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Vk commodore Rochester quadrajet seems to be flooding

Andrew Ivanic

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Hi all. I have a vk commodore 308 with a Rochester quadrajet that’s already been rebuilt. The carb seems to be filling up with too much fuel causing fuel to come out of the accelerator pump. Currently it’s only got a new mechanical fuel pump Higher output one and no electric pump.
the guy at the performance shop tested the carby and said I may need a return line back to the fuel tank and I’m missing the little piece just before the carby that has the return fuel line also. I think this works as a regulator of some sort. Any idea where the fuel return line would connect into my petrol tank as I can’t see any spare holes.
thanks
 

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Andrew Ivanic

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Thanks Crew chief. Have you ever had any issues from the pump pumping more fuel than the reg lets out to the carb ie fuel spike ets... ? Iv also read it will work with one of these too. Also what psi do you have it set at I might do the same for mine if it’s working for you.
 

Lacksballs

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Late model VK & VL's went away from a mechanical fuel pump & went "low pressure" in tank electric fuel pump with a "fuel vapour separator" (return line back to the tank, just prior to the carb), it also reduced some of the "fuel vapour" issues HDT & the Police Force were experiencing. I would check the fuel pressure and see if its is still within spec.

Screen Shot 2020-07-11 at 1.44.17 pm.png
 

Smitty

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Late model VK & VL's went away from a mechanical fuel pump & went "low pressure" in tank electric fuel pump with a "fuel vapour separator" (return line back to the tank, just prior to the carb), it also reduced some of the "fuel vapour" issues HDT & the Police Force were experiencing. I would check the fuel pressure and see if its is still within spec.

ummm... nope, sorry

VKs and VLs got BOTH mech and low pressure in-tank pumps.
the in-tank pump was there to fix a hot-start issue the police (NSW police mainly)
found after a long hot run on the highway, the fuel in the bowl 'percolates' and
the car won't start. Bad news when you are on highway patrol. Crooks get away ... ;)

GMH fix dreamt up by LP was to add the in-tank leccy pump to
fill the Quaddie's fuel bowl with nice cool fuel from the tank.
Starting problems? ... gone
but
as pointed out, you needed a return line back to the tank.
 
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Smitty

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Hi all. I have a vk commodore 308 with a Rochester quadrajet that’s already been rebuilt. The carb seems to be filling up with too much fuel causing fuel to come out of the accelerator pump. Currently it’s only got a new mechanical fuel pump Higher output one and no electric pump.
the guy at the performance shop tested the carby and said I may need a return line back to the fuel tank and I’m missing the little piece just before the carby that has the return fuel line also. I think this works as a regulator of some sort. Any idea where the fuel return line would connect into my petrol tank as I can’t see any spare holes.
thanks

mate.. simple

the needle and seat that is at the entrance to the Quaddy's fuel bowl is either
wrongly adjusted, out of place (ppl who rebuild Quaddies get the spring retainer wrong ALL the time)
or..
you got some grit jammed under the needle in the entrance to the fuel bowl or
or
and this really S#*Ts me... hey, lets set the fuel level HIGH (adjusting the float)
so
the Quaddie produces more power.

Arrogant nonsense... Quaddies when set up correctly will run a 200ci 4cyl, a 8litre
Cadillac engine or a Holden 308 at 8,000 (just ask Alan Grice or Les Small)

Take the bloody carby to whoever 'fixed' and tell them to FIX IT PROPERLY.

ps...
I run a Quadrajet on my VK race car, I build 'em myself and set them up myself.
They work fine, just watch out for the 'F*%KHEADS" who tell you otherwise
 

Andrew Ivanic

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Hi smitty, thanks for your advice. I took the carby back to the place that built it today and they ran it on one of their test engines and seemed to work ok in front of me. He said the test engine runs 6psi and he thinks it might be my fuel pressure. It seems like fuel is coming out from the accelerator pump when I floor the car or cruise on the highway at a consistent speed. Do you think it could be still related to needle and seat or fuel bowl set incorrectly ? Mate if you lived in Sydney I would just bring it to you :)
 

shane_3800

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Everyone is just pissing in the wind without knowing the fuel pressure.
I'm a mechanic by trade.
If you don't have a fuel pressure gauge take your car to a workshop get it tested.
 

Vin999

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Hi all. I have a vk commodore 308 with a Rochester quadrajet that’s already been rebuilt. The carb seems to be filling up with too much fuel causing fuel to come out of the accelerator pump. Currently it’s only got a new mechanical fuel pump Higher output one and no electric pump.
the guy at the performance shop tested the carby and said I may need a return line back to the fuel tank and I’m missing the little piece just before the carby that has the return fuel line also. I think this works as a regulator of some sort. Any idea where the fuel return line would connect into my petrol tank as I can’t see any spare holes.
thanks
sounds like your new higher output fuel pump might be to much pressure.
The return line goes into one the 2 pipe sender plug unit on the fuel tank, other pipe is obviously the fuel to carby line.
The intank fuel pump is a low pressure one running at 30-40 kpa

The rochester 4 barrell is a capable carby for most situations and done right is capable of handling fuel/power and aggressive cam, just look at the H series V8's
My mates VL 4.9 calais has the small intank pump which only operates for a few secs to start car on ignition/key and then turns off and works fine with manual fuel pump on block and the rochester, this is a stock factory car.
 
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