748-916 fuel pump relay woes. - Ducati.ms - The Ultimate Ducati Forum
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Old Aug 8th, 2019, 6:19 pm Thread Starter
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748-916 fuel pump relay woes.

So...........................i have a 1998 748 with a 1998 916 Motor with a 916 eprom.

When i go to start the bike and turn the key i get the pump kicking in as it should via some ''action'' , clacking and the like from relay #2.

The bike will start and run fine. the problem beings after ive turned it off and want to turn it on again

l can turn of the bike and on again and it will be fine as long as i do this under around 10 seconds, if i wait longer than that i will get a clack from relay #1 and the pump will not engage when the key is turned on.

lf i then swap the relays over the pump will kick in fine

lf i then take out the relays and put them back in the same place pump will not work

lf i then just take relay 1 out and swap it with another spare it will work

lf i disconnect and reconnect the battery the pump will work

Scenario repeats itself if you use the kill switch instead of the key

l have tried this with 4 relays, 2 old 2 new, mixed all ways, this scenario repeats itself over and over

lts like the first relay is getting a signal it shouldnt..........................i fuggin hate electrickery

Pleeeeeeeeeeeeeeeeease help, as a gallon of petrol and a lighter is beginning to make me feel warm and fuzzy all over

Last edited by anyoldiron; Aug 8th, 2019 at 6:33 pm.
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Old Aug 9th, 2019, 12:10 pm
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It's normal for the one relay to stay energized for around 10 seconds after the key is turned off. Not sure what's happening exactly, but I assume it's the ECU safely booting down... Maybe it's saving data of some kind. Someone here will know, but the point is that's normal and not something to chase. What's not normal is that it will not restart once that engine management relay is de-energized. Swapping in various new and used relays and disconnecting / reconnecting the battery having the impact that it does makes me think you should be sure the ECU ground is sound as a start. Also check the big ECU and associated relay and fuse connectors for corrosion.

Has the bike run without this problem at any point, or is this something you've had from the start? Did you just complete the 916 swap and now you have this issue? Did it run fine before and you did some work on it and now this? Is this something just out of the blue?

Helpful to know that info.

Maybe be sure your chip is seated properly too. Not loose, no pins sticking out (missing the socket).
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Dan. "Painfully mistaking my big talk for the truth" Samantha Fish.
2003 ST4s (The Truck)
1995 916 (Junk Yard Dog)
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Old Aug 10th, 2019, 9:12 pm Thread Starter
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Hello SS904,
Thank you for that, i needed to take a ''step back''. The long and short is having read your post throughly the only thing outstanding was checking the new eprom. l swapped in the arrow 748 one and the pump now behaves like it should, i haven't run it, but the pump cycles up the way it should after the 10 second deal.

So, problem solved,my mistake for assuming a new chip would work, i might actually get to ride it this season without it crapping itself yet

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