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alternator problems gt6


lincolnsix
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After a 65/70 mph run I got stuck in a 20 minute jam into town, the electric fan was on all the time. The idle started dropping from it's usual 950 rpm until I had to use the throttle to keep it running.

 

I was only one mile from home when the jam cleared and was running o.k. (30 mph limit) when suddenly the engine died, after 3 or 4 goes it started, revved freely and I got home. I switched off and then switched back on which it did first time back to 950 idle. -- the fan not running.

 

I assume that the alternator is on the way out,  but what worries me is what caused the engine to suddenly die?

 

               Any ideas?       Thanks in advance,           John

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What makes you think it's the alternator? Any more clues? The red light may come on due to low idle but not necessarily an electrical fault.

It could be a fuel fault; overheating in the jam could have caused a vapour lock, the fan runs due to the heat, but the engine dies due to lack of fuel. It could be running rich - the carbs flood, the engine dies but once the excess fuel evaporates it runs normally again - been there! It may also have been something as simple as dirt in the fuel line, stirred up by the long run. The fan may just be a red herring.

Do you have the mechanical fan fitted or can you refit it? I'd try a few runs without the electric fan just to make sure there isn't a combination of issues, and clean out the fuel system just in case, refilling with good fresh petrol.

Nice to see a Triumph getting good usage this time of year!

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I  would echo Colin n this  too hot  too rich , not enough  under bonnet air flow  worse still  if you have pancake filters sucking in loads of hot air.

 

hot engine lost power due too hot/rich and fan load makes the alternator drag the idle down till it died .

 

 refit  engine driven fan and lean it off.   

 

Pete

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Colin and Pete beat me to it .... what they said!

 

If you were able to spin the engine on the starter, start up and run , the battery has remained charged and then later start up normally then alternator sounds ok.

Only ever had one alternator fail .It was working then it wasn't.The battery went down quickly.As it did so, The ignition warning light glowed even when the ignition was switched off - and key removed- which I thought was intriguing ( but inconvenient more than anything at the time) .Presumably caused by the diodes failing quickly shorting out and draining it flat as a battery can get.

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Thanks all for your replies,  I don't have a mechanical fan to try,  the air filters are standard,  I have a glass fuel filter fitted before the standard fuel pump which is clean.   I have approx 1/2 tank of BP Ultimate that's been in about 3 weeks.

 

It looks like it was a fuel issue,  thinking back, when it did fire up there was quite a strong petrol smell.

 

                                      John

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My friend had exactly the same problem with his GT6. Despite lagging the fuel pipe the problem persisted but to a lesser degree. It was finally traced to fuel boiling in the pump. A dedicated fan switched with the main fan was mounted on the side valence directing air to the pump. This has cured the problem.

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It is a mk 3 with the yellow compensators on the carbs.   The carbs have been rebuilt but I left the compensators alone.

 

I don't have the side valences fitted only the one in front of the radiator.

 

                                                                      John

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John, take them off , screw the small nut to fully close the plastic plunger onto its seat

 

if the thing is open at normal , or sucking air as the 2 o ring seals are degraded you artificially weaken

the idle mixture and it get set on the rich side to get a even idle, the result is its too rich with the throttles open

 

there are careful tests to set these to the book, but for most having them open when they should be closed is the main culprit, so block them off or set them shut at normal temperature is the best diy solution then adjust the mixture

with your CDSE you need the tool with a hex key to adjust the needle height

 

they are there to lean the mixture by bleeding air around the throttle plates when very hot, certainly would aid your hot idle but if they are as most wear into an open setting , your whole mixture is wrong right up the revs range

 

if that makes any sense

 

pete

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