I need help solving a rough running K100RT!

My K100RT was starting to run rough on what I thought was some bad fuel that I used from a storage tank.  I put some fuel stabilizer into the tank and it seemed to be a little better.  The next time I filled up, I put in some SeaFoam motor treatment into the tank but was distracted and overfilled the tank (to the very top).  Nothing spilled out but the cap just barely closed.  When I left the gas station, it was a little sluggish but within 5 miles it started to drag and when I came to a stop it would not idle with out back firing and then dying.  It will stay running above 1500 rpm but it feels like one of the cylinders is not firing

Since the overfill, I drained and cleaned the fuel tank, replaced the fuel filter, the inside fuel hoses, the spark plugs, and the spark plug wires.  I have also checked the compression, the coils, and the vacuum lines.  I am assuming the battery is good because it has no problem starting the bike if I give it enough throttle.

Does anyone have any other ideas on what I should check?  Is there something I could have damaged by overfilling?

Veets

Will the engine start without excess throttle and idle smoothly if the fuel cap is opened and remains open during starting, veets?

Not sure that I would be putting "fuel stabiliser", whatever that might be, or Seafoam, another unknown over here, into a bike that has a bullet proof engine and runs on rubbish petrol in far flung corners of the world.
Probably just change the fuel filter and put neat petrol into it and see what happens. Some of these additives might contain stuff like acetone which may eat the fuel filter material. 
Best thing is to use what BMW say to use, just petrol.

Laitch, it runs the same whether fuel cap on or not.

I reckon drain out all the petrol and clean out the tank of any crap to the point where it is nicely dry inside, fit a new fuel filter and only put back known good petrol and see how you do. As BobT says!!

If it's not then running right come back here, but no real point in going at anything until you know for certain the fuel supply is clean and good. Your trouble started with putting fuel in so best to get that ruled out first.

Filling tank to the top should not really be an issue as the tank and filler cap design means there is still quite an air volume above the fuel for expansion etc. I have always filled the tank to the top and never an issue, I just don't do it and then immediately park in bright sun and 40c heat.

Hello Olaf,

Since I experienced the problem, I have already:

• drained and cleaned out the fuel tank
  
• replaced the fuel filter and internal fuel line
  
• replaced the air filter
  
• replaced the spark plugs
  
• replaced the spark plug wires
  
• checked the battery
  
• checked the compression
  
• checked vacuum lines
  
• checked the oil for water
  

Any other ideas?

And forgot:

• Checked the coils
  

There is a vent line/overflow chamber at the top of the tank, so if you did happen to fill it too full, it would just run out onto the ground.  If the vent line were plugged by a dirt dobber nest then it could stall, but the open gas cap test kinda indicated that wasn't the problem.

When you drained the tank, how much water did you find in the fuel?

Anymore if there are fuel issues with water, ethanol, sea oil or snake foam involved,  i would have to recommend an end-to-end check of the system--start with a completely dry and empty tank, on to the pump and filter, all the fuel and vacuum lines, and down to the rail and the injectors. 

Once the fuel system is verified clean and functional, then it becomes an issue with electrical, air supply or compression.

edit:
rust in the fuel rail, clogged injectors

Check the plug connector to the Fuel Injection Control Unit under the seat, make sure its fully seated as in open and reconnect it. I have seen a bad connection here do something similar.

Also, when you run with the tank open, you should actually see/hear the return fuel coming into the tank and be able to work out if that stops BEFORE the engine cuts out.

Kennybob,

Thanks for the reply.  When I drained the tank, there was not any water.  I also removed the fuel rail and injectors and verified that they were clean and working correctly.  I checked all of the fuel lines and replaced one of the hoses that went from the throttle body to the fuel regulator.  Other than that, the vacuum lines were in good shape.  I replaced air filter and no blockages in the air intake.

Veets

Olaf,

Thanks for the help.

I opened and reconnected the connector on the fuel injection control unit but no change.  I also did observe the fuel continued to return to the tank until it completely died.

Steve

veets wrote:It will stay running above 1500 rpm but it feels like one of the cylinders is not firing.

There was an engine malfunction on MOTOBRICK.COM recently with symptoms similar to your bike's problem. The owner was asked to double check the plug to coil connections, even though he had asserted they were correct. When he did, he discovered incorrect connections. Once they were corrected the engine ran smoothly. In the spirit of that successful outcome and with the utmost confidence that an ancestral curse is not underpinning all this, I offer this post containing a diagram.

Just out of interest, how much of the seafoam did you put in your tank?

Laitch, thanks for that thread.  His symptoms are almost sound identical.  I smell gas in the exhaust as well.  I will double check the coil to plug connections tomorrow.  I read the thread from Motorbrick but did not see where it ended up being the coil to plug connection that solved it.

Holister, I put about 2 ounces of SeaFoam in a full tank.

@veets, it sounds like you have covered the bases on air, fuel and compression, with minimal impact due to snake foam or sea oil

so i'm betting on this being an electrical issue, with my favorite being a bad jetronic unit, specifically a cracked solder joint on the transistor that fires the injectors.  Quick to check if another unit is available in your area.

But for further troubleshooting, did you ever make a spark plug check--are the plugs wet and sooty, or dry and ashy?  Wet plugs and the jetronic is getting a bad input signal, likely air or water temperature.  If dry plugs then jetronic is not firing.

Given you're smelling fuel in the exhaust I would guess one or more of your injectors are not closing properly or stuck open. probably due to the dislodged debris from the Seafoam clean out. That would give you all the symptoms you mention including the backfiring/popping as well.

I know you said you took the injectors out and checked them but I think it would be worthwhile to take them out and reverse flush them with carby cleaner. Leave the old O-rings on but remove the mini filter in the top first. Plenty of Youtube vids to tell you how to do that. All you need is a 10ml syringe, a 9V battery wired with some alligator clips and a spray can of carby cleaner or similar.
You can buy new kit cheaply on ebay

Two ounces of Seafoam in five gallons of gas won't do anything, good or bad.

veets wrote:I read the thread from Motorbrick but did not see where it ended up being the coil to plug connection that solved it.

That's because I posted that thread only for its diagram. This symptom surfaces regularly and the causes vary. At the rate you're going though, you'll probably run down the cause sooner than later.

Laitch - I have the right coil to plug connections

kennybob - I pulled the plugs out again and they appeared to be wet and sooty to various degrees.  Number 1 is on the right and quite sooty and wet, Number 4 is next and looks quite clean, Number 3 is 2nd from the left and is quite sooty and wet, Number 2 is the far left is wet but not very sooty.  The threads are quite wet/oily.  Any idea what this might indicate?

Holister - I took out the fuel injectors and cleaned and back flushed them with carb cleaner, re-inserted them, and no difference in performance. 

veets wrote:My K100RT was starting to run rough on what I thought was some bad fuel that I used from a storage tank.

For how long and how many miles had it been running "rough", Steve, before you entered the distraction zone and overfilled it?

Laitch - It had been intermittent before my distraction.  It had been coming and going for about two weeks.  But it was not as bad.  It did not stall or back fire.

Distance - A couple hundred miles.

Thanks, Steve. 

I just read your posts describing your bike's history and that confirms it's had engine operating glitches since you've had it—white smoke, wet plugs. This thread might be relevant. Although your bike starts, it hasn't had an overriding tendency to run well so the description of operating elements and tests described in this document might also be helpful if you haven't read it, yet.

veets wrote:Laitch - I have the right coil to plug connections

kennybob - I pulled the plugs out again and they appeared to be wet and sooty to various degrees.  Number 1 is on the right and quite sooty and wet, Number 4 is next and looks quite clean, Number 3 is 2nd from the left and is quite sooty and wet, Number 2 is the far left is wet but not very sooty.  The threads are quite wet/oily.  Any idea what this might indicate?

 I've had to look at your profile to find what bike you have, is it an 85 K100, if so then methinks you are using the wrong spark plug. This pic shows a D8EA which I believe is used on the 16 valve you should be using a D7EA.

D7EA is correct for the K100 8 valve but over here I have been running all the time on D8EA as fitted by local BMW guys. These are not resistor plugs. Never had any issues with them. I can't ever seem to find D7EA and would fit them if I did.

I have an idea the 16 valve uses resistor plugs which would be DR7EA or something like that.
The photos of the plugs don't show if the bobbins are fitted........and they should be.

The spark plugs all look wet to me--looking at the insulator behind the tip.

Those two heat ranges for plugs wouldn't cause your issue.

i would guess that either the water or air temperature sensors or air flow meter are not within spec and the jetronic is running rich based upon those inputs.  Go thru the troubleshooting guide and follow the flowchart, you have done most of it already it seems.  You will find the culprit or it will point towards replacing the jetronic unit, which are cheap on ebay.

92KK 84WW Olaf wrote:D7EA is correct for the K100 8 valve but over here I have been running all the time on D8EA as fitted by local BMW guys. 

The NGK site lists D7EA for the RS, D8EA for the RT. Steve's got an RT. Regardless, it'd be nice if Steve could get away that easy but, like Kennybob implies, he's headed for some more Klassik K rituals.
He's got the right plugs, it looks like.

That's an interesting difference between RT and LT plugs. Never spotted it.

The FICU unit if you do a search of eBay using the Bosch part no you will find brand new in a box quite reasonable. Used in some mass produced cars such as Volvo 340.

I checked the water sensor resistance.  At 12 C it read 2.9k ohms which is consistent on the graph.  I started the bike up and waited 10 minutes and could tell the water was getting warmer by touching the hose, and the resistance was 560 ohms which from the chart relates to about 65 C.  This seems reasonable.

I checked the air temp sensor with the bike off and it is reading about 198 ohms at 23 C (where the filter is located).  I used an infrared laser thermometer.

What is a good way of getting a second reading without pulling out the air flow meter?  Can I start the bike and use a hair dryer to heat up the intake air?

Those readings indicate the sensors are reading okay and within spec, so it's looking to me like the jetronic unit is at fault, and i would get another one to try.

Did you measure the resistance of each injector, should be ~16 Ohms.

This was an interesting statement from the troubleshooting guide:
If your injector is leaking internally or failing to close fully the bike might run OK depending on just how bad the problem is. The way to check for this problem is simple. When you change spark plugs inspect them. If one or two are a lot blacker then the others you probably have a leaking injector on those cylinders. If the leak is bad or the injector never closes, the bike will run poorly at low RPM but improve at high RPM when the engine is sucking in enough air to burn the fuel.


From the pictures you did have 2 that were blacker than the others.


So another test might be to pull the rail with the injectors and crank it over while aiming the injectors into a bucket or pan--then observe the spray and/or capture the fuel from each to determine if the amounts are equal.


These sort of intermittent issues are the worst to solve, been there done that...endeavor to persevere.

I did measure the resistance of each of the units and they all were right at 16 ohms.  I also got a second set of re-conditioned fuel injectors from "Mr. Injector" and put them in today with no improvement or no noticeable difference.  I am fairly convinced it is not the fuel injectors.  I will run the bike and see if the spark plugs look the same as before or if things have changed.

I have not tied pulling them out while still connected to the fuel rail to see how the bike controls them.

I think I may get a backup FICU to test.  The number on my jetronics unit is a Bosch 0 280 000 313 

I have found a couple used units on e-bay but nothing compatible with a Volvo.  Am I missing something?

veets wrote:. . . Since I experienced the problem, I have already:

• checked vacuum lines
  

     . . .

Did this include detaching the vacuum line from the fuel pressure regulator then checking the line and pressure regulator's vacuum port for traces of fuel?

Laitch wrote:

92KK 84WW Olaf wrote:D7EA is correct for the K100 8 valve but over here I have been running all the time on D8EA as fitted by local BMW guys. 

The NGK site lists D7EA for the RS, D8EA for the RT. Steve's got an RT. Regardless, it'd be nice if Steve could get away that easy but, like Kennybob implies, he's headed for some more Klassik K rituals.
He's got the right plugs, it looks like.

I'd be guided more by the K100 service manual, Riders Manual and BMW oem parts list which specifies Bosch X5DC (NKG D7EA equiv) for all K100 8V.
D8EA are ok but it will come down to what's best for your own machine and to a point, the conditions you're riding in.

I agree 100% with the listing of the D7EA, wasn't aware there was actually a D8EA listing for the LT.

But the local BMW guys have all fitted D8EA and no one seems to stock the D7EA.

Last time when I got a service kit it came with the correct Bosch plugs which were in it when we went to France but they didn't seem to make any difference.

We are not a hot climate, we would rarely exceed 25c in local conditions and even when we do we don't have a big enough country to do 400 miles straight run at that temperature. 6 1/2 hours ride time can get you from North Antrim Coast right down to Mizen Head on the south west.

As an aside when I was in France at one time put this E85 petrol in the K and it most certainly did not like it. It was the only one available and as soon as it reached the cylinders it started to run like crap. The regular stuff these that's seems to have 10% ethanol and they don't tell you or label it accordingly but the E85 is much higher ethanol content.

In France regular has no more than 5% ethanol, E85 is 15% ethanol and 85% petrol hence the name.
One index number on the heat range of a spark plug will make bugger all difference to an engine unless it is a highly tunes race engine.

Unless you are using it in an extremly hot climate or running it very fast over extended periods then I would not recommend using D8EA. All that will happen is the plugs will carbon up quicker and therefore not last as long.
I have not seen anywhere that a D8EA is recommended for either the K75, K100 or K1100. If as you state it is in one of the catalouges then I would say there is a mistake.

Full agreement with Rick. IME fitting D8EAs to K100s makes them run like sh!te in very short order.

For some reason D7EAs aren't readily available here.... I always have to order them in.
My K-naked was running a bit hot so I used D8EAs. Seemed to do the trick. She's off the road now for a refurb.

Veet. Try disconnecting your TPS and/or test it to make sure the 'Throttle Off' and WOT switches are working. They input to the Jetronic which will then adjust mixture. It could be one of those switches has a closed circuit short creating a richer than normal mix.

veets wrote:I did measure the resistance of each of the units and they all were right at 16 ohms.  I also got a second set of re-conditioned fuel injectors from "Mr. Injector" and put them in today with no improvement or no noticeable difference.  I am fairly convinced it is not the fuel injectors.  I will run the bike and see if the spark plugs look the same as before or if things have changed.

I have not tied pulling them out while still connected to the fuel rail to see how the bike controls them.

I think I may get a backup FICU to test.  The number on my jetronics unit is a Bosch 0 280 000 313 

I have found a couple used units on e-bay but nothing compatible with a Volvo.  Am I missing something?

I don't think you are missing something.

My RT and LT are both 8 valve engines and I swapped the FICU from one to the other without any problem. BUT they did have different Bosch part nos on them and I only checked one of them out sods law being it was the one on the 84RT. I will have a look and see for you. I don't think you got the particular Volvo engine in the US so its unlikely to show up on your own eBay.

The Bosch 0 280 000 313 was used in '84 and '85 models and possibly later (my '89RT police bike has a 313 but I can't say it's original). The first L-Jet unit before that (0 280 000 360 I think) was only used for a year or so. There was another unit introduced in '86 which ran till the end of the 8V epoch but I don't know what the Bosch # is but its oem#13611461828. This one is not backwards compatible with earlier models. That maybe the one I have in my '88RT which is very standard and pure as the driven snow. I'll check it in the morning and post back.

L-Jets were made for cars like Alfas and even Landrovers but I don't think these would be suitable for a K100 as they utilised different sensors and were mapped differently. There was a member here earlier this year who bought a second hand L-Jet from a parts dealer who assured him it was the right one but his K ran like crap. Turned out it was for a different vehicle.

I had a quick look around ebay and found a few 313 L-Jets for sale for greatly varying $$. Maybe you can find someone you can do a swap test with first.

I wonder did different Bosch nos get used around the world?

My K100LT at no 0193214 is one of the last made in 91 but the unit went straight into the 84 RT at is no 0022575. Just posting the numbers to see if anyone finds anything. I was surprised as I had damaged the retaining clip on the one in the RT and just tried the swap to see if would save me being off road if I was stuck with buying a replacement. 0 280 000 313 is on the one I took out of the 84 RT.

ive just checked my 8v ECU's and both the 1987 naked and the 1988 rt both have 313 ECU;S as does the 1989 lt parts i bought recently so they seem to be the mainstay ECU for the 8 valve K thats my 2 bobs worth

There are at least two different types of AMP connector used on the ECU (and maybe three - I'm not sure about that). That may account for the different part numbers on the ECU.

I know I asked the question....bobbins on the NGK spark plugs? Didn't see them in the photos.

 I must mention one time a misfire crept in I struggled to find it. Bobbins off and then retightened and cleaned up helped, some were loose. One plug cap was not engaging properly.

I must go look a the other FICU in the RT but at the moment the RT is wrapped under a cover and its raining. Bah Humbug.

Holister, you wrote:  



Is there a good procedure explaining how to check the throttle position sensor (TPS) and wide open throttle (WOT) switch on a 85 K100?  

Also, before I do anything else, I think I should also check all of the electrical connectors.  Starting with the MAF.  Is there a good diagram with all of the main electrical connections?  I have a bottle of DeoxIT and need to rule out the connections and grounds.

Olaf, yes there are bobbins attached and they are clean, tight, and in good working condition.

veets wrote:Also, before I do anything else, I think I should also check all of the electrical connectors.  Starting with the MAF.  Is there a good diagram with all of the main electrical connections?  I have a bottle of DeoxIT and need to rule out the connections and grounds.

Check the condition of the crankcase breather hose while you're at it. A failing hose will cause rough running.

Hello Laitch, good suggestion.  I did replace the crankcase breather hose this past weekend along with the vacuum line for the fuel pressure regulator because they both had some cracks in them.  Unfortunately, it did not make any difference on the performance but they are back to good operating condition.

veets wrote:Hello Laitch, good suggestion.  I did replace the crankcase breather hose this past weekend along with the vacuum line for the fuel pressure regulator because they both had some cracks in them.  Unfortunately, it did not make any difference on the performance but they are back to good operating condition.

I'm going with the ancestral curse theory then.