March 2020

A man whose bikes I have been working on for some time asked if I might look at something slightly more modern for his friend. The bike had not run for 5 years odd, and my man was concerned that his friend might give up riding altogether if his bike was not sorted fairly soon, thus this machine kind of pressed its way into the general scheme of things.

It did not look very pretty when it arrived. Much of the bodywork had been removed in at least one attempt to get the beast going. The tyres were totally flat, and after the two gents had gotten it off the trailer and left, I found that I could hardly move it, so out came the compressor and a few rounds of inflation took place. Even then it was a very ungainly thing to manhandle, and it took several attempts to convince it to jump the edge of the floor slab and make its way into the shed.

There was a reasonable amount of fluid in the bottom of the airfilter housing, and the contents of the fuel tank - a most ugly grey plastic thing - smelt like the residue of a varnish factory, the obvious pong of rotten fuel. Unfortunately this stuff had been pumped around the fuel circuit in attempts to elicit life from the engine, so was now throughout the pump, lines and injectors. This could prove to be a rather expensive exercise if these items were now damaged by the evil smelling goo. Hardly suprising it would not light up.

Fuel tank and various body bits came off, and I emptied several litres of old fuel into some long grass that I wanted to kill. I reckon its a sure thing. I left the tank outside rather than stink my shed out. Various bits of old dross also came out of the tank. No way of knowing what the current status of pump, fuel gauge sender and other bits might be, so I would flush the tank with new fuel and then attempt to pump some through the lines to flush them also.


I removed the air intake ducts and cleaned the intakes of the throttle bodies. There was a lot of old fuel which had decayed to the consistency of a light oil, as all the lighter elements had evaporated off. The injectors were removed and cleaned but there was no way of ensuring they would be happy to supply fuel in future. Attempting a start would probably be the ultimate proof. All these bits got refitted and now looked like this.


The fuel tank still smelt really bad even though it had been drained and left in the sun with the filler neck removed to help evaporation to take place. Adding some fresh fuel would likely be the best way to overcome the old fumes while rinsing the submerged fuel pump and remaining fuel lines. Only by powering it up would I find if the pump still worked.

The same would apply to the fuel sender unit which would likely contain a low fuel light switch, and all of these things are relatively delicate and could easily be gummed up by old fuel residue. The annoying thing is that it will all need to be reassembled to test, so if there are still problems it will have to come apart again.



Fuel tank refitted and fresh fuel added. All fuel lines and drains reconnected and electrics reinstated. I decided to remove the spark plugs to allow the engine to breathe some fresh air in order to expel any unwanted residues. This model has 2 spark plugs per cylinder, one underneath the cylinder and one in the top centre. BMW thoughtfully provides a plastic tool in the toolkit for removing the coilpacks for the centre plugs, but on this bike at least, the tool was totally useless. I used some improvised means involving two large screwdrivers to prise them out then remove the plugs.

I placed a container beneath both lower plug apertures before cranking the engine over on the starter. A large dollop of what appears to be engine oil got spat out of the left cylinder. This is the cylinder which hangs down when the bike is on the sidestand, and I am not sure if this may play a part.


I had removed the injectors from the throttle bodies to observe whether any fuel was issuing forth, but not a drop. Nor could I hear the fuel pump in the tank operating, neither when the key was initially turned on, nor when cranking on the starter.

I suspect that we would not be experiencing any great amounts of spark though..


So the current status is this. Either the fuel pump has failed, or the injectors are gummed up, or both. It does not look like it is possible to remove the fuel lines from the injectors without damaging the retaining clips, but the lack of any whirring noises from within the tank would tend to signify that the pump is not running. I now need to ensure that my methodology is correct before attempting to extract any more bits - which may or may not prove to be at all serviceable.

I have a vision of cash registers whizzing over like one-armed bandits.

Lawdy.!


Having completed other projects I came back for another go at the Beemer. Courtesy of the internet I found a wiring diagram and a picture of the layout of the fuse and relay compartment. Fuse No.6 was for the fuel pump, so I plucked it out and tested it. Failed. I fitted another fuse and tried turning the key on briefly a few times. On the second attempt the new fuse went off with a slight pop and rewarding flash. Looks like the fuel pump is coming out of the tank then.

I also did a search for new fuel pumps and found several places in the USA selling them and stating that they were still doing business. I shall remove this one first to see what it looks like. I shall also try another new fuse with the fuel tank wiring disconnected, as there are other places being supplied by the same fuse. We are narrowing the field.

Ok. Fuse test with tank disconnected proves no fault now exists, so fuel pump is No.1 suspect. Tank off and drained. All internals removed. Like this.


Whatever was in the fuel tank for all those years has turned the internal hoses into some kind of sticky mush. No doubt the inline filter will not be worth trusting.


I located a complete replacement kit from the USA, with pump, filter, strainer, rubber pump mounting, hoses and clips. I have ordered it today and hope it will make its way past any blockades. Holding breath..


Progress to 2 April 2020.