane Carters on it earlier, then the car was off the road for three years undergoing major cosmetic rehab. As often happens, I didn't expect the project would take that long, so never thought about fuel preservative in the tank. Result: when I finally got the car ready to go, the old fuel had the Carter pump so gummed up that it wouldn't turn, so when I switched it on, the motor windings overheated and burned out.



A good sign that the Walbro or AC "clicker" pump has a bad bellows/diaphragm is if it clicks really fast and doesn't slow down in a few seconds (the latter indicating that it's built up some fuel pressure).

[Deleted User]

Nevada Hudson wrote:

Both my Hudson 6's and v8's get vapor lock when the temp gets over 90 degrees in both freeway driving and stop and go. ( Even with a backup electric fuel pump!) Never used to have this problem with the old gas. This new formula gas that's been out the last 6-7 years has it happening all the time. Any remedys? Would octane booster help? The highest octane available here now is 91.

Don't fool around, if you have Walt's tech tip books, go to volume one, page 39 and read how to drive your car in hot weather. I drive my car across America in 100-110 degrees with this set up. Have to buy gas in every state and have never been stuck with vapor lock. Vapor lock is in the fuel pump and no place else. Had to make one improvement which I send to all that bought my books, just send a small SASE and I'll send it to you. On new orders I include it with it. Walt.

tigermoth

hello, i may have missed it, but your original post asked about octane in regard to vapor lock...no connection. you probably figured that out when all the responses posted were about keeping it cool under the hood and head pressure on the fuel.

now if your car pings...



regards, tom