Fuel pump wiring, ecm bypassing?

[Raje]

so I’ve searched and there’s so many threads, haven’t exactly found what I’m looking for.
Long story short, got a 89 shorty, p/o had no clue about the engine as it ran like crap.

Had a 79 dually with a mild built big block that got hit and written off..anyhow yanked the tbi 350 out and shoved the big block.

Started going through the wires and such, would like to keep the stock pump and feed it into the regulator and to carb..now is it possible to bypass the oil pressure sensor to activate the pump as well as heard ecm acts as a ground for the relay.. as I heard ground the wire going to the ecm, but nothing about the oil pressure sensor..
Can I wire that into a switch or splice it into another wire or can I just delete that wire (Grey and orange I believe) that goes to the oil sensor?

I do have the option to reroute the fuel lines to the mechanical pump but it’s tight along the frame that I feel it’s easier to just rewire the pump relay..and would like a better idea of how’s its done.

Thanks in advance

 

[Tweakergeeker]

Youd be better off getting a sbc mechanically fuel pump. For me im running a 5.7 l31 i converted from tbi electronically bs to old school mechanical because the motor was running like **** and it already had new cam and internals. Kinda like you. Wiring your pump is just like wiring a aftermarket light you throw on the bumper. Youd need to it on a switch on your dash to tur n it on and off. Tbi fuel pumps has roughly 55-60psi being pushed to your carb. Mechanical fuel pumps bolt right on the block passenger side sorta next to the headers. Acts like a vacuum and pulls fuel to the carb because your camshaft has a lobe for the pump to have a pinion sit on. Sorta kind like your push rods and lifters. Most mechanical pumps are setup for carburetor applications. You wouldn't need to mess with any wiring, just reroute fuel lines and depending if you cant pull fuel from your electric pump in your tank youd have to take your old electric pump out and drop a fuel line into your tank cut. (Cut it at 45° so the new fuel line wont suck itself to the tank. Ive been there myself haha) through this all and much more on my 89chevy racetruck. Your truck will have fuel pressure and start even if you dont have oil pressure to start the engine with a mechanical fuel pump. If your truck isnt starting because of no oil pressure that will help get it able to run at least so you can fix it

 

[evilunclegrimace]

Youd be better off getting a sbc mechanically fuel pump. For me im running a 5.7 l31 i converted from tbi electronically bs to old school mechanical because the motor was running like **** and it already had new cam and internals. Kinda like you. Wiring your pump is just like wiring a aftermarket light you throw on the bumper. Youd need to it on a switch on your dash to tur n it on and off. Tbi fuel pumps has roughly 55-60psi being pushed to your carb. Mechanical fuel pumps bolt right on the block passenger side sorta next to the headers. Acts like a vacuum and pulls fuel to the carb because your camshaft has a lobe for the pump to have a pinion sit on. Sorta kind like your push rods and lifters. Most mechanical pumps are setup for carburetor applications. You wouldn't need to mess with any wiring, just reroute fuel lines and depending if you cant pull fuel from your electric pump in your tank youd have to take your old electric pump out and drop a fuel line into your tank cut. (Cut it at 45° so the new fuel line wont suck itself to the tank. Ive been there myself haha) through this all and much more on my 89chevy racetruck. Your truck will have fuel pressure and start even if you dont have oil pressure to start the engine with a mechanical fuel pump. If your truck isnt starting because of no oil pressure that will help get it able to run at least so you can fix it

'89 TBI fuel pump runs 9-13 psi. '96 and up Vortec engines run at the higher pressure

 

[evilunclegrimace]

so I’ve searched and there’s so many threads, haven’t exactly found what I’m looking for.
Long story short, got a 89 shorty, p/o had no clue about the engine as it ran like crap.

Had a 79 dually with a mild built big block that got hit and written off..anyhow yanked the tbi 350 out and shoved the big block.

Started going through the wires and such, would like to keep the stock pump and feed it into the regulator and to carb..now is it possible to bypass the oil pressure sensor to activate the pump as well as heard ecm acts as a ground for the relay.. as I heard ground the wire going to the ecm, but nothing about the oil pressure sensor..
Can I wire that into a switch or splice it into another wire or can I just delete that wire (Grey and orange I believe) that goes to the oil sensor?

I do have the option to reroute the fuel lines to the mechanical pump but it’s tight along the frame that I feel it’s easier to just rewire the pump relay..and would like a better idea of how’s its done.

Thanks in advance

Why do you want to rewire the OP switch? just plumb it into a pressure galley and it will work just fine

 

[Tweakergeeker]

Why do you want to rewire the OP switch? just plumb it into a pressure galley and it will work just fine

Thats still a lot of pressure being sent to the regulator that you dont need. Mechanical fuel pumps are usually only produced max of 10psi for carbureted applications. He would be better off with the mechanical pump instead of wiring a relay. Get the wrong wire connected tk the spot **** will melt or worse.

 

[evilunclegrimace]

Thats still a lot of pressure being sent to the regulator that you dont need. Mechanical fuel pumps are usually only produced max of 10psi for carbureted applications. He would be better off with the mechanical pump instead of wiring a relay. Get the wrong wire connected tk the spot **** will melt or worse.

OK NO! A regulator is more than capable of handling 13 PSI of fuel pressure.And as far as the wiring goes he can use the factory wiring to control the fuel pump just like the millions of these trucks have for the last 30 years

 

[Tweakergeeker]

Buddy my daily driver is converted 89 k1500 with a 750 carb, highrise, hei distributor, pocketed heads, and some long tube headers. Not to mention all my other ****. Ive already been throu all the **** hes talking about. Yeah sure it will work. But for a RELIABLE source of constant fuel pressure on a mechanical engine hes better off with the mechanical pump. Those ecms and fuel relays go to **** on on the 89 k1500 models. Op act as a kill switch tk the fuel pump ie why it wont start. Its shorted most likely like mine. Bypass the ecm and reroute a fuel line to a mechanical pump then to a regulator then carb. That easy never have tk question tbe fuel system again

 

[PlayingWithTBI]

Well, going back to a carb was your 1st mistake. Thinking you know it all about TBI was your 2nd.

 

[Tweakergeeker]

so I’ve searched and there’s so many threads, haven’t exactly found what I’m looking for.
Long story short, got a 89 shorty, p/o had no clue about the engine as it ran like crap.

Had a 79 dually with a mild built big block that got hit and written off..anyhow yanked the tbi 350 out and shoved the big block.

Started going through the wires and such, would like to keep the stock pump and feed it into the regulator and to carb..now is it possible to bypass the oil pressure sensor to activate the pump as well as heard ecm acts as a ground for the relay.. as I heard ground the wire going to the ecm, but nothing about the oil pressure sensor..
Can I wire that into a switch or splice it into another wire or can I just delete that wire (Grey and orange I believe) that goes to the oil sensor?

I do have the option to reroute the fuel lines to the mechanical pump but it’s tight along the frame that I feel it’s easier to just rewire the pump relay..and would like a better idea of how’s its done.

Thanks in advance

Just wire it to your ignition. Not your heis power supply. Pretty positive its a pink wire off the old distributor. You need a constant 12v, throw a inline fuse in there too. That will make the pump pressurize when you turn your key on. When i first built my 500horse l31 thats what I did temporarily till i got a big badass badass mechanical pump with a bunch of goodies on it.

 

[Tweakergeeker]

There isnt anything wrong with a mechanical engine if you take the time and do it right. I started with my block bare ,balanced my crank all new bearings. Machine shop did that and shaved my deck a wee bit. Forged pistons and connecting arm new bearing torque to the machine shops specs. Oh yeah that crank is 400 small block crankshaft in a 350 block hmmm that would make 383 cubic inch displacement Vortec heads polished up and flow tested. New roller rockers roller lifters etc. Comp cam. Highrise intake manifold with a 2in lifter plate with a rebuilt 750 carb, big psi badass mechanically fuel pump with a regulator and return line built into the pump. To bypass the ecm and oil pressure sending unit killswitch. Hei distributor not getting into my timing. Longtube headers. 2 v belts because serpentine belt suck in my opinion, power steering, alternator and one belt also has my water pump hooked it. I left info out of the description, cry about it.

This is different motor than my first attempt building the truck because my ecm was shorting everything out before i converted it. Idk much about engines i guess. Carburetors have their place just like efi has its place. ‍