1150GS Twin spark - No spark, no injector spray. Help !!!

[*touring ted*]

Hey all.

I've inherited a sickly R1150GS Twinspark. I've been asked to see if I can get it going. The bike was a good strong low mileage bike until one day it started cutting out and then it cut out for good.

There is no spark to any plug. And when I pull the injectors and crank the motor there is no spray. If I pull the fuel hose off the injectors and crank I get pumped with fuel. Definitely fuel pressure there.

1)The HES has been replaced with a new one. It tests perfectly on the bench with the LED test system. The fuel pump also fires every 180 degrees when you turn the crank. I'm confident its fine.

2)The motronic is energised. I get full dashboard and also 5V at the TPS. I've also tested the Motronic on another bike and it works perfectly. The clutch switch and side-stand switch work as they should. Neutral light works. I'm trying to start the bike in neutral with the side stand up.

3)When you turn on the key, the pump primes and the injectors are momentarily energised while the pump motor primes. This is (I think) normal as it's what happens on my friends bike. It makes sense as the injectors are powered by the fuel pump relay.

4)When you cycle the ignition and crank the engine, you occasionally get a single spark and a spray of fuel from the injectors. But just once. You have to cycle the ignition again for this to happen.

5)I've tested the main coil under the tank. I get 0.5 Ohms on the primary (Normal) but 55 Kohms on the secondary (should be 7.5 KOhms). This is out of spec and a new coil is on order, but it doesn't explain why the stick coils and the injectors don't fire.

6) When I test the voltage when cranking over, it drops to about 10V. I get the same reading on the alternator.


Question. Will the 1150 Twin spark run JUST on it's stick coils ??? I think it should.

Should the injectors only be energised momentarily or should they always have a 12v live with the ignition on ??


My guess is that the motronic is not earthing the injectors (to fire them) and not earthing the coils (to fire them). But why ?? It works on a different bike.

I have to start thinking is something sucking all the current out of the ignition system ? I think i'm correct in thinking that the bike would fire and run even with a dead alternator with a fully charged new battery.

Any ideas ??

 

[ratty]

Starter motor, Try swapping with a friends, All of half an hour job!

 

[DrFarkoff]

Yes it should run on Stick coils only Had it an Alarm fitted????


Pull the power connection to the under tank coil and that eliminates any issues with it

Did you swap the motronic into another bike?? IS that why you say?

My guess is that the motronic is not earthing the injectors (to fire them) and not earthing the coils (to fire them). But why ?? It works on a different bike.

Those bikes are very rugged and whatever is wrong is likely simple

AS Steptoe says One step diagnosis is the best path i.e. Do not bang a load of parts onto it and then wonder which bit fixed it!

If you have a similar bike to swap parts from into Its worth the effort to track the issue and likely much faster

The motronic is just a big calculator it takes input values and gives outputs for fuel and spark and that's all it does, Inputs such as Intake Air temp Engine temp, Engine crank position (x2), throttle angle

All of the above can be out but the bike will still spark and run

Cleaning the starter motor out if it sounds like its labouring ?? Sometimes the grease plates dislodge and stick to the front of the armature

 

[Ian J Hartley]

Question. Will the 1150 Twin spark run JUST on it's stick coils ??? I think it should.

Yes it should, provided they are in good working condition. They are after all the primary ignition point.

Should the injectors only be energised momentarily or should they always have a 12v live with the ignition on ??

The injectors are powered when ever the fuel pump runs. The fuel pump relay which controls power to the injectors and the fuel pump is controlled by the motronic. Once the motronic senses the engine is turning via the HES, it pulls in the fuel pump relay to provide power, from then on the motronic Is in control.

My guess is that the motronic is not earthing the injectors (to fire them) and not earthing the coils (to fire them). But why ?? It works on a different bike.

I have to start thinking is something sucking all the current out of the ignition system ? I think i'm correct in thinking that the bike would fire and run even with a dead alternator with a fully charged new battery.

Any ideas ??

Not really. It sounds like you’ve covered most of the bases, Some bikes have a second load relief relay fitted, which is for the stick coils to provide additional power source. It’s a small yellow relay front row far right. It’s the same as the normal load relief relay on the front row far left. And can be swopped with any of the small black relays.

Because you have had connectors off the injectors and the motronic, it might be an idea to revisit them just in case you have inadvertently unseated a contact pin pushing it back in the housing. Just check all contacts are firmly seated and not unlocked.

I take it you’ve tried starting it with a additional battery attached to give added boost. It could be that you have a ground problem somewhere on you bike.

Ian

 

[topcat2006]

Wiring around the headstock?

Oh no, not another signature....

 

[ShakeyGS]

Sounds like the sort of fault you might get where a core in the wiring loom Has worn through.....perhaps at a frame contact pointor indeed, as Topcat says, at the headstock.

Is it this era of bike that has an issue with a cable tie bringing two parts of the loom together at the front, between the headstock bearings?