Vapor/Vacuum Lock??

[sunbee1224]

66 Belvedere, 383, 4 speed, Holley 750 double pumper.
My issue....awhile back, 6 weeks or so, I fueled up forgot to put gas cap back on and noticed it when I heard it rolling on the road. Went around the block, parked let the car run grabbed the gas cap off the road and put it back on. When pulling away from parking spot car ran like total crap. Stumbling all over itself to the point it would die. Was able to get it going after awhile and drove the 10 miles home with no issues. Fast forward to a month ago. Again, stopped for fuel and took off. Car was running fine until 15 miles later. Car again died and started stumbling all over itself. This time was not able to get it going so I had to get a tow. Couple days later when I was able to look at it, hit the key and started right up. Last week Sunday, fueled up again, left gas station made it about 1/2 mile and it died. Once again stumbling all over itself. Pulled air cleaner hit the throttle and gas was shooting in carb no problem. Was able to get it going and drove the 25 miles home. Car ran great!!! Seems to me I'm having a vacuum/vapor lock of some sort after getting gas. Car has new tank, fuel lines, fuel pump and the fuel filter is nice and clean. My fuel line is routed well away from heat sources. Like I said, in between these issues the car is running great. Let me know what you all think I should be looking for. Thanks

 

[mopar 3 B]

All from the same gas station? Same weather conditions?

 

[WileERobby]

Do you have a vent line ? Are you using a vented or non-vented gas cap ?

 

[twecomm]

Was everything good before the first instance of this happening the 6 weeks ago with the gas cap thing ? When was all the fuel system work done you describe ? You may have a worn fuel pump push rod. Many years ago I had all kinds of fuel delivery issues on a 383 similar to what you describe but not related to anything with filling up or gas cap. My push rod was worn down by 3/8" ! Just enough rod remaining to slightly stroke the pump lever. Might be fine one minute and many miles and just crap out like you describe. Easy to replace. about $ 35.00.

 

[sunbee1224]

All from the same gas station? Same weather conditions?

Two different stations. I would say weather was very similar all three times. 80 degrees lower humidity.

 

[sunbee1224]

Do you have a vent line ? Are you using a vented or non-vented gas cap ?

Vent lines are whatever the stock set up was for 66. Filler tube etc... non-vented gas cap

 

[WileERobby]

Make sure any vent tube is not clogged/blocked you may be trapping air

 

[sunbee1224]

Was everything good before the first instance of this happening the 6 weeks ago with the gas cap thing ? When was all the fuel system work done you describe ? You may have a worn fuel pump push rod. Many years ago I had all kinds of fuel delivery issues on a 383 similar to what you describe but not related to anything with filling up or gas cap. My push rod was worn down by 3/8" ! Just enough rod remaining to slightly stroke the pump lever. Might be fine one minute and many miles and just crap out like you describe. Easy to replace. about $ 35.00.

Was everything good before the first instance of this happening the 6 weeks ago with the gas cap thing ? When was all the fuel system work done you describe ? You may have a worn fuel pump push rod. Many years ago I had all kinds of fuel delivery issues on a 383 similar to what you describe but not related to anything with filling up or gas cap. My push rod was worn down by 3/8" ! Just enough rod remaining to slightly stroke the pump lever. Might be fine one minute and many miles and just crap out like you describe. Easy to replace. about $ 35.00.

Was everything good before the first instance of this happening the 6 weeks ago with the gas cap thing ? When was all the fuel system work done you describe ? You may have a worn fuel pump push rod. Many years ago I had all kinds of fuel delivery issues on a 383 similar to what you describe but not related to anything with filling up or gas cap. My push rod was worn down by 3/8" ! Just enough rod remaining to slightly stroke the pump lever. Might be fine one minute and many miles and just crap out like you describe. Easy to replace. about $ 35.00.

Yes, everything was fine 6 weeks ago. All mentioned fuel system work was done early 2016.

 

[mopar 3 B]

So your still useing the original factory vented cap? Just about all Chrysler fuel tanks used a vented cap untill 72 with the exception of California cars.
A non-vented cap on a systems with vented requirements will soon create havick and possibly a collapsed fuel tank.
Check your cap over real well. It possible some damage occurred.
The cap on your car is quite different, hard to replace and easly damaged. Not something you want to toss across the roadway.

 

[sunbee1224]

Dont worry. The cap is not the original 66 only cap. I refuse to pay $500 for a gas cap. The cap on it is a Stant g28. I believe it is non-vented. So I guess I will try to find a replacement vented cap. Pic is current cap I'm using.

 

[mopar 3 B]

Dont worry. The cap is not the original 66 only cap. I refuse to pay $500 for a gas cap. The cap on it is a Stant g28. I believe it is non-vented. So I guess I will try to find a replacement vented cap. Pic is current cap I'm using.

View attachment 502961

Yea but that original was a beauty and now you have non-matching quarters.

 

[sunbee1224]

There are some things that I will dish out the money for. A gas cap is not one of those things. Car looks good without!

 

[mopar 3 B]

There are some things that I will dish out the money for. A gas cap is not one of those things. Car looks good without!

Unfortunately I understand that one.

 

[451Mopar]

#1 - make sure the tank is venting
#2 - gas these days boils much easier than when these cars were built.

Adding a return line from near the carb back to the tank works great in fixing vapor-lock.

 

[mopar 3 B]

#1 - make sure the tank is venting
#2 - gas these days boils much easier than when these cars were built.

Adding a return line from near the carb back to the tank works great in fixing vapor-lock.

Would require removing the tank sending unit and tapping in a return line. Will not hurt anything but may make no difference. He said car was doing fine before the gas cap ordeal.

 

[Ranger16]

Just about all Chrysler fuel tanks used a vented cap untill 72 with the exception of California cars.

My '69 Road Runner has the original cap, non-vented. Tank vent comes up through the trunk and back out the bottom. (upper right hand corner)

 

[mopar 3 B]

I know for a fact his Belev vents threw the filler neck and has a vented cap if it is still of factory configuration. Doesn't matter how any other models vent.