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Thread: Fuel injector help

  1. #1

    Fuel injector help

    Dear BMW Forum Brain Trust,

    I have finally put back together the 1996 bmw R850R I have been fixing over the last year. I won't say restoring, as that would imply the bike is better to look at now.

    I have replaced the tank and fuel pump/filter etc. along with several parts some related, some unrelated. The bike sat outside under a deck with ethanol fuel in the tank for a number of years and consequently the tank had rusted completely through. (some previous posts on here) The previous owner indicated they spent some amount of time trying to get it to start. Basically all of the fuel tank and pump are new.

    At this point, it is back together 90%. When I attempt to start the bike with a little carb cleaner in the throttle bodies it fires and will run briefly. If I pull the fuel lines from the fuel injectors, the there is plenty of fuel that comes out - the pump is working and I have confidence that is operating. When I turn the key, you can hear the fuel pump whir up and pressurize. It seems to me that the fuel injectors are just not firing - sending fuel into the Throttle bodies. I have checked the fuses and found them all fine.

    I have pulled the injectors and doused them with cleaner. There is no visible varnish or gum. Fuel isn't flowing through either injector, so I suspect something electrical.

    What else should I check?

    Thank you in advance!

  2. #2
    Pepperfool GSAddict's Avatar
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    Does the bike have the original hall Sensor?
    Likely the insulation has failed.
    The upper sensor controls the spark
    The lower one controls the fuel pulse
    '
    Ufda happens..........

    Need your R11xx Hall sensor rewired? PM me.

  3. #3
    Neglected Bike Adopter
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    GSAddict has it right -- if you see no injector spray at all on either side when cranking the bike, you've likely got a failed Hall Sensor and/or its wiring harness has failed. There is enough flex in the nylon fuel lines going to the top of the injectors that you can undo the two hex screws holding the injectors into the throttle bodies, pull them out, and point them each at a piece of cardboard to check for a spray pattern with the fuel lines still attached. Just be careful not to flex them too much. If you get no spray whatsoever then that'll confirm it.

    If you're handy and experienced with soldering electronics you can order the correct materials and attempt a repair yourself (and you have to make sure to thoroughly waterproof the resulting repair) -- however, if you are not, GSAddict does excellent work in rebuilding the sensor wiring harness with better-than-new wiring for significantly cheaper than a new part.

    Good luck with your R850R. I just went through nearly the same exact process with my own 1997 and am still working out more problems as I find them. My own Hall sensor wiring was completely cooked at just 35k miles. I fixed my injectors the lazy way, by pulling the dirty originals out and replacing them with an upgraded Bosch EV14 set.

    Oh, and if you haven't yet, now's a great time to clean out the inside of those throttle bodies. Mine were still full of black carbon dust from a failing charcoal canister even though it had been removed years before I ever bought the bike.
    Owner of the saddest 1997 R850R you ever did see.

  4. #4

    Hall

    Quote Originally Posted by GSAddict View Post
    Does the bike have the original hall Sensor?
    Likely the insulation has failed.
    The upper sensor controls the spark
    The lower one controls the fuel pulse
    Thank you - actually I sent this to you to be rebuilt! Is there an easy way to check this without pulling it out?

  5. #5
    Quote Originally Posted by senseamidmadness View Post
    GSAddict has it right -- if you see no injector spray at all on either side when cranking the bike, you've likely got a failed Hall Sensor and/or its wiring harness has failed. There is enough flex in the nylon fuel lines going to the top of the injectors that you can undo the two hex screws holding the injectors into the throttle bodies, pull them out, and point them each at a piece of cardboard to check for a spray pattern with the fuel lines still attached. Just be careful not to flex them too much. If you get no spray whatsoever then that'll confirm it.

    If you're handy and experienced with soldering electronics you can order the correct materials and attempt a repair yourself (and you have to make sure to thoroughly waterproof the resulting repair) -- however, if you are not, GSAddict does excellent work in rebuilding the sensor wiring harness with better-than-new wiring for significantly cheaper than a new part.

    Good luck with your R850R. I just went through nearly the same exact process with my own 1997 and am still working out more problems as I find them. My own Hall sensor wiring was completely cooked at just 35k miles. I fixed my injectors the lazy way, by pulling the dirty originals out and replacing them with an upgraded Bosch EV14 set.

    Oh, and if you haven't yet, now's a great time to clean out the inside of those throttle bodies. Mine were still full of black carbon dust from a failing charcoal canister even though it had been removed years before I ever bought the bike.
    It looks like a chimney in these throttle bodies. I pulled back the tubes going into the airbox and I swear I heard fiddler on the roof. I note also the rubber is all fairly rotten, but I was excited to get the tank back together - not trivial! - and hear it run. I suppose since the maiden voyage is delayed, it is worth tearing all that down and putting in new rubber.

  6. #6
    Neglected Bike Adopter
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    How unfortunate! It's to be expected with one that sat for so long -- I had to replace the throttle body boots and O-rings on my own machine too.

    Now that you mentioned it, I think I heard the chimney sweep from from Mary Poppins singing somewhere when I pulled my own throttle bodies out.

    You are welcome to PM me if you've got any other questions, as I've done pretty much everything to a neglected R850R to get it working short of pulling the engine.
    Owner of the saddest 1997 R850R you ever did see.

  7. #7

    update

    With these clues, I went back to the HAL sensor and found the plate had moved from its original marks. I also found the connector was from the HAL sensor to the main unit was not completely together. Adjusting these two items, I pulled the fuel injectors and held them up to a paper towel. Only the tiniest bit of fuel is coming out. Which means, I think, that the HAL sensor is working correctly now, but likely the injectors need replacing. Ah, more parts...

  8. #8
    Neglected Bike Adopter
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    Low injector/fuel pressure could also be a sign of a bad fuel pump, clogged or bad fuel filter, leaking or burst in-tank fuel lines, or a bad fuel pressure regulator. You mentioned you replaced the tank and its internal items, but have you ever done a fuel pressure test?
    That nasty rust and ethanol could have easily gotten into the pressure regulator and caused it to stick open, which would mean you have no fuel pressure and the injectors can't inject.

    This doesn't necessarily mean your injectors aren't bad or otherwise clogged, though. When you cleaned them, did you use a battery to open them up while forcing cleaner through them, or did you just douse them externally in cleaner?
    When I was having trouble, several people recommended I send mine to a professional shop to have them cleaned and flow tested, and it's not expensive.
    Owner of the saddest 1997 R850R you ever did see.

  9. #9
    Fuel pump and fuel lines have all been replaced, but that is an interesting point about the regulator. When I pulled the old tank off, it looked like chunky tomato soup. When I "cleaned" them, it was just giving them a good dousing with cleaner, not running any fuel through it or anything. Do you think I need a motorcycle-specific shop for that, or any shop will do?

    Also, I just read your signature. I can't challenge your assertion since mine is a 1996, but I guarantee you I'm going to be the only person who is glad to lay eyes on this bike, haha.

  10. #10
    Quote Originally Posted by derrickstone View Post
    When I "cleaned" them, it was just giving them a good dousing with cleaner, not running any fuel through it or anything.
    I'll confess I came across something on the Internet that told me not to mess with trying to clean the injectors, that I'd damage them.

  11. #11
    Neglected Bike Adopter
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    It's possible to build cleaning rigs with common home materials (all that's required to open the spray valves is a 9 volt battery) but your best bet is to send them to a professional. Matched flow rate on injectors matters a LOT on these twins -- even a 5 percent mismatch can have a huge impact on how smoothly the bike runs. It's not really possible to do an accurate flow test for each injector at home for the $40 or so a shop charges for cleaning and testing on the proper equipment.
    Try searching for "fuel injector cleaning and testing" on your favorite search engine. I don't have any recommendations as it's a service I've never needed, but usually you have to mail them out to a specialty shop that will fix them up for you and have them for a couple days.
    And to answer your question, no, you don't need a motorcycle-specific shop. Injectors are pretty standardized parts and any shop that services car injectors should be able to clean them.

    My tank wasn't quite as nasty as yours but it was getting there, so I replaced my own fuel pressure regulator just to eliminate possible fuel system failure points. I'm actually replacing my own tank soon with a better-condition used one, and at that point the only original fuel system part left will be the distributor. Ethanol gas really kills when it sits for years.
    It's possible to change out the fuel pressure regulator but the factory-equivalent ones aren't cheap. BMW's price right now on the part is $107. https://www.shopbmwmotorcycles.com/p...531465106.html
    Quantum also makes an equivalent one that's $60 and has a built-in particle screen: https://www.highflowfuel.com/quantum...s-16141341231/

    I went with a Quantum myself that's set to 3.5 bar of pressure instead of the stock 3.3, because it pairs well with my upgraded injectors. The one I linked is stock-equivalent 3.3 bar.

    The Clymer and BMW service manuals will tell you that you have to lift the rear subframe of the bike and scoot the airbox back to change out the pressure regulator; that's baloney and I have no idea why they say so. It's under the battery box facing the front of the bike and it can be done the cheaty way just by removing the battery box. If your bike has ABS, this is quite a pain, but on my non-ABS model it went pretty smoothly.
    Last edited by senseamidmadness; 09-06-2021 at 01:55 AM.
    Owner of the saddest 1997 R850R you ever did see.

  12. #12
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    Good day,

    How lamentable! As an owner of a recently procured but well-maintained 97 R850R over in Chattanooga, I am most distressed to hear of your ongoing woes with yours.

    Just a quick note in case you are not aware: when removing the injectors to clean or service, do replace the o-rings regardless of appearance. I do hope our paths cross one day so we can compare our cycles. Don't give up - when properly running, the model is both pleasant and reliable.

    Be well, ride safely.

    RK

  13. #13

    Progress update

    Well... first off, it isn't fixed yet. It was a good clue that both injectors had the same feeble output. Because it was one of those projects, I replaced the injectors, anyway. And yes, I have new gaskets for where the injector is pressed into the throttle body. But all this rubber needs to be replaced.

    At any rate, that didn't fix it. I then replaced the fuel pressure regulator. The amount of fuel coming out of each injector is much better. While the bike will still not fire on gas, you can actually smell gas in the throttle bodies.

    I next rechecked the HAL sensor to make sure it matched up to the marks I had made when I removed it, and pulled the spark plugs to watch for spark. Faint - could only get a barest hint of a spark and not consistently.

    So... I've ordered a replacement ignition coil.

    More to come.

    Derrick

  14. #14

    And...

    While I am waiting on parts, I replaced the tires, something I've never done.

  15. #15
    Registered User jrogers's Avatar
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    I bought a R1100S BCR and right away had problems with it starting. I contacted the previous owner and he told me the hard starting problem just showed after he had replaced the Battery a few days earlier. I did all the usual stuff buying a new to me bike, replaced all filters, fluids, spark plugs, adj. valves, replaced some weathered rubber parts and rewrapped wiring looms. Plus all new brakes, pads, rotors and S.S. lines. With everything back together the bike seemed to be starting fine except first off in the mornings, had to turn it over for a long time before it fired. Rode it for about 1000 miles this last month and it went back to very hard starting first off in the mornings but eventually started and worked fine. I decided to check for spark and pulse at the Fuel Injector, they where fine. Called my BMW friend/dealer and he said to check the fuel pressure. So taking the tank off I noticed some fuel residue around a couple of the hose clamps. I had bought some quick connects and new clamps and hose (Beemer Boneyard) so I installed them today. Bike starts right up now. I'm guessing the fuel pressure wasn't quite high enough for the injectors to work properly with the old clamps the previous owner used on the fuel lines when changing out the Battery.
    So it sounds a bit funny but you might want to install new fuel line and clamps to make sure you're not leaking air into the system and having a low pressure problem.
    02 R1150R ABS, 04 R1150R, 04 R1100S BCR, 05 R1100S BCR, 16 S1000XR

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