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Qjet flooding with electric fuel pump?

7

77crewcab

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Need some help here. I have a 87 crewcab that at some time in the past has been converted from TBI to carb/propane and then to just carb. I am trying to get it running and am having an issue with the q-jet flooding (gushing) fuel everywhere. The truck has an aftermarket electric fuel pump which is putting out 4.5 psi (verified with guage and fuel pressure regulator). I have rebuilt the Qjet and checked float level per spec with the kit. Running 70 jets 32 primary rods G hanger and DR secondary rods. Everytime I turn the fuel pump on it starts pouring fuel from the carb. I am stumped as to why. Any ideas?
 
Is the pressure you are reading with the gas pouring out of the carb? Try plugging the fuel line and see what the regulator stalls out at.
4.5 is a little high for some carbs, so you might want to turn it down a little. But 4.5 with the gas pouring out may turn into 7 or 8 when there is no flow.

J.
 
Is there a provision for a fuel return line to the tank?

StromTrooper has a carb on a truck that used to be TBI, and IIRC he runs at 3psi... maybe ask Dave
 
I agree with the above, try 2-3 psi.
 
The 4.5 psi is deadheaded. I turned the regulator down to .5 psi position (about) 2psi on the guage deadheaded and it still floods. I do have the return line and thought about hooking it up, but not sure if I should do it on the "in" or "out" side of the regulator. I have the regulator set up where the "out" side has a t-fitting one line goes to the carb and one to the guage. Hooked up this way the guage reads 0 and the fuel pours out of the carb. One thing I thought of is that I am not running the stock style fuel filter but an inline style. But I have removed the stock filter and spring in other trucks and run an inline filter with no side effects so I ruled that out. How should I plumb the return? Any other thoughts on what could be happening?
 
So either the float is full w/ fuel, doesn't actually float, and can't shut off the fuel flow at the needle, or the needle isn't working/crooked/can't settle properly into seat, or the pressure is so high it blows the needle off the seat and fills/floods the bowl. Methinks w/o the return fuel pressure might simply be too high.
 
X2 on the float being bad or you bent the needle.

But I have to ask.Why would you switch from TBI to carb/propane?
 
Kinda what I was thinking too. Tomorrow I wil try hooking up the return both before and after the regulator and see what happens each way. I am thinking it might just be a matter of having the right pressure but too much flow. With the fuel line disconnected I turn the pump on and it shoots fuel out like a water hose. I don't think it is the carb. I had a Holley on it to start with that the PO had "rebuilt" and it did the same thing. I just assumed it was a botched rebuild and rebuilt the Qjet to take the place of the Holley. But since it doing the same thing I am thinking that it is really a matter of too much fuel. The pump is a universal pump for a V8 carb application so I am a little surprised at having this issue.
 
Does your regulator have one "in" and two "outs"? If so run one "out" to the carb and the other "out" to the return line. Also, you might want to check your gauge against another gauge just to make sure you are getting what you think you are getting. With the return line hooked up there won't be any build up of excessive pressure. And X2 on checking the floats and needles. Good luck!
 
Only one in and one out. I am going to try setting up the return line both before and after to see which has the best result. I really think that the issue lies with the fuel pump rather than with the carb. If all else fails I have everything needed to swap in a mechanical pump, I would rather try to get it working as is for now though. I need it as a driver while I make plans for future upgrades.
 
Massacre-77 said:
is thare a power gain running a eletric pump over mech.
Click to expand...

For me it is more a mater of trying to work with what I have without having to swap out all the lines to go with a mechanical pump. I am building another engine to take the place of this one. It will be fuel injected so I would like to be able to keep the fuel lines "as is" for now. The electric pump was put on by the PO because both TBI intank pumps went out.
 
Massacre-77 said:
is thare a power gain running a eletric pump over mech.
Click to expand...
I like the simplicity of a mechanical pump. you can get up to 170gph pumps in mechanical. That should handle 800hp or more.
 
Well with a little trial and error I think I have it figured out to where it is driveable for now which was the intent. I still haven't hooked up the return line yet but installed a small ball valve between the regulator and carb and set the deadhead psi at 2psi. The problem seemed to be with too much flow. Wit the ball valve I can limit how much gets to the carb. I plan to install the return line once I get it home and can tinker with it more. I have had it in storage since I got it last summer with no time to work on it. Just needed to get it running well enough to drive the two miles home so I can play with it more. But I was able to drive it around the storage lot today and it is doing pretty well.
 
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