The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 12-05-2010, 10:29 PM   #1
Seatown-gmc
Registered User
 
Join Date: May 2010
Location: Seattle
Posts: 12
Question starves for fuel when warmed up

I have a 2wd 1970 GMC pick up with a factory 396. The truck starts up everytime and idles fine but when it warms up and im driving the truck it sputters and pops like it is running out of gas. I thought it was the fuel pump so I changed it. Not the problem. so I put a clear filter on the fuel line so i could watch the fuel and see what it was doing. when the motor is cold the filter is full but when the motor heats up the filter gets bone dry the motor must be runnng on fumes only but it doesnt die. The fuel intermitently skirts into the filter after it is warm but not what it should be. My truck does have headers do you think this is my problem?

Last edited by Seatown-gmc; 12-05-2010 at 10:32 PM.
Seatown-gmc is offline   Reply With Quote
Old 12-05-2010, 11:24 PM   #2
So.Cal.Super
It'll Buff Out!
 
So.Cal.Super's Avatar
 
Join Date: Apr 2007
Location: San Diego
Posts: 603
Re: starves for fuel when warmed up

first, Welcome to the board.

Second, I have headers and the problem I am fixing is the sock in the tank. Check out my post here and you can see pics of an almost 40 year old tank sock.

http://67-72chevytrucks.com/vboard/s...d.php?t=434265

third. There is no other filter between the tank and pump correct?
(discussing this on my post also)

let us know.
__________________
"Instructions are just another mans opinion"

Become a Supporting Member
http://67-72chevytrucks.com/vboard/payments.php

Man Card Rules
http://67-72chevytrucks.com/vboard/s...d.php?t=634550

72 Chevy Cheyenne Super 400 LWB
So.Cal.Super is offline   Reply With Quote
Old 12-05-2010, 11:34 PM   #3
Jacfourteen
Big Red - Now its a SWB!
 
Jacfourteen's Avatar
 
Join Date: Jun 2009
Location: Oroville, Ca
Posts: 1,624
Re: starves for fuel when warmed up

Quote:
Originally Posted by So.Cal.Super View Post
first, Welcome to the board.

Second, I have headers and the problem I am fixing is the sock in the tank. Check out my post here and you can see pics of an almost 40 year old tank sock.

http://67-72chevytrucks.com/vboard/s...d.php?t=434265

third. There is no other filter between the tank and pump correct?
(discussing this on my post also)

let us know.
Same thoughts I had, also how is the condition of your tank and lines? If they are all cruddy they can clog up.
__________________
68 3/4 ton (Project)-350 Small Block, .030 over, 10:1 comp, 3998993 heads, C3BX edelbrock intake, comp cams XE268, Holley 670 SA, long tube headers, dual flow 40's, E-fan, Alum rad, currently under the knife getting shortened and bagged build thread
41 3/4 ton (wife's)-flatbed, fully restored to original
01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's
02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's
Jacfourteen is offline   Reply With Quote
Old 12-05-2010, 11:48 PM   #4
Seatown-gmc
Registered User
 
Join Date: May 2010
Location: Seattle
Posts: 12
Re: starves for fuel when warmed up

there is not a filter between the pump and tank other than than the sock in the tank. Im sure that the sock in the tank is factory and has never been changed. Do you think that would affected the way the fuel flows when the motor is warmed up though?
Seatown-gmc is offline   Reply With Quote
Old 12-06-2010, 01:37 AM   #5
So.Cal.Super
It'll Buff Out!
 
So.Cal.Super's Avatar
 
Join Date: Apr 2007
Location: San Diego
Posts: 603
Re: starves for fuel when warmed up

When I started mine cold it was at 7.0 psi, just what the regulator was set at. Over the course of idling for 30 mins it was dropping .5 - 1 psi every 5 mins or so. When I would hit the throttle, the pressure would drop to 0. When I shut the truck off the line would fill back up and I would have more pressure on the next start up for a few mins.
I have full length headers on a big block and the fuel lines are 99% in the stock locations minus what I modified above the valve cover for the Regulator, heat was never a problem.
In the last few months the truck would run half throttle but fall on its face above that. From a dead stop it would run through first and second then nose dive like I hit a pole because it had sucked the fuel line dry. If any of these problems sound familiar there is a chance it’s the sock or from what I have read pin holes in the pickup tube due to rust and age.
Hope that helps.
__________________
"Instructions are just another mans opinion"

Become a Supporting Member
http://67-72chevytrucks.com/vboard/payments.php

Man Card Rules
http://67-72chevytrucks.com/vboard/s...d.php?t=634550

72 Chevy Cheyenne Super 400 LWB
So.Cal.Super is offline   Reply With Quote
Old 12-06-2010, 11:35 PM   #6
Seatown-gmc
Registered User
 
Join Date: May 2010
Location: Seattle
Posts: 12
Re: starves for fuel when warmed up

do I have to take the tank out to get the sending unit out or just remove the seat? also I have two other tanks on the truck I have ran it on all three tanks and it does the same thing do you think it is likely that all three socks are clogged or have you guys ever heard of the tank selector valves causing a problem?
Seatown-gmc is offline   Reply With Quote
Old 12-07-2010, 12:32 AM   #7
lindstromjd
Gentleman Jim owner x2
 
lindstromjd's Avatar
 
Join Date: Oct 2010
Location: West Des Moines, IA
Posts: 464
Re: starves for fuel when warmed up

It could be a vapor-lock, too. Since it only does it after it warms up, that would suggest that heat is a factor. How close does your fuel line run to your exhaust?
__________________
1975 GMC Gentleman Jim #1
-357 / 700r4
1975 GMC Gentleman Jim #2
-350 / TH350
lindstromjd is offline   Reply With Quote
Old 12-07-2010, 01:08 AM   #8
etg
Registered User
 
etg's Avatar
 
Join Date: Apr 2006
Location: San Diego
Posts: 147
Re: starves for fuel when warmed up

You don't have to remove the tank, and you don't have to remove the seat but it helps. Have a flathead hand, and poke a tab until you turn the locking wheel/plate enough to loosen and pull it off. You'll have to undo the fuel line, make sure you have a rag and no open flames . Also be careful you don't puncture the float.
etg is offline   Reply With Quote
Old 12-07-2010, 03:14 AM   #9
cdowns
Senior Member
 
cdowns's Avatar
 
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
Re: starves for fuel when warmed up

it could b wrong gascap, after running try taking cap off if there is a wooshing noise that means you have later style cap and your tank isnt venting

also if you have the stock carb . there is a fuel filter inside the carb, where the inlet tube goes in carb that very big nut on the carb body holds filter in place
__________________
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

Last edited by cdowns; 12-07-2010 at 03:17 AM.
cdowns is offline   Reply With Quote
Old 12-07-2010, 09:43 AM   #10
RenoKeene
Florida Edition

 
RenoKeene's Avatar
 
Join Date: Oct 2010
Location: Fruitland Park, FL
Posts: 4,028
Re: starves for fuel when warmed up

^What cdowns said.
__________________
70 GMC Short Stepside "Rose"-An American Beauty: Factory 402/TH400, AM/FM, AC, Tilt, Tach, Buckets, Posi, PS, PB, 3-5 Drop, Complete Resto-Rod
67 C-20 Slant Back Wrecker "Mad Max"
67 C-10 Ratrod "Step-N-Wolf"
71 Serro Scotty Sportsman camper "Scotty"
97 LT1 Z28 "The Hornet"

Link to more pics of "Rose" http://67-72chevytrucks.com/vboard/a...p?albumid=1684

Check out my "Cheap Tricks" thread and add to it if you can, lots of good info there. http://67-72chevytrucks.com/vboard/s...d.php?t=489394
RenoKeene is offline   Reply With Quote
Old 12-07-2010, 05:31 PM   #11
So.Cal.Super
It'll Buff Out!
 
So.Cal.Super's Avatar
 
Join Date: Apr 2007
Location: San Diego
Posts: 603
Re: starves for fuel when warmed up

Quote:
Originally Posted by cdowns View Post
it could b wrong gascap, after running try taking cap off if there is a wooshing noise that means you have later style cap and your tank isnt venting

also if you have the stock carb . there is a fuel filter inside the carb, where the inlet tube goes in carb that very big nut on the carb body holds filter in place
Never thought of the gas cap, what makes me think it's not the carb filter is he mentioned The sight glass on the filter he has emptying and that it's between the pump and carb. now i'm curious...
__________________
"Instructions are just another mans opinion"

Become a Supporting Member
http://67-72chevytrucks.com/vboard/payments.php

Man Card Rules
http://67-72chevytrucks.com/vboard/s...d.php?t=634550

72 Chevy Cheyenne Super 400 LWB
So.Cal.Super is offline   Reply With Quote
Old 12-08-2010, 11:21 AM   #12
Seatown-gmc
Registered User
 
Join Date: May 2010
Location: Seattle
Posts: 12
Re: starves for fuel when warmed up

I looked at how close the header gets to the fuel line last night. It's pretty close I would say less than a half inch or so. The fuel line is in the stock location running in the center of the frame rail. I think it might be getting cooked!
Posted via Mobile Device
Seatown-gmc is offline   Reply With Quote
Old 12-08-2010, 11:23 AM   #13
Seatown-gmc
Registered User
 
Join Date: May 2010
Location: Seattle
Posts: 12
Re: starves for fuel when warmed up

Also the wrap on the headers looks pretty old and looks like Hellen Keller put it on. There is slot of spaces between the wrap.
Posted via Mobile Device
Seatown-gmc is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 05:59 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com