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 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 07-15-2005, 11:55 AM   #1
PHOENIX
Registered User
 
Join Date: Oct 2002
Location: Phoenix, Arizona
Posts: 4,703
Carb Problems, Flooding

Been having some trouble with my truck lately.
I believe its carb related, but not sure.
Truck seems to run fine when cool (morning and night).
It runs rough and dies when in the heat.
I can drive it about 6 miles or so then it dies.
Doesn't want to start.

When it dies I pull the air cleaner off and notice gas coming out of the carb (A & B in picture).
Some gas also comes out of the sides and puddles on the manifold.
Not sure where these leaks are coming from but my guess is around
linkage and maybe the gasket.
C (front barrels) in the picture has a little bit of white/grey looking smoke, very little bit.

My guess is the float or needle and seat are not functioning correctly
and flooding the carb and killing the engine. Its odd though that it only
seems to do it in the heat, or maybe it only does it sooner in the heat.
It starts to idle low, then dies usually at a stop, sometimes on take-off.
Have not been able to drive it too much because it shuts down.

Anyway died three times on me yesterday, wouldn't fit on a friends trailer so I had to get towed, $62.00 .

Full manifold vacuum is about 17-19
Timing is 8 degrees
Idle it about 725rpm (manual trans)
Operating temperature is normal.
Oil level and pressure is normal.

What do you guys think?
Anything to try?
Attached Images
 
__________________
* AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

Last edited by PHOENIX; 07-15-2005 at 11:59 AM.
PHOENIX is offline   Reply With Quote
Old 07-15-2005, 12:07 PM   #2
rockman20
"The dude abides"
 
rockman20's Avatar
 
Join Date: Apr 2003
Location: North Dakota
Posts: 472
What is your fuel pressure?

It does sound like something with the float and needle assembly.

I guess that is where I would start.
__________________
RockMan

1993 Chevy Silverado C3500 1 ton dually
1994 Honda Civic
1969 Oldsmobile Cutlass S
1953 IH Farmall Super M
New to the fleet:
1992 Subaru Loyal
rockman20 is offline   Reply With Quote
Old 07-15-2005, 12:20 PM   #3
PHOENIX
Registered User
 
Join Date: Oct 2002
Location: Phoenix, Arizona
Posts: 4,703
I don't know what the fuel pressure is.
I have a Mityvac 4000, I do not believe this can be used, can it?

I have a fuel pressure gauge for fuel injected, shreader (?) valve type.
I will have to look at it when I get home and see if I can use it with an attachment or something.
Its kind of like THIS ONE.
__________________
* AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *
PHOENIX is offline   Reply With Quote
Old 07-15-2005, 02:46 PM   #4
SSC's76
No No
 
SSC's76's Avatar
 
Join Date: Jun 2005
Location: Pueblo Colorado
Posts: 1,781
Since I see the choke is open, it's probably not sticking. Most likely you have crap stuck in the needle/seat assembly. Start the truck up with one hand throttle it up to 3-4K then with the other hand close the choke flap for a second or two, keep the throttle open. It will bog down real bad but do it a couple times, this will suck dirt out of the needle and seat 70% of the time. If it were the float that was bad it would be flooding the second you started it up.
__________________
1976 Custom Deluxe SWB Med FMB.3/4 Drop.
Gen VI 454, Muncie HD 3 speed With Modified OE Hurst Shifter, 3.73 12 bolt, GMPP HO roller cam, Hooker headers, Performer intake with modified Q-jet, Accel distributor. Best 1/4 12.3 @108. Funnest run 19.84 @88 full 1/4 mile burn out.
1997 K1500 ext cab 5.7 stock except muffler
SSC's76 is offline   Reply With Quote
Old 07-15-2005, 03:22 PM   #5
PHOENIX
Registered User
 
Join Date: Oct 2002
Location: Phoenix, Arizona
Posts: 4,703
Is it normal for fuel to come out of the A & B "ports" when flooding?
__________________
* AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *
PHOENIX is offline   Reply With Quote
Old 07-15-2005, 03:44 PM   #6
corn
Registered User
 
Join Date: Dec 2003
Location: here
Posts: 5,789
If the needle is sticking it will come out of "A" for sure(its the float boal vent). Ive had good luck freeing up a needle & seat by smacking the carb front with a screwdriver handle. Works (almost) every time...corn
corn is offline   Reply With Quote
Old 07-15-2005, 09:26 PM   #7
ureckme
ureckmefixit2@cox.net
 
Join Date: Dec 2004
Location: Mesa AZ. (Phoenix)
Posts: 1,284
We live in Arizona ( Phoenix ) it's HOT. last week record high. Theres some things it could be. Fuel line by pass side moter mount running to close to headers. Fuel line from pump to carb getting over heated. pluged tank vent?. Any of these will make your fuel pressure go way above 5psi. You might be able to lower your float level but you need to cool the fuel down to keep it from expanding so much. But just getting a regulator may not solve the hole problem. Matt
__________________
That's U RECK ME FIX it 2
74 Chevy Short Bed
355ci Sportsman II 64cc Angle Plug
Crower Custom Grind .462in .486ex
Dyno Test 422hp @ 5600
And it's got a Holley
3.73 Gears
12 Bolt 3.73 w/Posi
700R4 Going In
I'm a Body Man So There!
That's why it's not painted
ureckme is offline   Reply With Quote
Old 07-16-2005, 06:13 PM   #8
PHOENIX
Registered User
 
Join Date: Oct 2002
Location: Phoenix, Arizona
Posts: 4,703
This is the first summer with headers on the truck.

So I should check the fuel pressure before removing the carb?
If the pressure is high, then I know its probably heat related.
If the pressure is normal then its probably the float or needle and seat.

???
__________________
* AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

Last edited by PHOENIX; 07-16-2005 at 06:16 PM.
PHOENIX is offline   Reply With Quote
Old 07-16-2005, 06:56 PM   #9
Prerunner1982
Registered User
 
Prerunner1982's Avatar
 
Join Date: Oct 2002
Location: Edmond, OK
Posts: 5,904
could always make a "cool can" a small coffee can, ice and extra fuel line... and see even if its 100+ outside how far the truck will run.. if it runs fine, theres your answer.. its heat related..fairly inexpensive way to find out....
__________________
Jon
1982 Chevy Silverado 350/th350.... RETIRED
1993 Jeep XJ 2 door(Cherokee) 4wd 4.0ltr/AX-15 (5spd)/NP231
....
Oklahoma Roll Call
Prerunner1982 is offline   Reply With Quote
Old 07-16-2005, 10:08 PM   #10
ureckme
ureckmefixit2@cox.net
 
Join Date: Dec 2004
Location: Mesa AZ. (Phoenix)
Posts: 1,284
Headers Thats part of the problem. When I put mine in they were touching the fuel line by the pass side moter mount. Matt
__________________
That's U RECK ME FIX it 2
74 Chevy Short Bed
355ci Sportsman II 64cc Angle Plug
Crower Custom Grind .462in .486ex
Dyno Test 422hp @ 5600
And it's got a Holley
3.73 Gears
12 Bolt 3.73 w/Posi
700R4 Going In
I'm a Body Man So There!
That's why it's not painted
ureckme is offline   Reply With Quote
Old 07-16-2005, 10:15 PM   #11
ureckme
ureckmefixit2@cox.net
 
Join Date: Dec 2004
Location: Mesa AZ. (Phoenix)
Posts: 1,284
If it started to flood on a cold start up I would say it was the float or some thing in the needle seat. After it warms up I would say heat or fuel pressure.
__________________
That's U RECK ME FIX it 2
74 Chevy Short Bed
355ci Sportsman II 64cc Angle Plug
Crower Custom Grind .462in .486ex
Dyno Test 422hp @ 5600
And it's got a Holley
3.73 Gears
12 Bolt 3.73 w/Posi
700R4 Going In
I'm a Body Man So There!
That's why it's not painted
ureckme is offline   Reply With Quote
Old 07-16-2005, 11:27 PM   #12
MylilBowTie
Right turn Clyde
 
MylilBowTie's Avatar
 
Join Date: Nov 2002
Location: Cincinnati, Ohio
Posts: 2,911
If you try the cool can thing I would coil the gas line a few times for more fuel volume.
__________________
1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73
1992 Camaro RS 305 TBI
MylilBowTie is offline   Reply With Quote
Old 07-27-2005, 11:58 AM   #13
PHOENIX
Registered User
 
Join Date: Oct 2002
Location: Phoenix, Arizona
Posts: 4,703
OK the needle/seat and float seem fine.
I am thinking of replacing them anyway, just to be safe.
Anyone know what size needle and seat the Edelbrock Q-Jet 1904 comes with?
All I can find online is "high-volume".
Are there brass floats available for Q-Jets, if so should I consider brass instead?

I plan to wrap the fuel lines by the header.
Run a different line from the pump to carb.
The electric fan I have is a 2-speed and the low speed doesn't work.
I have an extra fan just like it in perfect condition.
I am going to install that one and have it run on low all the time.
Maybe set it up so the high speed can be manually controlled.

I have heard mixed things about gasoline expanding when heated.
What do you guys know about this. It seems like that is the problem
because it only happens when hot and the carb is flooding.
__________________
* AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *
PHOENIX 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 08:30 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2025, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com