fuel injection test tank

[moto pierre]

We sometimes need to work on our bikes with the tank removed. With gravity feed to carbs this is easy, but harder with fuel injection which must recirculate fuel through a back pressure regulator to maintain pressure at the injectors. Here’s my solution:

Drill a hole near the bottom of a small metal can and solder in a half inch brass hose barb fitting. I used a gallon Coleman fuel can because the weight and size make it balance better and the handy bale makes it easy to hang above the bike; but a smaller can would work fine. Connect this fitting with vinyl tube to a half inch barb T and run two tubes to a half inch nylon double barb and a half inch-quarter inch double barb. These connect to the fuel pump inlet and the regulator inlet hoses respectively. Suspend the tank and let the lines fill, then restrict the regulator side with a clamp or simply hold the tube folded as shown in the pics. The engine will start, run, and rev normally and you can see the return flow bubble past your restrictor. Tighten all hose clamps, especially on the regulator side as pressure is considerable and a blown fitting will shoot a nice geyser of gas around your shop (big fun). I wired the barbs for the same reason. This rig is a big help for jobs that would be impossible with the tank in place, and it is dirt cheap. Winter fun…. Motopierre

[Kiwi_Roy]

It's not quite clear how you keep the regulator in circuit.

The regulator on my V11 is screwed into the bottom of the tank, if you bypass it the fuel will be at a different pressure and the mixture will be wrong.

Please clarify

 

Thanks

Roy

[moto pierre]

It's not quite clear how you keep the regulator in circuit.

The regulator on my V11 is screwed into the bottom of the tank, if you bypass it the fuel will be at a different pressure and the mixture will be wrong.

Please clarify

 

Thanks

Roy

[moto pierre]

It's not quite clear how you keep the regulator in circuit.

The regulator on my V11 is screwed into the bottom of the tank, if you bypass it the fuel will be at a different pressure and the mixture will be wrong.

Please clarify

 

Thanks

Roy

[moto pierre]

It's not quite clear how you keep the regulator in circuit.

The regulator on my V11 is screwed into the bottom of the tank, if you bypass it the fuel will be at a different pressure and the mixture will be wrong.

Please clarify

 

Thanks

Roy

 

I guess I wasn't clear enough. The regulator is not in the circuit. You are the regulator by folding the tube the is attaced to the regulator input thereby restricting return flow to the test tank and/or line to the fuel pump. For more precise control of back pressure, use a clamp on the return line. Motopierre

[Kiwi_Roy]

As I said, if the pressure is different I think the fuel mixture will be different but it's not that sensitive, to double the flow you have to square the pressure.

I looked in the workshop manual sure enough the regulator is set at 3 bar(g) and the pump relieves at 5 a difference of 2 so even if you pinch the return right off you will not get a lot more fuel, 25% more worst case.

if you added a small pressure gauge you could set it close to 3 Bar by pinching the hose.

It won't matter if you are just trying to run the motor, not tune it.

Thanks

Roy

[raz]

Having a proper regulator would be more kosher but generic in-line regulators are more expensive than I initially thought: They seem to be the order of 100-150 USD. But you can probably get one pretty cheap at a breaker - it seems 3 bar is a common pressure for cars too. I too have had thoughts of making a test tank (btw thanks Pierre for sharing ideas) but I don't want to spend lots of money on this.