Starter Motor Gremlin...

[Oftenlost]

I have a problem.... My Sommer has an electrical Gremlin lurking. I can't get my head around it and thought I would throw it out for ideas.
My ignition switch is a two position, sprung car type. The first position fires up the lights and energises the fuel solenoid. The second sprung position engages the starter motor solenoid.

What happens. The first position gets the idiot lights up but when I go to the second I get a click, no starter motor engage and the idiot lights go out. If I switch the ignition off and back on the lights stay off. This is completely random. Might do it from cold or when i have just ridden hours and stopped for fuel.

I have found that if I undo the neutral strap on the battery and refit it, it clears the problem and the motor will now start normally? Very frustrating.

I have pulled the starter solenoid wire and soak tested the ignition for ages without recreating the fault. I get a solid 12V+ with no locking up. This convinced me it had to be a motor problem. I dropped it into a local workshop and they stripped and cleaned it. They also replaced the solenoid unit. So a "New" motor. Damn if it didn't glitch again!!!

My current plan is to run a new wire from the ignition switch direct to the starter. I am not sure how the builder routed this cable as it goes from the switch into the headlight. Changes colour into the loom and winds up at the motor via the harness. There may be other joints I have not spotted yet. The tank is off and I am exploring... A wiring diagram would have been nice Jochen.

So, any ideas. The reset by popping off the battery lead makes it look like a stuck relay/solenoid. Other than the motor I don't believe there are any others. I am beginning to think the fuel solenoid might be the cause but how and why?

Any ideas, cheers in advance

Ian

P.S Only 35 days to the LeMans 24 hour bike race and I intend to be the only diesel in the village.....again!

[the grinch]

hi
Sounds like a bad conection will be either where the ignition and the starter get its feed or where the earths are more likley to be on Pos side if you are running chassis earth unless its the main earth. It may be even the battery conection. If the lights go out everything is going. If it was the starter it would maybe just dim the lights. To loose everything with a click to me suggest a conection problem. I would go for the main feed earth or even battery connectors especialy it the cable is screwed into rather than crimped to the conection. Check for rust and dirt between everything.
good luck.
Alex

[Diesel Dave]

Where does the click sound come from?

If it’s not the main solenoid on the starter motor then you must have an additional relay on the feeder circuit and that’s the click you hear.

Do check the heavy live cable for corrosion or a loose crimp as this can cause a big enough voltage drop to prevent the starter motor activating but the solenoid will work. Can you put a moving coil voltmeter into circuit and see if the voltage drops when you have a starter fail? If it shows a voltage drop down to 10v but the motor doesn’t turn over then you know the feeder circuit is fine and your just going to be looking at the heavy cabling - especially the earthing route.

If you look at the specs for the motor I’m betting it will specify something like a 44AH battery and 70 amp cabling for the starter and almost every bike I’ve looked at has less than half that specification. Ideally use marine cable as well as this is tinned for corrosion protection (also easy to solder the connectors on as the crimping tool for 70 amp cable is HUGE and expensive).

Best of luck

[GuzziJohnO]

This sounds similar to an intermittent problem my diesel mazda had, that was finally determined to be caused by worn contacts inside the ignition switch. The "start position" solenoid current surge seemed to burn/arc the worn contacts, creating a dead spot. Sometimes wiggling the key would complete the circuit, and the starter would engage. It gradually got worse. I bought a used switch from a gas mazda, disassembled it to learn how to possibly fix the faulty diesel switch, and was able to recombine them both into one that worked. When the faulty one was disassembled, the problem was obvious - the brass contact plates where burned, pitted and eroded where they made initial contact as the key was rotated, requiring further rotation as time went on to attain adequate electrical contact to close the relay. Eventually the contacts ran out of material to make solid electrical contact. Diesel starter solenoids, in general, seem to create greater back-current pulses than their gasoline cousins, which may be why this problem is less likely to be found there.
Would it be convenient to try wiring in another switch, in place of the "current" one, as a test?
Cheers,
John

[Oftenlost]

Thanks for the input. I have been away or the weather has been rubbish (No Garage) so just managed to dive in for a closer look. The Live cable to the motor and the Earth strap are both quite heavy duty about 7/8mm with well crimped terminals. they look sound. I have copper slipped their bolt points in the past so they are clean connections. No joy there.
I have pulled all connector plugs and they are clean and waterproof.
So just to try something I have run a new cable from the ignition switch to the solenoid. Suck it and see.
Do you think the ignition switch might play up under load. When I stuck my volt meter on the solenoid end and switched on I am not really loading it so it might give me a false positive every time?
If the new wire doesn't clear up the problem I will hot wire in a temporary ignition button and see what that does.
I will just have to work my way through it a bit at a time. Most frustrating and way to random for my liking!

Cheers, Ian

[Diesel Dave]

Ian, am I correct in thinking that your bike lives outside and the key switch is mounted flat on top of the bars?

I’m thinking such a setup would be prone to water ingress and I doubt the switch was ever designed to be used in this way. Even if the switch is rated for outdoor use it would only apply if mounted vertically.

Can the switch be dismantled or is it a sealed for life unit?

[Oftenlost]

Hi Dave.

My bike lives under its cover. But yes the ignition switch is pretty much inviting water in as it is fairly flat and open. I remember somebody at a rally saying he had an ignition switch problem due to water ingress.... not my Gremlin I think his lights shorted.

I will have to pop out and size the switch up to see if it will come apart. It is probably a one shot construction. I hate it when those micro springs and ball bearings ping across the room!

More food for thought....

Cheers.

[gilburton]

Sounds like a standard universal car switch has been used. There are plenty on ebay. I myself used such a switch on my MZ conversion.
They are not waterproof. Probably ok in a side panel or under the tank?
Surely all you have to try is bypassing the switch eg take off lead 4(starter) and touch it to 3 to test the starter? If it does the same thing it's not the switch. This is how they used to "hotwire" old cars lol

This sounds like a classic bad connection fault. You could also try disconnecting the battery and then using a known good battery and jump leads bypass the bike battery. Put the earth jump lead straight on the engine and the positive to the disconnected positive battery lead(being careful not to let it touch the frame)
Here is an example of the switch with connections
https://www.12voltplanet.co.uk/4-positi ... gILTfD_BwE

[Oftenlost]

Thanks for the input. My problem isn't that it doesn't work, It is that it randomly doesn't work and locks up all the electrics.

The ignition switch is a standard German Herth and Buss sealed unit. I have been chatting to Jochen the builder and he has said these switches do not fail. Having built over 500 of these diesels I am inclined to give him the benefit of the doubt.

I am still waiting for him to come back with any ideas. In the meantime I have it all back together and will try it with the temporary Solenoid wire in place to see if it will play up or not, It is impossible to predict when. Most annoying.

Ian

[gilburton]

Just for info copper based grease is not conductive so it's best to remove any in that area.

[Oftenlost]

I followed the advice and cleaned all the contacts around the starter motor and battery that I could find. I reseated using those serrated washers to make sure they were tight with lots of metal on metal bite.
Last Thursday I took a ride over to France for the Le Mans 24Hr bike race. Pleased to say my Gremlin did not show..... I can't say it is solved but fingers crossed for now. Everything ran well and it was great opening to my bike season. I didn't get wet!

Cheers for the advice, Ian