1200 Adv fuel pump repair

[Bobbin-Man]

So is the pump Bendy's referred to purely fitted to the GSA?

 

[Kenny Rodkiss]

No, GS and GSA use the same fuel pumps. It's just the GSA with its 33 ltr. tank needs a way to transfer fuel from the right side of tank over to the left side ( where the pump is). BMW use a sucking jet pump, which is a venturi type suction jet that uses the return fuel flow to syphon fuel from one side to the other. Standard GS tank does not require this so return flow is just dumped back into the tank.

 

[Bendy toy]

My net search threw up this info .....

Here's the actual function of the controller. It does not reduce the voltage to the pump, to extend pump life. In all BMW bikes that use a fuel rail that has no return line, the fuel rail has a pressure sensor. As the throttle is opened and closed, varying amounts of fuel are used, so a constant-speed pump would not keep the required constant fuel rail pressure.

In this system, the fuel rail pressure sensor sends a signal to the controller, which causes the controller to vary the average voltage it feeds to the pump to keep pressure constant. If the throttle is opened, more fuel is used, and in order to keep the fuel pressure constant, the controller increases the average voltage fed to the pump, which makes the pump speed up to maintain fuel pressure.
When the throttle is closed, the reverse occurs

I think I saw this information in the Bosch "bible" publication on FI and motor management systems. Anyway, to sum up, you may recall that there are two different types of inlet port injection systems......
First is the traditional electronic injection, where a positive displacement "roller cell" pump, pumps fuel into the fuel rail. The injectors take what they need, and the remainder is forced through a pressure regulator and back to the tank. The regulator is a simple mechanical one that provides a constant backpressure (about 40-45 psi usually) for the fuel rail. This type has been used since Bosch made its first electronic injection system (the D-Jetronic system originally used in the 1968 VW Squareback). It's main advantage is that it's simple! Its main disadvantage is that the fuel picks up heat as it is constantly circulated past the motor. This results in increased fuel tank temperatures and increased fuel evaporation. Recent strict EPA limits on this resulted in the so-called Non-Return system I described in my earlier comments.

As a way to solve fuel tank heating and subsequent increased evaporative emissions, the Non-Return system I described has become more common in the last few years. As I mentioned earlier, this consists of a variable speed, NON-positive displacement turbine pump, whose speed (and pressure) is electronically controlled by pressure sensor feedback in order to maintain constant fuel pressure, inder all conditions of fuel flow to the injectors.

So does the GSA work on a traditional return system, meaning the FPC does a different job?

This does not explain why removing the fuel strip suddenly causes the bike to stop with fuel remaining in the tank. In my case the bike was running ok. My fuel strip failed at least a year ago (maybe more) but I just used the trip and carried a spare can for the inevitable time that's I'd forget to check the elapsed mileage.

One day I removed the fuel strip and fitted a totally separate fuel level gauge. The bike ran out of fuel about 100 miles later with at least another 80 miles worth in the tank. It continued to do this until I replaced the fuel pump.

There is a very long thread on ADVRider which eventually works out that the pump controller does increase pump output when the gauge shows 1/4 full. A new pump solves the return flow problem but who knows how long it will last when constantly running at full power due to a broken fuel strip.

Fuel strip output to spoof a full tank reading
http://advrider.com/index.php?threads/fuel-strip-spoof-results.1040056/

Huge thread about how the system works
http://advrider.com/index.php?threads/faulty-fuel-level-strips.758453/

 

[Kenny Rodkiss]

Bendy t, I understand where you are coming from, but, as the GS uses the same hardware as GSA what is the point of a pump controller on the standard GS as it has no syphon pump to drive with its return flow when the tank gets low. I think there must other parameters that request less than full output from the pump? Glad your new pump has sorted out your premature emptiness.

 

[Bendy toy]

I'm sure the pump controller does other stuff. It probably limits pump output so that return flow is minimised and the pump should last longer. Then the GSA has the additional feature override the controller to make sure the tank gets emptied. My old pump at normal duty was good enough to run the engine but too weak to fully empty the fuel tank.

The new pump now empties the tank properly on normal duty (I don't have a fuel strip to tell the ECU when the tank is nearing empty) but who knows how long the pump would last if always run at full power.

 

[Kenny Rodkiss]

You would think it would be OK cos the old 1150 ran full bore all the time and they are still going strong. Pass.

 

[Bendy toy]

My fuel pump had done 60K with the fuel strip showing tank empty for the last 10 to 15K. Maybe the strip had no effect but a car fuel pump will easily do 100K so what's going on with a bike that uses the same type of pump?

 

[BlueBird]

ummmm

lately when my 05 gs gets low on fuel it gets really lumpy on tickover and will cut out if your not super careful with the throttle,
fill it up and its fine again, changed the fuel pressure thing a while back so dont think its that, bike has 130k up it so im gona get the fuel pressure output of the pump checked to see if there anything going on with it.

 

[Bendy toy]

lately when my 05 gs gets low on fuel it gets really lumpy on tickover and will cut out if your not super careful with the throttle,
fill it up and its fine again, changed the fuel pressure thing a while back so dont think its that, bike has 130k up it so im gona get the fuel pressure output of the pump checked to see if there anything going on with it.

I had these symptoms and what really made me sort it out was the issues low fuel levels.

The new pump has virtually stopped the lumpy tickover, speed hunting, stalling, coughing, etc. The thing is that none of that was ever consistent. Some days it would stall twice before I gout out of my home side street others would be fine. Somedays it felt rough at speed or could be hunting (like the brakes were slightly dragging for a second then ok again. Other days it was fine. The slight hunt has all but gone so its probably part of the ECU program, but the old pump exaggerated the effect. The stalling has all but gone and the cough back though the throttles has stopped.

The one downside is that when it now runs dry there is no warning. It just dies. Previously all the above getting worse were early warnings

 

[BlueBird]

I had these symptoms and what really made me sort it out was the issues low fuel levels.

The new pump has virtually stopped the lumpy tickover, speed hunting, stalling, coughing, etc. The thing is that none of that was ever consistent. Some days it would stall twice before I gout out of my home side street others would be fine. Somedays it felt rough at speed or could be hunting (like the brakes were slightly dragging for a second then ok again. Other days it was fine. The slight hunt has all but gone so its probably part of the ECU program, but the old pump exaggerated the effect. The stalling has all but gone and the cough back though the throttles has stopped.

The one downside is that when it now runs dry there is no warning. It just dies. Previously all the above getting worse were early warnings

exactly the symptoms im getting Bendy, although my fuel guage is fine being the earlier type,sounds like with out the head of fuel its struggleing to lift it when its low.

 

[Bendy toy]

Mine certainly runs smoother with the new pump. Properly atomised fuel will burn better and less likely to pop back through the throttles as it used to do.

If you use the pump repair kit, be careful how you cut the fuel hose crimp from the pump and be careful how you slip the hose off the pump. You will be re-using that very hose so cracks or cuts in the wrong place =

If the hose is shot you will need something that won't "neck" if curved too tight. The supplied fuel hose isn't suitable. Some soft copper tube with rubber hose at each end is probably the best option.

 

[MattW]

My net search threw up this info .....

Here's the actual function of the controller. It does not reduce the voltage to the pump, to extend pump life. In all BMW bikes that use a fuel rail that has no return line, the fuel rail has a pressure sensor. As the throttle is opened and closed, varying amounts of fuel are used, so a constant-speed pump would not keep the required constant fuel rail pressure.

*ill-informed diatribe cut*

As a way to solve fuel tank heating and subsequent increased evaporative emissions, the Non-Return system I described has become more common in the last few years. As I mentioned earlier, this consists of a variable speed, NON-positive displacement turbine pump, whose speed (and pressure) is electronically controlled by pressure sensor feedback in order to maintain constant fuel pressure, inder all conditions of fuel flow to the injectors.

So does the GSA work on a traditional return system, meaning the FPC does a different job?

That danger of cut and pasting from other people who've cut and pasted what they don't understand...

As above boxer BMW's *do* have a fuel pressure regulator and return line. The fuel pressure regulator is used to mantain a constant over-pressure at the fuel rail. Lower pump speeds reduce pump wear and noise (and to some extent reduce fuel heating).