I'm converting from carb to TBI and using a frame mounted electric fuel pump. I mounted it in a convenient low place on the frame, but now I'm being told that maybe it's too far from the tank?

Does it really matter? It doesn't seem like it's any harder for a pump to pull fuel through a line than it is to push it, is it?

Also, does it matter if the pump is high or low relative to the tank? I opted for low, but to get closer I'd have to go higher.

Thanks for any insight.

 

You don't want it to far from the tank. Think of it as this. Is it easier to drink from a straw that is 3" from you or in the other room. Those twisty straws make your jaw hurt in no time.

 

Yeah, but in this case the pump is also pushing the gas up to the throttle body. Say it has to go 8 feet total, why is it better to suck 1 foot and push 7 as opposed to sucking 2 feet and pushing 6?

 

Well the stock pump as well as all other electric pumps push the fuel all the way from the rear of the car. The pump desing requires it to be like this. Physically there is no real difference in force required to move a liquid as such, however the impeller design in the pump makes it as such.

 

Okay, so closer is better, but how about height above the tank? Is it better to be closer or stay below fuel level? I can get so close being about level with the bottom of the tank, then to get closer I need to go up over the rear axle.

Thanks.

 

Anywhere along the frame rail should be fine. Level with the bottom of the tank should be fine. Woulnd't it be easier to just replace the in tank pump?

 

What in tank pump? I'm going from carb.

 

I would stay away from GM pumps since they are junk but I would look at any of the Holley or Walbro pumps. They can be had brand new for about 100 bucks or so and can support gobs of power. The walbor 190 and 255 units are the most popular for TBI cars. I am not sure about the compatability of the carb in take sending unit and such though. You may need to visit a junk yard for that.

 

I'm finally back working on this project. I had to get the throttle body repaired because I foolishly cracked it by over-torquing something...

Anyway, I have a fuel pressure gauge on the inlet to the TBI now, and I'm getting 15.5 PSI. For some reason, the guy I bought the carb-to-TBI conversion kit from has set the fuel pressure regulator to 17 PSI and has programmed the chip accordingly. Doesn't this seem high?

Anyway, I'm kind of stuck now. My fuel pump (not sure the brand, but replaces a factory Ford external pump) is nicely secured on the frame rail and all my lines are cut. I really don't want to move it closer to the tank unless I'm sure this is the fix. It's a PITA bathing in gas while cutting steel lines, etc etc...

What I'm seeing is super low O2 readings all the time (like 0 and 1). I really have no feel for whether 1.5 PSI can make that much difference, but I wouldn't doubt it.

Any ideas would be great.

 

Okay, another question. After troubleshooting for a while, I looked at the fuel pressure and now it's only 13 PSI. What might cause this? Do the pressure regulators fluctuate, or does this mean my fuel pump is unable to keep up? It seems weird because at idle, how much fuel could I be kicking out the injectors? It seems impossible that I couldn't maintain fuel pressure at idle, which makes me think it must be the regulator.

When they say factory is 9-13 PSI, is that range for one vehicle, or the range of random pressure settings GM rolls out of the factory?