Hello. I have just acquired a 1984, 24,000 mile K100. It broke down on the previous owner, since when it has been standing for a few years. The problem seems to be at the injectors, which aren't getting any current. The injector relay opens and closes ok, but there doesn't seem to be any current getting to pins 30 and the two marked 87. In fact, when I tried testing the resistance across the wires to pins 30 and the two marked 87, with the relay removed, one of the 87s showed no resistance, but the other shot up - far higher than just touching the two probes together. This stopped happening when I removed the temp sensing switch unit, also when I removed fuse no. 6. What can it all mean? My last experience with motorcycles was a 1976 Triumph Tiger, so the BMW is all too weird and sophisticated for me. My Haynes manual simply says I should replace anything suspect - without, as usual, giving any hint of possible symptoms - but the cost of some of the components, like the fuel injection control unit, and even the temp sensor switch, make this a bit prohibitive.

I've checked the water temperature sensor, and it seems ok - the resistance is the same on both pins, and high but not short-out high.

Any help, suggestions, or names of places that sell cheap or second-hand parts gratefully received.

Thanks.

roddaw wrote:Hello. I have just acquired a 1984, 24,000 mile K100. It broke down on the previous owner, since when it has been standing for a few years. The problem seems to be at the injectors, which aren't getting any current. The injector relay opens and closes ok, but there doesn't seem to be any current getting to pins 30 and the two marked 87. In fact, when I tried testing the resistance across the wires to pins 30 and the two marked 87, with the relay removed, one of the 87s showed no resistance, but the other shot up - far higher than just touching the two probes together. This stopped happening when I removed the temp sensing switch unit, also when I removed fuse no. 6. What can it all mean? My last experience with motorcycles was a 1976 Triumph Tiger, so the BMW is all too weird and sophisticated for me. My Haynes manual simply says I should replace anything suspect - without, as usual, giving any hint of possible symptoms - but the cost of some of the components, like the fuel injection control unit, and even the temp sensor switch, make this a bit prohibitive.

I've checked the water temperature sensor, and it seems ok - the resistance is the same on both pins, and high but not short-out high.

Any help, suggestions, or names of places that sell cheap or second-hand parts gratefully received.

Thanks.

Remove tank, clean and tight every contact. Check the contacts on the top of injectors. Check the big connector in ECU. When shure everything is clean and tight, you can start to search

Pin 30 is a direct unswitched connection to the + of the battery. There are often 2 or 3 red wires direct onto the + terminal check to make sure there aren't any red wires hanging around loose there, possibly broken away from the connector that attaches to the battery, and as Nino said clean every electrical connection you can find. These old Ks are very prone to bad connections.
If you put a post in the introduction section you will be able to get access to some very good material on troubleshooting that our esteemed leader Bert (Crazy Frog) has put together.

The way the injectors work on these bikes is that there is constant 12 Volts on them and the injection pulse frequency/length is determined by the ECU, which switches the ground on the injectors. Be extremely careful with just starting to measure, always detach the connectors of the main ECU and the injection ECU or you might create more problems than you're trying to solve. Alternatively have a good look at the wiring diagram to make sure what goes where. In all fairness the system isn't too difficult as it was used on cars for quite some time as well.

Had a look at the diagram/relay contacts. Relay is powered between 85 and 86. 30 is input and 87/87a is switched contacts.

30 is supposed to come directly from the battery so you should be able to measure 12V on that. 87/87a go to fuse No 6 (fuel pump) and the other to the injectors/fuel injection ECU etc.

Have a look HERE for some info on the relays and have a good look in Bert's diagrams at the 'Portal'.

Hello and welcome, I have just been through the process of checking the functioning of the injectors on my bike and I received plenty of helpful advice from old K hands on the forum. You may find it useful to read the following thread:
http://k100rt.aforumfree.com/t3598-troubleshooting-guidance-requested
And I'm sure further relevant info will be unearthed by using the 'search' function as well as from members responding to your posts.

Cheers, Chris

Thanks for the suggestions everyone. I've already had the tank off and cleaned the connectors as much as possible, but will soon try the Deoxit recommended on the Forum.

The connection between the battery positive and the 30 pin at the injector relay seems good, and when I connect pin 30 directly to the two 87 pins, there's a reading at the injector connectors. With the relay back in, however, and the contact closed, the reading is much lower. Strangely, today for the first time, when I turned the key I heard relays click but no instrument lights came on for a while. Then did suddenly.

Usually, all the electrics work except the hooter. And you can hear the hooter relay click when you press the button. I've replaced the fuel pump - the old one had merged with its mounting rubber after standing in old petrol too long and it makes all the right noises, and pressirizes the system well enough to burst the old pipe. I've also checked the injectors (they click open and closed and I've poured injector cleaner through them), re-made earths, and sprayed everything with WD40.

I've bought new spark plugs, and get a good spark.

Apart from re-cleaning connectors, and now that I have a source of sensibly priced relays (Thanks ReneZ) is the most sensible option just to replace the fuel injector relay?

TRhanks again for your help and time.

Have a look, I think some of the relays are the same, maybe you can switch them and test again?
Alternatively try to bridge the contacts (30 to 87/87a) and see if it runs OK.

You seem to have a minimal knowledge in electricity and your best friend will be this web page (unless you are colorblind).

CF

Thanks for all the suggestions, and the wiring diagrams. The problem proved to be dirty connections, specifically the connector under the tank. I thought I'd aready cleaned them, but eventually resorted to scraping with a jeweller's screwdriver, and water paper wrapped around a small stick, then squeezing the connectors slightly, and even when I was sure I had a good connection it proved intermittent. But it's all ok now. The engine started so eagerly, it took me by surprise. Sadly though, there's white smoke pouring out of the exhaust. It's strange, because the engine sounds good, and revs willingly, but the amount of smoke is incredible. The previous owner swears there was none when he gave up on the bike. I've let it run long enough to burn off any oil that might have got past the rings while the bike was on its side stand, and the smoke just got worse. Should I just junk the thing?

When I got my K bike it sat for a few weeks while I was getting the sidecar ready. It was on its sidestand. When I eventually got it going it blew smoke like a bad 70's metal concert. I mean REALLY blew smoke. It did that for about 35 km, then cleared. That was 5 years ago. Still running strong and only blows a bit of smoke on start up when its been sitting for a week or so. Give it a bit of time and take it for a decent ride...on a backroad...so you don't get chased by the fire brigade. Or deranged ACDC fans.

roddaw wrote:Thanks for all the suggestions, and the wiring diagrams. The problem proved to be dirty connections, specifically the connector under the tank. I thought I'd aready cleaned them, but eventually resorted to scraping with a jeweller's screwdriver, and water paper wrapped around a small stick, then squeezing the connectors slightly, and even when I was sure I had a good connection it proved intermittent. But it's all ok now. The engine started so eagerly, it took me by surprise. Sadly though, there's white smoke pouring out of the exhaust. It's strange, because the engine sounds good, and revs willingly, but the amount of smoke is incredible. The previous owner swears there was none when he gave up on the bike. I've let it run long enough to burn off any oil that might have got past the rings while the bike was on its side stand, and the smoke just got worse. Should I just junk the thing?

White smoke is moisture, not oil (if you are lucky). If not, could be a problem with cilinder head gasket. Check the coolant level.

The oil will sometimes get past the rings and exhaust valve and lots of it gets into the exhaust system and so takes ages to burn out.
Take it for a ride and give it a good while to clear then if it is still bad take it futher.