Fuel pump question

[watchman]

My friend Rick and I have been discussing the pinging on the 1600 Nomads. We where wondering if anyone new anything about the fuel pump? If it was adjustable and if maybe increasing fuel pressure would stop the pinging? Or restricting the return flow might increase pressure enough to do it.? How about installing the injectors from the VN2000? Just food for thought.

[nomadd]

The F.I. fuel pump is non adjustable. Right after you turn the key to on and pump starts pumping it runs at 44 psi. After pump runs 3 seconds and pump stops it is at 41 psi. With engine idling and fuel pump running it is 44 psi. It is a pressurized system with no tank return. This info is right out of the service manual. The pinging is not related to the fuel pressure, but to preignition of the fuel. Some causes of preignition are low octane, carbon buildup, engine timing or a lean running condition.

[dogdoc]

+1, plus weather temp., humidity, altitude, and many many more items. :-)

I've heard lots of folks complain about 1600's pinging bad, and others who've had no problem. Some have spent hundreds on a PC-III & dyno time to solve the issue, on an otherwise stock bike.

I'd first be sure I was using top quality gas. If you think you are, try adding a little octane booster. Not too much! See if the ping abates.

If that's not an issue, I suggest doing the TPS mod, or the resistor mod & see if that makes a difference. Niether cost's much of anything to do except a little time. All the instructions are on Gadget's Fixit Pages for the Nomad.

[watchman]

I have done the TPS mod and no longer have any problem. We where just brain storming looking for other options. Other than loss of 2 MPG.

Well, think of it like this: You haven't lost 2 MPG. You've saved a $2000 valve job.

[rick]

if a person could increase the fuel pressure that in turn would increase the fuel to the injector,which would deliver more fuel to the cylinder ,and might stop the ping ,if the problem is fuel related. I have tried the octane booster with not much results,I known in the fuel injection cars you can up the fuel pressure which will help the throttle response and performance[according to air flow tech in Cal.]so my question is if the pressure is not adjustable and the timing is not adjustable then is the injector orifice on the 2000 larger then 1600?

[blowndodge]

Increasing fuel pressure does nothing that would make the injector deliver more fuel. Fuel injector cycling time controls the amount of fuel injected. The fuel pumps only job is to supple the required amount of fuel to the injector and make it constant. It doesn't control the speed or volume of fuel. Sort of like a garden hose that you turn on and then control the flow by squeezing the sprayer on the end. The water pressure is there for standby. Them's the facts.

[rick]

I will disagree with you if you restrict the fuel return line on a car it will flood,and if you lower the fuel pressure too low it will not run,so if the pressure is up one pound you will increase the fuel delivered throw the orifice,that has been research by airflow tec.,and a water hose at 10 pound well not deliver the same amount of water as a hose with 50 pounds

It's my understanding that there are different types of injectors, and they behave differently.

Anyhow, if the bike only pings at certain throttle settings, at certain places in the RPM band, and under certain loads, then increasing fuel pressure (which would probably alter delivery at all RPMs) might be a mistake.

I can't determine exactly, but from looking at the diagrams it appears to me that the 2000 injectors wouldn't fit anyway. They're also about $100 each with tax & new o-rings. I doubt this would be a smart move.

The resistor mod is easy to do and easy to undo, especially if you can solder. You can even do a temporary trial using wire nuts and extra lengths of wire, and swap resistors out on the road to see which value works best for you.

When one friend bought his 1600 Nomad (2006 model), he had serious pinging problems which weren't resolved until he bought a PC-III and had it mapped on the dyno.

Also, you might try running with the fuel cap cracked open to see if that makes a difference. If the tank isn't getting vented properly, fuel pump output may suffer. On a car this will set the check engine light, but on a Nomad it doesn't. At least mine didn't when I ran it with the cap open.

...And maybe not. One friend with an FI Classic accidently pinched his vent hose closed when replacing his tank. The pump sucked so much vacuum in the tank he couldn't open the gas cap, and when he finally did pry it open the top of the tank actually flexed up with a *pop*. The rush of pressure also caused his fuel gage float to smack up to the top of the tank and dent it from the inside! He now has a tank pimple.

[blowndodge]

You mis-understand the role of the fuel pump. Before fuel injection, gravity was the "fuel pump" for all motorcycles including the high performance ones. It still is on a lot of bikes. The fuel flowed down hill and filled up the float bowl where the main jet lived. as the vacumm sucked the fuel up the main jet the gas in the float bowl would fall and the floats would drop and gas would "refill" through the float plunger. The motor would flood without this. That If you somehow pressurized the tank the enging would want more fuel is wrong. The engine will suck (vacumm) only what it can use.

Think I'm wrong? Open up the right hand side cover to view the injectors and get a can of carburator cleaner. Start the bike and turn the throttle wide open the shoot the carburator cleaner into the injector (might as well clean something while you theory is crashing) and tell us if this extra fuel made your bike pick up RPM's or if the engine bogged as you sprayed the cleaner into the injectors.

Those who have cleaned your injectors this way: Did the engine rpms fall as you sprayed inside the injector? My guess is that it did.

The fuel pump is not connected directly to the injector orifices. The fuel pump in the Nomad has no play in how fast the injector pump fuel into the motor. It only determines how fast and/or how much is presented to the injector body. The injector body sets the pressure with it's own system and injects into the motor on timed intervals.

Modern cars had mechanical fuel pumps or electric pumps sometimes located in the gas tank because the engine is not below the fuel source and therefore gravity cannot be used.

I think BD is essentially correct here. If the fuel pump is working OK & there's no blockage/pinched hoses/etc. the pump always provides excess fuel. The unused fuel just returns to the tank.

However: if a factory regulator (or pump) has been mis-designed or purposely retard3d to lean things out as an afterthought for emissions compliance, then a better regulator (or pump) may well improve performance. This is particularly so if other parts of the intake system have been modified for more power.

My feeling is that the standard FI mapping of the Vulcans is purposely lean to reduce emissions at the point where v-twins make a lot of smog: Large throttle openings from mid-RPM. This is where mine always used to ping badly.

After doing the TFI/Baggers/coasters/filters combo, it's much better, but I can still make it ping when it's 100^oF here.

[blowndodge]

That's what I was tying to get across. Unless the pump is defective 42psi is PLENTY of fuel to supply with what the injectors can possibly squirt. I'm still working on other fixes for 100 degree weather caddmannQ. Posted elsewhere.