Low Fuel Indicator Part Number

olddog58

Member
My 08 K9 EFI's low fuel light comes on somewhat arbitrarily and stays on anywhere from 5 minutes to 5 weeks... I replaced the Relay which didn't help. It doesn't seem to be loose wiring (not triggered by bumps). I plan to pull the tank off to see if maybe there is tank liner crudded up all over the unit, but if not I would like to just replace it. How do I find a replacement part?
 

Iman

Well-Known Member
it could be a wire inside the speedo rubbing against the bucket. my neutral light stayed on all the time till i wrapped all the wires up with electrical tape
 

pknowles

RETIRED
some where on here there is a diagram of the fuel pump. BigDogBro1put it on here awhile back. The light operates thru a thermistor that is in the tank. As the fuel drops below it, the light comes on dim then goes bright Your problem seems more like a grounding wire. I'm not a mechanic by no means. as far as the liner coming apart, take a flashlight and look down in the fill tube. Hope this helps. The good thing about the fuel pump is they are used in some garden tractors.
 

olddog58

Member
Ok I pulled the fuel pump unit off the gas tank and my thermistor has a crack in the wire connection. I'll pull the speedo off next and look for loose or grounded wires. But in the meanwhile... Anyone know whether this crack is meaningful?
 

Attachments

BigDogBro1

Made in the USA
2007, 2008, EFI, Low fuel indicator, Thermistor

Sorry, can't see the crack you're talking about unless you mean the brass entry collet rim.

Normally a crack in the wire insulation wouldn't affect the thermistor bead function.

Here's how it works:
When you have enough gas covering the thermistor bead in the metal case it keeps the thermistor cooled down and at a higher resistance (NTC type). When the gas drops below the thermistor for a period of time it will allow the thermistor to warm up due a limited amount of electrical current designed to flow thru it and ambient air temperature when it's warm outside. Once the thermistor begins to warm up its resistance will begin to drop in proportion to the temperature. Once the thermistor reaches a predetermined resistance trigger point the electronics will turn on the LOW FUEL LED.

The problem with NTC type thermistors is when the resistance drops the more electrical circuit current will flow thru it. If the circuit isn't properly designed the thermistor resistance will bottom out and excessive current flow thru the thermistor will cause it to overheat and eventually self destruct.

You can test the thermistor using an ohm meter.

Test from the thermistor wire end to the thermistor case. You should see some high resistance possibly 10k to 100k ohms, hard to say what without the spec. As the thermistor warms up you should see a decrease in the resistance measurement if it's a NTC type thermistor. If you cool it down (baggie full of crushed ice) you should see an increase in resistance.

You would see the opposite reaction if it's a PTC thermistor.

You could use a hair dryer to warm up the thermistor case. Don't get it hot, just warm it up a bit to see if it changes.

The thermistor could be available thru Walbro, Walbro retailer or BDM | A Complete Solution for Big Dog Owners. Your New Source for Parts, Accessories, Apparel & Gear for Harley, Metric, European and Off-road Motorcycles..

Walbro F20000107, fuel pump only.

Additional information at this post:
http://www.bigdogbiker.com/forums/387287-post3.html

If it does change then chances are it works and the problem is elsewhere in the circuit.

Hope this helps...good luck with the repair.







 
Last edited:

Jwooky

Well-Known Member
I pulled my tank/fuel pump trying to diagnose a cut out issue.

The wire/connector and guts of my thermistor are gone???

BDM wants $39 for it. I wonder who makes it and if we could buy direct.
 

BigDogBro1

Made in the USA
I pulled my tank/fuel pump trying to diagnose a cut out issue.

The wire/connector and guts of my thermistor are gone???

BDM wants $39 for it. I wonder who makes it and if we could buy direct.
Lots of info on EFI cutout problems here. You need to do a search on EFI cutout.
 
Top