Sticky starter - new solenoid needed?

[Geoffrey Gould]

Hi all, as regards the instrument dimming mine has always done this when the brakes are applied, over time new battery,alternator,ign. switch etc. clean earths and the multi-pin connectors under the battery which always show some corrosion no matter what is done, usually packed with Vaseline. Still does it without making a new harness with some better quality wire then I live with it, ( cured by cheating - replaced bulbs with leds.)
Still gain 2 bar of oil pressure when the heater blower is put on and the headlamps also.
I keep meaning to find out what the wire is made of, particularly as it corrodes black, had the same problem with bus wiring that was plated steel because it was cheaper than copper, harness as thick as your arm and only had 1 colour BLACK, that was fun trouble shooting.
G.

[electrokid]

That was the difficulty in diagnosing the problem - when the starter is working correctly you're trying to measure a brief transient voltage. So I had to wait until it reoccurred to be able to measure anything meaningful.

Yes that's true. As I was writing that I wondered how I would check it and decided I would use the storage scope hooked up to a printer. That would mean taking the scope off the test equipment stack, finding the printer and probably trying to find a new ribbon and some tractor-fed paper as well - that's far too much to bother with.

And of course since my "it starts in half a second" boast the weather has turned a bit cooler and it's now taking longer. I did wonder if the glow plugs could do with changing so I bought some... that was 3 years ago and they're still not fitted.

[Mickey taker]

Mat, what size fuse have you used in the feed from the battery to the relay ?

[mat_fenwick]

I didn't use a fuse Before I get shot down for wiring like this, can I point out that I have simply attached a relay to the injector pump (above the starter motor), and run the feed with a couple of inches from the main starter motor terminal. It's neat in terms of very little extra cable required, but probably not an ideal long term location for a relay (heat/vibration etc). The main starter cable is not fused, and neither is the original trigger wire from the ignition switch.

That may be because the solenoid requires a time delay fuse rather than a standard blade fuse, I don't know. If I was running an extra wire direct from the battery I would fuse it just in case it shorted out anywhere. I would guesstimate a 15 Amp fuse would be sufficient from the thickness of the original wiring, but you may need a higher rating due to the initial surge of current...suck it and see!

[electrokid]

I don't see any problems with that - not a lot of inductance in the solenoid so initial surge will be very short - milliseconds - a standard fuse should handle that ok and I agree that 15 amp should cover just fine.

Heat / vibration will only be a problem if the relay physically falls apart - worst case scenario is contacts coming together and staying there which would provide an 'interesting' few minutes trying to find the spanner to disconnect the battery

[mat_fenwick]

If that happened I'd simply yank the connections from the relay, but it does remind me of an amusing tale.

I was driving to work one morning (not in a BX) when the engine started cutting out intermittently. I cut to a layby and turned it off, popped the bonnet up and started looking for any loose connections around the coil. To my great surprise, the engine suddenly started turning over as I was leaning over it (with a dangling tie ). I ran round to the driver's seat to see WTF was going on, to see smoke leaking out from around the ignition switch. Correctly deducing that this was not 'a good thing', I frantically disconnected the battery.

Upon investigation the ignition switch was a molten mess, so a quick bypass job did the trick to get me going. It was (or would have been!) my first day in a new job, and fortunately they agreed to my rather cheeky late request for the day off so I could trawl scrapyards in search of a replacement.

[Mickey taker]

I think the funniest part of that story was the thought of you in a tie Mat !!!

[Mickey taker]

To save me looking it up can someone post up which numbered terminal go's to where on the relay .
I know its earth ,feed from the battery (fused ), wire from relay to male spade on solonoid and female spade wire that went to the solonoid to relay

[mat_fenwick]

I think the funniest part of that story was the thought of you in a tie Mat !!!

Here is proof that it does happen occasionally!

Relay terminals - most have them printed on the case but if not then connect terminal 30 to the battery, and 87 (usually the one opposite it) to the starter solenoid terminal. The other two; connect one to earth and the other to the old solenoid feed.