Quadrajet hard start fuel bleed off.

[Ricko1966]

Something just occurred to me as I was reading another quadrajet extended crank after sitting thread. I haven't had a chance to explore this,because I just thought of it 2 minutes ago. Many people have extended crank after their qjets sit a few days. Some of you know and some of you don't,but there are 2 types of needle and seat for a quadrajet windowed and not windowed. Windowed has windows in the side at the fuel bowl floor,non windowed do not they are tube with no windows. I have a theory that the fuel is boiling off or evaporating off enough to let the float drop. Now as soon as the float drops the needle will open and let the fuel drain all the way to the floor of the fuel bowl. Now a non windowed seat would not let the bowl drain completely.Also the correct fuel filter for a qjet on a 3 port pump vehicle is supposed to have a check valve in it. I suggest anyone having an extended crank problem try a non windowed needle and seat and be sure they have the correct fuel filter. Post your results,as soon as I have one with a problem,I'll try it to see if we have a fix.

 

[squaredeal91]

Very interesting theory and have thought about why for years and figured evaporation too so i will ride along with your theory.
Interesting about the 2 different needle and seats. Is one more for off road?

On a separate note I've been plagued with bad well plugs. I'm going to be doing the fix sooner or later.

 

[Ricko1966]

Very interesting theory and have thought about why for years and figured evaporation too so i will ride along with your theory.
Interesting about the 2 different needle and seats. Is one more for off road?

On a separate note I've been plagued with bad well plugs. I'm going to be doing the fix sooner or later.

You asked,so I looked, according to Cliff GM went to non windowed to stop fuel drain back,also just as I've recommended in the past he says not to run the clip on the needle. I learned that from Lars forever ago. Mike's Quadrajet parts sells the non windowed needle and seat,claiming it helps with hard starts and that it allows .400 more fuel level if the needle leaks. The reason for not running the clip is when the float sinks,with no clip the needle doesn't pull up. I still like the factory filter in a stock application,new cars didn't have a problem with them no reason they should suddenly become a problem.GM put the filter with the check valve to stop fuel bleed back through the return port.There is no check valve on the return port,like the pressure port,just a restrictor.

Qjet fuel drainback information

Well I personally haven't had fuel drain back problems with a qjet,but turns out that there are reasons and fixes for the problem. I did not know this but when GM went to return lines on the fuel pumps the fuel pump was no longer a positive stop,at the same time GM changed the fuel filter...

www.gmsquarebody.com

 

[fast 99]

Have seen the needles stick closed on various carbs. Filter should stop drain back. Leaving the clip off may not always be desirable. My trucks sometimes sit for 6 months+. They are going to have extended cranking no matter what. For trucks driven more frequently leaving the clip off could be redundant.

 

[squaredeal91]

If My tractor sits 5 days or 5 months seems I have to tap on Boal to make it start. (Gravity flow )