WMO fuel pump in a 7.3

[oregon101]

Ok I'm running WMO in my 89 7.3 and have a question on the fuel system. I have mounted a filter plate with a spin on oil filter outside the gas tank to run the fuel threw to catch any "junk" I miss filtering before going in the tank. After that I have mounted a Holley Red fuel pump wired to a key on source. My question is should I leave the stock fuel pump on it or bypass it and only run the Holley pump? I was thinking that the Holley pump would put less strain on the stock pump because the waste oil is thicker than the diesel. Am I missing something?

 

[discbrks]

I don't see any reason that it would hurt having both pumps working.

 

[GenLightening]

The only issue you'll have is when the diaphragm in the stock pump ruptures from the pressure the electric will put on it and fill your crankcase up with diesel. Run one or the other, not both.

 

[oregon101]

The Holley pump puts out 14psi at 115gph. I didn't think that this was any more than the stock pump?

 

[GenLightening]

The Holley pump puts out 14psi at 115gph. I didn't think that this was any more than the stock pump?

The stock unit puts out 7psi and about 30gph. The problem would be that the diaphragm isn't strong enough to withstand much input pressure, just creating output pressure. With the Holley putting out that much pressure, the stock pump would become a regulator and the weak link is the diaphragm. I've read the IP doesn't like much above 10psi. You may want to install a regulator.

 

[oregon101]

OK, that makes sense. Should I just disconnect the stock pump or take it off and install a block off plate?

 

[GenLightening]

You can do either. If you remove it, just pick up a Chevy 454 block off plate.

 

[Papabear]

The only issue you'll have is when the diaphragm in the stock pump ruptures from the pressure the electric will put on it and fill your crankcase up with diesel. Run one or the other, not both.

quick question could a guy theoretically run them parallel and have a check valve between the 2 so that no pressure from the auxilary reaches the factory pump yet insure that the engine does not starve for fuel

 

[GenLightening]

quick question could a guy theoretically run them parallel and have a check valve between the 2 so that no pressure from the auxilary reaches the factory pump yet insure that the engine does not starve for fuel

I don't know if a check valve will cause a big restriction. You could run manual shutoffs to bypass each pump, since unless the electric pump failed you wouldn't need the stock one. You would need to crawl under there to swap things around if needed.

 

[oregon101]

Well I ran the truck for a while today and it ran a little rough. It wanted to die at idle until it ran for a while. It also smoked more than usual and surged at idle on occasion. I'm thinking that I will need to put on a fuel pressure regulator. Any suggestions on what pressure it should be set at?

 

[oregon101]

Finally got a fuel pressure regulator on it today. It runs and idles much smoother. It seems to run best at 8-9psi.

 

[subway]

thanks for the info i just put a holley blue in which runs in the 10-14 range. i figured it might come in handy when the oil is harder ot push cold. i plan to put the included regulater in after the filter so i am not pushing to hard through the injection pump but i get the most through my filter.

 

[oregon101]

I have a spin oil filter base right outside the fuel tank, then the Holley pump, the regulator and then the OE filter. It seams to be working out so far.