Q'Jet float level
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
A word of advice. If you DO undertake this yourself, be VERY careful to NOT overtighten the top of the unit when reinstalling it, you can very easily warp the top of the carb which will then cause internal leaks. Also, not sure what sort of problems you might be experiencing with it now, but it's advisable to check the top with a straightedge when you remove it to make sure it isn't already warped. Most already are...
Thread Starter
Instructor
Joined: Nov 2013
Posts: 166
Likes: 8
From: Acworth GA
Worst thing about a QJet. You HAVE to take the top off the carb to measure float level & drop. Sorry, but that's just how they are, and it's a big reason why so many QJet-equipped cars had their carbs replaced by Holleys down the road...
A word of advice. If you DO undertake this yourself, be VERY careful to NOT overtighten the top of the unit when reinstalling it, you can very easily warp the top of the carb which will then cause internal leaks. Also, not sure what sort of problems you might be experiencing with it now, but it's advisable to check the top with a straightedge when you remove it to make sure it isn't already warped. Most already are...
A word of advice. If you DO undertake this yourself, be VERY careful to NOT overtighten the top of the unit when reinstalling it, you can very easily warp the top of the carb which will then cause internal leaks. Also, not sure what sort of problems you might be experiencing with it now, but it's advisable to check the top with a straightedge when you remove it to make sure it isn't already warped. Most already are...
I was hoping for an indirect way to assess if the float level is "close".
Last edited by Rich123; Jun 26, 2019 at 09:11 AM.
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
Thank you, I think I'll check elsewhere for a solution before I do that. I took it off once about 5 years ago and I was never able to get it back together right. I had to send it to Lars and have him rebuild it.
I was hoping for an indirect way to access if the float level is "close".
I was hoping for an indirect way to access if the float level is "close".
Team Owner
Joined: Aug 2000
Posts: 21,453
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From: Massillon,Ohio USA
2020 C3 of the Year Finalist - Unmodified
Cruise-In VI Veteran
St. Jude Donor '08-'09-'10-'11-'12
...I just re-did my '68's Q-jet, disassembled about 3 times before I felt I got it right. One I thing I learned if the carb spews fuel out the needle & seat could be bad or the float is set too low. I like Q-jets, but they can have "issues".
Last edited by Paul Borowski; Jun 26, 2019 at 09:04 AM.
Tech Contributor
Joined: Aug 1999
Posts: 14,373
Likes: 6,371
From: At my Bar drinking and wrenching in Lafayette Colorado
Thank you, I think I'll check elsewhere for a solution before I do that. I took it off once about 5 years ago and I was never able to get it back together right. I had to send it to Lars and have him rebuild it.
I was hoping for an indirect way to assess if the float level is "close".
I was hoping for an indirect way to assess if the float level is "close".
Lars
Last edited by lars; Jun 26, 2019 at 05:21 PM.
Thread Starter
Instructor
Joined: Nov 2013
Posts: 166
Likes: 8
From: Acworth GA
Thanks Lars, it must be a fuel pump problem. It once in a while, after it's up to operating temps it tries to die while accelerating, then catches up and runs. It was like the bowl level was not sufficient to maintain acceleration. But that has just started and like you said, it shouldn't change.
Last edited by Rich123; Jun 26, 2019 at 05:58 PM.
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Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
It's been quite a few years since I went through that carb (2014), so if you haven't changed the fuel filter, it may be time to do so. If the problem persists, it may be a good idea to install a fuel pressure gauge at the carb inlet and see what the fuel pressure is doing when the problem occurs. 
Lars
Lars
Thread Starter
Instructor
Joined: Nov 2013
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From: Acworth GA
It's been quite a few years since I went through that carb (2014), so if you haven't changed the fuel filter, it may be time to do so. If the problem persists, it may be a good idea to install a fuel pressure gauge at the carb inlet and see what the fuel pressure is doing when the problem occurs.
Lars
Lars
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Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
You do that by installing a "T" into the fuel line between the carb and your existing fuel line. Run a rubber fuel line (well clamped) off the branch T connection, to the back of your hood, and up to your windshield. Connect it to the pressure gauge and tape the gauge to the outside of your windshield so you can watch it while driving. We do it all the time for troubleshooting - no problem! (But change the fuel filter first to eliminate that $3 issue as the problem).
Lars
Lars
Thread Starter
Instructor
Joined: Nov 2013
Posts: 166
Likes: 8
From: Acworth GA
You do that by installing a "T" into the fuel line between the carb and your existing fuel line. Run a rubber fuel line (well clamped) off the branch T connection, to the back of your hood, and up to your windshield. Connect it to the pressure gauge and tape the gauge to the outside of your windshield so you can watch it while driving. We do it all the time for troubleshooting - no problem! (But change the fuel filter first to eliminate that $3 issue as the problem).
Lars
Lars
When the thing first acted up, the first thing I did was pull the filter out of the carb inlet. It didn't seem to change anything.
Drifting
Joined: Apr 2011
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From: Deerfield Illinois
2022 C3 of the Year Finalist - Modified
C3 of Year Finalist (appearance mods) 2019
You are describing a problem I had which seems very similar to yours. During a hard acceleration I would lose power and then it would go away and power would come back. I would be fine if I was light on the throttle, small power bumps. Cruised fine.
Changed carb filter- same issue, checked timing and plugs, wires, tank sender screen- problem still persisted.
Checked fuel pump and would provide enough fuel while checking, but hard acceleration it sputtered.
detemined it was the fuel pump I installed a new one and that solved the problem!
Took the old one apart and had a small tear in the diaphragm.
Bought the new one from Summit around 50 dollars
Changed carb filter- same issue, checked timing and plugs, wires, tank sender screen- problem still persisted.
Checked fuel pump and would provide enough fuel while checking, but hard acceleration it sputtered.
detemined it was the fuel pump I installed a new one and that solved the problem!
Took the old one apart and had a small tear in the diaphragm.
Bought the new one from Summit around 50 dollars