I swapped in a 350 TPI in place of the 305 TBI and I am told I need to upgrade the fuel lines to bigger ones to get more fuel to the motor. Which ones do I need? Can I just upgrade the main line and leave the return and vacuum the same size? I need to know so I can order them and get the damn car very streetable.

 

You need to upgrade the in-tank electric fuel pump, not the fuel lines.

 

the lines are fine you need to upgrade your fuel pump like five7kid said

 

We already did that, upgraded to the TPI fuel pump. The guy who tuned the car and is familiar with this stuff said you had to upgrade the fuel lines as well. The car runs and drives fine, but can't get the fuel it needs at startup.

 

Get a new mechanic. What is the problem if it runs and drives fine? What makes him/you say you aren't getting enough fuel at startup?

 

Well, the car won't start. We spray a little starter fluid in there and it fires up and drives fine, it is just the initial startup.

The car is also only getting 26lbs of fuel pressure, when we put the 75lb pump in there. Will a fuel pressure regulator help? Maybe an external fuel pump? I really don't want to drop the damn tank again.

 

I thought TPI needed around 45 psi fuel pressure? Maybe you just got a bad pump?

 

I would do the fuel pressure regulator first. If that doesn't help, you may have a bad pump. Are you using the factory wiring for the pump or did you rewire it yourself?

 

Shouldnt have got another intank pump (if u plan on keeping the car) w00psys, maybe next time huh. But ya the lines r fine.

 

k, I'll try a regulator and see if that helps.

If it doesn't, can I run an external pump withouth having to remove the in-tank one?

 

Nope you cant lol, I already thought of that and it dont work my friend. Sorry time 2 drop the tank tho.

 

You CAN run an external pump with the in-tank pump, as long as the in-tank pump doesn't flat-out die. If it's producing low pressure but still has plenty of volume, that's all the booster pump will need. Ford used this system for years on their full-size vans and some trucks (volume pump in tank and "booster" pressure pump on the frame rail.)

However, if the in-tank pump quits working altogether, the booster pump won't pull through it.

 

Normally a TPI car runs at 45 psi because that's what the fuel pressure regulator is made to do. The fuel travels through a loop from the fuel tank and back to the fuel tank again. Some of it is used by the engine but most of it goes right back to the fuel tank again. If you could close down fuel flow (send less back to the fuel tank) it would raise fuel pressure to 80psi or more. If you just let fuel go back to the fuel tank unrestricted then the fuel pressure will drop significantly below 45 psi (perhaps 26 psi??? ). The key to solving your problem is to install a fuel pressure regulator that can regulate the fuel pressure to the proper level for your TBI system, which is way below the 45 psi needed for a TPI system. Basically, you installed a higher flow pump. You need the right regulator to control everything.

It's like a water hose. You can let it run wide open under low pressure or you can stick your finger on the end and let it run under high pressure. Your finger is the pressure regulator.