1985 k100Rs will not start

[aldan0392]

Hey guys, I have some issues going on with my bike, I rode it home the other day, went inside my apartments and when I came back bike just refused to start, my bike is 1985 K100rs, Cafe Racer. So far I checked hall effect sensor, it is working, my fuel pump is working, and it shows 36psi, funny thing is, the bike will start sometime and run for like 30 seconds or a minute, but than it just stalls, if you try to crank it up long enough  it will start but than die again. I went and bought another coolant temp sensor, funny thing is if I disconnect the sensor and I get to start the bike, which does not happens very often, and I plug it to the sensor that is still COLD it will race the rpm, but if I plug the one that is currently on the bike and had warmed up already the bike will shut down. Normally, I can start the bike when it is still COLD, lets say in the morning, first try it normally starts, but after it warmed up it gets harder to start it again.
My suggestions are it is not compression in the cylinder (because it starts and runs)
It is not Fuel Pump (again, because it runs sometimes)
It is not hall effect sensor (I tested it using LED light)
Resistance on air flow meter connector seem to be normal
FOR some reason I don't get 12v EFI on PINS 2 and 3 which go for IDLE SWITCH i don't get the signal when I twist the throttle and when I don't touch the throttle, other pins are showing what they are supposed to show
Anyway, I'm a little stuck... not sure what else to look at. The bike by the way has air leak from intake manifold on cylinder 4, can that be the issues too? (but why it would start.... before it just bogged a little when you twist the throttle quickly)

[aldan0392]

Ok, here is the deal from yesterday. We were messing around with the bike, and I noticed that it starts ALWAYS with the first try in the mornings when its cold, or if it sits for several hours, we started the bike let it run until it stalls and stops starting back up, removed the plugs and they are WET, so plugs are flooded with fuel, after this I found one of the OVERFILL lines on the bottom of the gas tan being plunged with some hose and screw in it, as soon as we removed it and blew some air into return valve (to make sure it is not stuck) bike started and ran like it should, we started it and shut it down, let it sit for like 20 min idling, everything was perfect, until it stall and refused to start again.
Here is the second part lol! We removed the plugs and they are dry, so no fuel gets to the engine, we started to do inspection again.
I hear the pump running and we connected the fuel pressure gauge in series with fuel rail (I connected the pump hose, not return line) I was getting 30 to 31 psi, with engine running, when engine refuses to start I'm getting 35 to 36 psi (ENGINE NOT RUNNING), so I assume the pump and the regulator are fine (according to troubleshoot guide)
I have spark and I'm sure it is not timing, how do I know BIKE STARTS WITH STARTING FLUID
Using the same guide we started checking wiring to EFI computer and air flow sensor, I'm getting all the results from the pins on EFI, except for pin number 1 (RPM signal) In guide it says that I'm supposed to get 10-20mV, but I'm getting 500-550mV (may be the bike does not know how fast the engine is turning?) I don't have any Cluster on the bike, if that matters....
I'm getting 12 volts to each injectors connector (and when I put screw driver one side to the injector and another side to my ears I can hear the clicking while I'm staring the engine), so I assume they are opening (and the bike ran 20 min before that, all of them cannot go bad at the same time, or cannot get clogged up at the same time), After I removed the fuel rail from the engine and tried to see if any fuel will be spraying out when I press start button, very small amount of fuel was going out of there. (Not sure, but I think that computer closes the injectors too fast, and it does not get enough fuel to run)
We fixed the Throttle Butterfly Switch ( adjusted it, it understands when throttle is closed and when it is fully open, also tried to start the bike with TBS disconnected, no difference)
 

[aldan0392]

http://tomwade.me/motorcycles/technical/k100troubleshooting.pdf

Here is the guide that I'm using to check the bike

Can someone tell me how does the bike understands how much fuel to give to the bike.
It takes information from COOLANT TEMP SENSOR (funny thing, before if I get the bike to start without the coolant temperature, and I let the bike to warm up a little AS SOON AS I PLUG THE SENSOR BACK BIKE WOLD SHUT DOWN, that was the reason I went and bought another coolant sensor, because I read in the guide wnen coolant sensor fails It could send wrong signal to EFI and that would not let the bike start.
Air Flow meter (vane which is not being counted under 900rpm) and air temp sensor (I tried to cool it down and measure the resistance, according to the chart it seems to be working, but still no start)
And it should get rpm signal to know how much fuel to give

This is my thoughts and my rough understanding how it works, correct me if I'm wrong.
Thank you for replies BTW

[kennybobby]

When the starter motor turns the engine, the Hall Effect Sensors generate timing pulses which are sent to the Ignition Control Unit to tell when to fire the coils/spark.  The ICU then sends a timing pulse from pin 8 to the jetronic fuel injection control unit pin 1, to indicate what the rpm is and when to fire the injectors.  There is a big transistor in the jetronic that switches the 12V thru the injectors.  Sometimes the solder joints on that transistor break due to age and vibration.  Sometimes ants build a nest in there and short circuit the controller.

So if you can borrow another jetronic, to test and eliminate that as a culprit, or

pry the clips up and open the jetronic to inspect the solder joints and bugs.

if you work thru the flowchart in the troubleshooting you will find the culprit and be able to solve this.

[aldan0392]

We did pri it open, and I dont see anything broken, at least no soldering, but it could be broken resistor, orany other component... I'm getting higher voltage than I should before I plug the connector to efi... do you think could that be bad temperature sensor on air flow meter? Or may be bad ignition contron unit, since rpm signal goes from there to the efi, but if air flow meter or ignition control box go bad, will bike still start with starting fluid?

[kennybobby]

If it starts with ether, then the hall sensors are working okay, and the ICU is firing plugs okay.

To see the signal on pin8/pin1 you really need an oscilloscope to be sure, but there is a test at the injectors to see if the jetronic is pulsing them using an LED and a resistor.  It is in the troubleshooting flowchart file,  search for k100troubleshooting.pdf

A weak spray from the injectors with the rail pulled out could be clogged injector screens or bad jetronic or transistor.  If it has setup for awhile the ethanol turns to gel and can clog injectors and such.  Requires mechanical cleaning with solvents and airgun (vs snake foam or sea oil chemicals which do nothing) to open up clogged injectors.

[aldan0392]

The bike only set with this gas for  less than a month, it is not gas, will tdo led test, see whats going on there...

[Laitch]

. . . snake foam or sea oil chemicals . . .

:hehehe

[aldan0392]

Opened that yesterday, there is no spring in there and ball moves freely

[aldan0392]

Does anyone knows how to check temperature switch unit?

[aldan0392]

Hey Guys Wondering if anyone here in houston who have the same bike? May be I can come to you and test my EFI module or ignition, just plug it to the running bike to see what is the issue...

[Laitch]

It is not Fuel Pump (again, because it runs sometimes)

Two questions, aldan:

• Have you looked closely at the wire connections to the fuel pump? Recently a member here had similar starting troubles. One of the reasons was that one of the pumps wire's was almost broken and preventing its full function intermittently.
• Have you installed the replacement coolant temperature sensor?

[aldan0392]

Yes, I just checked and cleand all the wire connections today, and  swapped the temp sensor. Also, we just tested again mass airflow sensor, everything checked out. Right now what happend, if I close the trottle, and try to start the bike ot seem like it is trying to start, but as soon as I open the throttle it cuts off and does not start, starter and pump still spinning, but it refuses to start. And I moved the plugs, they are wet... I want to do led light test for the injectors tomorrow and check the hall effect sensor too

[aldan0392]

Sode stand was just delited, is it just metal line that prevents clutch from mooving right? Or there is an electronic component? Bike has been converted just recently, I only rode for like 200 miles on it

[Laitch]

Sode stand was just delited, is it just metal line that prevents clutch from mooving right?

You're correct.

[Laitch]

I want to do led light test for the injectors tomorrow and check the hall effect sensor too

That was kennybobby's suggestion a while back and that seems to be the way to go now.

[aldan0392]

OK, what have I done yesterday. First I did LED light test, I get 12 volts on my injectors, the LED is blinking, and took them outside again to see if they spit any fuel, yes they do, but I have no Idea if that is right amount or no, will take them out today and try to clean them with some brake cleaner or carb cleaner. I fixed all my air leaks, rubber boots that go from intake to intake manifolds we a little worn, and one was cracked, and intake manifold O rings were dry, I made new tubes for intake manifold, and put some silicone on intake manifolds, put it all back sprayed some staring fluid around them while trying to start the bike, NO AIR LEAKS. I did Compression test, with Throttle fully open #1 - 130psi, #2- 130psi, 3#133psi, #4 140psi. So everything enough to start it. Still, If I spray some STARTING FLUID inside the intake, the bike will starts, so problem is still with fuel, if I try to start the bike with throttle closed, it will try to start but dies the same second, but if I twist the throttle even a little, it will just spin the engine without even trying to start.
So far
1)I have compression, so engine is not bad
2)I have Spark (will double check again, but when I took my injectors out I could clearly see spark, and took my plugs and wires out they all have spark)
3) I put another coolant temperature sensor
4) Fuel get to the injectors (looks like it is not enough fuel gets there, so ether injectors close too fast or may be they are stuck... which does not make sense to me because the bike ran great for like 30 min, so how all of them got clogged up at the same time)
What is the minimum fuel pressure LE Jetronic can operate with?
5)I tested the AIR flow meter (to me seem like all specs are there) I will post the numbers when I do test again

[Laitch]

First I did LED light test, I get 12 volts on my injectors, the LED is blinking, and took them outside again to see if they spit any fuel, yes they do, but I have no Idea if that is right amount or no,

The should be spraying a mist of fuel. Maybe that's what they're doing and you're calling it spitting. Anyway, your making progress with your diagnostic procedure.

How about removing that valve with the ball in it entirely, reconnecting directly and trying that?

[aldan0392]

That was kennybobby's suggestion a while back and that seems to be the way to go now.

I did this tests before, right now I'm just doing it all over because I don't know what else can go wrong there... and it does not hurt to double check. 

[aldan0392]

The should be spraying a mist of fuel. Maybe that's what they're doing and you're calling it spitting. Anyway, your making progress with your diagnostic procedure.

How about removing that valve with the ball in it entirely, reconnecting directly and trying that?

Will try doing that and see if that would make any difference, which is very unlikely because last time I took it out it moves very freely, there is no spring at all, and than I tried to plug the return line and start it, return tine started to expand, so there is plenty of pressure to move that freely moving ball out of the way....

[Laitch]

I did this tests before, right now I'm just doing it all over because I don't know what else can go wrong there... and it does not hurt to double check.

I'm all for your doing those tests. That wasn't the topic of my post. My post was about experiment with something else that you've already done, too, which you have just answered. I think you will isolate and fix the problem eventually.

[aldan0392]

Hopefully as soon as possible...thank you

[kennybobby]

i think the HES are okay since it fires and runs when it has starting fluid, ether or gasoline in the intake.

The injectors should pulse a stream of fuel, not a spit and not a mist.  Be careful with the rubber orings and you can just clean the injector screens and flush the injectors with carb cleaning solvent and compressed air.  i use a 5 Vdc power supply to open the injector while flushing solvent thru it with a syringe and small tube. 

But another test on the bike that you may want to do first, is to pull the fuel rail with the injectors, pull the connectors off the injectors and apply voltage to the terminals with either a power supply or small battery.  Then you can observe the spray pattern with the injector totally ON without pulsing--it should be a strong stream until the pressure in the rail gets bled off.  If the pressure gets low then crank it over a few seconds and it should pump back up.  This test would tell you if the injectors are clogged or not.  If clogged then clean as above, but if they work fine here, then the issue is in the jetronic.

[aldan0392]

Does anybody know who is this guy? It is some sensor on the fuel rail, right behind throttle switch.

[kennybobby]

It's a sensor that turns on the choke light on the instrument cluster--not involved in starting or running whatsoever.

And that's not a fuel rail--just a piece of aluminum to hold the throttle bodies in place.

That lower clamp on the rearmost intake looks loose or not seated properly?