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Old 04-27-2011, 11:29 AM
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Having fuel problems

I swapped a carb 350 candid bolt style non vortec into my 1988 Iroc Z. I'm using a q-jet carb and an engine mounted fuel pump. It was flooding out, so I changed the plugs and bought a new Holley 600 carb. It was still flooding out(actually the Holley flooded worse) I noticed the fuel pump in the tank was still hooked up(the previous owner used a manual pump, so I figured it wasn't hooked up) So I cut the wire, Now It runs for a while then bogs out. I checked the fuel pressure none at all. I replaced the manual pump, same thing happens. By this time I put the q-jet back on, I reconnected the pump in the tank and it doesn't seem to flood at all with q-jet. Holley flooded through top of carb. So I ran it alot the rest of the day w/o any problem. Today I run it and it bogs down again. Should I remove the fuel pump in the tank? I also did this before on another car and didn't have to remove the fuel pump in tank. I used and external electric pump to the carb then though. Any help would be appreciated.

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Old 04-27-2011, 01:31 PM
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Is the Holley carb new or was it removed from another vehicle? If it was swapped from another vehicle it could be that the float bowl is not working properly, which would allow for too much fuel. Another possibility would be the jetting within the carb.

Have you tried adjusting the air/fuel mixture screw. Don't go crazy turning the screws.
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Old 04-27-2011, 02:01 PM
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Holley was brand new but I have since returned it. The problem I'm having now is the gas isn't getting to the carb consistently. Should I remove the in tank fuel pump to free up the engine mounted one that I have? Keep in mind their both currently pumping right now. The in tank FP is pushing anywhere between 65-90 psi it seems the engine mounted FP is working as a regulator. The Q-jet isn't flooding anymore. Just gas isn't making to carb all the time.
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Old 04-27-2011, 02:14 PM
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Ok, so it sounds like you're going to stick with the Quadrajet. Just so I understand you would like to use the mechanical pump correct? If so, I would recommend that you physically remove the pump since the mechanical pump is trying to "suck" through it. In addition the electric fuel pump puts out way too much pressure for the quad.

IMO it would be best to run at approx. 9psi.
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Old 04-27-2011, 08:51 PM
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Thanks for the help bro. I will definitely pull out the FP in tank ASAP. Also is there a a way to make sure the mechanical pump functions at 9 psi?
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Old 04-27-2011, 10:02 PM
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Well the easiest way is to check with a fuel pressure gauge. you dont need anything expensive. Just a simple one. The second option would be to put a mechanical fuel pressure gauge.
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Old 04-28-2011, 07:47 AM
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I agree with toofast415. Remove the in tank pump, mechanical fuel pumps won't suck as good as they push. With a stock mechanical pump you should'nt have to be concerned about to much pressure but Q jets will flood over if to much pressure is introduced. Don't forget to use the filter that is in the inlet of the Q jet I feel it is necessary even if an inline filter is used. With a mechanical pump, if you decide to use an inline filter be sure to place it after the pump and not before. After you remove the in tank pump make sure the tank is vented or you will still have a problem. I love Q jets and use them whenever possible.
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Old 04-28-2011, 11:38 AM
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I will remove the in tank as soon as possible. It's currently raining cats and dogs here. Thanks for the help guys. p.s. I'm thinking about upgrading my heads later. I currently have iron candid bolt style heads non vortec w/ Lunati Voodoo cam 268 int. 276 exh. .489 lift to .504 lift & a small stall 2300-2500 I want to make power but am kind of on a budget. Any recommendations?
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Old 04-28-2011, 11:40 AM
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Oh forgot to mention I think the pistons are stock. I didn't remove heads on other upgrades.
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