Fuel pump bypass or remove

[85ltd]

I am nearly finished with the 351 swap, but now I want to run a mechanical fuel pump. Do I need to completely remove the electric pump, or can I bypass it? Also, I have return lines and a line running to a charcoal canister. I no longer want these lines, can I just remove them or can I cap them off? On another note, i took the intake and 4 bbl off an 85 van, i also got the distrubitor, but forgot the box. Is it ds2 or ds3? Thanks.

Blane

[gadget73]

I would remove it and make a sump out of brake line. Other folks will tell you they just suck through the electric, but me being overly me, I would be afraid of it causing a restriction.

85 van may be DS3. if its got 3 plugs, its DS3. Jumper the third plug together, and run it if thats what you have. That will bypass the spark retard mode and just let the distributor's internals handle advancing. If its got 2 plugs, just plug and pray.

You can dump the charcoal canister. Cap the steel line off that comes from the back and bin the rest off it. The old fuel return line can also be capped off.

[marquisman]

yea, that mech fuel pump will have issues supplying fuel to the carb with that pump in there. remove it and make your own pick up in the tank.

[King_V]

Am I correct in assuming that using the electric pump and just switching to a fuel pressure regulator that will keep the pressure low enough for carburetors is not an option? Because, uh, I was going to suggest that...

[sly]

IIRC... those fuel pressure regulators can be problematic and cost way more than it's worth.

[marquisman]

much better if you can eliminate the fuel pump.

[DuceAnAHalf]

Am I correct in assuming that using the electric pump and just switching to a fuel pressure regulator that will keep the pressure low enough for carburetors is not an option? Because, uh, I was going to suggest that...

you can do that provided you use a bypass style pump. this will bleed off the excess fuel pressure back into the tank.

http://aeromotiveinc.com/tech-help/f...ed-regulators/

I want to convert my EFI engine to carburetion, how can I “knock the pressure down” coming out of my EFI pump? Does Aeromotive have a regulator for this application?
The greatest misunderstanding about fuel pumps is that they “put out” pressure. It’s best to think of the pump as a source of flow-volume. A bypass regulator creates pressure by restricting the volume flowing from the pump, thereby driving the pressure up to the set point. Once the pump has created enough pressure to open the regulator bypass, the regulator leaks just enough flow to maintain the desired pressure. The Aeromotive 13204 bypass regulator can flow enough volume on the return to handle most medium to larger EFI pumps, if the return line itself is large enough. Note: Most stock EFI return lines are too small for a carburetor conversion, creating more backpressure than the regulator. At minimum, carb conversions with a 13204 regulator will require a –6 AN return line for small OE pumps and a –8 AN for medium to larger pumps. Contrary to some conventional beliefs, the return line can never be too big if the regulator is right for the job. When in doubt, the bigger, more free flowing return line is the better choice.

[1987cp]

One guy reported OK results just using a tee fitting by the carb, no regulator at all, and keeping whatever pump his CFI (IIRC) system had used. Doesn't seem like logically a very good idea, though.


Scotty, I assume you mean bypass-style regulator?



If you really want to use a return line with a mechanical pump, you can get the return-style mechanical pump used on 351W fleet cars. But, it's rated at only 30gph versus 40gph for a stock replacement deadhead pump, so go figure.

[gadget73]

It just seems that all of the solutions to not remove the stock fuel pump cost a lot more time to implement than dropping the tank and making a sump or replacing the pump hanger with parts from a carb vehicle. I myself refuse to pay $100+ for a part that is made uneccesary with an hour of work and a couple dollars in parts. Besides, mechanical fuel pumps are highly reliable. I'd question how durable one of those expensive regulators are in the long run.

[King_V]

Yikes! I wasn't aware that they were THAT expensive.... Egad!

[1987cp]

Yeah, for less than that you can get a nice Eddybock mechanical pump that's rated at more GPH than most of us will ever need and doesn't even require a regulator like my Summit pump does. And a stock '79 pump is more like $20.