My '57 T-Bird with an OT ( year 68 ) Ford engine vapor locked, leaving me stranded at intersections. After carb spacers, wrapping lines, electric pump, and heat shields the vapor locking continued. I replaced the fuel pump with one with the same pressure but much higher volume. This solved the problem. It is possible the pump I replaced was weak or faulty, but now my peace of mind is great. Ernie
Vapor locking occurs in the non-pressurized part of the fuel system, line from tank to pump, suction side of pump and carburetor. Electric pump, insulation and recirculating are good remedies. A small amount of oil or diesel fuel in the gas can help.
boiling can also occur in the pressurized part , just at a slightly higher temperature. Take measures and precautions to reduce heat absorption on the pressurized lines after the pump also, or it will not be totally cured, and can still catch you by surprise. WHY BE ORDINARY ?
OK I finally got enough parts to start working on this. First issue I see is that my fuel pump fittings are 1/4" ID which seems like it won't be large enough to push fuel throigh the system without bottlenecking. The fuel tank was originally tapped for 3/8" line which is what I'm using up to the mechanical fuel pump. From the pump to the carb its 5/16". Maybe I'm overthinking it but if you guys would't mind taking a look and letting me know what you think I would really appreciate it. I can use reducer fittings as needed but I would like to not have the car up on the lift any longer than necessary. Sent from my SM-N950U using The H.A.M.B. mobile app
The vernier shows a 1/4" inner diameter on that hose bib (adapter). My estimate is that the hose bib plugs into a 5/15" fuel line. Most hose fittings have a smaller inner diameter than the hose inner diameter.
Yes, but it is a smaller issue there. Boiling before the pump causes vapor in the line, and the pump can't pump that = you won't get fuel to the carb. Boiling after the pump just means you will have bubbles in the gas reaching the carb, it'll still get all the gas it needs. But sure, if the carb is hot enough to keep it boiling you certainly have an issue.
My 64 Pontiac with a 462 had a bad time with vapor lock. It had a mechanical fuel pump. The issue was not enough gas (Vol) getting to the fuel pump. I sumped the tank with a dual 3/8" ports then ran two 3/8" steel lines to a tee in the fuel pump. Problem solved! It was like I swapped a different engine ...
Ok I'll run the line as is and connect with 5/16" fuel line. On another note, this couldn't have been helping much. This fuel line was less than 2 years old! I replaced it when I changed fuel filters. Sent from my SM-N950U using The H.A.M.B. mobile app
Consider the ethanol fuel could have eaten any seals in your fuel pump, it may be weak. Replace any rubber line with ethanol compatible, the old line can swell internally as its being eaten up by ethanol I like the new factory style of heat shielding, usually on exhaust. I grab this stuff off late models. Cut it into strips and bend into a U with the open side facing down. You can hammer the edges into a flange after cutting. It holds no water that way
I have been running Carter Electric ( Rotary ) Fuel pumps for 45 years on my 50 merc. Never had a Problem.! Just my 3.5 cents Live Learn & Die a Fool
Update- I ran a new hard line and return line staying away from heat sources as much as I could. Electric fuel pump is near the tank, fuel pressure regulator and fuel filter with a return port is mounted on the firewall now. Next is to run a wire back to power the pump and to braze in a return line connection to the fuel filler neck. I'll remove the neck completely so there's no safety issue of an open flame and fuel vapors! Pics are half-assed so I'll take better ones and post them when I work on it next. Thanks again everyone for their invaluable input! NAES Sent from my SM-N950U using The H.A.M.B. mobile app
Will do for sure. Hopefully this process will help others in the same boat. This Ethanol diluted fuel is no joke! Sent from my SM-N950U using The H.A.M.B. mobile app
My father had a stock 1936 5 window that would stall in hot weather. (Texas) He installed an electric fuel pump with a switch, like you. That resolved the issue. Whenever the motor began to stall he would flip the switch. No more sitting along the road with the side panel up. Sent from my iPhone using The H.A.M.B. mobile app
For what it's worth I had pretty much exactly the same symptoms and have gone through all the things mentioned above until finally one day when it wouldn't start I happened to check to see if the spark plugs were firing and guess what they weren't. So after all the repiping adding a electric fuel pump running a line back to the tank and doing all the things that have already been mentioned on this thread I found that the HEI module would simply stop firing when it got hot. I still don't know if I really had vapor lock or not since I had already done everything possible before I replaced the module. Rather than try to explain it here just go to this link on my website. https://49fordcoupe.smugmug.com/Fighting-Vapor-Lock/
Update: I'm still in the same boat. Airtex 4 1/2lb pressure fuel pump installed near the tank. New line run along the inside frame rail to a Holley adjustable regulator. From there it goes to a fuel filter with a return barb on it then to the carb. The return line goes back down the same path as the feed line to a return port I brazed into the filler neck. Got the system primed and fired up. Fuel pressure is a steady 4 1/2lbs at the regulator. Tuned the carb and rechecked timing. I'm at 31* at 2500rpm with this Chrysler 360 engine which is in spec. Adjusted the carb for lean best idle. Facing the carb, the mixture screw on the right whistled and was less sensitive as I got down to where RPM dropped. Left was "normal" sensitivity. They're both at 1 1/2 turns out as of now. 85-90* outside today so not too hot. I ran around the block a few times and all was well. Came back and rechecked all fittings for leaks, etc. Decided to go on a freeway run. Ran like a champ for a solid 5 mile pull. Got off, parked and rechecked under the hood. All was well. On the way back pinned it for about 30 seconds and all but coasted for about 2 miles before my exit. As I slowed I could feel the familiar stumbling and as I threw it in neutral and blipped the throttle it stalled and died. Took about 2 mins to get restarted but had to keep the throttle about 1/2 open and I'm guessing around 2000rpm or so. Otherwise it would crap out and die. So I limped home and popped the hood. IR temp gauge showed the carb at 140-150*. metal feed line to the carb 160*. Fuel regulator 140*. Feed line up the firewall to bottom of regulator 150*. The exhaust runs about 4" away from the fuel line on the rail so the lines were warm but not super hot. I'm going to pull the carb and clean it out. Its pretty much sat for close to a year with occasional start ups. I can't think of any other culprits at this point and am REALLY at a loss. The HEI should be OK because the engine runs at higher RPMs so it still feels very much like a fuel delivery issue. Soooooo frustrating! Here's a couple of quick pics. Thanks everyone for any help you can offer. NAES Sent from my SM-N950U using The H.A.M.B. mobile app
I know it been said before, but the things that have worked for me are, carb Spacer, plastic one. A good fan and shroud. A good radiator. Wrap the headers with header wrap. Get the heat out of the engine bay. Maybe try a test drive without the hood. See if louvers would help? Double check your timing, and if you are running too lean or too rich. Hope this helps. Apologies if its all been said too many times before. Good luck
I pointed out in a previous post about HEI module failure. It's easy enough to do. https://www.summitracing.com/parts/msd-asy14548
I would insulate the crap out of your hard fuel lines. Look for a DEI product, even a wrap-around for plug wires would be good.
When it restarts, is it blowing black smoke? Do you have to hold the throttle wide open to start? Does it finally clear out and run normal? Have you pulled over, looked down the carburetor to be 100% sure it's out of fuel? Vapor lock should pass, with cool down and the engine should run as normal, holding the throttle at 2000 just to keep it running sure sounds like a different problem. I would guess the floats or needle & seat since it only happened at wide open. Vapor lock should not be a problem at wide open as the fuel has a place to go, most vapor lock I have seen was setting in traffic at low rpm, where the fuel just sets in the fuel lines.
Factory MOPAR ignitions do not like low voltage below 10v they will lose spark. Maybe it is not fuel. Pull the air cleaner and work the throttle see if you do have fuel. I remember in the 70s helping get a 383 Plymouth started the car would crank but no spark after messing with it the battery got low so we jumped it and the car fired right up. With the electric fan at an idle the alternator might not put out enough to keep the ignition happy
Years ago the family had a 64 Buick Wildcat with 401. In the heat of summer (Dallas, Tx) or usually when driving out of state on summer vacation, the car would vapor lock on the highway. Tried lots of different things (one dealership blew out the in-tank filter, another changed inline filters, etc) To make a long story short the fix was to move the hard line away from the engine block and insulate it. No more problems. Try wrapping the hard line going into the carb with some aluminum foil and take a test drive. If that makes things better, try a new, shorter hard line with just 2 bends, not 3, get it away from the engine and insulate it. Also check that the line from the tank to your regulator is not close to an exhaust pipe. Hope you find the solution!
This thread prompted me to poke around on the internet. For what it's worth, I found this........ The boiling point of gasoline = 185 degrees F. (Any other chemicals added to gas weren't mentioned.) The boiling point of ethanol = 12 degrees less at 173 degrees F. It didn't say, but these temp numbers are probably at sea level, so higher elevations can vaporize/boil at lower numbers due to lower air pressure. My uneducated guess is that the 10% ethanol blend commonly sold would begin to produce some ethanol vapor bubbles at the lower temp. And the gasoline portion could vaporize at the higher temp resulting in a 2-stage problem. Maybe??? I also found this blog by a Historical Military Vehicle owner that sort of has all the talking points in one place. It pretty much makes sense to me so give it a read if you have a spare 5 minutes....... https://www.militarytrader.com/mv-101/notes-from-the-field-ethanol-vapor-lock-and-other-gas-woes
This is going to sound pretty dumb, but try buying your gas from a different station with a different brand of gas. In the mid 80s I worked at a small town Mopar dealership. We ran into a streak of the mid 80s new cars that were experiencing vapor lock. At the time, Mopar was experiencing vapor lock issues with carbed mechanical fuel pump vehicles and they had a kit dealers installed replacing the mechanical pump with electric pumps and rerouted fuel lines. Even after the change over to the new pumps and lines, we were getting cars with a vapor lock systems. Testing did indeed prove there was a vapor lock situation going on, but we discovered all the troubled vehicles were buying gas at the same station. We discovered the gas from that station had the ethanol mix at more then 25% instead of the 10 % advertised. The station had the tanks flushed and the problem went away for a few months then it resurrected again, and we found the same station again had the ethanol back at the 25% range. That time the State closed the station down and new tanks were installed. I only worked there another 6 months after the station opened with the new tanks, so I don't know if the problem returned again or not. The problem you are having may be related to the station you are buying your gas at. It would be pretty easy to test that by changing stations and see if the problem goes away. Gene
Alot of the old flat head ford engines would vapor lock. My 48 ford would vapor lock. An old man put a half dozen wooden closepins on my fuel line. The wood draws the heat off the fuel line . WALAA no vapor lock
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