Series 3 Electrical/Ignition Problem

Technical advice Q&A

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SESH
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#1 Series 3 Electrical/Ignition Problem

Post by SESH » Sun Jul 05, 2015 10:08 pm

I have a 1973 Series 3 OTS. About 4 weeks ago I took the car out for about a 20 mile run. On the way home the car started to cut out and misfire then backfire and re-start again. I managed to get it home with this intermittent problem. My local classic garage took the car away on a trailer and later test drove it and they had the same issues. The Distributor, Amplifier and Ballast resistor were removed and sent back to SNG Barratt for testing as they had been replaced a year earlier. These came back as no fault found. The earth straps and connections were checked and found ok. However, they tell me that there is no charge from the alternator, but what is strange is that the ignition light was not coming on and the electrical charge/discharge was showing satisfactory. But now when the key is removed from the ignition the red ignition light is staying on! The alternator and voltage regulator have now been removed and sent away for testing. Any ideas or has anyone seen this before! Thanks. Mike
1973 Series 3 OTS Signal Red

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42south
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#2

Post by 42south » Mon Jul 06, 2015 3:08 am

Hi
Those faults sound like ignition amplifier, is it still the original opus amp.
I'm sure SNG would know this, but normally the amp only faults when hot.
Worth a chat with SNG to see how they tested it.
Mark Brown
1971 S3 Etype
Son: when I grow up, I want to be a pilot
Dad: You’ll have to choose.

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mgcjag
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#3

Post by mgcjag » Mon Jul 06, 2015 8:01 am

Hi Mike....a friend of mine had a very similar problem in his series 3...had to be trailered home from France....changed all the ignition etc.......ended up that one of the fuel pumps was cutting out and then cutting back in again.....the car will run with one but as you speed up it starts to strugle and cuts out..even the rev counter was flickering which made it look like ignition...then starts again.... worth a check.......Also worth looking at the ignition switch...if your key is out and the ign light on you could have a faulty switch, if faulty this could also cause the initial problams ...... Steve
Steve
1969 S2 2+2 & Building a C type replica

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Topic author
SESH
Posts: 381
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Location: Southend-on-Sea, Essex
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#4

Post by SESH » Mon Jul 06, 2015 3:27 pm

Not sure if we have the problem sorted. However the Alternator overhaul specialist says that the rectifier in the alternator has failed. In the opinion of the mechanic the engine was drawing on the power from the battery and as the power reduced in the battery the engine started to misfire due to low electrical energy. The Alternator wasn't charging the battery. The SNG amplifier is the new type and only one year old (500 miles), they tested it and said no fault found. The alternator is coming back Wednesday so I will report if that has cured the problem. I have to say my first inclination was the amplifier had failed again when hot. The fuel pump isn't the normal SU type, it's been upgraded to a new one and the misfire/loss of power really felt like ignition. Mike
1973 Series 3 OTS Signal Red

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SESH
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#5

Post by SESH » Mon Jul 13, 2015 7:27 pm

Problem seems to have been sorted. Alternator overhauled and re-furbished plus new rectifiers. Car now running as it should!
Mike
1973 Series 3 OTS Signal Red

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