Help Electrical Problem - - Excellence in Motion
LinkBack Thread Tools Display Modes
post #1 of 6 (permalink) Old May 27th, 2013, 4:51 pm Thread Starter
Join Date: May 2013
Location: Kingston, MA, USA
Posts: 2
Help Electrical Problem

I have a 98 RS that keeps blowing the the fuse for the fuel pump. I have unplugged everything on that circuit. It blows everytime if the relay is plugged in. I have replaced the relay and still blows as soon as key is turned on. Any help would be great.
RS98 is offline  
Sponsored Links
post #2 of 6 (permalink) Old May 27th, 2013, 5:58 pm
Join Date: Mar 2004
Location: , , UK
Posts: 3,750
Have you unplugged the connector to the fuel pump under the right side plastic? It is no good just unplugging the relay unless you go to fuel pump connector and also try disconnecting that.

If the fuse stays good then your fuel pump is faulty. You may get lucky and find the wires to the pump itself (inside the tank are bad).

I hope you are replacing their 15 amp fuse on F4 with 10 Amp. I discovered recently that later bikes have 10 Amp fitted in that position and if the fuel pump seizes or the fuel filter blocks then 10 amp will blow, but 15 Amp seems to burn out the pumps. As I see it, when the fuel pump gets seized or blocked, pressure and current rises, but it can burn out before a 15 Amp fuse can blow. In the process of the pump motor burning out THEN the fuse blows and it is all too late to save the pump..

That was the easy bit and the good news.

If you disconnected the fuel pump and the fuse still blows, then you could have a problem with your Motronic ECU since that fuse feeds both the ECU and the pump. So your next step is to pull off the big fat connector on the ECU, turn on the ignition and see if F4 blows. If it does with both fuel pump and ECU disconnected, then the good news is you are probably looking for a wiring short somewhere and not a new ECU or fuel pump.

Never pay again for live sex! | Hot girls doing naughty stuff for free! | Chat for free!

Last edited by voxmagna; May 27th, 2013 at 6:05 pm.
voxmagna is offline  
post #3 of 6 (permalink) Old May 27th, 2013, 7:14 pm Thread Starter
Join Date: May 2013
Location: Kingston, MA, USA
Posts: 2
Still blows with pump disconnected with relay in. I pulled the ecu and did not blow, but does that meaan the ecu is bad or did that disconnect all the wiring? Is there a way to test the ecu ?
RS98 is offline  
Sponsored Links
post #4 of 6 (permalink) Old May 27th, 2013, 8:52 pm
Join Date: Aug 2004
Location: , ,
Posts: 296
Follow the pump wires to the electrical box, looking for worn insulation.
54089093 is offline  
post #5 of 6 (permalink) Old May 28th, 2013, 5:17 am
Join Date: Mar 2004
Location: , , UK
Posts: 3,750
I pulled the ecu and did not blow, but does that meaan the ecu is bad
Well I did help you with what I thought was going to be the 'either/or'.

A 15 Amp fuse is a relatively big fuse, so blowing it means a serious fault, and even more serious if you unplugged the fuel pump and it still blows.

I am a bit puzzled by the problem linking to the fuel pump relay. The ECU does control the fuel pump relay coil with a relatively small current and I suppose you could have a wiring short or cross point short in the wiring from the ECU to the fuel pump relay. I think a short inside the ECU so bad that it blows a 15A fuse would mean it is toast. But a short in the wiring loom between the ECU plug and the relay box may be a life saver (for your ECU).

OK so there is something else to try first before moving on to check wiring between the ECU plug and everything else: Lets say you have a short in the fuel pump power wiring AFTER the relay. The relay is turned on by the ECU to power the fuel pump. Removing the relay would stop fuses blowing. Also, removing the ECU plug would stop the relay being turned on, so a short after the relay on the power side would not blow the fuse. Before you think the expensive ECU is dead (and that is a possibility), check out the wiring coming off the fuel pump relay for short circuits. I assume you have disconnected the fuel pump at the tank connector and you did actually disconnect the correct connector and not the fuel tank sender? In fact, with the ignition turned off,you should be able to poke your resistance meter across the terminals going back into the loom (relay) and in the opposite direction towards the fuel pump. The fuel pump should have a low resistance around 5 ohms. There should be no resistance measuring back from the pump connector to the relay box.

Also check the circuit diagram to see if the handlebar 'kill switch' has any wiring linked to the fuel pump relay. Some bikes have aftermarket theft alams fitted. I know my alarm has its wiring spliced into the fuel pump relay circuit and these alarm installers do not always do a decent wiring job and the alarm units can go faulty.

You need to stop blowing and replacing fuses or risk further expensive damage. Buy yourself a Clymer manual if you do not have one to study the wiring inter connections between the ECU connector and the relay box including the fuel pump.

Never pay again for live sex! | Hot girls doing naughty stuff for free! | Chat for free!
voxmagna is offline  
post #6 of 6 (permalink) Old May 28th, 2013, 11:43 am
H96669's Avatar
Join Date: Jun 2009
Location: Burton, British Columbia, Canada
Posts: 1,782
Check the pump wires where they come out of the hard sheating under the tank. Mine were compromised right there and would have eventually contacted together and blown the fuse or even just getting wet could have brought out the gremlins.

That was hard to see, almost missed that when re-installing the tank. I think they broke just from flopping around and the weight of the connector, they should be ziptied to the pump flange as per the pictures in the manual.I went a few steps further.

And I was re-installing the tank because I had to replace the fuel filter at way less than the recommended milleage. Plugged almost solid and the only signs were stalling when starting in cold weather. Never blew the fuse. Yes I did the 10A mod for now but when I have more time will install a 5A just for the pump.

I don't know how long I ran with the plugged filter, did not like that bad for the pump. Tests OK for fuel pressure and glad that some have found easily available/cheaper alternatives at autoparts. Just in case it dies on the road.....I think I can get going again.

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
H96669 is offline  

Quick Reply

Register Now

In order to be able to post messages on the - Excellence in Motion forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

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


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

Email Address:


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

Similar Threads
Thread Thread Starter Forum Replies Last Post
85 K100 electrical / starting problem PsychoRallye Other K-Bikes Discussion 18 Jan 21st, 2017 6:42 pm
85 K100RT Running & Electrical Problem mjlough Other K-Bikes Discussion 4 Nov 17th, 2011 10:16 pm
Electrical problem - starter running 9533Zero Other K-Bikes Discussion 16 Feb 27th, 2011 3:51 am
Ignition / Electrical problem ABonjour Technical, Repair and Maintenance 3 Oct 4th, 2008 11:36 am
New k75 owner, questions on shifting and weird electrical problem, need help! random903 Other K-Bikes Discussion 6 Jul 9th, 2008 7:07 pm

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