Got an odd question for you life time pro mechanics (like AK Racings big Al ) I am always coming up with contingency plans for anything and everything i own in the event of a breakdown(RV, boat, bike, cars/trucks etc). I've always carried spares like water pump impellers, props, fuel pump, etc. My question is about stock FI systems. I ran across a Merc SAE J1171 in-line high pressure fuel pump the other day and i got to wondering if it could be used to temporarily feed an FI system through the schrader valve? I'm actually wondering in a non marine application though. My motorhome has a gas 460 and also a 4K gen, i could very easily feed the pump off the gen's fuel pump and pre-make a nice high pressure rig that could go on the fuel rails shrader valve. Mind you this would be a well constructed "emergency only" item that would only be used to get off the highway or something. Does sound feasible or even possible? Just something i was wondering . . . . as always thanks all

You just have to make sure the stock setup has a check valve/one way valve in the stock fuel pump or else it will just bleed past it and possibly not have enough fuel pressure.

i would think they all pretty much do, seems like every time i tested any of my Ford FI systems there was residual pressure when i attached the test line. Good info though to check into.

yes it would be strictly to get off highway or to where the problem could be properly taken care of. I also thought pulling the valve core might be a good idea. .

First thing that pops into my mind.

It would also depend on where in the system the fuel pressure regulator is and where it dumps the excess fuel. Might need to add a regulator to the setup you build.

regulator is always after the schraeder valve on fi with a return line, which 99% have.

As mentioned above, if the pump does not have a check ball, or one that is not working, the system won't pressurize properly as that will let the fuel flow back to the tank.

Speaking of pumps, glassdave, the auxillary pump has to be rated to push against the engine's prescribed fuel psi or more.

You could mount the aux pump down low back by the fuel tank and plumb it so the normal pump would bypass it under normal circumstances and pass thru a check-valve mounted between the input and output of the aux pump.. If the main pump fails, you would hit the switch for the aux pump and it would suck fuel thru the main pump and into the normal fuel line before filter. The check-valve prev mentioned would prevent the aux pump from pumping in a circle. Like prev mentioned, need to verify the aux pump is press rated above normal fuel press on inlet and outlet. Here's a quick sketch.

oops
missed that this was for a motor home

^^^^ He was thinking boats as he and I always do, I knew where he was coming from. ^^^^ We both know each other thru the marine industry very well for many years and I mean many years. The odd thing is we never MET in person ever - he lives in MN and I live in TX but both know the long history we have in the marine industry.working on boats. Like a combined history of 65 years. Thats alot. . Just saying sorry for misdirection here.

Mercruiser and Volvo have check vales in their stock fuel pumps FWIW .. . .