• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Vapor lock / hard restart

DownZero

DownZero

Well-Known Member
Local time
8:41 PM
Joined
Nov 24, 2019
Messages
106
Reaction score
196
Location
Maryland
Think I have the dreaded vapor lock problem. Hard to restart when hot. The most effective remedy that I've seen is to install a fuel filter with a vapor return line. Question I have is did a 69 charger come factory with a return line to the tank? If not what would be the best way to install one?
 
I don’t think it’s hot enough yet in MD yet for vapor lock.

We’ve lost touch with carbs with our modern cars IMO. I have 5 cars with carbs, Quadrajet, 2 Thermoquad, AFB and one AVS aftermarket. All are tuned and adjusted properly and in good working order. All chokes set correctly too.

Every single one has its own ‘touch’. From cold start to hot restart, all need something a bit different.

It might help if you walk us through what you do with your foot when it’s hot and how long from shutting off to re-fire. I have two cars that I need to slightly open the throttle when I restart hot. If I don’t they won’t start right up. Others I can hit the key with no throttle and they fire right up.

I may have better gas in PA but I run 93 out of pump on everything and I’ve not had any rapid evap, boiling or vapor lock issues. All but one car is single fuel line.
 
DownZero said:
Think I have the dreaded vapor lock problem. Hard to restart when hot. The most effective remedy that I've seen is to install a fuel filter with a vapor return line. Question I have is did a 69 charger come factory with a return line to the tank? If not what would be the best way to install one?
Click to expand...
Check a few things out first -
  1. Is the fuel cap the correct type - Pressure/Vacuum
  2. Are the breather tubes at the front of the fuel tank clear? Might need to blow air through them to check
  3. Is the Fuel Pump Push Rod actually in good condition? These rods do wear out, and will cause a similar symptom.
And then eventually look at carb tuning, phenolic spacers under the carb (heat soak) and maybe then the fuel pump itself.

If the car never had a breather line, and nothing much has changed, installing a breather line will not be the answer.
 
Pretty sure 69 cars with a 440 had a line going back to the tank; I used to run a charcoal vapor separator that did as much. I also remember the sending unit for 440 cars had a port for a return line.

Get a wood or phenolic carb spacer at least a 1/2" thick. A little more drastic, I'm also running an electric fuel pump so even on hot days with no spacer the car would start...
 
If you have access to ethanol free gas I would start there. Is your coolant temp where you like it? I also agree with Kiwi on the carb spacer. I'm using a 2-ply 60123 base gasket instead of the thin paper type.
 
And I believe blocks my the heat Crossover, or at least drilling a 1/4 hole in the blocker will help?
 
DownZero said:
Think I have the dreaded vapor lock problem. Hard to restart when hot. The most effective remedy that I've seen is to install a fuel filter with a vapor return line. Question I have is did a 69 charger come factory with a return line to the tank? If not what would be the best way to install one?
Click to expand...

I'm actually about to install a factory style upgrade on my Super Bee.

From the factory my car is originally a 5/16" feed. I'm upgrading to 3/8" with the 1/4" return line. Fuel sending unit, pump, reproduction vapor separator and reproduction fuel filter were all purchased through Mancini. I was lucky enough to find my fuel lines on this site.
 
I thought I had a vapor lock issue for a while, I installed insulation around the fuel lines and installed a insulator plate under my carb. Nothing seemed to help then my engine builder called me and told me he figured out the problem. The fuel pump push rod on my new fuel pump was a new style, it was hollow with end caps that would fall off the push rod. He went on to explain the push rods used to be solid metal, but apparently the manufacturer switched to hollow push rods with end caps, the end caps had a tendency to fall off the push rod. He discovered this issue with a Road Runner that was having vapor lock like issues similar to me. Since he discovered the issue, he replaces the hollow push rods with old remilled solid metal push rods, no more vapor lock type issues.
 
66plysat said:
I thought I had a vapor lock issue for a while, I installed insulation around the fuel lines and installed a insulator plate under my carb. Nothing seemed to help then my engine builder called me and told me he figured out the problem. The fuel pump push rod on my new fuel pump was a new style, it was hollow with end caps that would fall off the push rod. He went on to explain the push rods used to be solid metal, but apparently the manufacturer switched to hollow push rods with end caps, the end caps had a tendency to fall off the push rod. He discovered this issue with a Road Runner that was having vapor lock like issues similar to me. Since he discovered the issue, he replaces the hollow push rods with old remilled solid metal push rods, no more vapor lock type issues.
Click to expand...
Do they still make the solid ones?
 
Are you sure it is vapor lock? I was running a 190° stat with no shroud and would run 200°+. It once got to 230° in a traffic jam and still never vapor locked.
Are you sure the choke is adjusted properly?

P.S.
A 180° stat and shroud solved the temp problem.


69L48Z27 said:
Every single one has its own ‘touch’. From cold start to hot restart, all need something a bit different.

It might help if you walk us through what you do with your foot when it’s hot and how long from shutting off to re-fire. I have two cars that I need to slightly open the throttle when I restart hot. If I don’t they won’t start right up. Others I can hit the key with no throttle and they fire right up.
Click to expand...
I agree. Mine is a bit finicky on a hot or warm start. Sometimes I get it just right, sometimes I don't.
 
It actually runs cool. I'm assuming vapor lock because a hot restart is difficult. I'll have to crank on her 6 or 7 times and pump the accelerator. It's a 383 with a 4bbl eldebrock. Just wondering if heat tape on the fuel line will help.
 
DownZero said:
It actually runs cool. I'm assuming vapor lock because a hot restart is difficult. I'll have to crank on her 6 or 7 times and pump the accelerator. It's a 383 with a 4bbl eldebrock. Just wondering if heat tape on the fuel line will help.
Click to expand...
What is your timing set at with vac adv plugged? What type of ignition system are you running? Are plugs the correct heat range for your engine, and in good condition? Is the choke fully open hot? Can you verify the amount of fuel in the bowls after it's been running? Lots of variables.
Edit: Do you have any indications of blowby? (Oil being pushed out of vc breather)
 
Last edited:
DownZero said:
It actually runs cool. I'm assuming vapor lock because a hot restart is difficult. I'll have to crank on her 6 or 7 times and pump the accelerator. It's a 383 with a 4bbl eldebrock. Just wondering if heat tape on the fuel line will help.
Click to expand...
Before I changed the stat and added the shroud (same engine and carb as you have), I could hear the fuel percolating after shut down (but no vapor lock). The stat and the shroud solved that for me.

If you are pumping the accelerator on a hot start, you might be flooding it. Have you tried simply cranking with no accelerator input? If that doesn't work, maybe try cranking it with the pedal to the floor (no pumping). As 69L48Z27 said, you might just have to find the right technique. They can be finicky *******.
 
Engine runs cool with no shroud. Cranking with no pedal input doesn't work. Haven't tried putting it all the way to the floor yet. Ambient temp has no affect. It happens weather it's 70° or 50°.
 
Ignition points or electronic?
Gear reduction starter, original?
 
I've been watching this thread; my car has never vapor locked and runs great on a 104 degree day. Even idling in drive and seeing the temp gauge climb to 200F I do not have any driveability issues. However, I do have the extended crank when hot. It is not flooding, and I can do no gas, 1/4, 1/2, 3/4 pedal, a few pumps, whatever and it is a 10-20 second crank, or another 10-20 second crank hot to get it started.
Edlebrock 1406 with paper gasket, Edlebrock intake, 180 thermostat, shroud, and my fuel pressure is between 5 and 7 psi. So I'd like to hear more comments and possibilities on the extended crank when hot.
BTW "hot" is when I shut it off and ambient > 95F and it heat soaks >220F for a brief shut down.
 
Billccm said:
I've been watching this thread; my car has never vapor locked and runs great on a 104 degree day. Even idling in drive and seeing the temp gauge climb to 200F I do not have any driveability issues. However, I do have the extended crank when hot. It is not flooding, and I can do no gas, 1/4, 1/2, 3/4 pedal, a few pumps, whatever and it is a 10-20 second crank, or another 10-20 second crank hot to get it started.
Edlebrock 1406 with paper gasket, Edlebrock intake, 180 thermostat, shroud, and my fuel pressure is between 5 and 7 psi. So I'd like to hear more comments and possibilities on the extended crank when hot.
BTW "hot" is when I shut it off and ambient > 95F and it heat soaks >220F for a brief shut down.
Click to expand...
Try the 9266 edelbrock base gasket
 
You must log in or register to reply here.

Similar threads

Rob'68Net
Vapor Return lines
Replies
10
Views
550
68 Sport Satellite
68 Sport Satellite
70b5bluerunner
69 Coronet R/T fuel pump
Replies
12
Views
481
turbine68rt
turbine68rt
S
69 383 roadrunner fuel problem's
Replies
5
Views
855
PlymCrazy
PlymCrazy
J
72 Charger 318 fuel return line and/or fuel vapor line?
Replies
8
Views
1K
Bee1971
Bee1971
GTXDAN
Fuel line inst at tank on 70 GTX
Replies
2
Views
379
GTXDAN
GTXDAN
Auto Transport Service
Back
Top