Yoshimura EMS Units and Fuel Pump Cycling

[Paul Flis]

I have had (2) units almost within the same week have similair problems.  One was on a stock '02 GSXR750 w/ Micron slip on (by stock I refer to the electronics on it) that when the EMS is hooked up ith would not shut the fuel pump off when ignition is first switched on, if you left it on it would fill the motor with gasoline.  Unplug the unit hook up stock ECU and the problem is gone.  Yosh said the map was wrong for the bike and the TPS readings were backwards (Closed setting for wide open and vice versa).  Got the unit back, will find out Saturday if it fixes it.

Second unit was on a '02 GSXR1000 w/ air shifter, 2 step, shift light, all the racing goodies and worked fine for a while, and then once in a while when you turn the key on it would go through the fuel pump cycle over and over again (you cold hear the relay click on and off)  Unplug the unit and the problem goes away.  Anyone else have problems with the EMS units?  Input would be greatly appreciated.

Thanks,
Paul

[Johnnycheese]

how does a fuel pump not shutting off cause cylinder to fill up???
the injectors hold the fuel back  

[Steve A]

If the ECU went to 100% duty cycle it could keep the injector open and fuel would then flow through it.

[Johnnycheese]

yeah but when was the last time you saw that happen.
plus that is what the screen would say if it was happening

[Steve A]

Personally never seen it happen but it is a possibility and could then flood the engine/cylinder.

Never won the Lotto yet either, but I keep trying!!!

My theory is that every time you use one of these "add-on" units it is a possible way to malfunctions.

[Paul Flis]

On the 750 the fuel pump never stopped running from the point the key was turned on and the bike NOT started/running.  I would only assume since the pump did not build it's 40 some psi pressure that it was dumping the fuel it did pump into a cylinder(s).  On the 1000 I did not see any changes in fuel pressure during it's "cycling" of the fuel pump so I would assume the problem is different but slightly related to the 750.  i did not check to see what was happening with the fuel pressure on the 750 though.  Yoshimura has suggested several things, all of which did not help the problem, but a tech did mention that they have had to fix around 600 of the EMS units.

[Johnnycheese]

so was it filling the cylinders or not?

[Paul Flis]

It did on the 750 but not the 1000.  On the 750 th epump would not shut off.  On the 1000 it would simply cycle on and off w/o a pressure loss.
I guess this problem is not that common, I've never had this kind of problem with powercommanders.

[SLEEPERBUSA]

Let us know how it comes out , please.  

[Paul Flis]

Plugged the "Yoshimura Tested" EMS back on the 750 today and instead of the pump staying on non stop this time it would cycle back and forth like the 1000 had done.  Either way I think the the EMS unit is nice for all that it offers, but I do not like the idea of them being so fragile or vulnerable to damage.

[Paul Flis]

Seems that if you have a fully charged battery (on the 1000) the problem goes away, and comes back a little bit later.  This does not explain why I have the problem on the 750 which is stock minus the slip on and K&N with a new battery.  The 1000 is loaded with electronic gadgets, which should not pull any kind of amperage unless they are toggled on, but will funtion properly with or w/o fuel pump cycling when it is started.  Of course when it is started the fuel pump runs like it should while the engine's running.  This is not true on the 750 which will fight to even start, and then run on 3 cylinders if you're lucky.

Johnny, you ever been outside of central Texas?

[Johnnycheese]

why yes I have

I would be sending the 750 one back for a new one