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Unread 12-20-2009, 02:53 PM   #1
CJman77
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1977 CJ7 
 
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Fuel Sending Unit and Fuel Injection Question

OKay so I have a Chevy 350 thats gonna put out about 350-375 Hp. I have an aftermarket howell multiport fuel injection system. What do you guys think about the fuel sending unit? Will the stock one be okay? Will it flow enough?

I have a 21 gallon poly tank. I know I will have issues if the jeep is on extreme angles. That really isnt a major issue for me as I live in florida and dont 4x4 it too much. If I do I will keep the tank full!


Last edited by CJman77; 12-21-2009 at 04:49 PM..
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Unread 12-21-2009, 04:37 PM   #2
Coiz
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When I hear someone say fuel sending unit I think you are referring to the sending unit for the fuel gage. Are you referring to the actual fuel pump? What fuel pressure does the Howell system run? If it is any type of high pressure system then you will have to install a high pressure pump as the stock pump will definitely not work. More details?
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Unread 12-21-2009, 04:45 PM   #3
CJman77
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Quote:
Originally Posted by Coiz View Post
When I hear someone say fuel sending unit I think you are referring to the sending unit for the fuel gage. Are you referring to the actual fuel pump? What fuel pressure does the Howell system run? If it is any type of high pressure system then you will have to install a high pressure pump as the stock pump will definitely not work. More details?
I am talking about the fuel pickup which is part of the sending unit in an old cj or at least in mine.

I am not sure of the fuel pressure. I believe stocks aroun 40-50 psi? I believe. It may be a bit higher then that. It currently has a intank pump in the vehicle the system is currently in, but in the jeep I believe I will have to go to a external pump with the poly jeep gas tank I have.
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Unread 12-21-2009, 04:58 PM   #4
Coiz
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The fuel pick up in the stock tanks are 5/16" along with 5/16" lines feeding up the frame rail to the engine compartment. 5/16" are stock for most fuel injected engines as well so you should be fine with that size pickup and lines. Stock CJ with carburetors are obviously low pressure systems so a high pressure pump will have to be installed.

The issue you might run into, which is the same one I have been looking at lately, is that the stock return line from the engine to the tank is 1/4". Going from 5/16" feed to 1/4" return may cause some back pressure or pressure spikes in the fuel rails. Even if you step up the line to 5/16" for the return, which is what I did, it is still a 1/4" line at the sending unit where it feeds back into the tank. I figured 6" of 1/4" would be less restrictive then the entire 10' worth of return line at 1/4". I should note that I actually swapped the 1/4" fuel return line with the 5/16" vapor canister feed line since they are both already in the right place. So the vapor canister feed line is now the 1/4" line. I figured that was ok since the nipple from the valve that feeds the vapor to the canister is also 1/4".

I've got a Mustang engine and stock Mustang supply and feed lines are 5/16". The tech support at the company who makes my fuel pump also suggested I step up to the 5/16" return line. But there is still that 6" worth of 1/4" right at the sending unit at the tank. Anyone know of a sending unit that fit into a CJ tank that has 5/16" supply and return hook ups?
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Unread 12-21-2009, 05:01 PM   #5
CJman77
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Quote:
Originally Posted by Coiz View Post
The fuel pick up in the stock tanks are 5/16" along with 5/16" lines feeding up the frame rail to the engine compartment. 5/16" are stock for most fuel injected engines as well so you should be fine with that size pickup and lines. Stock CJ with carburetors are obviously low pressure systems so a high pressure pump will have to be installed.

The issue you might run into, which is the same one I have been looking at lately, is that the stock return line from the engine to the tank is 1/4". Going from 5/16" feed to 1/4" return may cause some back pressure or pressure spikes in the fuel rails. Even if you step up the line to 5/16" for the return, which is what I did, it is still a 1/4" line at the sending unit where it feeds back into the tank. I figured 6" of 1/4" would be less restrictive then the entire 10' worth of return line at 1/4".

Okay well the vehicle I am pulling the motor out of already has SS braided fuel lines for supply and return.. I am not sure of the size. But they look pretty big and I wont be hopping the engine up too much more. I am hoping they will work and I will just have to shorten then a bit.
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