I don't drive my car a lot so usually the carb is empty when I want to start it. To help with this problem I am thinking about adding an electric fuel pump back by the gas tank that is connected to the ignition. Then I can turn the key forward and let the carb fill up before I turn the engine over. I would like to leave the mechanical pump in place and push the gas through it prior to engine turn over. Then when the engine is started both pumps would be operating. Has anyone tried this or know if this will work?

thanks,
phil

 

I have in the past, a lot of guys have.

For safety's sake, it's a good idea to have the pump in series with an oil pressure switch (no oil pressure, no power to pump). But, in order to accomplish your objective of filling the bowl b/4 cranking, you'd have to tie in a timing relay parallel to the oil pressure switch.

 

Why not just fix the problem of your carb fuel bowl going dry
over night. Its a common problem on Qjets and is easily repaired.

 

Ok, what's the repair? hehe I've got a problem with one going dry over a day or two.

 

I think he is referring to puting epoxy over the 4 plugs inside the carb. I did do that. Maybe i did it incorrectly, but it still seems to dry out in a couple days somehow.

phil

 

Phil- Qjets get dry in a few days. I don't know how, but they do. I've been dealing with these little buggers for 19 years and I'm still not sure why. I think it has something to do with the fule inlet being in the FLOOR of the carb float bowl, and the fuel eventually drains back through the fuel line. It's actually quite rare to find a Qjet these days with leaky plugs. The factory pretty much solved that problem 25 years ago (not to say it doesn't happen occasionally).

I have run the pusher electric + mechanical on block setup several times. It's my absolute favoite street setup, requiring no major fuel system surgery. I use it on my blown 383 Malibu (~450 HP, mid 12s on street tires) and my previous 79 Malibu with nitroused 400 (~500 HP, high 11s on street tires). It flat WORKS. And having a backup fuel pump to get home on if one goes bad is a nice feature, as is being able to prime the carb at startup.

here's how:

1. Pick your electric fuel pump: 2 pumps come immediately to mind (I've used both). The Carter electric street pump (5 PSI, 72 GPH, 4.5 Amp draw) and the Holley Red pump (7 PSI, 97 GPH, ~7.5 amp draw). The smaller Carter is what I have typically used and it's fed my engines well to 500HP, so don't think you have to go gonzo with your pump choice.

2. Get a fuel pump relay kit. Summit and everyone sells them for not a lot of bucks. You don't want to draw the amperage to run the pump directly off a fuse in the fuse panel- you might get away with it, but it's really kinda pushing things and THE PUMPS GET VERY INEFFICIENT IF YOU DON'T SUPPLY THEM A FULL 12V!!! You NEED to use a relay and tap the pump's power wire into a good battery voltage source to ensure adequate volts/amps.

3. You can add an in-line pressure switch to the system so the pump will turn off if oil pressure drops to zero. However, this will prevent you from priming the carb before a startup. I don't use one, but I also admit that can be dangerous in the event of an accident situation (the pump will contiue to run and pump gas). You decide.

DO YOU NEED A REGULATOR? No. The front-mounted fuel pump, since it runs at about the same pressure as the electric, will not get "overrun" by it. The mechanical pump's internal relief spring is all the regulator you will ever need. My setup holds a constant 6 PSI under ALL conditions from idle to WOT/redline.

 

Thanks much for the very complete response. The relay sounds like good advice. Is the Carter very noisy?


I saw that Napa had a electric fuel pump for $30. It looks like a Puralator from the picture. Do you have any info on that. link below:

http://www.napaonline.com/cgi-bin/nc...grpid=49802171



phil

 

I've been thinking of adding an electric pump also. My plan is to use a microswitch that will switch on a pump relay at WOT. This could be used to prime the carb by switching on the ignition, then holding the gas pedal to the floor for a few seconds. I'm looking at the Carter P4070, its $60 at Summit.

 

The Carter is a little noisier than the Holley. Over loud exhaust you won't hear it but if your exhaust is quieter than my 2 chamber Flowmasters with turn-downs underneath the car you may want to use the Holley instead. I was quite surprised how much quieter the Holley was considering it flows more at higher pressure than the Carter.