04-17-2015, 08:00 PM | #1 |
Senior Member
Join Date: Jul 2011
Location: Oakland County, Michigan
Posts: 562
|
Vapor Lock
What are the symptoms of vapor lock? Can it happen while you're driving?
Today was the first really nice day of the year here in Michigan with temps in the low 70s. I took my car out for a drive of about 80 miles. The first half it drove beautifully but after that it started to lose power at certain points intermittently (seemingly around 45 miles an hour in high gear), which necessitated me hitting the momentary switch that turns on my in-line Airtex electric fuel pump. Doing this brought the engine back to life so to speak. When the car lost power it also made a faint moaning sound, which was very strange. While driving the engine temp fluctuated between about 150 and 170 degrees on my aftermarket temp gauge. Does this sound like vapor lock or something else? I'm puzzled . Also, the car has been fully restored with all-new fuel line, a fresh filter, a rebuilt mechanical pump, etc. The engine is a 59L at about 251 cubic inches with a stock camshaft and a Stromberg 97 with stock jets. Thanks! - Craig |
04-17-2015, 08:08 PM | #2 |
Senior Member
Join Date: May 2010
Location: Star, MS
Posts: 4,024
|
Re: Vapor Lock
Vapor lock or not, if running the auxiliary pump restored the power I'd say it was a fuel delivery problem. You didn't mention the fuel pump push rod as new. MAYBE it is the problem, or worn camshaft lobe, or bad rebuilt pump. Just thinking out loud.
|
Sponsored Links (Register now to hide all advertisements) |
|
04-17-2015, 08:13 PM | #3 |
Senior Member
Join Date: Jul 2011
Location: SF Bay Area
Posts: 6,635
|
Re: Vapor Lock
Craig, the term vapor lock is anathema to many people, so I'll just confirm that yes, you had a lack of fuel situation that was improved by the use of your electric fuel pump. But of course you already knew that! Many things can cause a lack of fuel, from dirt in the lines; air in the lines; mechanical pump issues; and yes, vapor lock. As your air temperature wasn't hot today, I'd suggest you go through your system from tank to carburetor bowl in search of the culprit... And stay away from oxygenated and/or Ethanol laced fuel, which is the elephant in the vapor lock issue in these modern times.
__________________
Alan |
04-17-2015, 08:19 PM | #4 |
Senior Member
Join Date: Jul 2013
Location: Sacramento, CA
Posts: 368
|
Re: Vapor Lock
|
04-18-2015, 08:48 AM | #5 | |
Senior Member
Join Date: Jul 2011
Location: Oakland County, Michigan
Posts: 562
|
Re: Vapor Lock
Quote:
|
|
04-18-2015, 10:13 AM | #6 | |
Senior Member
Join Date: May 2010
Location: Florida and Penna.
Posts: 4,471
|
Re: Vapor Lock
Sponsored Links (Register now to hide all advertisements)
Quote:
and summer isn't here yet. That's why a year or two back I did extensive testing every day for a fairly long period of time and posted the results on this forum. The only sure fire fix is a SMALL fuel return line after the pump back to the tank. When going very slow or at idle the fuel stays in the pump to long and at about 130 degrees it boils and turns to vapor. The small amount of cool fuel running through the pump and back to the the tank is enough to keep the pump cool and prevent VL. Don't forget there is a .098 inlet hole at the needle valve of the carb so very little fuel is flowing through the pump and the 1/4" line. You can only have a return line less than .125 or the carb will starve at higher RPM's. A little higher pump pressure, 4 lbs cold helps as the pressure drops as the pump gets hot and down around 1 1/2 to 2 lbs when hot the problem starts. G.M.
__________________
www.fordcollector.com |
|
04-18-2015, 08:10 PM | #7 |
Senior Member
Join Date: May 2010
Location: pgh.pa.
Posts: 321
|
Re: Vapor Lock
had a problemwith vapor lock in my 1985 s-15.the fuel line routed from front of 2.8 v6,to rear of carb.line was getting heated from the head,and problem stopped when I put a section of foil tube between line and head.Yes,it happened while driving,had to keep a fast idle,and it was backfiring.
Last edited by al pa.; 04-18-2015 at 08:13 PM. Reason: added yes,etc. |
04-18-2015, 08:21 PM | #8 |
Senior Member
Join Date: Oct 2010
Location: Orem, Utah
Posts: 5,762
|
Re: Vapor Lock
Vapor lock does not need extreme ambient temperatures to happen. I get it regularly even at 70-80°. You've already got the best solution - your Airtex electric back up pump. That's what I use regularly.
__________________
Prof. Henry (The Roaming Gnome) "It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness |
04-19-2015, 12:08 AM | #9 |
Senior Member
|
Re: Vapor Lock
With Temperatures in the low 70s I don't think you have vapour lock ,you possible have a faulty pump or its sucking air .You should also check the temp of your coil .My car runs 180 to 190 water Temperature so under hood is up there I have never experienced vapour lock .high Under hood temperatures should = a boiling Radiator .
|
04-19-2015, 08:54 AM | #10 |
Senior Member
Join Date: May 2010
Location: East Shore of LAKE HOUSTON
Posts: 11,106
|
Re: Vapor Lock
It's not the AMBIENT temps that matter. It is the temperature of the FUEL in the pump and carburetor (under the hood......on top of that HOT engine) that is critical. Many of these newer fuels have a relatively low boiling point, at which temp the liquid begins to boil and change state into vapor state. The real answer is to control the fuel temp. DD
|
04-19-2015, 09:32 AM | #11 | |
Senior Member
Join Date: May 2010
Location: Florida and Penna.
Posts: 4,471
|
Re: Vapor Lock
Quote:
__________________
www.fordcollector.com |
|
04-19-2015, 12:49 PM | #12 |
Senior Member
Join Date: Sep 2014
Location: oroville calif
Posts: 893
|
Re: Vapor Lock
lol, the real experts on here say there is no such thing as vapor lock, so no matter how much evidence you present that there is they all will say you don't know what your talking about
|
04-19-2015, 02:07 PM | #13 |
Senior Member
Join Date: Jul 2011
Location: SF Bay Area
Posts: 6,635
|
Re: Vapor Lock
I've always rankled at G.M.'s word "guesspert", however, I'd say the quote above may well prove the existence of same.
__________________
Alan |
04-19-2015, 02:31 PM | #14 |
Senior Member
|
Re: Vapor Lock
Sorry that I am not towing the party line ! I think the Admiral is entitled to a alternate view ,I am sure vapour lock does exist but in his case I think he should consider other options as well .Ted
|
04-19-2015, 03:40 PM | #15 |
Senior Member
Join Date: Jul 2011
Location: SF Bay Area
Posts: 6,635
|
Re: Vapor Lock
Ha ha! Ted, We agree! My comment about G.M.'s Guessperts was not addressed to you!
I knew the subject "Vapor~Lock" would get the blood pumping!
__________________
Alan |
04-19-2015, 03:49 PM | #16 |
Senior Member
Join Date: Jul 2014
Location: Iowa
Posts: 1,634
|
Re: Vapor Lock
With a new fuel line and associated parts, I'd check the ignition coil. When an original coil gets hot, it mimics the infamous "vapor lock". If it hasn't been rebuilt, send it to Skip Haney. Another suspect is the ignition switch. The Bakelite base usually wears grooves where the contact rides, reducing the contact pressure. The base and the "brush" (the moving part) should be changed as a pair. Finally, be sure the gas cap is vented properly.
|
04-19-2015, 04:07 PM | #17 |
Senior Member
Join Date: Sep 2014
Location: oroville calif
Posts: 893
|
Re: Vapor Lock
Ted, I agree he needs other options, but if the engine starts to die and an electric fuel pump cures that problem, what do you think caused the problem?, fuel boiling in the pump causes it to loose suction, thus no fuel to carb, (vapor lock.) a hot coil will not get any better with an electric fuel pump operating in the system, by all means, check all posibilties, bad electrical connections included
|
04-19-2015, 04:35 PM | #18 |
Senior Member
Join Date: Jul 2013
Location: Sacramento, CA
Posts: 368
|
Re: Vapor Lock
Fuel boiling in the float bowl is a pretty good clue that it's fuel related, but only a true expert can say for sure.
|
04-19-2015, 05:00 PM | #19 |
Senior Member
|
Re: Vapor Lock
OK Alan I get your point .The electric pumps making up for the Mechanical one not doing its job ,set up a vacuum gauge at the tank end and check for leaks .Also the reduction in performance of a mechanical pump pulling fuel through a Artex pump has to be considered ,Tests ? Ted
Last edited by FlatheadTed; 04-19-2015 at 05:13 PM. |
04-19-2015, 05:15 PM | #20 |
Senior Member
Join Date: May 2010
Location: Qld, Australia
Posts: 4,212
|
Re: Vapor Lock
With the tiles on the space shuttle being able to keep the heat on one side oNly,you think there would be some modern material that could be used to insulate the fuel pump and carb from the engine and manifold,
It's easy to insulate the fuel line ,but no so the pump and carb, I have made a small air scoop that fits in beside the radiator and takes air from in front of the radiator via a 1-1/4 hose to the fuel pump,this helps ,also have a spacer under the carb, But in 39c the fuel will still vaporise. Any one work for NASA who get get us one of those tiles? Lawrie |
|
|
Sponsored Links (Register now to hide all advertisements) |
|