The Stovebolt Site Forums The Shop Area The HiPo Shop electric fuel pump on my 350

I have a line on a good vortec 350. I want to use it on my hotrod, the issue I am concerned with is it has no opening for a mechanical fuel pump and I have heard possible bad things about using an electric pump. I will be using a carb on this engine. Thoughts? Dave

Use an oil pressure sensing switch to run the pump. If the engine stalls and the oil pressure drops, the pump shuts off to prevent a possible flooding situation. You can use a pressure regulator if necessary to give the carb the proper fuel line pressure, although most electric pumps that aren't designed for racing should be in the ballpark without a regulator. The pressure switch used on General Motors fuel injected vehicles combines an idiot light ground with a normally-open 2-contact switch for powering a fuel pump.

http://deden-menenen.rhcloud.com/airtex-os75-oil-pressure-switch/B0027I8CU8.html

Jerry

Lots of good electric pumps available. I ran electric pumps on hot rods 50 years ago w/o any problems. All new cars run electric so I would think reliability issues have been resolved. I would recommend wiring so that when the key is off the pump has no power to it.

I had an external electric fuel pump on my FI 383 SBC for 7 years before I sold it. The pump was a quiet Edlebrock. I installed a regulator and a pressure gauge. No problems. The only thing I was told to watch out for was cavitation in the pump due to too small a line going in, or too restrictive of a filter going in. I had a 10 AN line going in, and an 8AN line going out, which eventually necked down to a 6AN at the injectors. Had a 100 micro fuel filter at the inlet. Lots of pumps available, but try to get one that's durable and quiet.

I've never heard of wiring a pump to an oil pressure switch, and it's not necessary.

There are many reliable pumps that work with carbs reliably.

It is a safety precaution. If you are in a collision, hopefully it stops your engine and that stops the pump.

A stopped engine does not mean the electricity is off.

I had a vapor lock issue with an '83 Trans Am with a Chevy 305 (carburated and mechanical fuel pump). It was a from-the-factory issue. It had to do with the routing of the fuel line near something hot. I solved it with a Holley electric fuel pump and an adjustable pressure regulator with a return line for the excess fuel. This solved the vapor lock by creating a constant flow of fuel going through the fuel line. I did not run the electrical through an oil pressure switch. I would have, had I known about it.
Bottom line: Don't fear a quality electric fuel pump with a regulator in a hotrod.
Carl

A stopped engine has no oil pressure. If a fuel pump is wired to a pressure switch it will not operate with no oil pressure.

Some poker players will draw to an inside straight. That doesn't necessarily make it a smart choice.
Jerry

Always wire in an oil pressure switch to run an electric fuel pump. Best safety device ever. I learned that the hard way.

Even if the ignition switch gets left on, the pump won't run if the oil pressure isn't there to close the switch.

In a wreck with a straight wired pump, the pump can continually run and pump fuel every where if a broken fuel line happens.

I have seen the crankcase of a friend's engine completely filled with gasoline, and gas dripping out of the exhaust pipes from a flooding carburetor and an ignition switch left on. That one was a fun job to clean up after a trip home by a wrecker.
Jerry

Are newer vehicles which came with electric fuel pumps wired through an oil pressure switch or do they have another way to shut it off when the engine stops running?

All GM fuel injected vehicles that I'm aware of use an oil pressure switch to power the fuel pump. There is a 2-second "priming run" to pressurize the fuel rail anytime the ignition is turned on, and/or the pump runs continuously while the starter is engaged, then the switch takes over to keep the engine running. It used to be called a "rollover switch" to be sure the engine would stop in case of a rollover accident. Ford used something similar, an "impact switch" that would trip in a wreck with more deceleration than a fender-bender. The idea is to make sure the fuel stops flowing anytime there's the possibility of broken fuel lines or any possibility of gasoline spillage.
Jerry

A deer ran into the side of our Cougar while we were traveling highway speed and it tripped the impact switch. Took me a minute or two to figure why it killed the engine.