Symtoms and cures for vapor lock - The 1947 - Present Chevrolet & GMC Truck Message Board Network

crm318 · 10-28-2010, 01:53 AM

I have noticed lately that when my truck gets hot from highway driving or even in town driving, the truck will have a low idle and sound like its going to die. It also sometimes wont start if it has been sitting and I have to use starter fluid. When this happens, gas is still squirting from the accelerator pump though. Tonight on the freeway, when ever I came to a stop, I had to keep my foot on the gas and brake to keep the truck alive. I also noticed that the clear fuel filter was empty and only little burps of fuel was going through it (I couldnt believe the truck was still running). The fuel pump is new. Could this be vapor lock? What are ways to cure this?

shiner2001 · 10-28-2010, 02:35 AM

If it is indeed vapor lock, a phenolic carb spacer can help some with that.

shiner2001 · 10-28-2010, 02:40 AM

Ha, crm318, just noticed your avatar...the donor car for my engine was a "Melba Toast," 70 Chevelle SS. I think the one in the movie might have been an LS5, but I still get a kick outta having that connection.

cdowns · 10-28-2010, 05:39 AM

do you get a pressure buildup in your gastank? wwhen this happens try taking the gascap off , if you hear a whooshing sound that means you have a venting problem from not having the tank vented

many times with old vehicles there can be alot of crap in the tank. it is not unusual for the sock strainer on the pickup tube in the gastank to be clogged with gunk and crap

cam.man67 · 10-28-2010, 07:16 AM

Quote:

Originally Posted by shiner2001

Ha, crm318, just noticed your avatar...the donor car for my engine was a "Melba Toast," 70 Chevelle SS. I think the one in the movie might have been an LS5, but I still get a kick outta having that connection.

allright allright allright! I LOVE that movie!

And yes, Wooderson's Chevelle was an LS5.

jcis4me · 10-28-2010, 12:21 PM

Aloha
"Man I love them red heads!"

Mine did the same thing I replaced and re routed the fuel line away from the headers and mounted the fuel pump on the out side of the frame rail, still was getting air in the fuel filter, put on new lines from the tank but still had the problem, so I changed the fuel pump and the problem went away, now I know you said you even put on a new pump , so I would check the fuel lines from the tank making sure they are all tight.
My buck 2.98's worth!
Aloha
Marty
PS btw our fuels now have alcohol in em and it evaporates faster than gas, I have heard here in Hawaii they want to add more alcohol to the gas! costs to much to import oil here I guess,

crm318 · 10-28-2010, 02:11 PM

I just had the had the tank out the other day to empty and clean it. The sender was clean and I removed the sock a while back. I will check the cap the next time it happens.

BADPURPLE70CHEVY · 10-28-2010, 03:13 PM

Had the same problem on a 68 once. Got a locking gas cap and it solved it. The locking cap seems to let the vapors escape better...just a thought

kevmic28 · 10-28-2010, 03:23 PM

What carb do you have? I have been dealing with this problem for a while now.
New tank, new lines, new fuel pump, new fuel filter and still there. The only thing I can figure is that my rochester carb float is sticking a occassionally or the choke. Its an intermittant problem. The only thing I can think it is my carb. Gonna replace it when I have the cash for an Edlebrock I think.

vincentgkirkland · 10-29-2010, 09:36 PM

i pressurerd my tank with air and found my fuel line had a cracks in it and was sucking together and causing vapor loc replaced line and problem solved.

crm318 · 10-30-2010, 02:57 PM

I have a quadrajet. Ill inspect the fuel lines.

STOCKISH · 10-30-2010, 03:04 PM

Might sound crazy, but you can put a few wooden clothespins on the metal fuel line by the carb to act as a heat sink. Of course for a long time fix it would look pretty silly but if it cures your problem at least you know for sure it was vapor lock!

Little Red · 10-30-2010, 05:27 PM

Quote:

Originally Posted by BADPURPLE70CHEVY

Had the same problem on a 68 once. Got a locking gas cap and it solved it. The locking cap seems to let the vapors escape better...just a thought

I agree, A bad gas cap can definately cause vapor lock. Back in the 80's, I had a 77 Ford with the tank behind the seat and it would vapor lock on the freeway all the time. Used to reach out the window and pull out on the cap to release the pressure. Too lazy to buy a new cap back then.

I have a locking gas cap on my 69

kevmic28 · 10-30-2010, 05:41 PM

Quote:

Originally Posted by crm318

I have a quadrajet. Ill inspect the fuel lines.

Yep same carb as me. Im betting its the carb, at least for my issues. When mine bogs down and tries to die it I have a lot of smoke coming out only the drivers side exhaust pipe.

kevmic28 · 11-06-2010, 10:13 AM

So CRM318 did you fix your problem yet?

crm318 · 11-08-2010, 02:17 AM

Not yet Kevmic28. The other night I was stranded in a parking lot for 20 min while my truck cooled off. I notice that if I used starting fluid (which I didnt have on me), it will usually crank up.

76 gmc k15 · 05-05-2017, 12:45 PM

My dad has a 86 c10 with the 305 in it and it always vapor locked on us after shutting it off. I ended up cutting the metal line from the pump to the carb and replaced it with a rubber fuel line and moved it away from the engine as much as possible. Solved the problem. The factory fuel line was in-between the bock and water pump. It got so hot I couldn't even touch it with out getting burned. now I just have to fix the evaporation from the fuel bowls so we don't have to spend 15 mins to get gas to the carb every time. Thinking about putting in a 1 way valve.I'm only 18 btw.

1976 gmc k15-86 chevy c10-1994 chevy s10-03 chevy duramax 2500-05 Buick lacross

10-28-2010, 01:53 AM	#1
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Symtoms and cures for vapor lock I have noticed lately that when my truck gets hot from highway driving or even in town driving, the truck will have a low idle and sound like its going to die. It also sometimes wont start if it has been sitting and I have to use starter fluid. When this happens, gas is still squirting from the accelerator pump though. Tonight on the freeway, when ever I came to a stop, I had to keep my foot on the gas and brake to keep the truck alive. I also noticed that the clear fuel filter was empty and only little burps of fuel was going through it (I couldnt believe the truck was still running). The fuel pump is new. Could this be vapor lock? What are ways to cure this? __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies Last edited by crm318; 10-28-2010 at 01:55 AM.

10-28-2010, 02:35 AM	#2
shiner2001 Registered User Join Date: Sep 2010 Location: Fort Worth, TX Posts: 222	Re: Symtoms and cures for vapor lock If it is indeed vapor lock, a phenolic carb spacer can help some with that. __________________ Derek 72 Chevy Cheyenne Super LWB 454 SS LS6 90 GMC Suburban V2500 350 ----------- 64 Chevy El Camino 357 73 Jeep Wagoneer 360 78 Jeep Cherokee 360 79 Scout II 345 88 Jeep Wrangler 4.2L 91 Jeep Wrangler 4.3L 98 Lincoln Mark VIII 4.6L 01 GMC Yukon 5.3L *"If it's not broken, fix it 'till it is!"*

10-28-2010, 02:40 AM	#3
shiner2001 Registered User Join Date: Sep 2010 Location: Fort Worth, TX Posts: 222	Re: Symtoms and cures for vapor lock Ha, crm318, just noticed your avatar...the donor car for my engine was a "Melba Toast," 70 Chevelle SS. I think the one in the movie might have been an LS5, but I still get a kick outta having that connection. __________________ Derek 72 Chevy Cheyenne Super LWB 454 SS LS6 90 GMC Suburban V2500 350 ----------- 64 Chevy El Camino 357 73 Jeep Wagoneer 360 78 Jeep Cherokee 360 79 Scout II 345 88 Jeep Wrangler 4.2L 91 Jeep Wrangler 4.3L 98 Lincoln Mark VIII 4.6L 01 GMC Yukon 5.3L *"If it's not broken, fix it 'till it is!"*

10-28-2010, 05:39 AM	#4
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Symtoms and cures for vapor lock do you get a pressure buildup in your gastank? wwhen this happens try taking the gascap off , if you hear a whooshing sound that means you have a venting problem from not having the tank vented many times with old vehicles there can be alot of crap in the tank. it is not unusual for the sock strainer on the pickup tube in the gastank to be clogged with gunk and crap __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

10-28-2010, 12:21 PM	#6
jcis4me Registered User Join Date: Aug 2010 Location: Jersey shore Posts: 115	Re: Symtoms and cures for vapor lock Aloha "Man I love them red heads!" Mine did the same thing I replaced and re routed the fuel line away from the headers and mounted the fuel pump on the out side of the frame rail, still was getting air in the fuel filter, put on new lines from the tank but still had the problem, so I changed the fuel pump and the problem went away, now I know you said you even put on a new pump , so I would check the fuel lines from the tank making sure they are all tight. My buck 2.98's worth! Aloha Marty PS btw our fuels now have alcohol in em and it evaporates faster than gas, I have heard here in Hawaii they want to add more alcohol to the gas! costs to much to import oil here I guess, Last edited by jcis4me; 10-28-2010 at 12:24 PM.

10-28-2010, 02:11 PM	#7
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Re: Symtoms and cures for vapor lock I just had the had the tank out the other day to empty and clean it. The sender was clean and I removed the sock a while back. I will check the cap the next time it happens. __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies

10-28-2010, 03:13 PM	#8
BADPURPLE70CHEVY 406 Powered Join Date: Aug 2009 Location: waynesville,n.c. Posts: 877	Re: Symtoms and cures for vapor lock Had the same problem on a 68 once. Got a locking gas cap and it solved it. The locking cap seems to let the vapors escape better...just a thought __________________ 70 GMC 68 c10 2002 silverado 72 4x4

10-28-2010, 03:23 PM	#9
kevmic28 Registered User Join Date: Jun 2009 Location: Arlington Texas Posts: 602	Re: Symtoms and cures for vapor lock What carb do you have? I have been dealing with this problem for a while now. New tank, new lines, new fuel pump, new fuel filter and still there. The only thing I can figure is that my rochester carb float is sticking a occassionally or the choke. Its an intermittant problem. The only thing I can think it is my carb. Gonna replace it when I have the cash for an Edlebrock I think. __________________ 1970 GMC truck 1988 Harley 1200 Sportster

10-29-2010, 09:36 PM	#10
vincentgkirkland Registered User Join Date: Mar 2010 Location: lucedale Posts: 49	Re: Symtoms and cures for vapor lock i pressurerd my tank with air and found my fuel line had a cracks in it and was sucking together and causing vapor loc replaced line and problem solved.

10-30-2010, 02:57 PM	#11
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Re: Symtoms and cures for vapor lock I have a quadrajet. Ill inspect the fuel lines. __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies

10-30-2010, 03:04 PM	#12
STOCKISH Formerly- 1972SuperCheyenne Join Date: Oct 2008 Location: Wake Forest NC Posts: 5,782	Re: Symtoms and cures for vapor lock Might sound crazy, but you can put a few wooden clothespins on the metal fuel line by the carb to act as a heat sink. Of course for a long time fix it would look pretty silly but if it cures your problem at least you know for sure it was vapor lock! __________________ --Josh My Build Thread:http://67-72chevytrucks.com/vboard/s...d.php?t=799218 A good crossthread is better than Loctite any day. Life is not about what you have, but who you have to share it with.

11-06-2010, 10:13 AM	#15
kevmic28 Registered User Join Date: Jun 2009 Location: Arlington Texas Posts: 602	Re: Symtoms and cures for vapor lock So CRM318 did you fix your problem yet? __________________ 1970 GMC truck 1988 Harley 1200 Sportster

11-08-2010, 02:17 AM	#16
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Re: Symtoms and cures for vapor lock Not yet Kevmic28. The other night I was stranded in a parking lot for 20 min while my truck cooled off. I notice that if I used starting fluid (which I didnt have on me), it will usually crank up. __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies

05-05-2017, 12:45 PM	#17
76 gmc k15 Registered User Join Date: May 2017 Location: alamosa, colorado Posts: 1	Re: Symtoms and cures for vapor lock My dad has a 86 c10 with the 305 in it and it always vapor locked on us after shutting it off. I ended up cutting the metal line from the pump to the carb and replaced it with a rubber fuel line and moved it away from the engine as much as possible. Solved the problem. The factory fuel line was in-between the bock and water pump. It got so hot I couldn't even touch it with out getting burned. now I just have to fix the evaporation from the fuel bowls so we don't have to spend 15 mins to get gas to the carb every time. Thinking about putting in a 1 way valve.I'm only 18 btw. 1976 gmc k15-86 chevy c10-1994 chevy s10-03 chevy duramax 2500-05 Buick lacross



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