DFI Pressure

Hey Folks,

Seems like the last time I worked on this fuel injection system ( ZN1300 )it behaved differently.

I have a pressure gauge hooked up the fuel manifold, when I turn on the ignition the pump comes on and runs for five seconds. During these five seconds my adjustable pressure regulator can and does regulate the fuel pressure. I've seen 28 to 45 PSI.

Here's the rub: as I remember it, the fuel pressure would maintain for several hours after the system shut down.

What I'm seeing is this:

Key on, pump runs for five seconds, max pressure controlled by adjustable regulator. After five seconds of running the pump stops and the pressure quickly falls off, getting to zero in about five seconds.

My best Guess:

One or more of my injectors are gummed up and I'm losing fuel into the intake tract.

How about it? Time to pull the throttle bodies and injectors?

Bill R

You just said "after about 5 sec the pump just stops" I'd say you have a power problem to your pump? Also may be a problem with your regulator bleeding off?

Post edited by: Bluemeanie, at: 2008/02/02 20:07

Actually the manual documents this five seconds, so it's normal.

As soon as I hit the starter the fuel pumps starts again.

I could pinch that hose off after the pump stops to see which direction the pressure's going? Injectors or tank.

I pinched off the hose to the pressure regulator as soon as the pump stopped and the pressure still fell off rapidly. It's either bleeding through an injector or back through the pump itself.

Shouldn't the system hold pressure after the pump stops?

Bill R

Post edited by: KZCSI, at: 2008/02/02 20:39

I'm not the FI guy at work but we do test systems and if you bike is anything like auto's... yes, it should maintane operating pressure for quite a while after shutting down. I've seen pressure hold for more than an hour if working properly. As you say, you may have an injector bleeding off. I wonder if you could run a injector clean through like a car. I don't mean stuff in the tank, tap into fuel (disable fuel pump)rail and have bike run off cleaner only. Works really well but special equipment made for such an application. Cleaner in tank would work too just takes time.

Post edited by: Bluemeanie, at: 2008/02/03 11:38

if it was a injector seems like you would be seeing a lot of fuel in a cyl or the intake, dosent sound like that is going on, I would be looking at the regulator not holding

I pulled the injectors and tested them with air pressure. I don't believe that the fuel was leaking past the injectors, they're capable of holding 30 PSI fine. I'm left with wondering about the fuel pump it must have a check valve. Perhaps it's decided not to close after the layup.

On another note: I've been using a battery and a light bulb to try to get the injectors to click. I've found that if an injector does click, it'll only do it once till I reverse polarity at which point it will click one more time. The problem is that most of the time the injector won't click at all. I've got injectors from three bikes and I get the same results from any and all.

KZCSI