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LOW VOLTAGE ON FUEL PUMP CONTROL UNIT
Posted: Mon Apr 12, 2021 8:43 pm
by PeteJLbeemer
Can anyone help, the fuel pump stopped working and as a few people suggested replacing it as they are know for failing after a few years. Anyway with a new ( none original) pump on it still didn't work.
After a test with the meter found that only 3.5 volts are getting to the fuel pump control unit ( regulator) that is mounted on top of the pump/filter assembly. And the power reaching the pump is a poor 1.2 volts and strangely on both sides ( pos/neg Black/ red.
I've only got a rubbish manual on cd and not sure if there is a relay further up the line that could be to blame??
It's a 1200rt 2005 with 50,000 miles
Any help would be much appreciated
Re: LOW VOLTAGE ON FUEL PUMP CONTROL UNIT
Posted: Tue Apr 13, 2021 7:12 am
by David.
The Haynes Manual wiring diagram only shows the power supply to the fuel pump coming directly from the ECU. The -ve seems to come from the battery, might be worth checking that the earth is good.
Re: LOW VOLTAGE ON FUEL PUMP CONTROL UNIT
Posted: Tue Apr 13, 2021 12:02 pm
by Blackrat
Fuel pump relay is a known issue, mine failed on my 2006 RT a few years back. To confirm it was the problem I put 12v straight onto the pump and the bike sprang into life. Early relays were silver, later modified ones are black.
Gary
Re: LOW VOLTAGE ON FUEL PUMP CONTROL UNIT
Posted: Wed Apr 14, 2021 12:05 pm
by PeteJLbeemer
David. wrote:
The Haynes Manual wiring diagram only shows the power supply to the fuel pump coming directly from the ECU. The -ve seems to come from the battery, might be worth checking that the earth is good.
OK thanks for the reply, I hope its not the main ECU, could be expensive. The earth seems ok.
Re: LOW VOLTAGE ON FUEL PUMP CONTROL UNIT
Posted: Wed Apr 14, 2021 12:14 pm
by PeteJLbeemer
Blackrat wrote:
Fuel pump relay is a known issue, mine failed on my 2006 RT a few years back. To confirm it was the problem I put 12v straight onto the pump and the bike sprang into life. Early relays were silver, later modified ones are black.
Yes I agree that the pump relay could be at fault but I still need to find out why it's only being supplied with 3.5 volts, so might have a problem with the main ECU ( if that's where is it's fed from) Probably nothing to do with what's happened but only a few minutes before I hit a massive pot hole in the road, not sure if any control unit would have been damaged from the shock.
Gary
Re: LOW VOLTAGE ON FUEL PUMP CONTROL UNIT
Posted: Wed Apr 14, 2021 2:07 pm
by David.
Is the voltage at the fuel pump being measured whilst the engine is being cranked to start. I have read elsewhere that 12v is not present unless this is the case.
I have no experience of this problem myself, just did a "Google" search.
From BMWLT,
https://www.bmwlt.com/threads/r1200rt-f ... se.183241/
Re: LOW VOLTAGE ON FUEL PUMP CONTROL UNIT
Posted: Wed Apr 14, 2021 11:08 pm
by PeteJLbeemer
Hi David, Well spotted and it might be the case, Saturday the tools come out again so will check the voltage again while cranking the engine over.
Thnx