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#1 |
Registered User
Join Date: Jul 2008
Location: Eastern Oregon
Posts: 2,336
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QJet Prime Issue ?
I had the original QJet on my 71 GMC rebuilt twice by two different shops. I run non ethanol gas always. If the truck sits for any length of time it will not start unless you pump the gas pedal, last count 16 times. The well plugs where resealed both times. Looking for ideas on how to correct...thanks
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71 C-20 07 Magnum RT AWD |
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#2 |
Registered User
Join Date: Jan 2017
Location: Larkspur, Colorado
Posts: 916
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Re: QJet Prime Issue ?
Are you certain the choke is functioning properly and adjusted correctly?
Steve weim55 Colorado |
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#3 |
Post Whore
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Location: Portland Oregon
Posts: 11,117
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Re: QJet Prime Issue ?
I would let it sit and then I would remove the top of the carburetor to see where the fuel level is before trying to start it. If it is up where it should be then it's likely your accelerator pump has failed. With the second choice being the check valve not working correctly.
If the fuel bowl is empty or very low then it is likely one or more of the well plugs is leaking.
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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#4 |
Registered User
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Location: Tallahassee Fl
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Re: QJet Prime Issue ?
Correct fuel filter installed correctly in the fuel fitting also a good thing to check
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#5 |
Registered User
Join Date: Jul 2008
Location: Eastern Oregon
Posts: 2,336
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Re: QJet Prime Issue ?
Thanks guys ! Can you see fuel by looking inside the throat ? I didn’t think it would start if the accelerator pump was not functioning. Running a in-line filter and the one inside the fuel inlet....appreciate the help
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71 C-20 07 Magnum RT AWD |
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#6 |
Moderator
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Location: Cherryville, NC
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Re: QJet Prime Issue ?
Two things come to mind:
Fuel pump check valves are leaking allowing fuel to drain back to tank when shut off You do have the thick insulating gasket between the carb and manifold ?....if not, the fuel will boil away after shut down I usually run an electric fuel pump on my own trucks...wired thru a shut off switch that hidden away...helps deter the "midnight spares" crowd.... ![]() ![]() ![]()
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#7 | |
Post Whore
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Location: Portland Oregon
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Re: QJet Prime Issue ?
Quote:
If the pump seal lip has failed or as Old Blue K and I have said the check valve is leaking you will have a poor accelerator pump shot. So if the pump shot is poor the first step is to see if you have fuel in the float bowl and that means pulling the top off of the carburetor without spilling fuel out of the carburetor. I usually just do this with the carburetor still bolted on the intake manifold. If you have enough fuel in the float bowl then it is highly likely the pump lip seal or the check valve is the culprit.
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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#8 |
Senior Member
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Location: Orem, Utah
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Re: QJet Prime Issue ?
Based on your observation, I would strongly suspect an issue with the choke rather than a lack of fuel in the bowl. If you're pumping the gas and it starts, that indicates there's fuel. If it only starts after it cranks a while, that indicates a lack of fuel.
When it's cold, take the air cleaner off, and without cranking it, depress the accelerator pedal and release it. The choke plate should snap closed and the throttle should be on the high idle cam. If that's not the case, your choke is either bad, disconnected, or incorrectly adjusted.
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#9 |
Registered User
Join Date: Jun 2008
Location: Moss Point,Ms.
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Re: QJet Prime Issue ?
A big part of your problem is probably evaporation.
If mine sits for more than week,I have to prime the float bowl. Takes about 5 ounces in the top vent hole. Same problem with my Edlebrockes. Mike. ![]() |
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#10 | |
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Location: Falls City, Nebraska "100 Miles From Nowhere"
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Re: QJet Prime Issue ?
Quote:
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Michael of the clan Hill, "Two Seventy Two's" 71 1-ton Dually 350 4-Speed 71 C/50 Grain Truck, 350 Split-Axle 4-Speed 02 3/4 ton Express 14 Indian Chief Vintage 1952 Ford 8N, "Only Ford Allowed On The Property" ![]() "Be American, Buy American" ![]() |
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#11 | |
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Join Date: Dec 2009
Location: El Dorado Ca
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Re: QJet Prime Issue ?
Quote:
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#12 |
Registered User
Join Date: Jul 2008
Location: Eastern Oregon
Posts: 2,336
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Re: QJet Prime Issue ?
Thanks fellas ! The truck will only start after pumping the pedal numerous times, even if it sits overnight. I will check the choke, it’s divorced type...Jack
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71 C-20 07 Magnum RT AWD |
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#13 |
Proprietor of Dale's Corner
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Location: Vacaville , CA
Posts: 16,100
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Re: QJet Prime Issue ?
Accelerator pump check ball not sealing. I had the same problem then I bough "Cliff Rugles " quadrajet book. I learned a lot and how to fix it. Use a old check ball and tap a few times with a punch. It forms a new seat. What a difference it made.
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"Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man |
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#14 |
Registered User
Join Date: Jul 2008
Location: Eastern Oregon
Posts: 2,336
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Re: QJet Prime Issue ?
Thanks OldBlue for your help.
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71 C-20 07 Magnum RT AWD |
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#15 |
Account Suspended
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Location: Tacoma, WA
Posts: 6,873
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Re: QJet Prime Issue ?
Your problem is probably evaporation but it could be leaking back through the fuel pump if you have a windowed seat in your quadrajet.
It could be a leak where the seat screws into the bowl. You can vacuum test the needle and seat by applying vacuum to a test fitting at the carb inlet. You can also vacuum test the fuel pump at the inlet, should hold vacuum. Parts changing possible drain back cures to be used with or without vacuum testing 1. Remove clip on needle which seals the seat regardless of float position. 2. Install fuel filter with built in check valve. 3. Install non windowed seat. |
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