1985 K100 RT That didn't run...does now with issues!

[Supershooter]

Laitch,

I read the thread you shared and then went to town and got a fuel pressure test kit on loan from auto parts store. I took a little video trying to start the bike today. This way you can see what's going on.



Hopefully the link works, this is my maiden voyage in the youtube world.

Supershoooter

[Martin]

I'll bet that if you pull the plugs they are wet. It still looks like it is flooding and you need to check the sensor connection and sensor. With the lack of body work it would be easier to access going via removing the radiator.  When mine first played up I could manage to get my hand by removing the air scoop and pushing up the coolant bypass hose and wriggle the sensor connector. I went in from the right hand side, however I do have small hands. And another time on a mates bike I managed with patience and luck to get the connector off by using a pick to spring the clip.
Regards Martin.

[Supershooter]

Does the bike have to be running to get a fuel pressure reading?

[Martin]

Once the bike has been running and is shut off there is residual pressure in the fuel rail for a while. The length of time will vary from bike to bike depending on the condition of pump, FPR and hoses. Any leaks will reduce the time the system retains pressure.
Regards Martin

[Supershooter]

Is it possible to test fuel pressure on a non runner? My fuel pump runs but the bike doesn’t, will I get an accurate reading?

[Martin]

The FPR requires engine vacuum to work. However you might be able to get a reasonably accurate reading. It should be around 35 Psi. After your last attempt did you check your plugs were they wet.

You can have spark and fuel and it can still fail to fire. A faulty temperature sensor or connector can cause an overly rich mixture which causes flooding and failure to start. If you get stuck by the side of the road you can get them to fire by removing the plugs and let the engine dry out for 15-30 min. Alternatively remove the fuel pump fuse No 6 marked as Krafftestoppe or unplug the fuel pump. Replace the plugs and start the bike it should run on the residual fuel left in the combustion chamber. As the engine starts to die ram home the fuse or reconnect the pump. With a bit of throttle manipulation you can keep it running albeit roughly. Two people make the job easier but it can be done with one. If you can start it with this method try cleaning the connector with DeoxIT. If that doesn't work test the sensor's value with a multimeter.
Regards Martin.

[The Mighty Gryphon]

Disconnect the fuel delivery line from the rail.  Run the pump and verify that you can get a liter of gas in less than two minutes(I believe the spec is 35liters per hour). 

Then put you gauge on the end of the line.  The blocked pressure should be around 65psi for the OEM pump.  It needs to be at least 40 to work with the pressure regulator.  Make VERY SURE the connections are tight and don't let the pump run for more than a couple seconds.  Be very careful disconnecting the gauge.  There will be some residual pressure in the plumbing. 

Low flow or low pressure and your pump is whack.

Then, tee into the line and connect it back to the rail.  With the pump running, the pressure should be 35psi.  If not, the regulator is whack.

[Timbox]

Fist off great vid on what the bike is doing, always helps to have pics and vids.  The Mighty Gryphon has the next great step IMHO to make sure you are getting the right  fuel PSI both from the pump and to the injectors. 

I wasn't too sure if you didn't want to crank it too much or you are just used to doing short starter button bursts?  I try to start my bikes for a good count of 10 but then hold off for a bit to cool the starter down.

Have you tried keeping the gas cap off and looking inside to the return line to make sure fuel is flowing back into the gas tank?  You would have to do this while the starter button is being pushed to activate the pump relay.

Those little backfires that we hear, are they coming from the injector ports?  I didn't see anything coming from the exhaust. 

[Supershooter]

The test kit from the local auto parts store only included a T in the test kit. So I was only able to test the pressure with the t fitting. After pushing the starter button the pressure in the line did rise to 35-36 psi, so I'm figuring the pump is good. I ran fuel into a gas can a while back and seemed to have gas gushing into the gas can even though I didn't measure how much was pumped.  If I've misinterpreted my findings please say so.

Martin, I haven't pulled the plugs to verify the plugs are wet, but I'd bet they are wet, after seeing what I've seen so far. I can pull the water temp gauge out again, but when tested before it tested within spec at different temps even though I didn't test it every 10 degrees. I think if I pull the spark plugs and dry them off if could get it to backfire some more and maybe run a little until it runs out of gas. I can take more video of what happens to show my issues if that helps.

Just let me know what direction I should from here.

Supershooter

[Martin]

Is the temperature sensor connection clean? Did you put thread tape or sealant on the sensor threads?
Regards Martin.

[Laitch]

I took a little video trying to start the bike today.

Nothing beats ending with bang.  :clap:

Let's pretend nothing is wrong with the fuel pressure regulator. Now it's time to check the injection system. Use Vogel's troubleshooting manual to test electrical power at the fuel injectors.

[Supershooter]

Martin,
I didn't use any thread tape or paste during reassembly, but did use deoxit on the electrical connections.

Supershooter

[The Mighty Gryphon]

With the engine not running, what is the resistance to ground on the injector terminals?  All the injectors should be unplugged and the big plug on the Jetronic should be unplugged too.  You want to see if there is a short to ground in the injector harness since the injectors are opened when they are grounded by the Jetronic.

[Martin]

An internal combustion engine requires fuel, spark and compression. And all these have to occur at the correct time. As the common sources of running rich in a Brick seem to be OK, FPR and the  temp sensor. Do you have compression?
Regards Martin.

[Supershooter]

Martin,
Its possible that I lost compression, but I'm skeptical. I plan to keep investigating. When I was testing to see if the alternator was charging or not I was able to easily start the bike like many times before. After shutting off in between tests it wouldn't start again. That's what has me stumped, it ran fine on minute and wont start the next and it didn't even leave the center stand....?

I'll keep checking things until I figure it out. Ill post some video from last year when I got it to run after what could have been 10 years according to the PO who inherited the bike from a deceased brother. There was shear elation in my life on Feb 16, 2017

Superhooter

[Supershooter]

Video 1



Supershooter

[Supershooter]

Video 2 More RPM's and a sticky throttle



After this I was able to ride the bike about 50 miles this summer, before it quit again.

Supershooter

[Timbox]

 Way to stick with it SuperShooter!  :clap:

My next step would be to pull the injectors out of the TB's,  but keep them on the fuel rail.  Take a bit of cardboard or something similar and lay the injectors on the cardboard.  Try to start the bike and see if the injectors are spraying on the cardboard in a good pattern.  I only say this because I didn't see a pic of the inside of the gas tank.  I did see how the rubber on the pump (like mine) was nasty.  This would give you the proof you need that the injectors are working.  The injectors have a locking system to keep them in the fuel rail, but be carefuller if you do this, they could pop out of the fuel rail and spray gas.

If the first time you removed the injectors you didn't clean out the TB side, some stuff could have gotten into the cylinders and caused some issues in the 50 miles you did have it running.  I really hope this is not the case.  The compression test will let you know how the cylinders are doing.

[The Mighty Gryphon]

I have just reread the last 4 pages of this thread. 

1.  It appears that the temperature sensor and the sensor wiring is good.

2.  The pump is working

3.  the pressure in the rail is correct

4.  you have have plenty of pump flow

5.  You have spark

6.  The engine will start and run a second or two with the pump unplugged after it floods

7.  The MAF appears to be working correctly.

Despite all the above, the engine is flooding.  Unless the ECU is whack, the only other cause would be injectors that are open all the time. 

The injectors are opened electrically by a GROUND pulse from the ECU.  They are all connected in parallel in the harness.  One terminal on each injector is connected to 12v whenever the bike is turned on.  The other terminal is connected to a circuit in the ECU that controls how long the injectors are opened.  The circuit has some transistors that act as switches connecting the injectors to the ground.

To test this, you need to get a 12v LED and some alligator clip test leads.  Disconnect the injectors from the harness.  Connect the POS wire of the LED to one of the injector connector terminals and turn on the ignition and touch the NEG wire to ground.  THe LED should light.  If it doesn't, reverse the connections and try again.

Once you can make the LED light, connect the NEG wire to the other terminal on the injector connector.  Turn on the ignition.  The LED should be out.  Hit the starter, and while the engine is cranking the LED should blink. 

I suspect from what you have been seeing that the LED will stay lit, meaning that the injectors are being held open, dumping uncontrolled fuel into the cylinders. 

If that is the case, the problem could be the ECU, or a problem in the injector harness.

The next test is to unplug the big connector on the Jetronic unit.  Take the POS wire from the LED and connect it to the Battery + terminal.  If the LED lights up, you have a short to ground in the injector harness. 

If it doesn't light up, reconnect the plug on the Jetronic.  If it lights up, there may be a problem in the Jetronic.  Turn on the ignition.  Does the LED go out?  If it stays on, the Jetronic is probably whack.

I have read about the output transistors in the Jetronic going bad.  It doesn't appear to be a common problem, but it has happened.  Someplace I read where there it can be repaired.  Something to do with resoldering a broken connection or something like that.  Maybe Laitch can find the link.  He's amazing at stuff like that.

[The Mighty Gryphon]

Stolen from the K100 Forum.  http://k-bike-knowledge.000webhostapp.com/electrical/EFI/bike-wont-start-EN.htm

If you buy a 12v indicator LED at the auto parts place you won't need the resistor.

To quickly check if the FI is working, plug an LED into one of the fuel injector connector.
 

[Supershooter]

Do I need a LED test light or can I get by with an old test light?


Side note, What's the trade count for?


Supershooter

[The Mighty Gryphon]

Test lights draw too much current and don't respond fast enough.  Even though they aren't able to get to a visible level of light output, they will have a good chance of overloading the output transistors of the the ECU that drive the injectors.  That is not good.

LED's are the only way to go.

[Laitch]

Do I need a LED test light or can I get by with an old test light?

You need a 12V LED according to the instructions developed by Bert Vogel that the Mighty Gryphon cites.

[johnny]

greetings...

the pulses come fast... incandescent isnt fast enough for separation... you gotts to keep them separated or they aints pulses...

you want something that looks like this from the truck stop or napa...

j o

[The Mighty Gryphon]

Here's what I use:

https://www.ebay.com/itm/8mm-12v-Amber-LED-Metal-Indicator-Light-Pilot-Dash-Pre-Wired-LED-US-Seller/272274437704?hash=item3f64d23648:g:GdcAAOSw8b1aLJ0z&vxp=mtr

https://www.ebay.com/itm/TEST-LEAD-ALLIGATOR-CLIP-JUMPER-WIRE-LOT-OF-5-PAIRS-RED-BLACK/292492109279?hash=item4419e365df:g:tv8AAOSweW5VFXkp

Solder the alligator wires to the LED and you're good to go.