Is this vaporlock or what? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Syco67 · 12-05-2004, 11:02 AM

69 GMC 3/4 2wd, 350-4bbl/4spd. In the begining the the truck would hesitate, after sitting in traffic too long. We figured vaporlock. We have added a spacer, replaced the carb,(edelbrock 600) replaced and rerouted the fuel line, replaced all the filters, pump is new, fuel pressure was excellent, adjusted points/timing/dwell, even took apart the new carb to verify it was clean. The truck never overheats, gauge has never even gone halfway up. Nothing has changed. If you run the truck for a while and shut it down, and let it sit for a few minutes, it is almost impossible to restart, and when you give it gas, you can hear it just sucking air. It sounds like it's not getting gas. Have I missed anything?

Gordo · 12-05-2004, 10:01 PM

Sounds like it's flooding, what is excellant fuel pressure? Maybe it's too much pressure and it's pushing fuel passed the needle and seat.

Cat Fuzz · 12-05-2004, 10:15 PM

Float level adjusted properly? Maybe you need a heat shield in addition to the spacer.

chickenwing · 12-05-2004, 11:37 PM

Think Gordo is hitting on it with the fuel pressure. Edelbrock recommends 5.5psi with no more than 6psi.

Syco67 · 12-06-2004, 11:01 AM

Fuel pressure was 8psi. But it is a stock replacement pump. Wouldn't the engine bog if it was flooding? It's not blowing black smoke or anything. It makes a dry sucking sound when you hit the throttle.

Carb floats were fine too.

Cat Fuzz · 12-06-2004, 11:52 AM

Try adjusting the accelerator pump. You might have two different problems.

Syco67 · 12-24-2004, 12:26 PM

Do you think I should get a pressure regulator? Set to 5psi? Where should I set the accelerator pump? It has 3 settings, it was on the middle setting, but I put the rod in the hole closest to the carb, that would result in more gas right? Sorry about all the questions, I can disassemble and reassemble almost anything, but can't adjust anything to save my own life.

**tnblazerk5** · 12-24-2004, 12:34 PM

wait just a min if its doing this

HTML Code:

It makes a dry sucking sound when you hit the throttle

it might be a vacume leak sumwhere

Syco67 · 12-24-2004, 12:38 PM

The sound is coming from the carb, but I did do the carb cleaner test to be safe and found no leaks.

**tnblazerk5** · 12-24-2004, 12:39 PM

did ya check around the intake too? and all the hoses ?

Syco67 · 12-24-2004, 12:42 PM

yeah, couldn't find a leak, but the engine is a lot cleaner.

**tnblazerk5** · 12-24-2004, 12:46 PM

clean hehehe is good

ok if ya think its not getting enough gas start lookin at the gas lines themselfs, once mine had a bad clamp but it didnt leak gas out it leaked air in ( it sucked air in around the hose )it would run good most the time and then all at once would die and it was a mother to get started back

Syco67 · 12-24-2004, 12:54 PM

I will take a look at that, with 3 tanks, there are plenty of hoses and clamps to go bad. May as well replace all the rubber under there anyhow.

Longhorn Man · 12-24-2004, 01:25 PM

The odds of havin vapor lock in you location at this time of year is pretty much nill.
have you messed with the fuel to air ratio at all

72MARIO · 12-24-2004, 02:00 PM

[/QUOTE]Where should I set the accelerator pump? It has 3 settings, it was on the middle setting, but I put the rod in the hole closest to the carb, that would result in more gas right?[QUOTE]

The hole closest to the carb would give it the smallest squrit. Because there is not as much travel. By putting the rod in the whole at the other end you would get the biggiest squirt. If you know you have 8 Psi thats way too much and it needs fule pressure to be set at 5 Psi.

Maximum Overdrive · 12-24-2004, 05:57 PM

How is the choke. I had one that would screw up after running for a while and make it hard to restart.

flip66 · 12-24-2004, 06:29 PM

just want to watch this tread

Syco67 · 12-26-2004, 12:47 AM

I know the temp is too cold, and I haven't had any problems, but I am sure it will come back next summer, and am trying to check everything I can to hopefully fix it by then. I just won't know what worked until then. Had another problem yesterday, had a radiator tube blow out and hose me with coolant after I replaced the pump. Now I need to spend $300 on a new 4 row radiator.

I will reset the accelerator pump, and get a fp regulator as soon as I can.

Huck · 12-26-2004, 10:14 AM

For your radiator--go on-line. There are several places that will sell you a 4 core for a lot less then $300. delivered to your door with a lifetime warranty.

I had hard starting / stalling problems on my 71. Replaced the HEI distributor module and condenser and the problem went away. Would only happen when the truck was good and warm or very damp out.

If the truck seems like it is starving for gas, take the air cleaner off and look down the carb (not running!!!). Now pull the accelerator and see it you get the "squert" more then likely, that's not the problem. That would only apply to acceleration---not idle. I tend to go with GORDO on most things as he seems to forget more then I know!hehehehe

12-05-2004, 11:02 AM	#1
Syco67 Registered User Join Date: Jan 2004 Location: Boise Posts: 64	Is this vaporlock or what? 69 GMC 3/4 2wd, 350-4bbl/4spd. In the begining the the truck would hesitate, after sitting in traffic too long. We figured vaporlock. We have added a spacer, replaced the carb,(edelbrock 600) replaced and rerouted the fuel line, replaced all the filters, pump is new, fuel pressure was excellent, adjusted points/timing/dwell, even took apart the new carb to verify it was clean. The truck never overheats, gauge has never even gone halfway up. Nothing has changed. If you run the truck for a while and shut it down, and let it sit for a few minutes, it is almost impossible to restart, and when you give it gas, you can hear it just sucking air. It sounds like it's not getting gas. Have I missed anything? __________________ If at first you don't succed, break something!

12-05-2004, 10:01 PM	#2
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	Sounds like it's flooding, what is excellant fuel pressure? Maybe it's too much pressure and it's pushing fuel passed the needle and seat. __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

12-05-2004, 11:37 PM	#4
chickenwing Lovin' Life in Miss.! Join Date: Mar 2004 Location: Puckett, Mississippi Posts: 1,937	Think Gordo is hitting on it with the fuel pressure. Edelbrock recommends 5.5psi with no more than 6psi. __________________ The truck... you hear that? No really, you did hear that?!!!

12-06-2004, 11:01 AM	#5
Syco67 Registered User Join Date: Jan 2004 Location: Boise Posts: 64	Fuel pressure was 8psi. But it is a stock replacement pump. Wouldn't the engine bog if it was flooding? It's not blowing black smoke or anything. It makes a dry sucking sound when you hit the throttle. Carb floats were fine too. __________________ If at first you don't succed, break something!

12-24-2004, 12:26 PM	#7
Syco67 Registered User Join Date: Jan 2004 Location: Boise Posts: 64	Do you think I should get a pressure regulator? Set to 5psi? Where should I set the accelerator pump? It has 3 settings, it was on the middle setting, but I put the rod in the hole closest to the carb, that would result in more gas right? Sorry about all the questions, I can disassemble and reassemble almost anything, but can't adjust anything to save my own life. __________________ If at first you don't succed, break something!

12-05-2004, 10:15 PM	#3
Cat Fuzz My son, my joy. Join Date: Sep 2003 Location: Spokane WA Posts: 463	Float level adjusted properly? Maybe you need a heat shield in addition to the spacer.

12-06-2004, 11:52 AM	#6
Cat Fuzz My son, my joy. Join Date: Sep 2003 Location: Spokane WA Posts: 463	Try adjusting the accelerator pump. You might have two different problems.

12-24-2004, 12:34 PM	#8
tnblazerk5 User #12137 Join Date: Apr 2004 Location: kingsport,upper east tenn Posts: 11,598	wait just a min if its doing this HTML Code: It makes a dry sucking sound when you hit the throttle it might be a vacume leak sumwhere

12-24-2004, 12:38 PM	#9
Syco67 Registered User Join Date: Jan 2004 Location: Boise Posts: 64	The sound is coming from the carb, but I did do the carb cleaner test to be safe and found no leaks. __________________ If at first you don't succed, break something!

12-24-2004, 12:39 PM	#10
tnblazerk5 User #12137 Join Date: Apr 2004 Location: kingsport,upper east tenn Posts: 11,598	did ya check around the intake too? and all the hoses ?

12-24-2004, 12:42 PM	#11
Syco67 Registered User Join Date: Jan 2004 Location: Boise Posts: 64	yeah, couldn't find a leak, but the engine is a lot cleaner. __________________ If at first you don't succed, break something!

12-24-2004, 12:46 PM	#12
tnblazerk5 User #12137 Join Date: Apr 2004 Location: kingsport,upper east tenn Posts: 11,598	clean hehehe is good ok if ya think its not getting enough gas start lookin at the gas lines themselfs, once mine had a bad clamp but it didnt leak gas out it leaked air in ( it sucked air in around the hose )it would run good most the time and then all at once would die and it was a mother to get started back

12-24-2004, 12:54 PM	#13
Syco67 Registered User Join Date: Jan 2004 Location: Boise Posts: 64	I will take a look at that, with 3 tanks, there are plenty of hoses and clamps to go bad. May as well replace all the rubber under there anyhow. __________________ If at first you don't succed, break something!

12-24-2004, 01:25 PM	#14
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	The odds of havin vapor lock in you location at this time of year is pretty much nill. have you messed with the fuel to air ratio at all

12-24-2004, 02:00 PM	#15
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,052	[/QUOTE]Where should I set the accelerator pump? It has 3 settings, it was on the middle setting, but I put the rod in the hole closest to the carb, that would result in more gas right?[QUOTE] The hole closest to the carb would give it the smallest squrit. Because there is not as much travel. By putting the rod in the whole at the other end you would get the biggiest squirt. If you know you have 8 Psi thats way too much and it needs fule pressure to be set at 5 Psi. __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD



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12-24-2004, 05:57 PM	#16
Maximum Overdrive December 21, 2012 Join Date: Apr 2000 Location: Black Eagle, Montana Posts: 1,634	How is the choke. I had one that would screw up after running for a while and make it hard to restart. __________________ *"!Ama Sua, Ama Kjella, Ama Lllulla!"*

12-24-2004, 06:29 PM	#17
flip66 Registered User Join Date: Jan 2004 Location: Garland TX Dallas area Posts: 658	just want to watch this tread __________________ 1998 Pontiac Grad Prix GTP 1969 C10 396 TH400 3.08 posi

12-26-2004, 12:47 AM	#18
Syco67 Registered User Join Date: Jan 2004 Location: Boise Posts: 64	I know the temp is too cold, and I haven't had any problems, but I am sure it will come back next summer, and am trying to check everything I can to hopefully fix it by then. I just won't know what worked until then. Had another problem yesterday, had a radiator tube blow out and hose me with coolant after I replaced the pump. Now I need to spend $300 on a new 4 row radiator. I will reset the accelerator pump, and get a fp regulator as soon as I can. __________________ If at first you don't succed, break something!

12-26-2004, 10:14 AM	#19
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,269	Starting problems For your radiator--go on-line. There are several places that will sell you a 4 core for a lot less then $300. delivered to your door with a lifetime warranty. I had hard starting / stalling problems on my 71. Replaced the HEI distributor module and condenser and the problem went away. Would only happen when the truck was good and warm or very damp out. If the truck seems like it is starving for gas, take the air cleaner off and look down the carb (not running!!!). Now pull the accelerator and see it you get the "squert" more then likely, that's not the problem. That would only apply to acceleration---not idle. I tend to go with GORDO on most things as he seems to forget more then I know!hehehehe

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