Author Topic: Downtown 300i - Problem with fuel pump check  (Read 1697 times)

EJiwe

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Downtown 300i - Problem with fuel pump check
« on: October 09, 2019, 04:14:01 PM »
Hello Everyone!

As you all know, after turning the key and self-test, the pump is checked within 1-2 seconds. So, my problem is that in 50% of cases, the check does not turn off and the pump starts pouring fuel into the engine continuously, the nozzle is open at this point. Naturally, after that the engine does not start.

If you wait for a while, the pump can run normally and the engine will start. But like I said, the problem is repeated from time to time.

In an attempt to check what the problem was, I checked the pump and all the sensors. Everything is within normal range. So I won't know what the problem might be. The only option I have left is the ECU. But unfortunately I have no one to borrow it from for the test. In my region, Downtown is an extremely rare scooter.

Maybe somebody has encountered something like this or maybe you can tell me what else to check.

Stig / Major Tom

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Re: Downtown 300i - Problem with fuel pump check
« Reply #1 on: October 09, 2019, 06:38:13 PM »
What region?

Stig

Boston Strong
Rural Ohio

And, I'm feeling a little peculiar.

CROSSBOLT

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Re: Downtown 300i - Problem with fuel pump check
« Reply #2 on: October 09, 2019, 07:30:44 PM »
I think your ECU is fine but your fuel pump relay is sticking closed. Both the fuel pump and injector are powered by that relay. Try exchanging relays like the one next to it or the closest relay. They are all the same, same markings as you will see and all 12 volt normally open single pole. Please let us know what you find.
Karl

Three motorcycles 1960-1977 (restored a 1955 BSA)
Agility 50
Yager 200i
Downtown 300i
Navy tech, Ships Engineer, pilot and aircraft mechanic

EJiwe

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Re: Downtown 300i - Problem with fuel pump check
« Reply #3 on: October 10, 2019, 02:55:11 PM »
What region?
Stig

Russia. Moscow.

I think your ECU is fine but your fuel pump relay is sticking closed. Both the fuel pump and injector are powered by that relay. Try exchanging relays like the one next to it or the closest relay. They are all the same, same markings as you will see and all 12 volt normally open single pole. Please let us know what you find.

Thanks for the tip. I completely forgot that there is also a relay. I will definitely check it and let you know.

Stig / Major Tom

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Re: Downtown 300i - Problem with fuel pump check
« Reply #4 on: October 10, 2019, 04:36:33 PM »
Welcome to the forum!

Hope you get it sorted.

Stig ( Ohio, USA)
Boston Strong
Rural Ohio

And, I'm feeling a little peculiar.

CROSSBOLT

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Re: Downtown 300i - Problem with fuel pump check
« Reply #5 on: October 10, 2019, 07:03:55 PM »
Russia. Moscow.

Thanks for the tip. I completely forgot that there is also a relay. I will definitely check it and let you know.

Yes, welcome! You better let us know about the relay idea or we will send one of our crooked politicians over there to stir things up! Har, har!
Your fuel pump relay should have two black wires, one blue with black stripe and one red with black stripe into the plug.
« Last Edit: October 10, 2019, 07:11:26 PM by CROSSBOLT »
Karl

Three motorcycles 1960-1977 (restored a 1955 BSA)
Agility 50
Yager 200i
Downtown 300i
Navy tech, Ships Engineer, pilot and aircraft mechanic

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