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748S wont start

3K views 9 replies 8 participants last post by  Nick Doll 
#1 ·
Hi guys i am having an problem with my ducati 748S i cannot get it to fire because the fuel pump wont prime i have checked the pump buy connecting it direct to the battery and it works fine i have checked the relays buy connecting them to the battery they click and beep on my tester . the bike cranks but with out the pump priming not joy no ridding . my dads 996R has a similar problem it runs perfect but every once in a while the pump does not prime then you leave it on for 15 20 min and it primes . pls help dying to ride my bike
 
#5 ·
I'm having a similar problem about which I just posted. I have the Haynes manual and it appears that switching for the fuel pump relay is done by the ECU and on the -vdc side of the relay coil. That would explain why it runs for a few seconds then shuts off until the bike is started since there dosen't appear to be any pressure switches on the fuel system. I'm hoping someone may know of a better solution than replacing the ECU. I know this doesn't solve our problem but maybe head us in the right direction.
 
#8 ·
I had a problem with my 748s for years and i couldnt find what was wrong with it , i checked everything ecu/pump/relays under the seat and cleaned wire connecting blocks and nothing . You would turn the key and sometimes the pump would prime and sometimes it wouldnt , it had a mind of its own . I then changed the side stand relay down at the battery and now it works perfect .:dance:
 
#10 ·
Richard, what year is your 748? If it is pre 200 then it does not have a sidestand switch. Here is something I would try. Coming off the fp relay you will see two brown with white stripe wires. One will be larger in diameter and one smaller. Grab the smaller wire and splice a piece of wire into it and ground it to the ECU box or chassis. By doing this you are bypassing the ECU's control of turning on the FP replay from priming/running. Thus, the FP should run at all times. If this works then it is most likely the ECU that has a bad resistor in it. You can open it up to look for obvious issues, but if you don't see any then it is best to replace the ECU. Good luck.
 
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