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bypass mechanical fuel pump when installing electric pump?
Posted: Tue Nov 15, 2011 12:34 am
by Wombat
Should I bypass the old mechanical fuel pump when installing a new electric one, or just have both? If I bypass the old one, do I need to connect its outlet and inlet with a loop of hose?
Re: bypass mechanical fuel pump when installing electric pum
Posted: Tue Nov 15, 2011 4:24 am
by SCOTTRODS
Wombat wrote:Should I bypass the old mechanical fuel pump when installing a new electric one, or just have both? If I bypass the old one, do I need to connect its outlet and inlet with a loop of hose?
Pull the stock pump. Install a cover plate with gasket. No more wondering.
Re: bypass mechanical fuel pump when installing electric pum
Posted: Tue Nov 15, 2011 5:59 am
by MinamiKotaro
Just remove the stock pump completely.
Re: bypass mechanical fuel pump when installing electric pum
Posted: Tue Nov 15, 2011 10:41 am
by Marc
Removing it looks more sanitary, and most blockoff plates can be drilled/tapped for a crankcase ventilation line.
I've usually left the stock pump in place (with a loop of hose connecting inlet & outlet) to provide an emergency backup. It's not a positive-displacement pump, so with no fuel demand there's very little motion of the internal parts - other than the pushrod rising/falling - so it's basically just going along for the ride.
Re: bypass mechanical fuel pump when installing electric pum
Posted: Tue Nov 15, 2011 2:06 pm
by crvc
Maybe it's a given but don't you need a regulator if you put in an electric fuel pump? I believe the stock carb needs 2-3psi at the float valve. Anything more overwhelms it and leads to flooding. My electric pump put out something like 20psi. I could never get the regulator low enough and gave up, going back to the stock pump.
kevin
Re: bypass mechanical fuel pump when installing electric pum
Posted: Tue Nov 15, 2011 4:49 pm
by Max Welton
It depends Kevin, on how much pressure the electric makes and how much the carbs need or can tolerate.
An electric pump putting out 20 psi almost sounds like an FI pump.
Max
Re: bypass mechanical fuel pump when installing electric pum
Posted: Wed Nov 16, 2011 6:49 am
by Jim Ed
SCOTTRODS wrote:Wombat wrote:Should I bypass the old mechanical fuel pump when installing a new electric one, or just have both? If I bypass the old one, do I need to connect its outlet and inlet with a loop of hose?
Pull the stock pump. Install a cover plate with gasket. No more wondering.
If you want to go this route, here is a link to the block off cover:
FUEL PUMP BLOCK OFF - BUG STYLE 12-1600 ENG.-TAPPED FOR 1/4 INCH NPT (NOT DRILLED COMPLETELY THRU)
https://www2.cip1.com/ProductDetails.as ... C10%2D5625
Re: bypass mechanical fuel pump when installing electric pum
Posted: Thu Nov 17, 2011 2:13 am
by Wombat
Thanks for the help guys. I'll bypass the old stock pump, and put in a loop of hose from the old pump outlet to inlet (keeping the old pump there is handy as a backup).
p.s. I deliberately choose an electric pump with low p.s.i. to suit the carb.
Re: bypass mechanical fuel pump when installing electric pum
Posted: Thu Nov 17, 2011 3:04 pm
by Max Welton
Wombat wrote:p.s. I deliberately choose an electric pump with low p.s.i. to suit the carb.
Be sure to measure it anyhow.
Max