TOPIC:

Tuomas wrote: Still wondering how ignition advancer works in this dfi system.

There is a small plastic box (approx. 20mm x 30mm) that sits underneath the top frame tube underneath the fuel tank (or at least that's where it is on my ZG) & there is a short tube that runs to the induction manifold measuring engine vacuum, that in conjunction with the igniter (measuring RPM) controls the ignition timing as far as I know.

Hey Phil,
Where can I get one of those crystal balls so I can see what's going on from 6,000 miles away?



You're good. I have to credit you here. Good point if the DFI unit is not seeing the intake vacuum. It will try to run basic timing waiting for the engine to fire, then change up the timing to running at idle. Hmmmmm.... interesting

Finally met the guy after few weeks and we measured the fuel pressure and tried to find out if ignition advance thing (it says "Boost sensor" on it) works.

First the fuel pressure. We had industrial fluid dampened gauge and we measured EIGHT bars of pressure at fuel rail (well that seems enough at least..) and THREE bars after that fuel presssure regulator. And it holds at eight bars so no injector leaks or return flow via fuel pump. Feels like kinda high....it is not original fuel pump but it has been there for years, working flawlessly. These results we got with ignition ON and bike was not running as it still does not want to.

Then we measured Boost sensor (ignition thingy): I hooked my multimeter to two of three terminals and we had some rubber hose and medium size syringe to create some vacuum to sensor. With ignition on we got some readings and they varied when vacuum was applied so it seems to work OK.

Then we hooked vacuum meter to manifold and cranked the motor, and it was clearly making some vacuum but that´s hard to say if it is what it should make.

Looking at the diagram= The fuel pump supplies fuel to the rail and the injectors. At the end of the rail is the pressure regulator. The regulator drops the supplied pressure the pump could obtain, down to the required 2.27 bar (33 psi) at idle and 2.47 bar (36psi) at just off idle. On the downstream side of the regulator is the return line to tank and it should be slightly measurable but basically atmosphere.


So if the pressure gauge is on hose #10. it should read 2.27 - 2.47 bar depending. On hose #12 basically nothing. If the injectors are pressurized at 8 bars the likelyhood of them closing after the signal pulse from the DFI would be nil. The spring in the injector is at a spring loading to close the injector under normal pressures. If it was too strong a pressure, the signal pulse that opens the injector by pulling the plunger via an electromagnet would not be strong enough to open the injector.
Then there's item #13 a check valve at the tank fitting? Somewhat unusual since the pressure regulator is in fact a check valve by nature. you might also want to pull that check valve and see if it's blocked or stuck. No way should there be 3 bar on hose #12. If the check valve is spring loaded maybe a couple of psi could be measured (0 .27 bar maybe?)

Sounds to me that your regulator is stuck partially closed.

I agree, you shouldn't see any more than 2.5 bar downstream of the fuel pump.

Sorry, I missed this the first time around Then we hooked vacuum meter to manifold and cranked the motor, and it was clearly making some vacuum but that´s hard to say if it is what it should make.

We've discussed this a couple of months back and a lot of the guys are seeing what I consider very low intake vacuum at cranking in and around the 4-6 inches of vacuum. I'm used to seeing 12-15 inches of vacuum on most engines.and on a stock running engine 20-24 inches of vacuum at 1000 rpm. so if you're measuring 4-6 inches of vacuum, I guess you can consider that normal?? A lot of this has to do with the camshafts and their timing. When I get my head back, I'm going to get into this.