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750 Breva fuel light

Discussion in 'Small Block' started by rossw, Jun 8, 2010.

  1. rossw

    rossw Cruisin' Guzzisti

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    I wish I had a reserve tap like my old bikes. :cry:

    Usually the warning light on my Breva 750 is "Start looking for fuel, you're going to run out soon". Tonight it was "You're running out of fuel ... nnnnnnnnnow!"

    The strangest part was that I could start it again and it ran for a bit, then the fuel light came back on and it stopped.

    Once I filled it up, it was fine. I learned two things

    1. Even a small block is heavy when you have to push it up a hill.
    2. THe fuel warning light is not to be trusted. It's back to using the trip meter instead.
     
  2. GTM®

    GTM® Administrator Staff Member GT di Razza Pura

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    #2 is wise. :pinch:
     
  3. oldmanjob

    oldmanjob Cruisin' Guzzisti

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    #2 is the only way to do it :D
     
  4. Holt

    Holt High Miler GT Contributor

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    Strange.
    Usually the Breva fuel light comes on when there's about 5 liters left.
     
  5. rossw

    rossw Cruisin' Guzzisti

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    That's what's supposed to happen. Normally it comes on intermittently at first while braking, then when it's on all the time it's time to find somewhere to fill up. This time it waited until the tank was virtually empty and then came on. When I checked the trip meter it showed 378 km, and it took 17 litres when I filled it up.

    I'm not even sure how the light triggers, but if it's a magnet and a reed switch like on some other models, then the magnet must have got stuck.
     
  6. Holt

    Holt High Miler GT Contributor

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    Maybe, didn't check what was what and how it worked when I changed the filter. I'd guess the trigger is the aluminum cylinder seen close right to the brass upper part of the pump.

    [​IMG]
     
  7. rossw

    rossw Cruisin' Guzzisti

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    That could be it. It is described in the parts list as a thermistor, which I had assumed was to protect the pump from overheating. On the wiring diagram I have the Low Fuel switch has the same symbol as the engine air thermistor and the head temperature sensor. That would make it a temperature based low fuel trigger. I suppose when it's temp exceeds a threshold, it assumes that it is no longer submerged in fuel. It was a cold night when it played up so that would fit the symptoms.

    If that's all true then it just establishes further in my mind that, at least in Winter, the fuel light cannot be trusted. :roll:

    I don't suppose you remember the part number for the BMW fuel filter or the model it came from?
     
  8. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    The thermistor has a voltage applied. As long as it is cooled by fuel, it doesn't conduct. When thefuel level is low enough tha tfuel doesn't cool it, it conducts and the fuel light goes on. The fuel filter is a BMW item for all the K and fuel injecdte R bikes. was lited in one ot the tech articles in the old forum, but is is BMW part number 16 14 2 325 859
     
  9. rossw

    rossw Cruisin' Guzzisti

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    So I need to look for open circuit or low volts feeding the sensor. (the light does come on, it's just that by the time it does it's too late to do anything about it.) The sensor seems to be made from unobtainium so far so it lloks like a replacement will be troublesome (unless I buy a complete fuel pump at > 500Euro :shock: ) That tripmeter method is looking better and better...
     
  10. Holt

    Holt High Miler GT Contributor

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    -thats the method I use. :mrgreen:
    As the low fuel lamp is lit way before end of fuel, it's a joke anyway.

    And yes, the BMW filter is identical to the OEM, ( and maybe even cheaper if you can find a "Mahle 145" filter) easier obtaniable, and the # John wrote.

    [​IMG]
     
  11. Mike.C

    Mike.C GT Reference

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    As I am responsible for our fuel supplies (being male seems to make me responsible somehow for her low fuel status!) I keep track of the Minister's 750 fuel using the second trip meter on the Breva - problem Is I never have to check it because I can be sure that as soon as 200Ks comes up or her light goes on there will be demand to stop at the nearest fuel - even though we might have heaps to get to our desitnation, it apparently is just not done to ride past a pertrol station with a light on the dash.

    Something about "I am NOT going to push the bike - it will be YOUR fault and YOU will push it!"

    Go with the flow - use the trip meter, it's how it's been done since the year dot, and until they can figure out how to make an accurate gauage will be how it needs to be done, unless you want to walk that is.
     
  12. rossw

    rossw Cruisin' Guzzisti

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    You're lucky the big Breva has two trip meters. I'm pretty sure the 750 only has one plus the odometer. It cycles odometer, trip, clock, temperature and back to odometer. If there is a second one and a trick to getting it, that would be handy. BTW the temperature this morning showed only 5°C. I need to fix my heated grips this weekend.
     
  13. Mike.C

    Mike.C GT Reference

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    Certainly the Nevada only has one trip meter, and I am almost 100% sure that the 750 Breva doesn't either.
     
  14. Holt

    Holt High Miler GT Contributor

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    Yep.
    Only one trip meter. And so as the odometer you cannot toggle between miles and km either.

    ( - and really, I don't know what to use a trip meter for, other than keeping an eye on the gas level. Goes for my car as well.)
     
  15. Mal

    Mal Tuned and Synch'ed

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    Well if you had 2 you could do how much fuel on one :) and then actually use the 2nd one as a “real” trip meter :p

    ….. unless you do more than 1,000km because it resets all the data like time and average speed when it rolls over :( Anyhow even with a fuel gage on the 1200 Sport and it’s clever little reserve light trip meter (Which can get confused) I still prefer to rely on my trip meter.

    But like Mike I’ll usually get the “I’m on reserve” signal ~200km. Now that’s a fair enough fuel range, I guess, but it’s strange how the bike with a bigger tanks gets 4L of reserve while the 750 gets 5L, seems like a waste. Not too bad on trips but around town I’d really like to use more of that 5L rather than thinking how long has that been on and did the trip meter get reset when it went on

    (I like to steal the 750 when I can {it has a ventrua rack for the groceries is my excuse} so I think she likes to leave it on reserve so I fill it up)

    Yes, well, apparently it is our job to monitor fuel........ as I accidently ran my partners out of fuel going up and down hills. Went up ok, but couldn’t pick up the remaining fuel when the bike was facing downhill. Oops. Still she started for the only 3 uphill bits, so no pushing required and it was sort of fun coasting downhill like a pushbikes, then she just waited with the bike as I went 5min down the road and smuggled some fuel out to her in a 1L water bottle.
     
  16. rossw

    rossw Cruisin' Guzzisti

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    Bought one of these from my local BMW dealer on Saturday A$55! :shock: I hope it won't need replacing too often. I bought it because I've only just got this bike and I'm not sure of it's history.
     
  17. Holt

    Holt High Miler GT Contributor

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    It's a Beemer-filter after all... :mrgreen:
    Think I had to pay about €22 for mine. The filter is also used for some Triumph and Ducati models. Will also be found under the name of "Knecht".
    Them Americans seems to obtain the filter at a significant lower price, your guess is as good as mine why it's so. :dry:

    After 60000 km:

    [​IMG]
     
  18. sign216

    sign216 High Miler

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    There are many different makes and models of filter that are a substitute for the Guzzi fuel filter. The BMW one is good, but pricey. There are many resources on the net for finding substitutes. A list of nine (9) other choices are in the Database section of this group ; http://autos.groups.yahoo.com/group/MG_750/

    The whole issue of the in-tank pump and filter makes changing the filter troublesome, and has caused other problems as well.
     

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