fuel pump no prime - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 21 (permalink) Old 09-02-2011, 07:53 PM Thread Starter
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fuel pump no prime

Ok 2000 rc51 the fuel pump will not prime. When i turn the key and then switch the kill switch to on I hear 1 click at a relay in the left tail section of the bike but fuel pump will not prime. Do you guys suggest a new fuel pump or other areas to check before i pull the fuel pump out? Also what size is the star or torx bit that is needed to remove the fuel line from the pump? thanks guys
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post #2 of 21 (permalink) Old 09-02-2011, 10:54 PM
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I'm guessing that click you hear is the relay failing or a fuse snaping. I would start with that. I've heard them click or buzz. Go to the svc manual and go thru the fuel system section. Could be simple.

http://www.rc51.info/index.php?page=service

US version, Section 5-54. It tells you how to test the relay.

John, 2000 RC51 #000100

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post #3 of 21 (permalink) Old 09-02-2011, 11:04 PM
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Determine which relay is actuating, whether it's the bank angle sensor relay or fuel cut relay.
The bank angle relay should actuate when the engine stop switch is set to Run.
When the bank angle sensor relay actuates, it completes half the circuit to actuate the fuel cut relay.
The ECU completes the circuit to energize the fuel cut relay coils and actuate the relay.
At that point the fuel pump motor energizes.
If both relays are actuated, and the pump doesn't run, then the fuel pump motor may be bad (actually the brushes inside may be worn out).

If you have downloaded the pdf version of the US RC51 service manual, go to page 5-52 to troubleshoot the fuel pump and both relay operation.
While you're at it, also download the UK service manual as the illustrations are better.

If the pump is bad, check Ben at RC51Parts.com to see if he has a fuel pump assembly on hand.

Last edited by SubSailor; 09-02-2011 at 11:07 PM.
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post #4 of 21 (permalink) Old 09-02-2011, 11:49 PM Thread Starter
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ok Thank you guys i was actually pulling the tank off and cannot get that last bolt under the seat. The relay that clicks is the one that is closes to the tail lights on the left hand side of the tail(bike). When the key is in the on position and i click the switch to run I hear 1 click. I went from off to run several times on the kill switch and each time i go to run i get 1 click. Also I would like to know if there is a way to check for engine codes? As I remember before the bike died on my buddy when he was riding the FI light came on earlier that week when he first started the bike. He then shut it off and started it bike up and the FI light was gone.

Last edited by leem23; 09-02-2011 at 11:51 PM.
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post #5 of 21 (permalink) Old 09-03-2011, 12:13 AM
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If your relay are still in the stock positions, ie no undertail mod, or maybe even if you do have an undertail, The relay you're hearing could be the bank angle relay. The manual shows it on the left and the fuel pump relay on the right end of subframe. I went back to 5-52 and started there, it looks like exactly what SubSailor said to do.

John, 2000 RC51 #000100

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post #6 of 21 (permalink) Old 09-03-2011, 03:07 PM Thread Starter
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Does our fuel pumps keep running once the bike is on? I was thinking of wiring the fuel pump to a toggle switch, would this hurt anything if the fuel pump is always running? I ask because after taking the pump out and hooking it directly to the battery it works. But when i plug the pump back into the harness and switch the kill switch to run i just hear the relay click and no prime. Thanks again for the help.
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post #7 of 21 (permalink) Old 09-03-2011, 04:44 PM
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The fuel pump runs continuously when the engine is running to maintain a constant pressure in the fuel rail
The fuel pressure regulator maintains and adjusts the fuel pressure depending on intake manifold pressure.
It would not be a good or safe thing to hard wire your pump to run continuously.
The purpose of the bank angle sensor is to shut off the fuel pump in case of a tip over or crash.

Here's a diagram of the bank angle sensor and fuel cut-off relays on an SP1.
When you set the engine stop switch to the Run position, the bank angle relay actuates.
The ECU is what actuates the fuel-cut off relay (with help from the bank angle relay).

If the bank angle relay is working and so is the fuel pump, it sounds like the either the fuel cut-out relay is bad, or a wiring problem may exist.

The headlight relay is the same 4-pole type. Try swapping the fuel cut-out relay with the headlight relay to test and see if the fuel pump switches on.

And yes, there is a way to check for FI codes on your bike, although it won't tell you a relay is bad.
There should be a green 2-pole connector in the rear section of your bike.
If you short the two poles and switch the key On, you should see the FI light flashing to indicate any stored codes.
A long (1.3 second) flash is a decimal 10 place, a short (.5 second) flash is a decimal 1 place.
The ECU shows all FI codes in order from smallest to largest.


Last edited by SubSailor; 09-03-2011 at 04:56 PM.
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post #8 of 21 (permalink) Old 09-03-2011, 04:57 PM
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Had the same problem a while back . Replaced the relay and problem was solved .
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post #9 of 21 (permalink) Old 09-03-2011, 05:00 PM
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Had the same problem a while back . Replaced the Fuel cut off relay and problem was solved .
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post #10 of 21 (permalink) Old 09-03-2011, 05:22 PM Thread Starter
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ok thanks i removed the fuel cut relay and used a jumper wire on the connecter and the fuel pump kicks on. I replaced the relay with one on the front left side of bike and still no prime but maybe that relay is bad too. Looking for headlight relay now. Also does the fuel cut off relay control the bike starting besides the fuel pump? I tried to start the bike with the fuel cut off relay connecter jumped with the wire but no start. I think maybe the battery may be to low on juice.

Last edited by leem23; 09-03-2011 at 07:29 PM.
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