Hi,

I've been an occasional lurker on this site for a few years but now need help with hard starting on my 87 K100RS. I've had the bike for about 15 years now and it presently has a Flexit sidecar attached. I am retired and split my time, mostly in Maine and here in North carolina where I'm trying to get my 87 K100RS running agin. It has been laid up for almost a year. I had a real hard time getting it going last week and also a year ago when I last rode. Last week I was able to get it going and went out for about a 40 mile ride during which it ran well. Since that ride I can't get it starting well at all. I suspected a fueling issue and started there.

After the recent hard starts, I started to dig in and see what was causing my trouble and have done the following during the last several days:

- battery is charged up but I'm beating it up pretty bad with the attempts to start. I have it on a charger that will act as a 50amp jumper which I've resorted too during my start trys.

- Drained tank and put in a some fresh no ethanol 90 octane that I can get here.

- Checked that fuel pump is working. Get lots of return line agitation for the pressure relief when I look in the tank with a light

- My fuel filter was changed a few K ago but I pulled it and verified that it wasn't clogged. I can blow through it easy

- Put a timing light on each ignition wire lead and all are functioning.

- Plugs were all the same and wet. I put in a new set of D7EA plugs, gapped to .024"

- I had never pulled my injectors, only running cleaner and suspected them. I got a refurbished set for mrinjector last weekend and put them in

Tried starting again and was only able to get it going after multiple attempts by holding the starter button in and NO fast idle aka "choke" on it. Pulled the headlight socket and parking lamp fuse to decrease load. Since it won't run if I "choke it", RPM is real low and alternator is trying to charge the battery (still on charger BTW).



- Checked for vacuum leaks around the plenum boots, air plugs,etc. with a small unlit propane canister. No increased idle speed so assume no leaks. Z tube replaced a year ago and good shape. Wish they were cheaper!



- Pulled the fuel tank again and checked for broken wire and plug insertion. I did have mouse nest on top of the motor under the air box but no where else so ...


- Pulled the air filter to make sure there was no mouse leavings. It was fine and I reverse blew out the filter. Its in great shape. Air supply to filter is unimpeded.



- Pulled the fuel injection plug and re-inserted


Did a bunch of searching on the net and especially here since I got so many hits. Next pulled out "Crazy Frog's" great diagnostic chart and started plowing through it.



- fuses all good and wiring and plugs intact


- Kill switch/starter button good and in good shape. I last re-furbed it about two years ago. I pulled it and checked the back and it is clean and has my dielectric grease on it.


- checked and temporarily pulled the plug off the idle switch with no change



- pulled the cover over my Hall effect sensors and verified wiring and visual condition good with no slippage of my timing. I put new Hall units in about 20K miles ago.


- Last Saturday during the last run in my garage of any length, the radiator and light kicked on. I also checked the resistance of the temperature switch through pin 10 of the FI unit and it is correct for temp during test.


- went through the "electronic ignition module test" where able. didn't check the "engine running" ones for obvious reasons. Pin out on the diagram is for the male spades on the unit and not the female plug sockets for info. I sent a note to Crazy Frog about this.


- I also tested the FI unit female pins and found no problems

- For the airflow meter pin checks I got:
   Pin 7-5  66.7 ohm
   Pin 7-8  324 ohm
   Pin 8-5  365 ohm
   Pin 8-9  202 ohm

- checked and verified resistance on primary and secondary circuits of my coils

- verified with my stethoscope that all the re-furbed injectors were clicking when last run Saturday

So I'm stuck now. The only way that I can get it to start and that is real rare now, is if I hold the start button in to richen the fuel mix. I can't get it to start with or without holding the starter on with the choke engaged. Gaps for the choke are correct and checked this after. Bike will maybe run two minutes and then stall out. Any attempt at throttle mostly fails.

Hoping that I missed something and looking for help here please. thinking my battery is not dong its job anymore too.

Glenn

If the bike is turning over strongly then for time being battery is doing its job and not the issue.

If you keep our finger on the start button does the engine keep firing as in has fuel and ignition? If so then these circuits are working, its sparking and fuelling.

If it cuts out as soon as you then release the starter button that is a clue for more.

A few simple checks are
The electrical plug connector into the fuel tank being loose/poor electrical contact.
The underseat Fuel Injection Control Unit [FICU] has a big plug connector into it. If disturbed or not correctly seated can do what you are experiencing. The same goes for the Ignition Control Unit [ICU under the front of the gas tank.


The ones below are the more obvious ones but you have done these:
Crankcase vent to the rear of no 4 goes into the airbox. Check this is not perished or holed.
Also the little rubber caps on the vacuum take off points, check they are good.
Also the vacuum pipe that goes from No 4 to the Fuel Pressure Regulator [FPR]

Hi,

"If you keep our finger on the start button does the engine keep firing as in has fuel and ignition? If so then these circuits are working, its sparking and fuelling."

Yes keeps firing until flooded. After release, RPMs are too low, around 6 o7 K maybe. Attempts to increase with choke kill motor most times.

"If it cuts out as soon as you then release the starter button that is a clue for more."

Not if it gets ignition but can't get RPMs up without stalling out.

"A few simple checks are
The electrical plug connector into the fuel tank being loose/poor electrical contact.
The underseat Fuel Injection Control Unit [FICU] has a big plug connector into it. If disturbed or not correctly seated can do what you are experiencing. The same goes for the Ignition Control Unit front of the gas tank."

[color=#ff0000]Yes, all checked and verified. FI and tank plug more than once.


"The ones below are the more obvious ones but you have done these:
Crankcase vent to the rear of no 4 goes into the airbox. Check this is not perished or holed."

Its almost new and real good

"Also the little rubber caps on the vacuum take off points, check they are good."

Caps good

"Also the vacuum pipe that goes from No 4 to the Fuel Pressure Regulator [FPR]"

Yeah, when I pull if off there is a definite vacuum leak so by deduction, hose is good. checked this yesterday.


Thanks,
Glenn

FPR can go faulty. What happens when you take off the vacuum pipe and plug the end of it with your finger so the engine doesn't take excess air? Do the revs change?

For some reason or other I am also thinking of the MAF airflow meter inside the airbox.

Either of the above can cause overfuelling. Big time.

I'd be inclined to do a injector check a squirt test with a pressure can of carby cleaner and a 9volt batt to actuate them. Apart from that I cant immediately think of a reason for such low idle or non start profile of symptoms. What about the smell in the exhaust? Or a plug chop to see if any are wet with perhaps a leaky injector the issue as apposed to a clogged unit or sooted with algae or what ever we call that much that gets in there from time to time. Time spent sitting idle sure is a sneaky thing when it starts annoying us with issues like this.

Check the earth points under the tank and on the gearbox as well as the neg on the battery. If it still wont run check and clean the contact of the pins on the ICU and finally the ICU itself.
Holding the start button down will supply fuel at start up to make it start easier and that is the only fuel you are getting.
Also check the fuel pressure.

Yes, checked both this afternoon. Clean tight and have a smear of dielectric grease over the connections. I also checked all sockets under tank and looked for frayed wire insulation. Nothing out of order there.

I forgot to mention that I did check the contacts on the ICU today and the FI unit. Several years ago a pulled every connection on the bike cleaned them and applied RailZip to the contacts. I applied it to the male spade ends pushed the connection in pulled it out, applied another coating, let dry and pushed back in. It has kept the contacts in good shape but maybe time to try again.

This bike lives inside BTW and other than a wash now and then and a rain shower, it doesn't  see bad weather. I don't live near the salt water either.

Can you smell gasoline in the exhaust?  You say the plugs are wet when you pull them.  That sounds like you may have flooded the engine.  If so, you may need to unplug the tank, crank the engine with throttle wide open for about 10 seconds to blow the fuel out, reconnect and try to start again.  

When I flooded my K100, that was the only way I could get it to start and run.  Once it flooded, the injectors kept putting more fuel in than cranking could blow out.  Pulling the tank plug was the only way to clear the cylinders of excess fuel.

Are the plugs getting sooty looking?  Not running at anything above a dead idle could also be a sign of fuel starvation.  While unlikely, it is possible for the filters at the inlet of each injector to get plugged, possibly with a shot of water or rust from the inside of the rail. 

Disconnect the fuel line from the pump at the rail, and crank the engine to get the pump to run.   Put the line in a container that won't let fuel splash all over the place.  You should get about 1 ounce of fuel for every 4.5 seconds the pump runs(approx. 33l/hour is the spec for pump flow).  Fill the container up and see if you are pumping any water with the fuel, water will settle out after a minute or so and make a layer at the bottom of the container. 

You can also do this test with the return line to the tank going into the container.  That will show the flow through the fuel pressure regulator and rail as well.

Did you say its not exceeding 711rpm? So that would not allow the brains to go into run mode and keep the pump running?? If I read it right perhaps it is the connector to the FIU, one of the pins isn't getting signal from the Hall sensor maybe??

Just in case... and I assume it is irrelevant given that it's your bike and sounds like you take care of it and know what you're doing...

Is the oil level correct?

I bought a second (fourth?) hand bike... wouldn't idle... had 6 litres of oil in it (not the 3.75). Even if you haven't overloaded the oil (obviously use the sight glass), is fuel not getting into the oil and raising the level.

I take solace in the fact the "all mechanical problems are finite"
You will get it 

Regards

GF

I think the door on the airflow meter is stuck (closed).

caveman wrote:I think the door on the airflow meter is stuck (closed).

That would do it.

Point Seven Five was saying "Not running at anything above a dead idle could also be a sign of fuel starvation." I have found that any of the K bikes will start and idle without the tank even being on the bike providing the engine is at operating temperature. Any engine will use a very small amount of fuel to idle and these apparently get enough just by the injector opening and the manifold vacuum drawing some through but as soon as you even think about touching the throttle it stalls but will start again while there is fuel available.  It could be that the pump only runs when the start button is pressed.
The earth to let the FI relay operate is extended from the ICU when the button is pressed or the Hall sensors are sending a signal to the ICU. I still reckon that the problem is there somewhere and from what you say the connectors and wiring is unlikely to be at fault. Have you tried swapping the ICU?

Good morning!

Yes I'm having trouble getting an type of revs out of it presently. I think it is getting too much gas or flooded. I've been clearing the cylinders by pulling the FI fuse, #6, second from bottom; cranking it for ten seconds or so and trying to wait a bit before a new start.

Note that on Saturday i was able to get it running and working properly with good throttle response. I let it cool down and then tried starting again after a few hours and intermittent starting but real sensitive to any type of throttle input including the choke.

Oil level is right in the middle of the glass.

Don't forget that i have clean tank, clean filter clean fuel lines and rail and re-built injectors installed Saturday from Mr Injector.

Lots of fuel returning to the tank vigorously when I crank and look through open filler cap.

Maybe the air flap is stuck but why would it have run Saturday and real good after hard starting and before all the fuel system changes last week? I ran it about 45 miles and probably 30 of it on the interstate to clean it out. Performed fine with no hesitation or hiccups.

Other than a couple of start instances in the past, this has always started well for fifteen years and about 50K miles. Yeah I should have more miles but I have four bikes ;-)

This is driving me nuts ....

Oh forgot to mention, I have no spare ICU or FI units to try and no contacts to try one.

have we tested the temperature sensor yet ?

could have it become loose on the connections

first test ...measure the socket on the under seat connector to the fuel injector computer
pins 10 and 13 ...the pin out is in the troubleshooting guide  also the relative reading it should be for the temperature

if the resistance is very high or non existent you might have a look at the behind the radiator  water stub connection  for the temperature sensor connector   these have been known to go faulty - dirty  causing flooding on start = poor running

just my 2 cents  ...as there are  quite a few possibilities  for errors ...

ps don't overlook the tps switch being corroded and short circuit inside

good luck

Hi Charlie,

Yes, I checked the resistance of the temp senser the other day and it agreed with the value at the ambient temperature at the time.

I think I'm on to something!

I was able to start the bike and keep it going  as long as I held the starter button in. I ran it for a few minutes at 3K RPM. I noted this starter button enrichment earlier in this thread.

This time though as I was holding the starter button and throttle cracked open, I gently pulled on the cable harness from the air control unit and the rpm went up. I think I may have messed either the plug insertion or the wiring when I checked the air filter last week. I always have an awful time getting the element out. So pulling the air box apart next and checking the sensor.

Glenn

Okay I got the air flow meter out. Wiring plug was seated fine. No broken wires and I already checked resistance at the female FI plug and no sign of an issue. The vane operates smoothly. What should I do now? I'm reluctant to crack the sealed cover to it.

- For the airflow meter pin checks I got:
   Pin 7-5  66.7 ohm
   Pin 7-8  324 ohm
   Pin 8-5  365 ohm
   Pin 8-9  202 ohm

Thanks,
Glenn

What if I just applied a hair dryer to the inlet to see if vane opens? I don't have a termometer with a remote probe to use.

glennpm wrote:. . . I always have an awful time getting the element out. . . .

It doesn't go like this for you?   I think you're on the right track checking for a connection affected during maintenance.

Resistance checks at air meter spades:

- For the airflow meter pin checks I got:
   Pin 7-5  61.6 ohm
   Pin 7-8  325 ohm
   Pin 8-5  367 ohm
   Pin 8-9  206 ohm

Voltage variation with vane movement:

applied 13.15 V between 5 (grd) and spade #8

Closed (cracked open slightly when closed) = 1.9V
Wide open = 12.89V

smooth variation through range

Temperature check with hair dryer, heat gun and meat thermometer ;-))

17 °C  = 206 Ω
30 °C  = 193 Ω
40 °C  = 190 Ω
50 °C  = 182 Ω
60-70 °C  = ~167 Ω

very rough measuring technique but it does drop with temperature increase.

Conclusion:

Looks like air meter is not the problem but what is????

Yeah takes me another minute or two to pull my filter! Looks way easier on a K75 ;-))

I probably should remove the lower fairing in addition to the tank but more stuff to put back together ...

glennpm,

So 4 out of 5 isn't bad but I know what you mean about the one that isn't running. I don't have a spare ignition box (Do you have spark?) but if you PM me your address I can send you my spare 2V FI box to see if that is the problem. Seems you have checked most everything other than the FI box.

Hi Caveman,

Yes, getting spark since I can get it to run on occasion, It will only run decently if I keep the starter button pushed in.

Sent you a PM about the FI loan too,

Thanks

PS I also bought a used ECU off of ebay yesterday and hope to try that in a few days. I'm pretty sure I've got an electrical issue and not fuel but what and where??

Hi,

Just did some checking at the fuel pump relay under the tank. I'm looking into the grounding of the #85 pin on the relay. Bert's "EFI/Electronic ignition K100 2v troubleshooting" guide says this:

"Electronic ignition module pin #7 sends ground to the coil of the FI relay as soon as the starter switch is depressed. The ground will stay on after the starter switch is released as long as the Electronic"

I have the tank off and the plug to the tank is loose. Everything else is connected and I measured these resistances:

- With ignition off at spade #85 = ~80Ω
- Ignition on = open circuit or "1"
- Ignition on, starter button pushed = 107 - 130Ω

The resistance pushing the starter button is momentary and intermittent.

Is this telling?

Hi,

Posted this on othe other thread too, https://www.k100-forum.com/t4309-k100-starts-and-dies#159206 but replying here as well for the sucessful conclusion.

Got her fixed!!

I got the used ignition ECU and the Jetronic FIU yesterday. The FIU came early than expected which worked out well. I cleaned all the contacts and then applied RailZip and let them dry overnight and slept like hell BTW ;-( thinking about "stuff".

So after all the testing, refurbished FI units, contact cleaning, etc., etc., it turned out to be a bad Jetronic unit. I'm wondering what made it quit? I put the ignition ECU in first and it was more of the same wouldn't run unless I kept the starter button in. Well then I put in the used Jetronic unit in all was well! Now its behaving like it always had and starts right up. I adjusted the throttle screws with my Motion Pro mercury carb synchronizer.

Thanks for everyone's input. This is a great site. Now I'm looking into installing a K1100 throttle body assembly!

Glenn

Well still not starting that great. I have to hold the starter button in longer than I normally would, several seconds but then it runs well. Not sure what the cause of this is but minor compared to the issue I had.

Glenn

I don't recall that you changed the fuel pump.  A weak pump might be slow building pressure to get adequate flow through the injectors.

If you shut down as soon as the engine startes and immediately try to restart, does it fire right up on the residual pressur in the rail?  What happens if you wait 15 seconds before trying to restart?

glennpm wrote:Well still not stating that great. I have to hold the starter button in longer than I normally would, several seconds but then it runs well.

It might be battery fatigue. Check the resting voltage before you start it. ≥12.5 should snap the engine into action—all other systems being in good condition and the ambient air temperature relatively mild.

Well its still toast ;-(

I'm going to replace the fuel pump even though it seems to work. I can't do the test that Point-Seven-five suggested, a good one thanks. Maybe later if I can get it going again.


Yes my battery is dying. I have a Harbor Freight charger that will jump it and have had to resort to that.

This is getting old ......

Glenn

I just got it started again but only by holding the starter button in for many seconds until it would start idling. Choke will kill it. Holding starter button and a little consistent twist on the throttle clears its throat and will get it running.

I did try the restart after a minute or two three times and it started right up so pressure seems to be adequate for fuel.

Glenn

I think and hope I've found the problem at last. I bought a fuel pressure gauge Monday and found that I had only 10psi/.7bar. I thought I had good pressure but not the case.

I bought one of the Ford FEP2042 fuel pumps, a new and hopefully improved rubber mount and isolator from Euro MotorElectrics and installed it last night. It was tough mounting the new pump. It tested at about 35psi. I let it stand overnight and hooked it up to the fuel rail this morning. It seems to be back to normal! Now waiting on a new battery. My old one is toast.

Glenn

This is all sounding familiar to me, but on an Oilhead. My 2004 R1150RT had gradually, over the course of a few years, begun to exhibit signs of slow to fire up, then lower than usual idle, and unwillingness to rev cleanly to redline, tho' she cruised steady state alright. Even when whacking the 'cold start lever' fully open when cold it would barely reach 1200 rpm, when prior it'd rev to 2500 instantly. I somehow managed good fuel mileage and could pass a coupla slow-moving cars ahead, even rode it to Alaska June of '16 with a passenger and a load of gear. I hadn't much use for it the past year or so with too many other motorbike distractions. 

So when I had the time I began to look at spark control, ignition, valves, compression, leak down, and went down a load of dead end paths and other mis-directions. I had a new R12 FPR buried somewhere in my spare parts boxes which fits and is is 4bar rather than the 3.5 bar of the original. Nada.

But what lies down there inside the tank all quiet and mostly efficient doing its job unloved? The bloody fuel pump. Yep, a years-long slow burn down to barely able to run. Mainly, my experience with failed fuel pumps had been side of the road flat dead, tongue out the side of the mouth, or intermittent coughs and spurts as a fair indicator of impending doom. Success.

Now, that Rhine West-chipped Motronic unit I grabbed off eBay early last year for a very short pile of filthy lucre will be the next thing to chuck at it now she's spinning freely once again. It should go nicely with the fat Remus headers, twice-as-big carbon fibre intake and Booster Plug.

Back to the K bikes, gents. Thanks for your time.

Yeah this kind of creeped up on me. The interesting thing was that although the rubber damper was deteriorated, it wasn't the black goo that others have found. There was just a wee bit of debris in the pump well of the tank after I pulled the pump and a little bit of hair and stuff on the bottom of the pump screen but not much at all. It just wore out ....

Bike is starting and still running great after fuel pump change!

Sounds like you got it!!!