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Old 04-24-2009, 12:31:06 AM   #1
Stak
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FUEL SYSTEM PROBLEM(Vapor lock?)

In the summer time, My z runs a lot warmer, and when I shut it off for 10 or 15 minutes, crank it and take off, by the time it shifts into 3rd, it cuts off like its starving for gas, the only thing i can figure is that maybe the gas it getting too hot from the under hood temp, it never does it in the winter time, only hot weather, and it has done it with my quadrajet, holley and my prosystems carb, it does it with the mechanical or electric fuel pump, I even have a new gas tank and 1/2 fuel line and it still freakin does it, but only in the summer time( u know how u can feel the heat even though y dont have it on?) l When it shuts off, and i try and crank it back up, i have to hold the pedal to the floor and it will finally start and bust up terribly then finally it will clear up, but it may shut off and do it all over again. Please tell me im the not only one to experience this problem> Thanks in advance as always!!
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Old 04-24-2009, 01:35:22 AM   #2
muscl car
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Quote:
Originally Posted by Stak
In the summer time, My z runs a lot warmer, and when I shut it off for 10 or 15 minutes, crank it and take off, by the time it shifts into 3rd, it cuts off like its starving for gas, the only thing i can figure is that maybe the gas it getting too hot from the under hood temp, it never does it in the winter time, only hot weather, and it has done it with my quadrajet, holley and my prosystems carb, it does it with the mechanical or electric fuel pump, I even have a new gas tank and 1/2 fuel line and it still freakin does it, but only in the summer time( u know how u can feel the heat even though y dont have it on?) l When it shuts off, and i try and crank it back up, i have to hold the pedal to the floor and it will finally start and bust up terribly then finally it will clear up, but it may shut off and do it all over again. Please tell me im the not only one to experience this problem> Thanks in advance as always!!


here's what you need to do ......


1] make sure you fuel lines are placed far enough away from area that get hot like exhaust pipes/headers and engine block surfaces . also make sure it has at least a few inches of an air gap surrounding the fuel lines so cool air can flow over them .if the fuel lines are to close you can get special heat wraps that will keep the fuel lines from excessive heat

2]make sure your fuel pump is putting out it's max pressure if not during the warm months this will cause the fuel to percolate as it isn't moving quick enough

3] purchase and install some sort of insulated carb spacer preferably wood and 2nd being a phenolic spacer of at least 1" tall .this will allow the heat to be removed from the carb and not allowing the fuel to boil in the bowls


heat sleeving for the fuel lines ..

http://www.jegs.com/i/JEGS/555/32014/10002/-1




carb heat shield ....

http://www.jegs.com/i/Mr.+Gasket/720/3710/10002/-1




wood carb spacer ....

http://www.jegs.com/i/Edelbrock/350/8720/10002/-1

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Old 04-24-2009, 05:59:06 AM   #3
Stak
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Thanks Muscl Car, I'm gonna give that a try today. I actually put that carb heat shield on yesterday and drove it around last night( thought it fixed it) but on my way home it started acting up. So today I'm gonna find that wooded spacer, and that sleeve for the fuel lines, and go over my lines all together and make sure they aren't right up against any heat, thanks for your help, I post back this evening or tomorrow after I see how it does...........
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Old 04-24-2009, 06:35:17 AM   #4
Cardinal
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Check the fuel pump pressure. I had a similar problem with our C10 pickup. Would start and run fine as long as the truck was cold but NOT when it was warm. The pump pressure has to be between 5 to 7 psi.
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Old 04-28-2009, 11:18:05 AM   #5
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maybe could use a trans cooler for fuel
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Old 04-30-2009, 10:00:40 PM   #6
bad71camaro
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i would like to get a answer to the same question ive replaced all the rubber lines on my camaro,3 fuel pumps,3 carbs, air gap intake,heat wrap,heat shields, and still if the car gets above 180 its done boils the fuel or so called vapor lock i never had this problem until i put a 406 in it i hope someone can help
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Old 05-01-2009, 07:01:49 AM   #7
grasmo
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i just went through this same thing and think i finally got it fixed. if it was any hotter than about 75* ambient, my carb would "spit" fuel out of the vent tube. i mean it would spit it like 3-4" out of the tube. i changed everything! even welded a fitting in the bottom of the tank for a new supply tap for my blue pusher pump. what was really strange is the carb. was never hot. the fuel was not hot in the bowl. i've had engines and fuel systems that were subjected to much more heat and never had a problem. i honestly believe they've changed something in the gasoline. anyway what i did was install this orifice in the second outlet port of my dead-head regulator and returned the fuel to the tank:

http://www.mcmaster.com/#orifices/=1ok3vg

i used the 2822t15 with a .032. i also went back to 3/8" supply line. i did have 1/2". the idea is to keep the fuel moving. so far so good.

Last edited by grasmo : 05-01-2009 at 09:08:00 AM.
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Old 05-01-2009, 04:40:08 PM   #8
Venom73
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Quote:
Originally Posted by Stak
In the summer time, My z runs a lot warmer, and when I shut it off for 10 or 15 minutes, crank it and take off, by the time it shifts into 3rd, it cuts off like its starving for gas, the only thing i can figure is that maybe the gas it getting too hot from the under hood temp, it never does it in the winter time, only hot weather, and it has done it with my quadrajet, holley and my prosystems carb, it does it with the mechanical or electric fuel pump, I even have a new gas tank and 1/2 fuel line and it still freakin does it, but only in the summer time( u know how u can feel the heat even though y dont have it on?) l When it shuts off, and i try and crank it back up, i have to hold the pedal to the floor and it will finally start and bust up terribly then finally it will clear up, but it may shut off and do it all over again. Please tell me im the not only one to experience this problem> Thanks in advance as always!!

I have the EXACT same problem. Let us know what fixes it because your issue is so spot on with mine it will probably require much of the same fix. Thanks to Muscl car, I will buy that hose for my fuel line.
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Old 05-30-2009, 12:12:27 AM   #9
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so, hate to bring back an old thread, but did anyone get a fix for their carbs??
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Old 05-31-2009, 06:29:50 PM   #10
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Mine isn't fixed yet
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Old 05-31-2009, 10:11:10 PM   #11
mopar
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My car had a return line from the factory. I'm running an electric pump to an inline filter with two oulets. From the filter outlet, I run one line to the return and one line to a regulator. Then from the regulator to the carb. The carb is on a spacer. Seems to be doing fine now. I rode today, in the city, 86* stop and go for about 30 minutes.
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Old 05-31-2009, 10:35:33 PM   #12
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Quote:
Originally Posted by mopar
My car had a return line from the factory. I'm running an electric pump to an inline filter with two oulets. From the filter outlet, I run one line to the return and one line to a regulator. Then from the regulator to the carb. The carb is on a spacer. Seems to be doing fine now. I rode today, in the city, 86* stop and go for about 30 minutes.

mopar, I may try your set up, where did you mount the filter and electric pump??
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http://i134.photobucket.com/albums/q...R/DSCN0249.jpg

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Old 06-01-2009, 06:22:32 PM   #13
mopar
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electric pump mounted under trunk just in front of tank. I think the filter is stock on a 2000 Jeep. filter is mounted inline where factory fuel pump was originally.
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Old 06-03-2009, 08:35:23 PM   #14
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Quote:
Originally Posted by mopar
electric pump mounted under trunk just in front of tank. I think the filter is stock on a 2000 Jeep. filter is mounted inline where factory fuel pump was originally.

Thanks mopar, just wanted to know what works for others!! No one around here seems to have an answer...guess i'll replace part after part.....
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Old 06-04-2009, 03:01:23 PM   #15
BADHOTROD
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Just my 2 cents

I had the same exact problem and I have a 565 with a big fuel system (elec. pump return line ect.) I've had my car for 22 years with and always had big compression race motors. this is the first pump gas motor i've ever built, and ever since I started putting in this cheap 10 to 15% ethenol oxygenated fuel is when I started having problems with fuel starvation and boil over. so I started putting in either leaded 92 or non-oxygenated (the type they sell for boats and motorcycles) and my problem disappeared.....
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