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Help with r1200c hard start


Giddy

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I've been fighting this bike for over a year with this same issue. Every morning I have to hold the throttle open and hold the starter until my bike finally starts. I've done plugs, plug wires, new injectors, new fuel lines, new fuel strainer, new fuel filter, new air filter, new HAL, new relays and finally a new o2 sensor. I'm at a complete loss. I've been asking on chromeheads for help, but no one has ideas past a vacuum leak or bad plugs.

 

The bike will (maybe) start, die a few times, finally start enough to get moving, die at the first few stop signs, then after about a mile all is fine. It's not 100%, but it isn't rough and won't die at idle. For the rest of the day the bike will start fine with no additional throttle.

 

Please any help would be appreciated.

 

The fuel pressure regulator and battery were going to be my next things to change. At this point I'm just slowly building a new bike piece by piece trying to find the problem.

 

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19 minutes ago, Giddy said:

Would that be the oiltemp sensor? I know it has oil temp and air intake sensors.

Morning  Giddy

 

To get a decent cold start both the oil temp sensor & the AIT (Air Intake Sensor) must input the correct ambient & engine temperature & be somewhat in agreement. 

 

You need to verify that both are working & registering correctly. 

 

Another place to look is at the cold start fuel flow & pressure, low (engine cranking) fuel pressure or low fuel flow during cold start can make cold starting a hit or miss deal. 

 

Any idea on what you battery voltage is during cold engine cranking? (if much below 10v that can also cause cold starting issues.

 

What year 1200C are you working with as those have an unusual fueling control system vs other boxer twins of that era, we need to pin the year down if we can.   

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Thank you for the reply! It's a 2003 normal r1200c.

I've pulled the injectors and watched them at cold start and they seemed fine. The battery is very old and while it seems to turn the starter fine, I know that dropping voltage can cause problems. Since I have to pull the tank I'll probably buy a battery since I've been putting it off. 

 

I do have a Booster Plug on this bike, I was thinking about pulling it off and trying the air intake sensor without it. 

 

Is there a way to check the sensors? Or are they too sensitive for a multi meter test?

 

I rode the bike for 3 years almost daily before this developed, now it's been a year of changing one thing at a time and trying it the next day.

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41 minutes ago, Giddy said:

Thank you for the reply! It's a 2003 normal r1200c.

I've pulled the injectors and watched them at cold start and they seemed fine. The battery is very old and while it seems to turn the starter fine, I know that dropping voltage can cause problems. Since I have to pull the tank I'll probably buy a battery since I've been putting it off. 

 

I do have a Booster Plug on this bike, I was thinking about pulling it off and trying the air intake sensor without it. 

 

Is there a way to check the sensors? Or are they too sensitive for a multi meter test?

 

I rode the bike for 3 years almost daily before this developed, now it's been a year of changing one thing at a time and trying it the next day.

Afternoon Giddy

 

Definitely remove the booster plug as a test, those things can cause issues on cold starting under some conditions.

 

If you have a volt meter put that across the battery posts then see what your cold cranking voltage is, that alone might point a finger at your problem.

 

You can test both your intake air sensor & your oil temperature sensor with an ohm meter, the resistance will not be linear from cold to hot but it will tell you if they are working.  Put the sensor in the freezer overnight, then remove & hook up your ohmmeter, then see if the resistance changes smoothly in relation to the temperature increase. 

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Thank you! Maybe there is hope for this old oilhead! 

 

I'm going to check the sensors and replace the battery. Am I looking for any specific range of resistance? Or just that it does change with temperature 

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1 hour ago, Giddy said:

Thank you! Maybe there is hope for this old oilhead! 

 

I'm going to check the sensors and replace the battery. Am I looking for any specific range of resistance? Or just that it does change with temperature 

Afternoon

 

 The BMW 1100/1150/1200c uses a negative temperature coefficient (NTC) thermistor for sensors. Those things are not a linear output sensor as far as ohms per degree goes. 

 

The colder the sensor is the higher the resistance so just look for a drop in resistance as the sensor warms up & that there are no holes or opens in your resistance readings as sensor warms up from cold. 

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Just one more question that I'm sure sounds stupid. 

I'm guessing when I pull the coolent sensor I will of course lose a lot of oil. Should I go ahead and order a filter and just drain the oil and do an oil change while I test the sensors?

 

 

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10 minutes ago, Giddy said:

Just one more question that I'm sure sounds stupid. 

I'm guessing when I pull the coolent sensor I will of course lose a lot of oil. Should I go ahead and order a filter and just drain the oil and do an oil change while I test the sensors?

 

 

Afternoon  Giddy

 

There are no stupid questions on this web site! Just ask away.

 

You won't lose much, if any,  oil (especially if you allow the motorcycle to sit overnight before removing the oil temp sensor) as the oil temp sensor sits way up high on top of the oil thermostat. 

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  • 3 weeks later...

I finally had time to pull the air temp sensor. It shows open circuit when I try and test it with my volt meter. 0 Ohms. I'm guessing this is my culprit for bad starting. I'm going to pull the oil temp sensor just to be sure though and test it. 

 

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42 minutes ago, Giddy said:

I finally had time to pull the air temp sensor. It shows open circuit when I try and test it with my volt meter. 0 Ohms. I'm guessing this is my culprit for bad starting. I'm going to pull the oil temp sensor just to be sure though and test it. 

 

Evening  Giddy

 

What scale was your ohmmeter on? At 70°f your Air Intake Temp sensor  should be somewhere in the 2K to 2.5K area. Make sure that your meter is set to measure in that range. 

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My meter usually sets it's range based on resistance automatically. I'll test one more time by setting it manually on the 2k range to be sure.

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I tried again and still no reading across the two prongs. I get a tone when I tap my volt meter leads together so I know my meter is working fine. 

From what I understand about how this bike cranks this could very well be my issue finally. Is it not normal for one to fail completely?

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The Fabricator

I have replaced a failed oil temp sensor on an R1100.  It is not easy to get to.  And not easy to get out, as the space is limited for swinging a wrench.

You might try measuring the resistances in situ.  You could run the engine until it is at operating temperature, then disconnect the sensor and measure the resistance as it cools down.

The failed sensor make the bike hard to start hot or cold.

It was years ago, but I seem to remember it did fail completely, meaning the resistance did not change with temperature.

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On my r1200c the oil temp sensor is quite easy to get to. My air intake sensor seems bad, so next test is oil sensor now that I've located it.

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Never mind I managed to get a reading from my air sensor. So I guess I do need to actually do more digging.

However. It's showing around 1.7k ohms at about 80degrees. I'll pull the oil sensor and see how both do over a temp range 

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12 hours ago, Giddy said:

Never mind I managed to get a reading from my air sensor. So I guess I do need to actually do more digging.

However. It's showing around 1.7k ohms for exactly 80°f . I'll pull the oil sensor and see how both do over a temp range 

Morning  Giddy

 

That 1.7k ohms at 80degrees is about right. I don't have an ohms vs temp for exactly 80°f as my temp measurements were taken  using °c  but that 1.7k ohms for exactly 80°f falls nicely within my measurements.  

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13 hours ago, Giddy said:

So. My oil pressure switch has a broken end. Where should this plug and what does the plug look like?

 

Morning  Giddy

 

The oil pressure SWITCH has nothing to do with the engine starting or operation, the oil pressure switch only effects the dash oil light. 

 

It's the Oil Pressure SENSOR that effects engine operation. 

 

On your question--  where does the oil temperature sensor connector plug into the engine harness?  On the 1200C I really don't know as I don't work on many of those & even if I did that isn't something that regularly gets looked at or addressed. 

 

You are just going to have to search for the connector remnants on the engine harness. The oil sensor plug looks like this so possibly the part that the wires pulled out of is still plugged into the engine harness.

 

  

 

 

 

 

oil temp sensor.2.JPG

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The only plug like that I see is right on the motronic unit. It has a female plug with nothing plugged in. In my Clymer manual it shows the Air and Oil Temp sensors wires connect before the computer. 

I was about to put the tank back on when I found the broken wire. 

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There is a wire connection that sits atop the motronic and has a metal clip to maintain connection.  Is that one present and connected?

 

I do not remember what it is for.

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54 minutes ago, Giddy said:

The only plug like that I see is right on the motronic unit. It has a female plug with nothing plugged in. In my Clymer manual it shows the Air and Oil Temp sensors wires connect before the computer. 

I was about to put the tank back on when I found the broken wire. 

Morning  Giddy

 

First off what year & exact model1200c are your working with? There are so many versions of those darn 1200c motorcycles we need that info to even begin to figure it out. 

 

I do show the motorcycle side wire colors for the oil temp connector as white/black & brown/grey so unless your 1200c is an outlier then look for those wire colors. 

 

As I mentioned above I am not that familiar with the 1200c wire connections but I would imagine that the motorcycle side connector that you are looking for has a wire bail on it (like a fuel injector or air temp sensor connector)

 

Use your existing oil temp pig tail as a guide as it needs to comfortably reach the proper motorcycle side connector so if it doesn't reach the connector easily & with some slack then it probably is not the correct connector.   

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13 minutes ago, Giddy said:

Mine is a 2003 r1200c classic. 

I've found a plug matching the color code in my Clymer book. 

Morning  Giddy

 

The one in your picture above looks to be correct. 

 

 

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2 hours ago, Giddy said:

Yay! Now to see if I can get the prongs back in the right holes. I want to try it before I order a new one with new connector.

Morning  Giddy

 

I looked at a number of my wire schematics & can't seem to find a wire color break-out on the sensor side of that connector but the oil temp sensor is just a NTC resistor so polarity shouldn't matter. But a good guess would be brown to brown as BMW typically uses brown derivatives as the low (ground) side. 

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I figured the "red" wire is really faded brown. I'm starting a new job next week at a motorcycle dealership. So as long as I can get the sensor to last a week then I'll probably just order a new sensor at work. I'm really just wanting to see it crank well a few times. If I connect it and it's still not cranking well then I will pull the sensor and test it. 

 

 

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7 minutes ago, Giddy said:

I figured the "red" wire is really faded brown. I'm starting a new job next week at a motorcycle dealership. So as long as I can get the sensor to last a week then I'll probably just order a new sensor at work. I'm really just wanting to see it crank well a few times. If I connect it and it's still not cranking well then I will pull the sensor and test it. 

 

 

Morning  Giddy

 

You can probably test it in place as it only has 2 wires coming out. I don't have the specs on the 1200C bikes but I would guess somewhere around 2K +/-  at 75°f.

 

The hotter the sensor gets the lower the resistance should be. 

 

Those sensors seldom fail & on the few I have seen fail they usually just fail open. 

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Thank you! I'll try and find a list of resistances. It probably shares a sensor with other oilheads anyway. I had asked about those wires being broken over at chromeheads over a year ago and everyone thought they were aftermarket. Ive been chasing this problem starting for a year so I'm hoping this sensor being unplugged was my problem 

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I plugged in the sensor. Put the tank back on. Hit the starter button and BAM she roared right to life! That's the first good start since I've owned the bike! 

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2 hours ago, Giddy said:

I plugged in the sensor. Put the tank back on. Hit the starter button and BAM she roared right to life! That's the first good start since I've owned the bike! 

Afternoon Giddy

 

That's called diagnostic progress. If it continues to start OK then it's called success.  

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So that was the issue with hard start. But now I have a new problem. My fuel pump died after 29k miles. It popped the 5 amp fuse and then started sounding terrible when I replaced the fuse and tried to limp home. 

The new fuel pump fried another 5 amp fuse. I put a 10 amp in to get home and the bike ran fine. 

Maybe a bad fuel regulator causing poor flow and more draw?

Any ideas of what could cause that sudden problem? It's happened three times. Two times before the pump died, under heavy acceleration. After the pump was replaced it popped the fuse at the SAME SPOT as when the pump died before. I got home but now I'm concerned about the problem coming back. 

The new pump I will admit is after market and maybe just has higher draw than the 4 amp factory one? But the fact the old pump had the same issue makes me worry something is starting to fail. 

 

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8 hours ago, Giddy said:

So that was the issue with hard start. But now I have a new problem. My fuel pump died after 29k miles. It popped the 5 amp fuse and then started sounding terrible when I replaced the fuse and tried to limp home. 

The new fuel pump fried another 5 amp fuse. I put a 10 amp in to get home and the bike ran fine. 

Maybe a bad fuel regulator causing poor flow and more draw?

Any ideas of what could cause that sudden problem? It's happened three times. Two times before the pump died, under heavy acceleration. After the pump was replaced it popped the fuse at the SAME SPOT as when the pump died before. I got home but now I'm concerned about the problem coming back. 

The new pump I will admit is after market and maybe just has higher draw than the 4 amp factory one? But the fact the old pump had the same issue makes me worry something is starting to fail. 

 

Morning   Giddy

 

You sure like to test me don't you?

 

We have a minor problem as I don't have a full BMW wiring schematic on your outlier 1200 classic. I have a number of 1200C wire diagrams & they pretty well all show a 15 amp fuse used for the fuel pump circuit.

 

So lets try to pin it down a bit more if possible. 

 

What fuse location is your fuel pump fuse in, is it fuse #1 or fuse #4  or a different fuse location than either 1 or 4 ? (hopefully this can help me find a wire diagram that is closer to what you have). Different 1200C variants have different items "also" powered by the fuel pump fuse. 

 

Any chance when doing your diagnostics that you got the wrong fuse back in the fuel pump fuse cavity???? 

 

In any case, a 5 amp fuse sounds too small for a fuel pump fuse in any 1200C as the fuel pump fuse has other items on that circuit. 

 

If you did get a 5 amp fuse in the fuel pump circuit then one of your other fused circuits might now be over-fused with a misplaced 15 amp fuse. 

 

Anything in your riders manual on fuse location, or possibly a fuse location map on or near the fuse box? 

 

 

 

 

 

 

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15 minutes ago, Giddy said:

On my C the top two fuses are 4 amp and the bottom two are 10+. It was a 4 amp that's been popping. I believe fuse 1 

 

 

Morning   Giddy

 

OK, that is some help (sort of),  on the couple of 1200C wire diagrams that I have that show fuse # 1 as the fuel pump fuse it shows that as a 15 amp fuse. 

 

I also looked at the old 1100R bike for fuel pump fuse as it probably has the least number of items on the fuel pump circuit & even that shows a 10 amp fuse. 

 

I can't totally confirm your outlier 1200C uses a 15 amp fuel pump fuse but can probably say it wouldn't be as low as a 5 amp fuse. 

 

You might ride it with a 10 amp fuse but carry a spare 10 amp & a spare 15 amp fuse just in case the 10 amp fuse is on the low side.  

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I started carrying a 10 amp fuse as a backup. I'll pull the fuse box cap and show it to you. I have the side covers off of the bikes since I have a trickle charger on it overnight during the cold. I ride it daily but I just got a new battery and don't want to risk the cold taking another one! 

PXL_20221019_114403651.MP.jpg

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18 minutes ago, Giddy said:

I started carrying a 10 amp fuse as a backup. I'll pull the fuse box cap and show it to you. I have the side covers off of the bikes since I have a trickle charger on it overnight during the cold. I ride it daily but I just got a new battery and don't want to risk the cold taking another one! 

 

Morning   Giddy

 

We need to dig into this a little more. 

 

I have a 1200C wire diagram that sort of matches that cover map but it shows fuse #1 as the brake lights,  dash lights, etc with fuse #4 being the fuel pump. 

 

Is it possible that your cover is on backwards or the fuse holder is installed reverse? 

 

4 amp fuse for the fuel pump doesn't sound logical!

 

I am going to look in my older archive wire diagrams when I get a chance (nowhere near my shop right now) but when it comes to those darn 1200C bikes that is a real crap shoot. 

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Morning   Giddy

 

Another thing to consider is that fuse map on your cover might not be for your motorcycle. Some of those decals were a later addition so possibly someone put the wrong decal on your cover.

 

If you get a chance you might try to figure out what each fuse effects, we don't need everything that each fuse effects but at least "something" that each fuse effects so we can try to match your fuse location up to an existing wiring diagram.  

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I'll pull one by one and see what happens. I know the dash lights never went out when the bike died. The oil light and speedometer light were still on when I rolled to a stop.

 

I'll crank the bike and pull fuses untill the pump stops. Then I'll know at least which one is which. 

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The Rocketman

He was reading the cover map upside down. We've seen the factory install fuse boxes upside down from new and found mistakes in owner's manuals & labeling. Mine is shown below:

 

1.jpeg

2.jpeg

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Yup. I'm use to cars where fuse boxes have a diagram or numbering. I figured you were meant to hold the cap right side up and install accordingly. However, my fuel pump failed at the same time any way so it was a good time to find that mistake! 

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