Fuel Pump/CANBus Problem

[Schtum]

My GS died today. It refused to start after I parked it up for about 30 mins. There's no fuel coming from either injector.

It was recovered....yes on the back of a flat-bed recovery truck..........and taken to a friend's workshop.

He writes.....

I need some help with the diagnosis. Here's what I've found so far:

Ignition on, self check OK, ECU happy. Turns over on starter but no fuel pump.

Fuel pump is powered through a "Fuel Pump Driver Module" from the ECU and the CANBus controller (Why can't BMW just use a relay like every other fecker :bang.

Pump itself is OK.

Can't find any power or signal going to the Driver Module from ECU/CAN when disconnected.

With everything connected I can't (easily) get in to measure a signal, however I'm seeing something on the output from the DM to the pump. Not 12volts, but something.

I don't know how the CAN bus works but my initial guess is that the DM is powered +12V through the CAN controller, so that no CAN = no engine, and gets its power earth through the ECU for the same reason. It then gets a separate signal from the ECU - not the CAN - to run the pump as appropriate.

So.....initial diagnosis is....

The DM is dead (I'll come back to why in a minute) and so won't drive the pump. With no DM connected the CAN and/or ECU shuts the thing down anyway so I won't and shouldn't expect to see a signal from the CAN/ECU.

To confirm the diagnosis I really need to know the following:

1 - Should I be seeing 12V at the DM power input when it's not connected or will the ECU/CAN shut it down as I suspect?

2 - Should I be seeing a signal on the signal wire for the DM when not connected? If so what does it look like (I've never poked around a CANBus before). Am I going to have to get the oscilloscope out to find it?

3 - If I make the effort to break into the feed to the DM when its connected what will I see? I suspect I'll see a permanent 12V power feed and some kind of on/off signal from the ECU. Correct?

4 - Anyone seen this before?

5 - Is the DM available as a separate module?



Now, the problem with the Driver Module is.....

It lives in a wee housing on top of the fuel pump mounting flange. It's sealed off from the inside of the tank with a fancy connector and from the outside world with a rubber gasket. The gasket on this one was not installed properly and was poking out. As a result the inside of the housing was full of a mixture of fuel (presumably from inside the tank and/or spills while filling) and water. The fancy connector has been soaking in fuel for so long it was spongy instead of solid (managed to get it off without breaking it, just!) but more importantly the contacts were well corroded.

Theory at the moment is that the extra effort of pushing current through the corroded connectors has proven too much for the DM and it has expired. Sound plausible?

One final question – If I ditch the DM altogether and wire the fuel pump through a relay that only activates on starter cranking/engine running will the ECU and/or CAN bus controller throw a wobbly fit?

Hope someone can help.....

[Beaker]

Sorry Schtum but I can't help with the technical side on this one.

Have you considered approaching BMW as the gasket had been incorrectly installed? I assume your bike is out of warranty?

Back in the early 80's I had a 750 Bonneville which lost power on one cylinder. Stripping the top end revealed that the circlip hold the gudgeon pin in on one piston had never been fitted resulting in it sliding out and severley damaging the bore. The bike was well out of warranty but I sent the parts to Triumph for examination. They agreed with my findings and sent me a new set of barrels, pistons and all relevant gaskets.

You never know, it may be worth a try?

Good luck!

[Schtum]

Well it's fixed now. I have to say that my good friend Dave, aka greenVFR, deserves a great deal of credit and another HUGE thank you from me.

Within 20 minutes of us getting the bike of the recovery truck it was on the ramp in his workshop with the tank off and the fault was pretty much diagnosed.

Further research on the 'net last night and today confirmed that it was a known fault for which there had been a recall. However, my dealer said that my frame no. was not within the range of the recall..... The fact that the dealership keeps the DM controller for the fuel pump as a stock item is pretty telling though. £50 later for a new DM controller and the bike's back together and running, although we haven't had a chance to road test it.

The service guy in the dealership has also submitted a warranty claim to BMW for the part, in spite of the fact that the bike's 6 months out of warranty.

[rcgd]

I had the same problem and the unit has been replaced by the dealer (at my expense). The engine cut out just after an overtake. Had it happened slightly earlier in another overtake the situation could have been catastrophic. I am amazed that such a critical part can fail (imagine if aircraft engines failed and they fell out of the skies because of defective pumps). I am writing to Mottorrad UK to complain. I wonder how common this problem is ?

[Tim Cullis]

Originally Posted by rcgd

I wonder how common this problem is ?

So far this year there have been more than 75 documented fuel pump controller failures amongst UK owners.

Tim

[StuWG]

And many multiples more than haven't..