[Diy_efi] 402 TO 454 VORTEC CONVERSION

Shannen Durphey shannen at grolen.com
Wed Mar 26 22:12:12 GMT 2003



"Eck, Joel (Houston)" wrote:
> 
> What I would do for the dual tanks is put a transfer pump from one tank to the other, and manually transfer fuel as needed. This way, the fuel return and pickup still go to your main tank.

GM uses a similar solution on the HD3500 trucks, but the transfer pump
activates when front tank reaches 1/2 of full.  It kinda sucks in areas
where there are large distances between fillups as a person can end up
with an improper guesstimate of fuel in the vehicle.  GM compound(ed)
the problem by forcing the fuel gauge to try and read both front and
rear fuel level sending units as a parallel resistance.  That problem
may be fixed now.

> 
> The other alternative would be to use a later model dual tank diverter valve (which isn't exactly cheap, from what I've heard) and switch so it can switch the pickup and return from one tank to the other. For this setup, I would copy the factory setup for the dual tanks so there is no confusion/problems down the road. This may require dual pumps, but there's info in the archives about using external pumps (they seem to work fine).

The dual tank TBI trucks use a fuel pump in each tank with supply and
return lines routed through the switching valve.  Diesel trucks use a
low pressure frame or engine mounted lift pump with supply and return
routed through the switching valve.  At one time I thought that using
the tank select valve from a relatively low pressure system would be
problematic in a high pressure application until I realized that the
high pressure source could easily be moved to a point after the valve. 
A low pressure pump bet. tank and valve to a high pressure pump on the
frame is likely to be a reliable solution which doesn't require constant
driver monitor and control of the fuel level in one tank.

Shannen

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