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R1100RT - Starting Problems (no gas through the injectors)


SWB

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I'm in the middle of "zero-zero" tuning my 2001 R1100RT. To review, I had a tranmission failure six months ago. It's rebuilt, back on the bike, and I performed a series of other maintenance procedures. After six months "off-line", the bike won't start.

 

Done already:

 

  • New ignition coil, plug wires, and plugs 2500 miles ago.
  • New fuel regulator
  • Removed throttle bodies (TBS) and "de-coked" them by soaking them in carb cleaner. (Removed TPS and fuel injectors first).
  • Replaced all "o" rings in the TBSs.
  • Replaced the 3 throttle cables and fast-idle-advance cable, plus the bowden box.

 

Checks performed:

 

  • Pulled right cylinder spark plug; it's dry. Tested for spark during ignition (starter) against the cylinder. It sparks.
  • Pulled the right fuel injector off, and cranked the starter. No fuel comes from the injector while cranking the starter.
  • Tested the right fuel injector power plug during cranking; It receives power (perhaps 0.2 to 0.3 Volts).
  • Pulled the right fuel injector from the fuel regulator connection. Fuel is in the line. It runs out in a regular trickle. Cranking the starter (potential sparks next to an open fuel source....yippee! we're having fun now), and the flow from the fuel regulator does not vary. I expect that this is the the way the fuel regulator is supposed to work. It doesn't gush out as under high pressure, but fuel continues to run (perhaps a cup a minute) under uniform pressure regardless of whether the fuel pump is on or off, whether the bike starter is engaged or not.

 

I didn't do much with the fuel injectors while I was cleaning the TBS. I think I sprayed carb cleaner on the exterior tips and cleaned them off, but since the injectors appear to be plastic I didn't do anything further to clean them up.

 

I haven't checked the left side yet, but if the left cylinder injector was producing fuel, the bike should have attempted to fire on the left cylinder (or at least backfired). Is it possible that just wiping off the ends of the injectors clogged them up? Or, worse, that they could have BOTH shorted out?

 

Any suggestions, other than replacing both injectors?

 

I'll pull apart the left side and run the same checks, but I don't think fuel's getting to the engine through the injectors. I'm definitely getting spark. The right side fuel injector test seems to prove that the problem is there.

 

(By the way, the first time I turned on ignition after assembly, I found a fuel leak from one of the supply lines under the tank. I had replaced the fuel filter earlier, the fuel supply lines had the original BMW clamps on them, and evidently one of them worked loose to the point of leaking. I heard a "pssssss" the second or third time I turned the ignition on, while I was checking the electronics and fuel pump. It sounded like an electrical short, which is what led to the right-side inspection and discovery of the fuel puddle. I fixed the leak, and could not find a circuit or wiring any place between the tank and right cylinder where something could have gotten wet and shorted out. The gas went direction from the tank down on to the cylinder, and down the the floor. Bottom line: I don't know what caused the "short-circuit" sound yet, or whether that sound was the fuel leak under pressure instead of something electrical.)

 

Thanks.

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ShovelStrokeEd

I'm thinking you might have the inlet and return lines switched going down to your fuel pressure regulator. The line to the injectors should be pressurized at 3 bar and that line is the line that exits your fuel filter. One of the lines should produce a pretty healthy squirt in response to the ignition on deal.

 

I'm not sure I like that voltage reading at the injectors. One side of the connector should be seeing 12 VDC, the other, is open and grounded by the driver chip in the Motronic. To test for this, you need to have the injector connected and probe the wires at the connector. I don't have a wiring diagram but you should see the voltage going back and forth from 12 volts to near zero as the motor is cranking. A digital voltmeter might not show the full swing but you should, at least, see a disturbance in the reading. Many DVMs have an analog scale for this (LED bar graph) that responds much faster than the actual readout.

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I'm thinking you might have the inlet and return lines switched going down to your fuel pressure regulator.

 

Dang, I wondered about that as I was assembling, and I thought "no.. that's the vent tubes that you're not supposed to switch, and I've got those marked with paint". I'll double check the fuel lines; I've probably switched them. dopeslap.gif

 

I'm not sure I like that voltage reading at the injectors. One side of the connector should be seeing 12 VDC, the other, is open and grounded by the driver chip in the Motronic. To test for this, you need to have the injector connected and probe the wires at the connector. I don't have a wiring diagram but you should see the voltage going back and forth from 12 volts to near zero as the motor is cranking. A digital voltmeter might not show the full swing but you should, at least, see a disturbance in the reading. Many DVMs have an analog scale for this (LED bar graph) that responds much faster than the actual readout.

 

I just wanted to see a voltage fluctuation. I simple probed the contacts with the DVM, red to red/white, and black to the other. The plug was off the injector. I can check it connected, with red probe to red/white and black probe to ground.

 

I'll check the fuel lines first.

 

Thanks.

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Fixed it! What *@#$#@!! noob I was. Should have known better.

 

The garage was closed, and neighbors are sleeping, but I think it actually "purrrred", like the carbs are balanced.

 

On to the tuning...

 

Thanks Ed!

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