Odd c41,c32,c33 problem fix

[cven]

I'll make this short as possible. I've had a intermittent start problem that I thought was the side stand relay so I jumped it and tossed the relay. I thought that while I'm in there I'd replace the fuel pump relay (64,000 miles) so I dug in there and replaced it with a spare heavy duty 30 amp relay (stock is 20 amp) ,the same type relay I used for the plus mod. Wired it up and bam, starts right up. Road the bike for about an hour and shut it off for 2 hours and it starts right up, stopped at the store shut bike off for 2 minutes and it won't start?? (FI light comes on but I can't pull codes) After drinking a soda (10 minutes) I tried again and it starts right up?

Now I'm stumped, next day starts right up, go for a ride, stop at friends not home so I go to leave and no start (always turned over, fuel pump always primed, just no start), let sit for ten minutes and starts right up. I go home and shut bike off , no start again. So I pull codes C41 C32 C33, hhhmmm?

This relay is new and worked fine when the bike started so I'm stumped again.
I took electronics in school and still have 3 good brain cells and they start kicking in, I wonder if the stock relay has a protection diode in it (it's not in the book) and this one does not and I fried the ecu??

Take hammer to old sidestand relay and I see a 1100 ohm resistor inside?? Now I'm cooking!! Get a 1100 ohm resistor and wire it acrossed the coil on the new HD relay and now she is A OK!!

The ecu must have got brain fade from the counter emf of the relay coil everytime I shut the bike off and tried to restart, but if it sat for awhile it would bleed off and start right up.

So if you are going to use another relay for the fuel pump you must put the resistor parallel with the coil. The ecu luckily did not fry. Hope this help someone.

[Steve TLS]

I only found this via the other thread you linked it to.

It was definitely a resistor? Not a diode? It is common practice to put a diode across the coil of a DC relay or contactor to take the back emf generated when the power is cut to the coil (freewheeling or flyback diode).

A resistor draws power all the time (only 11mA though) and I believe, it would still allow a large spike to be generated. It might be enough though.

[cven]

Ya I thought the same thing but when I smashed it I found the resistor.

I'm no expert but would guess the ECU is internally buffered (protected) on the coil driver circuit for the ignition coils and thats why the same relay worked for the plus mod but not for the fuel pump. The fuel pump circuit requires outside protection or you have the problems I had. Suzuki should have showed the relay resistors in the book. Glad I didn't damage my ECU!

Some protected relays have a diode and some a resistor but I have no idea why they use one in place of the other. In the future I will find out before connecting a relay to an ECU or use a protected one just in case.

[Steve TLS]

Interesting find.