Electric Fuel Pump Size

[garrett66]

Hey everybody I just put in my new CHP 347 the last couple weekends and ran into some fuel problems or lack thereof. I've got the engine tuned well but it will only idle for 1-2 minutes. I've got a speed demon 650 and you can just see the fuel disappear through the sight bowls. Alright so the fuel pump I am running right now is just a cheap napa product with like 20-ish gph. My question is what gph and max psi do I need? Thanks in advance.

 

[blown65]

7psi is what I shoot for, and even 20gph should have it idle fine. You might wanna look at something else causing it?

 

[garrett66]

I thought 7psi was going to be right. I thought for sure it was too small of a fuel pump. I had the idle set up high but that should not cause anything. I would look at the sight glasses on the carb and the fuel starts right at halfway through the glass but when I start it up I can just see it drain. It dies at the exact same time every time. It must not be refilling fast enough right?

 

[blown65]

If its holding 7psi while running, then its a restriction at the carb, needle/seat or something. If your pump is too small the pressure will drop.

 

[oh9mustang]

7 psi is enough like 65 said. It's most likely the filter.
Either replace the filter oooorr. Take the line off after the filter and with a can under the line turn the switch on to see how much fuel comes out, Now take the filter off and do it again. If there is a bunch more fuel with no filter it's the filter, if they are the same the problem elsewhere.

 

[garrett66]

Thanks 65 & oh9. I've got the filter placed before the pump. I didn't really know if it was supposed to go before or after so I put it before just to protect the pump. It's a new filter but just a cheapie so my best bet is to probably get a "faster" filter.

 

[oh9mustang]

Take the filter out of the system. If that makes the car run right then get a "Faster Filter" . I would guess your pump is out pulling the filters gravity flow capacity. Put the filter on the other side of the pump.

 

[garrett66]

OK thanks for the info!

 

[ron67fb]

To clarify (for me): you turn the key "on", pump starts and fills the bowl, and after you crank the car it starts, then the bowl starts to drain? It sounds like your fuel flow is completely cut off when the engine is running. The bowl shouldn't drain on its own at idle unless there's gas leaking somewhere or no gas is going into the bowl in the first place. Is the float set OK? Is the fuel pump wired incorrectly that it shuts off when the engine is running? Do you have a fuel pressure gauge to test all this?

A pre-pump filter is common and actually recommended to keep the crud out of the pump. A new filter, no matter where you put it, will not prevent the bowl from filling at idle. 2PSI is usually enough to idle a carb.

 

[garrett66]

I have the pump wired up to the solenoid so that it pumps when the key is in on and it is still hot while the car is running. The pump is hot while the car is running, I'm using 16 gauge wire (it doesn't feel to be overheating or anything) I don't know the fuel press. while it is running but I think the pump is working. I have ordered a fuel pressure guage and when I am around my car next which should be the 2nd I can tell. I noticed no fuel leaks or any other leaks, no spills on the concrete. I had it idling high like at 1500-2000 for the break-in so it should be using more fuel than a true idle bot not than damn much. It's a brand new 650 speed demon and should be set right out of the factory. I will try adjusting the floats.