Q-jet issue
Thread Starter
Cruising
Joined: Jun 2011
Posts: 12
Likes: 0
From: goshen indinana
Q-jet issue
Installed rebuilt Q-jet on my '71 LS-5. Runs and idles fine. However...... after sitting over night or longer, all the fuel is gone out of the bowl. repeated "pumping" and cranking, I finally get fuel back in the carb. Then it'll start and run just fine. IDEAS?
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
Yep, with this E-10 fuel additive we use now it can evaporate quicker
or the fuel is leaking from the bottom of carb
or the fuel is heat boiling into the manifold
or needle letting it drain back out of carb
or fuel pump diaphram bad and letting it siphon back, so just some ideas to look at.
Ed
or the fuel is leaking from the bottom of carb
or the fuel is heat boiling into the manifold
or needle letting it drain back out of carb
or fuel pump diaphram bad and letting it siphon back, so just some ideas to look at.
Ed
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
If you've read a few Q-Jet papers out there, you'll find some of the rebuilt jobs aren't very good. Most carburated cars I rarely drive have rear mounted electric pumps. Turn to aux for a few seconds to fill the bowl, and fires right up. Also a dash switch to cut the pump off stalling out on an empty bowl when putting things away.
Le Mans Master
Joined: Aug 2006
Posts: 7,423
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
You can try a "Roll over filter" (Napa 23051 or 23052) that was designed to stop you tank from emptying on roll over but it can help with your problem.
The check valve in the fuel pump may have failed which will siphon the fuel back to the tank.
To check run your vette for a few minutes and turn the motor off. Wait 10 minutes and crack the fitting at the carb inlet. If you still have pressure the check valve is good.
A non-windowed inlet seat can help. (if you can find one)
There is a "Clip" between the float and the needle valve, you can remove that.
Doing that lets the float drop without opening the needle and that (sometimes) can leave just enough fuel in the bowl to help with the next start.
Melting Slicks
Joined: Jul 2010
Posts: 2,762
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
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Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Yes, it's true some Q-Jet well plug seals have been known to leak, but not common, and actually on the upper part of the carb. When this happens, usually causes a rich dirty idle, and not sounding like your problem.