Triumph t90 electrics

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Triumph t90 electrics

Postby Neilgd » Mon Mar 08, 2010 5:22 pm

Having problems with my 1965 t90 (recently bought). Has been converted to 12volts and has Boyer ign
Investigating bad running developing into difficult starting and serious backfiring through exhaust I discovered battery all but dry !
Further investigation uncovered loose wire on rectifier I blieve theOne to zener Diode which would explain battery all but boiled.
Is there any way of testing to see if diode has failed?
I now have somehow recovered battery which has 12.8 volts, 12.4 with lights on.
I have spark at plugs but engine refuses to fire.
Timing out would explain. Checked stator and that appears to be ok - no reason why it shouldn't have been.
Any ideas.
Thanks
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Re: Triumph t90 electrics

Postby Bill » Mon Mar 08, 2010 6:42 pm

Only real way of testing them is to fit them and try them out. You should only be getting 14v max at the battery terminals with the engine running. If the zener is FUBAR, you'll blow bulbs, boil battery's (as you've found out) and can do damage to other wiring. The huge power in the circuits due to a faulty/lose zener may well have fried the Boyer box.. I've no idea how to test those, apart from to see if you're getting a spark.
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Re: Triumph t90 electrics

Postby Tman » Mon Mar 08, 2010 9:53 pm

Is there any way of testing to see if diode has failed?

Use a dvm or other meter to check if the Zener has gone short-circuit. I rather doubt that it has, as the sparks are present and the lights still work. If it's gone open-circuit, it wouldn't really affect what you're doing as a T90 alt really doesn't generate that much power in everyday use (or your present use) to make it an essential component.

I now have somehow recovered battery which has 12.8 volts, 12.4 with lights on.
I have spark at plugs but engine refuses to fire.
Timing out would explain. Checked stator and that appears to be ok - no reason why it shouldn't have been.
Any ideas.

Boyers don't like extreme operating voltages at either end of the scale. Low makes them misbehave and advance, and high fries 'em. There are several web-sites which have good Boyer diagnoses listed ("British Only", maybe?) which would be a start, but I believe Boyer also test the Black Boxes FOC (or used to).
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Re: Triumph t90 electrics

Postby MOUSE » Tue Mar 09, 2010 6:08 am

worm could backfire be air leak related and not electics, just a thought?
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Re: Triumph t90 electrics

Postby dig » Tue Mar 09, 2010 7:39 am

Hot air leak???? Mouse worm
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Re: Triumph t90 electrics

Postby Neilgd » Tue Mar 09, 2010 9:35 am

My limited knowledge of electrics means that I may well be talking from another part of my anatomy other than my mouth !
The fact that I get a spark means that, in theory, the Boyer box is working as I'm told that you either totally fry them or they work. A wild voltage whilst the battery was boiling would explain the rough running/backiring.
I'll try to get through to the Boyer technicnal help line this pm. You're right they do have a return to them testing service.
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Re: Triumph t90 electrics

Postby Graham B » Tue Mar 09, 2010 10:19 am

It may well be another bad connection somewhere or a component not working properly.

Try this ...

Charge up your battery. Check your ignition timing statically to make sure it's in the right ballpark. Disconnect and insulate the alternator wires at the rectifier. Disconnect and insulate the wire that feeds power to the Boyer. Run a wire directly from the battery to the Boyer - make sure power goes nowhere else. If it runs ok for this test then you know the Boyer. coils and timing are ok and the fault is either an alternator shorting to earth, broken rectifier, zener or intermittent connection somewhere.

A digital multimeter will help greatly in tracking down electrical problems - £10 ish from maplins
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Re: Triumph t90 electrics

Postby Neilgd » Thu Mar 18, 2010 2:41 pm

OK so new Boyer box now fitted and new battery. After a lot of kicking, cursing and swearing I did get it to start albeit running a bit rough ( I put that down to me playing around at the stator and it not being spot on)
That was last night . This morning nothing.
Checking to see if I have spark at plugs I hear the tell tale "click" but see nothing. Must be very weak. Changed plugs to no avail.
Any ideas anybody.
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Re: Triumph t90 electrics

Postby Neilgd » Thu Mar 18, 2010 4:03 pm

Correction from last posting. There is a spark but it's inside,if you understand what I mean - not across the gap. Never seen that before. Gap appears ok.
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Re: Triumph t90 electrics

Postby Graham B » Thu Mar 18, 2010 4:22 pm

New plugs would seem like a good idea

I think you'd make better progress if you approached it methodically. Isolate the alternator and battery from the system, wire the battery direct to the boyer, check with a multimeter that you're getting 12V to the boyer. Inspect and check all connections, preferably with the resistance setting of the multimeter.

Be methodical - it'll save heaps of time in the long run
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