Thomas,
After 21 years of GMCing, my unqualified recommendation is to eliminate the
selector valve completely. At least one electric pump is almost a
necessity with today's vapor lock prone fuels. Redundant pumps is even
better. So just eliminate the selector valve, put an electric pump on each
tank, and tee their outputs together. Use the tank selector switch to
select a pump. You'll need a couple of relays for that purpose (see the
link below for my wiring diagram -- which may not be the simplest
possible). The cost of the second pump should be little more than the cost
of the selector valve. You MAY need check valves on the output of the
pumps, dependent upon their designs. My 2 Carter 4070's do not require
them, but just in case I ever have to replace a pump on the road with one
that does need them, I included them anyway. That hasn't yet happened.
http://www.gmcmhphotos.com/photos/data/5494/Dual_Fuel_Pump_Wiring.pdf
By the way, a very capable GMCer just found that the cause of his baffling
engine failures was that the NEW valve he'd installed was sticking between
the two positions.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, Troy-Bilt APU, etc., etc., etc.
www.gmcwipersetc.com
On Wed, Aug 7, 2019 at 10:12 AM Thomas Mike via Gmclist <
> Hi Matt. I'm still trouble shooting the sonlioid in the OE valve. Then I
> have to decide if I replace it with aftermarket valve and ,then maybe add
> one
> electric fuel pump on the aux hose prior to the valve.
> --
> Mike Thomas
> Troy, MI
> 77 ex Palm Beach, 77 Royale (rear bath)
>
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