question for fuel injection guys or any pro auto techs
 

Got an odd question for you life time pro mechanics (like AK Racings big Al :D) 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.https://cimg6.ibsrv.net/gimg/www.off...426fcc2c48.jpg

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 .. . .

might be a moot point with the pump i found but the question still remains :D Having several vintage Ford Broncos and my motorhome being a E350 w/460 chassis i always kinda wondered if i could rig up a test system that would feed fuel in at the schrader valve in the event of a pump failure. The pres reg is on the rail near the valve and, as said, it the factory pump is check valved i would think it should work fine in an emergency. Again I'm mainly thinking in an emergency and truth be told its my motorhome I'd like to have a rig for, its a mid 90's Jamboree Searcher and its only got 50K on it but accessing the pump is near impossible. I would just like to have a contingency on hand. It would actually be pretty simple the pump for the gen could easily be used to pre-feed the high pressure emergency pump and from there would be about a six foot custom made stainless line with the shrader fitting on it. As a bonus it could be used with my Broncos for test purposes.


I dont recall where i got the pump i fund but its part number comes back a low press small Merc motor of some sort.

this is the number on it 861155-4 2025a

I worked in a tune up shop many moons ago and we had a roll-around machine that had a fuel pump and a reservoir built in we would fill with straight fuel inj cleaner. For fuel inj cleaning service, we would connect it to the schrader valve (after disabling the main fuel pump) and run eng at a fast idle for abt 20 mins. We would set the machine's fuel press low enough that it wouldn't bypass the regulator. So it can be done. If it should be done is another matter. A leak at that point could be disastrous.

You mentioned low press in your last post.. If it's made for a carb (6-8 psi), I doubt if it will work at all on a port inj eng (40-50 psi) but might barely work if eng has throttle body inj (10-15 psi generally).
Another issue is when you connect to the schrader valve, you're bypassing the filtration process. It doesn't take much to plug an injector, especially a port injector. 1 cyl goes lean while you're climbing a hill, eng goes boom.

If it turns out to be a carb type pump, you could always use it to de-fuel various types of fuel tanks.

yes i mentioned the pump i ran across was found to be a low press pump, i was no longer considering that particular pump and would locate a suitable in-line type 40-50 psi pump if i do decide to build a rig. I understand the safety implications fully, this would be strictly for getting off highway or something like that. I've actually built several GM based FI systems from scratch back in my street rod days so i understand much of the system (the hardware anyway). Good point though that this would be down stream of critical filtration, i suppose that being said i could improve my gens feed line but even still you are correct any little particle could be an issue. Most of this is just a thought that had been rolling around in my head as i really do like to be prepared for just about anything. On low psi carb stuff I've always kept an in line elec pump, which ironically has been used by several friends to get back to port but never once by me lol same with spare water pump impeller kits cant tell you how may of those i handed out :D