Help on fixing a vapor lock!!!

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SteveC124

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My 225 slant runs good when cold but it starts to putt and misfire and eventually die when it gets up to temperature. Now I’m pretty sure it’s something related to a vapor lock, if you let the motor cool it’ll run fine again. ALSO I ran the car until it died and noticed the filter was no longer full. There was almost none in it. As in almost no fuel in the plastic see through filter. I don’t think it’s an ignition problem(electronic ignition) it really seems like something with Fuel. All help is appreciated.
 
Real vapor lock is actually very rare, however, @slantsixdan has a fuel line reroute fix. I tagged him so give him some time and he will chime in.
 
Ok That seems like it might work because the line runs pretty close to the block.
 
My 225 slant runs good when cold but it starts to putt and misfire and eventually die when it gets up to temperature. Now I’m pretty sure it’s something related to a vapor lock, if you let the motor cool it’ll run fine again. ALSO I ran the car until it died and noticed the filter was no longer full. There was almost none in it. As in almost no fuel in the plastic see through filter. I don’t think it’s an ignition problem(electronic ignition) it really seems like something with Fuel. All help is appreciated.
Actually, vapor-lock usually occurs after shutting the engine off on a hot day, then after re-start it will have a "dead" period when the carb empties & the pump hasn't been able to prime. If it starts fine & runs the same, then dies out.....sounds like crap in the tank slowly covering the pick-up as You drive,....if that's clean then it may be an electrical component failing when it heats up. Exactly what are We working on,...year,ign. type etc....? BTW the fuel line re-route is a good idea no matter what so......
 
check coil and fuel pump, two items that can act up that are a pain to diagnose sometimes but will cause your issue.
 
Sounds like it could be a vacuum leak.

The choke could be keeping the engine running due to the high RPMs when cold. Once the choke opens up all the way, the engine drops down to curb idle and now the engine can't compensate for the vacuum leak and sputters out. I have a feeling it's not the actual temperature of the engine that's causing it. It's the carb coming off fast idle to curb idle and that just happens to happen when the engine reaches operating temperature.
 
do you still have the sock in the tank? If you got a compressor, open the gas cap and blow back into the fuel line from the fuel pump feed. Go slow so you dont blow the sock off the line. if there is a restriction, it could be a plugged sock. I had a truck do the same thing. Fuel pump was spent, it was a facet style electric jiggler. Cheap to replace. Would idle all day but as soon as you took off you had about 40 seconds until it died under load.
 
Too warm for carb icing as well, unless you live where its below 65 degrees and very high humidity.
Fuel filter doesent need to run full. If it was that important,all fuel filters would be clear.

Imagine a gravity fed fuel line where horizontal filter is mounted. A free flowing filter would only run 1/2 full,flowing out as fast as it flows in.
Dirty filter will restrict flow,backing up inside filter.

Water in gas could cause your symptom as well. Engine quits, water settles back to bottom of tank,engine restarts,water blocks sock in tank and engine quits.
Had a truck i found 3 gallons of water in tank. Would idle all day, shake truck and it would quit.

Also pull a couple spark plugs and see what they look like.
 
I found Dan's fuel line mod and read it. I had forgotten that he recommends trashing the hard line. I just don't recommend that. He does say to use fuel injection hose and that will certainly work, but I just don't like how running the hose over the valve cover looks. I haven't done it to mine yet, but I plan to do to my Valiant what I did on my 75 F250. I removed the fuel pump to carburetor line and covered it with 3/8" rubber hose split and put over it and fastened with zip ties. It made a difference with my truck. Rubber hose is a good insulator. This will allow you to keep the original line WHERE it is and not look out of place. Just one more way to do it.
 
Put a wooden close pin on the metal part of the fuel line as close to the carb as possible.old guy told me to.do that on my f350 it never did it again
 
Ok looks like I have some trouble shooting to do. Now with the idea of water in the tank...it is the original gas cap so that could be a cause for that.
I have no clue how a clothes pin will work but I am absolutely gonna try it lol.
And I’ll have to watch the choke on the car as idles.
 
Ok looks like I have some trouble shooting to do. Now with the idea of water in the tank...it is the original gas cap so that could be a cause for that.
I have no clue how a clothes pin will work but I am absolutely gonna try it lol.
And I’ll have to watch the choke on the car as idles.
If you are having a vapor lock the clothes pin absorbs the heat. I was kinda sceptical myself but it never did it again after I.put it on the fuel line rt at the carb
 
Wooden clothes pin serves as a heat sink, wicks heat away from the fuel in. I've seen 3 on one line. Some laugh at it, it does look goofy. Some say its a old wives tale, whatever, until they hear it does work.
I had the same fuel vapor problem ( stumble when hot ) with my 67 273. Thicker carb base gasket and rerouting fuel line which included re positioning the fuel filter, cured it. No clothes pins req'd.
 
That's not vapor lock. The best fix though for vapor lock is a three nipple metal fuel filter.
 
Fuel line mod Doesnt eliminate the major issue, the issue is the heat stove directly underneath the intake. and when you go an aluminum intake it gets even worse, what I did is I eliminated the heat flap welded it shut welded it shut and kept it from touching the bottom of the intake, if you live in colder areas you can have them touch with the top of the heat riser welded shut and will still provide a good amount of heat. My car runs way better I was able to run more timing with out ping due to the hot gas interning my chambers. Constant 22mpg and that passing cars, but the 3 nipple filter does Help a lot.
 

I agree 100% about the return filter. They are a great idea. Anything you can do to reduce the fuel temperature helps and keeping it recirculating certainly helps that. Says the professional typist.
 
I'll just bet your pump is sucking air, or the tank is not venting.
Sucking air is usually because the jumper-hose at the back is perforated; the hose that connects the sender to the hardline.
Some cars use the charcoal line for venting, which eventually rusts up solid.
So try again with the cap cracked. If the problem persists, do a fuelpump delivery test. With the engine warmed up and idling slow as per normal, reroute the fuel line to a clear plastic container;the car will run a minute or two with the gas that is in a full bowl.If you see bubbles in the line,check/ replace the jumper hose. If you have to use gearclamps, install 2 on each side with screw-heads staggered 180*.
If you still have a problem;I'll bet the pump is lazy cuz the arm return-spring is gone weak or just gone. If it is lazy, fill the carb again and this time run it at ~500 rpm for 1 minute. The pump should deliver 1quart when new.
For a lo-perf slanty I wouldn't throw it away until it gets to half that..... unless it is lazy; in which case just pull it off and check the spring and the arm.
 
I'll just bet your pump is sucking air, or the tank is not venting.
Sucking air is usually because the jumper-hose at the back is perforated; the hose that connects the sender to the hardline.
Some cars use the charcoal line for venting, which eventually rusts up solid.
So try again with the cap cracked. If the problem persists, check/ replace the jumper hose. If yo have to use gearclamps, install 2 on each side with screw-heads staggered 180*.
If you still have a problem; do a fuelpump delivery test. With the engine warmed up and idling slow as per normal, reroute the fuel line to a clear plastic container;the car will run a minute or two with the gas that is in a full bowl. I'll bet the pump is lazy cuz the arm return-spring is gone weak or just gone. If it is lazy, fill the carb again and this time run it at ~500 rpm for 1 minute. The pump should deliver 1quart when new.
For a lo-perf slanty I wouldn't throw it away until it gets to half that..... unless it is lazy; in which case just pull it off and check the spring and the arm.

Yellow Rose told me you know all about suckin. lol
 
Do the Fuel line mod. Make sure your manifold heat control valve is intact, free, and working. Make sure you have the correct thick insulator gasket between the carb and the intake manifold. Make sure your carb is in good condition with a float that hasn't taken on gasoline. The Daytona Float Valve is just a rename of the "Duro-7" inlet needle/seat that used to come with Tomco carb kits, but whatever we call it, it's an improvement—don't know if they have them for the Holley carb I have to guess you have (no year or carb info specified in your question).

Better ignition helps a lot with bitchy drivability issues like this, too; do the HEI upgrade and pay attention to the tune-up parts and technique suggestions in this post.

More broadly: mind the difference between vapour lock and percolation. Vapour lock is when a persistent vapour bubble develops in the fuel line in such a way that liquid fuel can't reach the carburetor. Percolation is when fuel boils in the line and/or carburetor, forcing its way out of the carb bowl and into the throat, flooding the engine.
Most of what people call "vapour lock" is actually percolation.
 
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