R1100RT - Fuel Pump Voltage Issue

[TwistTheWrist]

Howdy!

I've got a '99 R1100RT (non police model) with about 140k miles.  I've gone through and restored most of this bike over the last 2 years.

When I went to start it, I got a very hard start, rough idle.  Found out it was only firing on cylinder(1) by heat from that side.

 

Hall sensor was my first idea.  Replaced/tuned that and still the same issue.

Cylinder(2) is dry after cranking.  I think both sparks are firing.  No fuel from injector(2).

 

I read the voltage/resistances from the fuel injector wires.

One is 0v and flips up to high V when I roll the engine over manually (cylinder that fires).  Fuel pump also cycles at this time.  I think this side is operating normally.

The other fuel injector wire(2) reads a constant 5V and has half the resistance of the other and doesn't read a change when I roll the crank over by hand...

I'm thinking some kind of short, or something is up with the Motoric control unit?

I can take off and test, just not sure how to go about that..

 

Any thoughts?!

Thanks

 

[dirtrider]

32 minutes ago, TwistTheWrist said:

Howdy!

I've got a '99 R1100RT (non police model) with about 140k miles.  I've gone through and restored most of this bike over the last 2 years.

When I went to start it, I got a very hard start, rough idle.  Found out it was only firing on cylinder(1) by heat from that side.

 

Hall sensor was my first idea.  Replaced/tuned that and still the same issue.

Cylinder(2) is dry after cranking.  I think both sparks are firing.  No fuel from injector(2).

 

I read the voltage/resistances from the fuel injector wires.

One is 0v and flips up to high V when I roll the engine over manually (cylinder that fires).  Fuel pump also cycles at this time.  I think this side is operating normally.

The other fuel injector wire(2) reads a constant 5V and has half the resistance of the other and doesn't read a change when I roll the crank over by hand...

I'm thinking some kind of short, or something is up with the Motoric control unit?

I can take off and test, just not sure how to go about that..

 

Any thoughts?!

Thanks

 

Evening TwistTheWrist

 

If the issue is on the right side then probably your throttle cable isn't FULLY seated in the throttle body cable adjuster.

 

That allows the R/H side throttle plate to be opened too far (allowing too much air in) with no matching fuel sprayed in.  

 

If the cable is seated OK then possibly a fuel injector issue (bad injector, or the very small fine screen in the top of the injector inlet is plugged).

 

The HES fires both spark plugs from the same HES input & triggers both injectors from the same HES signal so if one side is working OK then that part of the system is working OK. Even the coil sparks both spark plugs together from the same coil (continuous loop)

 

But I have seen a spark plug wire partially pulled out of the coil while working on the motorcycle causing a dead or weak cylinder so do check that also. 

 

If for sure the Motronic isn't pulling the dead side fuel injector trigger side (green/gray wire) low once per crankshaft revolution then you either you have an open in the wire between the injector low side & the Motronic computer or some other open. 

 

On the 1100 Ma 2.2 BOTH fuel injectors are triggered by the same Motronic internal driver so if one side is working (injecting) then the other side also should also be injecting. Ohm out the injector green/gray wire between sides & also back to the Motronic. There is a splice in the green/gray wire that connects both sides together.

 

If there is no continuity in the green/gray wire between sides then suspect that splice is open, or at least the wire from the splice to the non-firing side injector is open. 

 

[TwistTheWrist]

Will check throttle cable first, but I think that's fine.

 

That was my conclusion as well.  I wrapped up the wiring harness and was trying to avoid pulling it back open .

So BOTH spark plugs fire at the same time? Makes sense based on the wiring and engine config.  I was thinking in terms of my old 4banger with alternating firing sequence..

I'll run it back to the splice this week and see what I find.

 

Thanks!

[dirtrider]

2 hours ago, TwistTheWrist said:

Will check throttle cable first, but I think that's fine.

 

That was my conclusion as well.  I wrapped up the wiring harness and was trying to avoid pulling it back open .

So BOTH spark plugs fire at the same time? Makes sense based on the wiring and engine config.  I was thinking in terms of my old 4banger with alternating firing sequence..

I'll run it back to the splice this week and see what I find.

 

Thanks!

Afternoon  TwistTheWrist

 

The BMW boxer does have alternate firing (360° firing order) but it also has a lost spark ignition system so the spark plug sparks at EVERY piston up but at every other stroke it sparks on the exhaust stroke (basically a dead cylinder). 

 

The ignition sensor is on the crankshaft (not the cam shaft) so the ignition sensor has no way of knowing which stroke it is on,  combustion or exhaust.