2003 rc51 fuel pump not priming - Honda RC51 Forum : RC51 Motorcycle Forums
 2Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 15 (permalink) Old 11-29-2019, 01:48 AM Thread Starter
Junior Member
 
Stljason's Avatar
 
Join Date: Nov 2019
Posts: 9
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Garage
Unhappy 2003 rc51 fuel pump not priming

fuel pump not priming through relay will work if i manually power it and it has constant power in the brown/black wire if i remove the relay then the brown/black wire powers up for a few seconds like it should
Stljason is online now  
Sponsored Links
Advertisement
 
post #2 of 15 (permalink) Old 11-29-2019, 02:19 AM
Senior Member
 
Join Date: Sep 2015
Location: Edmonton, AB
Posts: 1,534
Mentioned: 7 Post(s)
Quoted: 323 Post(s)
ok you aren't understanding how this all works.




here's how it works.


the black/white wire is powered by the bank angle sensor relay. your fuel pump relay is fed with a black/white on the coil side, a black/white on the contact side, then a brown/black on the coil side (that goes to the ecu) and a brown which goes to the fuel pump.


the black/white is +12v DC

the brown/black is connected to ground by the ECU to turn the relay on

the brown is the power to the fuel pump


here's a quick way to check.



turn the key on, with the kill switch in the stop position you should have 0 Vdc on the black/white

when you turn the kill switch to run, you should have 12 Vdc on the black white

if you don't have this, then you need to investigate the engine stop circuit. it starts at the ignition fuse (white/black), goes to the kill switch, comes back on black to the engine stop relay, then leaves on a red/orange to the bank angle sensor where it's connected to ground. any issue in this circuit will prevent 12v dc on the black white. it's pretty easy to diagnose this issue by a lack of FI lamp on the dash when you toggle the kill switch (when you click it to run, the FI lamp will come on for a few seconds as the ECU powers up, the ecu is fed by the black/white)


if you have power at the black/white, then you need to see if the ECU is calling for the pump to prime.

unplug the relay, put your meter between the black/white and brown/black. when you set the kill switch to run it should show 12 Vdc for a second or two, then go back to 0 Vdc.

if you plug in the relay, you should be able to feel the relay click on for a couple seconds, then off again as you cycle the kill switch.

if you're so inclined you can also put your lead between the solid brown and battery negative and verify 12 Vdc for a few seconds during the prime cycle



if you have all this, then the issue is further down the line


check for 12v DC between the brown and the fuel pump body. there's a green wire that bonds the fuel pump housing to the chassis. measure there.


if you have 12v going in, then it's likely that your issue is either a dead pump or a failed connection in the bulkhead that crosses between the outside of the tank and the inside. you can check for 12v at the pump motor connector itself.



chances are if you go through all this, you'll find the issue.
robertj1979 and Joe XR like this.
Wibbly is online now  
post #3 of 15 (permalink) Old 11-30-2019, 06:07 PM Thread Starter
Junior Member
 
Stljason's Avatar
 
Join Date: Nov 2019
Posts: 9
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Garage
ive got 12v going to the black/white wire i can toggle it off/on with switch but when its toggled on the fuel pump doesnt power up the only way i can get the fuel pump to come on is if i run a wire off the negative side of battery and ground it to the brown/black wire at the ECM it has a constant 12v not priming but if i unplug the fuel pump relay then the brown/black wire does what its suppose to when switched on there is voltage for a few seconds also theres no power coming out of the starter relay green/red wire ive done all kinds of tests but still fuel pump priming on its own
Stljason is online now  
 
post #4 of 15 (permalink) Old 11-30-2019, 06:27 PM
Senior Member
 
Join Date: Sep 2015
Location: Edmonton, AB
Posts: 1,534
Mentioned: 7 Post(s)
Quoted: 323 Post(s)
man can you please try to write in a way that's understandable? there's not one single piece of punctuation in anything you've said, it's very hard to follow. i've already told you everything you need to know but i'm not entirely sure you read what i told you.

this is the last post i'm going to make here.


if grounding the brown/black causes the pump to run then you have found your problem.



you are still not understanding how this works though. maybe you need to reread my post.



when you unplug the relay there will be 0V on the brown/black. this is because you have removed the coil from the circuit (the black/white feeds the coil, when you unplug the relay you have removed the power from the circuit)



if you want to troubleshoot you need to unplug the relay then set your meter to continuity and check between battery negative and the brown/black. when you cycle the kill switch you should see continuity for a few seconds, then it should drop out.

similarly you could measure the voltage between the black/white and brown/black, it should go to 12v for a few seconds, then back to 0 V



i don't know what you're expecting on the green/red at the starter relay. that's the negative for the starter coil. there won't be power on it as it's grounded by the neutral switch. the only time you'd see 12v on the green/red would be if the bike was in gear, and the clutch switch was open and you were pressing the start button.
Wibbly is online now  
post #5 of 15 (permalink) Old 11-30-2019, 07:45 PM Thread Starter
Junior Member
 
Stljason's Avatar
 
Join Date: Nov 2019
Posts: 9
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Garage
ok when i remove fuel pump relay and test the brown/blk wire it has voltage, test light comes on and goes off like it should But when i plug relay back in the brown/blk wire has constant power
Stljason is online now  
post #6 of 15 (permalink) Old 11-30-2019, 07:48 PM Thread Starter
Junior Member
 
Stljason's Avatar
 
Join Date: Nov 2019
Posts: 9
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Garage
and when i test for continuity in between brown/blk and black/wht wire it had continuity the whole time
Stljason is online now  
post #7 of 15 (permalink) Old 11-30-2019, 07:52 PM
Senior Member
 
Join Date: Sep 2015
Location: Edmonton, AB
Posts: 1,534
Mentioned: 7 Post(s)
Quoted: 323 Post(s)
Quote:
Originally Posted by Stljason View Post
ok when i remove fuel pump relay and test the brown/blk wire it has voltage, test light comes on and goes off like it should But when i plug relay back in the brown/blk wire has constant power

it can't have voltage on it when the relay is unplugged. it's not connected to anything.

this statement doesn't even make sense. you say when the relay is unhooked, the brown/black is live, and then when you plug the relay in, the brown/black is live.


this is impossible.
Wibbly is online now  
post #8 of 15 (permalink) Old 11-30-2019, 08:03 PM Thread Starter
Junior Member
 
Stljason's Avatar
 
Join Date: Nov 2019
Posts: 9
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Garage
no when relay is unhooked the brown/blk wire has voltage for a few seconds like it should when i turn start switch to run position
Stljason is online now  
post #9 of 15 (permalink) Old 11-30-2019, 08:07 PM Thread Starter
Junior Member
 
Stljason's Avatar
 
Join Date: Nov 2019
Posts: 9
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Garage
when relay is hooked back up with start switch in run position the brown/blk wire has constant power when it should only power up for a few seconds
Stljason is online now  
post #10 of 15 (permalink) Old 11-30-2019, 08:12 PM Thread Starter
Junior Member
 
Stljason's Avatar
 
Join Date: Nov 2019
Posts: 9
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Garage
and ive tried different relays that i know are good
Stljason is online now  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Honda RC51 Forum : RC51 Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome