Converting to electric fuel pump

[Leedanger]

Hi…Just did a block replacement on a 4.3, about a 1990. Does not have the counter balance shaft. The original cracked block had a mechanical fuel pump, the new block doesn't have the hole milled for one so I have to go electric. Obviously it is carb and there is no oil pressure switch to run from. Where should I run it from….? I'm pretty sure I have electric choke, I could solder and heat shrink into there. Or run it back to the starter? Is there a difference in the 4.3 pumps? What I mean is…If I get one say for a 4.3 LX carb'd version that should work, no?

 

[Watermann]

I have a tough time believing GM reworked the casting and deleted the fuel pump are you sure there isn't just a plate covering the opening?

Don't wire anything to your starter, your dealing with fuel and if not 100% sure what your doing you should have someone come and help you or take it to a shop. The power wire for elec fuel pumps can come from an ignition wire that supplies power only when on.

 

[stonyloam]

OK, not an expert here but don't think that is going to work. You need an oil pressure switch for safety reasons. You can "T" it into your current oil pressure location. You use a three prong switch that allows the pump to get power from the starter when cranking. Just splicing in will not work for power (draws too much power) but no problem, just go with a electric fuel pump relay kit. Do your splice and Power the relay off of the ignition through the oil switch and pick up power for the pump directly through the battery, maybe the hot slave terminal or starter + battery lug. All that stuff is pretty available, just make sure it is marine rated.

 

[dubs283]

I have a tough time believing GM reworked the casting and deleted the fuel pump are you sure there isn't just a plate covering the opening?

there are over 30 different variations of the 4.3 long block, you bet GM changed things on that motor!! most likely GM didn't machine the cavity for the fuel pump mount and actuator rod on the op's new block

The power wire for elec fuel pumps can come from an ignition wire that supplies power only when on.

that is why the op needs an oil pressure switch to power the fuel pump, if the engine stops running but the ignition is still powered, the way you suggest it the fuel pump will still run, not good. wired correctly, when the engine stops running, oil pressure drops and power to the pump stops

 

[midcarolina]

I am pretty sure the pump runs off the slave solenoid while starting........then when engine fires the pump then runs from the purple wire on the oil pressure switch.

any marine electric fuel pump for a carb setup will work........I think all carb fuel pumps have a max of 5-7 psi

 

[achris]

I am pretty sure the pump runs off the slave solenoid while starting........then when engine fires the pump then runs from the purple wire on the oil pressure switch.

any marine electric fuel pump for a carb setup will work........I think all carb fuel pumps have a max of 5-7 psi

Correct... But the wire from the oil switch to the pump is purple with a yellow stripe.The supply side of the pressure switch is purple, which is ignition switched.

 

[Leedanger]

Roger…Ya thanks guys. I was wondering if I was gonna have to wire in a oil pressure switch. Doesn't an oil pressure switch on a newer model get its power from the alternator? So from the alt (purple) to the oil pressure switch (purple -> purple/yellow) which then feeds both the electric fuel pump and the electric choke.

I wonder whats feeding my electric choke now? I guess that wire wouldn't work though being that the choke isn't as critical if active with just key in on position unlike the fuel pump.

 

[stonyloam]

You use a three prong oil pressure switch. One prong (switch normally closed) is wired to the starter and sees voltage when the starter is turning, provides voltage to the output prong wired to the pump (or better the pump relay). When the engine starts and oil pressure builds the starter prong switch opens and the third prong, attached to the ignition closes and provides voltage to the pump relay as long as the ignition is on and there is sufficient oil pressure. If you use the pump relay, wire it directly to a battery source and you will have plenty of power to run the pump and be safe. Wiring to the purple choke wire should be fine if you use a relay.