Electric Fuel Pump Doesn't work

[The_Handier_Man1]

From: cooneytunes  (Original Message)
Sent: 10/16/2004 1:13 AM

This question is posted in my maiden voyage discussion also. But I figured I also post it here so anyone else who want to do this could find it on message search.
Question? PO installed an electric fuel pump wired diretly off ignition, so when the key goes on, the pump comes on. I put a centrifical roll over cut off switch in it. I didn't like the idea of the pump not shutting down in case of an accident. The old vac. fuel pump lines are disconnected. The pump looks brand new. He said he got a lot of vapor lock in the summer, replaced original pump, did not solve vapor lock, so he installed the electric pump and disconnected vaccum pump. that solved the V/L problem.......
I should be able to re-connect the vaccum pump with the electric pump in line, but I believe I would need a pressure switch for the electric pump. Correct? I talked with a guy who works at NAPA,  he never heard of that configuration, and couldn't help. I was wondering if any one has that set up?  What brand switch is, pressure settings &  make or part # for the switch, and what the order of the lines, and wires would be?
Timmy



From: Sea Hag
Sent: 10/16/2004 8:25 AM

Timmy , I would go with one or the other , I wouldn't tie both the aftermarket electric and OEM type diaphram pump  together without some type of valved manifold . Neither pump type is designed for presurized input and may cause problems . I also think both pumps would have to be running to allow fuel to pass through them if they were on the same line anyway . Sea Hag 



From: DaveVa78Chieftain
Sent: 10/16/2004 9:32 AM

Fuel pump output pressure:
318: 5-7 lbs
413: 7-8 1/2 lbs
440: 6-7 1/2 lbs
Safety switch (oil pressure type):
http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=724&prmenbr=361

Dave



From: HeavyHaulTrucker
Sent: 10/17/2004 11:49 PM

Sea Hag is right; the electric pump brings fuel up from the tank, but unless the mechanical pump is working it won't get to the carb.  I am having this issue with mine right now; the PO ran the electric pump into the mechanical pump, then through a fuel filter to the carb.  In order to start the engine after an extended time, I have to let the electric pump run a minute or so before I crank it over so I don't crank the starter too long.

I think that I am going to remove the mechanical pump and seal off the opening with a plate/ gasket; of course, it will go into my "spare parts" box for an emergency (like if the electric pump craps out). 

In my case, the electic pump that the PO used is a big Carter racing pump (15 psi output!); even when running through the mechanical pump, I am still getting 10 psi to the carb -- it is literally blowing my float bowl needles out of their seats and letting the engine flood occasionally when I decellerate quickly.  Apparently, the engine uses enough fuel at high rpm (65 mph and above) to keep the fuel level in the bowls at a decent level -- but when there is pressure built up and the fuel demand drops suddenly, the floats are not bouyant enough to push the float bowl needles into the sealed position and the bowl fills too full.  With the ThermoQuad, when the bowl fills too full, the excess fuel comes out of the secondary air valve shaft hole and floods out the secondaries.  This shaft is run through the top of the float bowl, and has no seal to prevent fuel leakage -- one of the design problems with the T'quad.

I will be replacing it with a Holly as soon as I can scrape together the money.  I have rebuilt it a total of 3 times now, and I have had enough of it -- so everyone kindly disregard my earlier post where I mentioned how easy it was to rebuild! 

John



From: Sea Hag
Sent: 10/18/2004 10:59 AM

I would imagine that 15 psi would cause some problems . The specifications for the OEM fuel pump are 5 to 7 Psi . Sea Hag