MicroSquirt.com read only forum (Jan.15,2018)

Actually, I was thinkin' some more about the whole return issue. I am going to put a bigger tank of around 3.5 US gallons on her bike so that we both can go about the same distance between fillups. The tanks I have been looking at are like "quick bobs" of various types, and they have a hose that connects the two sides at the front like the tank on my FLHT. I think I can T into that line that connects the two sides for a return, no problem, and keep her Pingle valve, which was rather expensive in the first place is a really nice piece. So now, I just need to re-figure the fuel pump. I still don't see how this thing was originally mounted. I think I'm going to have to source a different pump/regulator setup unless I can figure out how to make this one work external.

Dr.Hess wrote:I still don't see how this thing was originally mounted. I think I'm going to have to source a different pump/regulator setup unless I can figure out how to make this one work external.

I would think that the cylindrical bit with the screen would fit into the bottom of the tank with an 0-ring and some sort of clamp arrangement. It may have a low fuel level sensor on it too by the looks of this:

http://www.badweatherbikers.com/cgibin/ ... POST476058

Ian.

That was helpful, thanks, Ian. It looks to me like the original pump mounted entirely inside the fuel tank, with the wires and the output pipe sticking through the side of the tank. I don't think that's going to work for my wife's bike. That thread also brought up the concept of fuel sloshing around and the pump running dry. I hadn't thought about that. These tanks have no baffles at all, so that could be a real problem. Nail it and the fuel will slosh to the back of the tank and might not go down the outlet pipe. This isn't a problem with a carb because of the float bowl. One poster said everything was fine with his Buell as long as he kept 1.5 gallons in the tank. Well, my wife's current tank is about 2 gallons and I'm looking for a 3.5 gallon tank for the increased range, not to carry around an extra 10 lbs of fuel.

Anyway, I'm thinking along these lines:
* Mount a large (~cup size, like on a Ford F150 or maybe the one from a carbed Toyota Truck) can type fuel filter somewhere below the level of the tank under the seat to act as a fuel reservoir. When accelerating or cornering, the pump would draw fuel out of the filter if the tank pickup was sucking air. Advantage: Acts as a fuel filter also. Disadvantage: Have to make it fit.
* Modify the pump I have to work externally by changing the pickup to a hose barb and changing the regulator output to a hose barb. Advantage: I already have it. Disadvantage: Pump will no longer be cooled by surrounding gas. Important? Dunno. Or:
* Look for another pump and external regulator. Nissan 6 cylinder cars have a nice external pump that is probably too big, but has a regulator on it. Maybe that regulator can be used. Or, modify the HD rail system to accept an aftermarket regulator, or maybe run a T with one line going to the injectors which deadheads, one line from the fuel pump and one line to the regulator which then goes back to the tank via the bridging line at the front of the tank. In fact, I bet I could use just about any automotive EFI regulator from a fuel rail by just making a fitting for it to screw into with a hose barb.

What Nissan 6 cylinder pump are you referring to? Those had in the 200hp range so should have a pump that makes less GPH and hopefully draw less amperage. Got any links to specs and pics like from Ebay?

I don't have any specifics except 80's Nissan inline EFI 6's. I pulled one at a pick-a-part about 1999 and still have it. I'm going to use it for my 4AGE 20v in my Locost. They mounted to the frame down by the axle. I probably should have written down what car it was, but at the time, I just wanted it to try and diagnose a miss I was having that I suspected was fuel related (it wasn't). Using one of these was pretty common in 20v swaps back then. It might be like a 1983 Nissan Maxima 2.4L EFI 6. I would guess them to be considerably under 200 HP, but I don't know. It is a fairly small pump, but then the in tank GM pump in my Esprit is pretty small too and they will support a lot of HP.

The return line from the regulator to the tank needs to be large and provide no resistance so as to boost fuel pressure. I don't think a T in the crossover connector tube between tanks is a good location. Better to have a larger metal pipe welded in somewhere preferrably more towards the upper part of the tank I would think. Crimped with a hose barb so a rubber line can be attached.

I was wondering if it's possible to run an aluminium canister mounted lower than the fuel tank that will receive the fuel pump and the fuel return. Could a single feed be used or it need a vent connected to the fuel tank.

Sure you can except it would prolly be better to return the fuel to the main tank I think. I forget what the official name of the secondary tank is that gets fed by the main tank. Anywho, that may facilitate mounting a typical motorcycle fuel pump.
If you don't wanna run a return line to the main tank you could just get a newer style fuel pump that has the regulator on it an does not utilize a return line unless you plan on using a Fuel Pressure Riser to compensate for a turbo or supahchagah.

Thanks for the reply, I figured that the main reason for the fuel return line was to cool down the used fuel so I guessed that a metal canister could serve as fuel radiator fed trough the single stock line and could look good once polished, specially on a Harley. VTR tanks are really small (200km autonomy).

The return line is part of the Pressure Regulation. Basically the pump runs and the regulator, which is after the rail and injectors, varies how much fuel is blocked and bled off. This keeps the fuel pressure constant on the rail. The single line pumps have the rail and the regulator on the pump itself and the line runs up to another rail which feeds the injectors. As long as pressure is constant it works the same as the two line system.