carb drain back - ClassicOldsmobile.com


Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old March 20th, 2017, 04:47 AM   #1
Registered User
Thread Starter
 
Join Date: Sep 2013
Posts: 2,340
carb drain back

My buddy has a problem with his quadrajet draining back. There is a new gas tank , new fuel lines, new vent line, new fuel pump. I think the manual fuel pump is a carter. I looked at what he has and i am at loss why he has this problem. Joe Padavano anyone else got any ideal what is causing this if the car sets 2/3 days.
wr1970 is offline   Reply With Quote
Old March 20th, 2017, 05:11 AM   #2
Registered User
 
aretubj's Avatar
 
Join Date: Oct 2009
Location: Southern Ontario
Posts: 152
Had the same thing happen to me. It turned out not to be draining back, the bowl was leaking into the intake.
Test:
Run the motor, shut it down. Crimp the rubber line to the fuel pump. Let sit for a few days. Remove the crimp devise and try and start car.
If it starts quickly, the fuel is draining back to the tank. Replace the fuel filter with one that has the back flow valve.
If it still takes takes a long time to start, the fuel is leaking into the intake.
Rebuild carb
Joe
aretubj is offline   Reply With Quote
Old March 20th, 2017, 05:46 AM   #3
Registered User
 
Quadrajet Power's Avatar
 
Join Date: Dec 2015
Location: Waring, Tx
Posts: 83
Keep in mind, fuel evaporation can be a contributing factor also.

And like Joe said, some of the well plugs do leak, but most after 70 do not.

Make sure float level is set high enough to allow most fuel in the bowl. The 60's and early 70's Olds Quadrajets still used the large float, so there is less fuel in bowl.

Make sure the clip is not on the needle, holding it to the float. This will allow the needle to sit in seat unless fuel is flowing in to the carb. The clip was necessary 40 years ago but not necessary with todays fuels in my opinion and experience.

Hope this helps.
Quadrajet Power is online now   Reply With Quote
Old March 20th, 2017, 07:19 AM   #4
Old(s) Fart
 
joe_padavano's Avatar
 
Join Date: Mar 2007
Location: Northern VA
Posts: 25,847
Also, be sure the fuel pump is in good shape. Ethanol can cause the rubber check valves in the pump to leak, requiring much longer cranking times to start fuel flowing to fill the carb.

The "leaking well plugs" on Qjets has been a boogeyman ever since Doug Roe wrote about it. In nearly five decades of working on these cars, the ONLY Qjet I've ever seen with this problem is the one on my 67, which has the stamped steel plugs, not the spun-in aluminum ones used from 1968-up. I've gotten the repair plugs with the o-ring seals for this one.

If you REALLY think your carb is leaking, prop it up over a piece of paper, fill the bowl, and let it sit overnight. If the paper is dry, leakage is NOT your problem. Simple, free test before jumping into expensive and possibly unnecessary repairs.
joe_padavano is offline   Reply With Quote
Old March 20th, 2017, 05:06 PM   #5
Registered User
Thread Starter
 
Join Date: Sep 2013
Posts: 2,340
Thanks guys will pass on the info. I will post back the cause if we find it.
wr1970 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Oil drain back cwb442 Big Blocks 9 February 9th, 2015 01:39 PM
Help on opening up oil drain back holes in heads rootney Racing and High Performance 12 November 20th, 2014 12:39 AM
Fuel drain back 66-3X2 442 General Discussion 29 October 16th, 2014 02:57 PM
external oil drain back brandon 455 Big Blocks 4 July 14th, 2013 04:16 PM
heads oil drain back holes. geckonz08 Big Blocks 3 November 25th, 2009 09:01 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -7. The time now is 10:06 PM.


All content Copyright 2017 by Internet Brands, Inc.