Starting Conundrum

[Steves_TR6]

ON electrical problems I always work on the basis that

1) Poor earthing is implicated in nearly all electrical faults

2) Next high contact resistance in old (tarnished) terminals/connectors and in old switches

 

So personally I would clean all terminals, earth connections etc and see if that fixes it. IF not next I .would see what happens with ign on and operating starter solenoid with a wire from/to battery (ie not using switch) Or you could just press the rubber end of solenoid in to operate it I suppose.

If fault remains then you have eliminated any possibilities on the starter circuitry and can look elsewhere and for slightly more odd solutions.

 

MIke

As Mike says, i'd vote for a corroded connection.

Could be on the 12v or the 0v side.

Dvm shows 12v but probably with no ability to carry current.

 

One other thing, with the luminition ( i have it on my 6) there is a separate 12v feed in addition to the 12v on the coil.

Another place to check for corrosion?

 

Steve

[RogerH]

Wow!, I thought this was going to a be straightforward conundrum not a convoluted conundrum

 

This is what was happening (it appears to have sorted it self now) -

The engine runs very well with the Ig key at the first click.

The engine turns over very well with the key at the second click.

However in this position the engine did not fire up (but there was 12V at the coil using a DVM)

Bring key back to first click and the engine fires up. (the momentum of the starting allowing this).

 

With a wire running from the battery +12V to the coil it starts perfecty/normally.

 

This suggests the 12V line is not right - but it runs well when not in the starting phase.

This also suggest to me that the earth side is OK/adequate.

 

As mentioned the dvm is a wicked tool of the devil and can lead you up the Swanny without a paddle.

 

It could be a 12v or 0v wire that has a poor connection and dropping too many volts when the starter is drawing current.

All the white wires and connectors will be replaced.

 

It is a Hi-Torque starter Using a separate solenoid.

 

Roger

Edited December 5, 2016 by RogerH

[ChrisR-4A]

Roger, have the connections on the back of the Ammeter been cleaned & tightened lately? Also check terminals on starter solenoid and control box for corrosion of wire.

Chris

[Steves_TR6]

Its a mystery, wrapped in an enigma, disguised as a puzzle.

 

Suggest you adjust your antenna Roger, the answer's out there!

 

Steve

[RogerH]

Hi Chris,

if it is a grubby connector (and after 18 years or so they happen) it could be almost anywhere. I'll start at the white wires and move on from there.

 

Hi Steve,

what has a German coding/decoding machine got to do with it.

 

 

Roger

[Lebro]

Roger.

Have you got an Avo meter or similar analogue volt meter?

If so, test the +12V terminal on coil as you either crank the engine(spark plug caps off to prevent starting), or turn over slowly by hand.

I would expect to see the 12V stay at 12 or close to. If it dips considerably when the (equivalent) of points close, then there is high resistance somewhere in the white wires. if not, then that is not where the problem lies.

 

Bob.

[RogerH]

Hi Bob,

I have a 1949 AVO from the Navy that would do the trick.

 

I shall give that a go.

 

Roger

[Charlie D]

Hello All,

I had a similar problem about 20 years ago on a Herald based Kit Car. The solution is NOT the same for you, but I mention it in case someone in the future reads this thread with a similar problem, and my solution may help.

My car NEVER started when it was cranking, it simply spluttered into life when the IG switch sprung back to the “Ignition On” position. After about a year of this happening I was bored one day and started to investigate.

It turned out that my IG switch has TWO terminals that went live when the IG was switched on.

But…
One of the terminals was meant for the radio, and when the car was cranking, this terminal switched off. (I think to stop loads of crackling from the radio as the starter motor spun.)

I had, of course, wired the coil through this terminal!

By putting it onto the right terminal the problem ceased.

Hope that may be of help to someone.

Charlie.

[RogerH]

Hi Charlie,

that would certainly cause a problem. As you mention mine problem is different - but annoying all the same.

 

Roger

[Peter Cobbold]

Roger,

High Torque starter.....

http://www.tr-register.co.uk/forums/index.php?/topic/58229-hitorque-starter-motor-hmm-no-thanks/?hl=%20starter%20%20torque

Could it be shorting internally dropping the voltage more than normal ?

Peter

Edited December 5, 2016 by Peter Cobbold

[RogerH]

Hi Pete,

I think that the SM is OK. No funny sounds and things working as usual.

 

I've just ordered new white wire and connectors so will replace this first and see what happens.

 

Roger

[Guest ntc]

Roger

Out of interest do you have any other electrical add on's fitted?

[RogerH]

Hi Neil,

I see you are into sleuthing mode.

 

I have a home made OD logic box connected to one of the white wires from the Ig switch.

I can't see this is the problem as it has been connected for apprx two years now with out fault.

 

Leccy Rad fan - but again it has been there a long time with no issue.

 

Roger

[DaveR]

Unlikely to be the starter solenoid or the earth to the engine or battery terminals if the starter is turning over at the normal speed. Its a real load test on the system.

 

One thought-

 

If you have an electronic ignition where does that get its supply from. Check both neg and pos.

 

Thanks,

Dave

[RogerH]

Will do Dave.

 

Roger

[Guest ntc]

Roger

Just trying to help fella disconnect every earth from those and the radio and reconnect one by one testing in between.Ask me how I know

[RogerH]

Hi Neil,

help much appreciated.

Being an intermittent fault it may be difficult finding the one fault. But I will be working my way through all the suggestions.

 

Keep them coming.

 

Roger

[graeme]

Hi Roger,

 

My money is on the ign switch, especially as it is an intermittent fault!

 

Cheers

 

Graeme

[Bodiam]

Hi, Roger,

 

In a previous incarnation working with Fords, this problem was very common at one time on the early 1970's models and I recall that the ignition switch was the culprit in every case I came across.

 

I see you have already tried a replacement switch, but it wouldn't be the first time we've been misled by a faulty replacement!

 

Good luck with your search.

 

Best wishes,

 

John

[RogerH]

Hi John/Graeme,

the thought of a duff new switch has not passed me by.

Both the old and new check out perfectly. I can recheck them using a beefier set up.

 

Roger

[Waldi]

Roger,

Did you check the ground wire inside the distributor, Moss item 153.645?

Waldi

[RogerH]

Hi Waldi,

no I haven't. Would that cause a problem in the 'starting phase' only.

The engine runs perfectly having started.

 

Roger

[DaveR]

Roger

Looking at the facts -

Unlikely to be the starter solenoid or the earth to the engine or battery terminals if the starter is turning over at the normal speed.

If you have 10 to 12 volts (Ignition supply) at the coil when it won't start then its unlikely to be the ignition switch.

More likely to - Coil, CB connection, including the lead, on the coil, Electronic ignition module, All the connections around the electronic ignition module i.e. Negative to earth, Positive 12 volt ignition supply, CB connection from coil.

This all supposes the TR wiring is standard apart from the electronic ignition.

Just my thoughts.

Dave

[Waldi]

Roger,

My thinking is that during starting, due to the high starter motor current, the potential (voltage) on the engineblock could be higher.

Good luck.

Waldi

[Lebro]

Hi Waldi,

no I haven't. Would that cause a problem in the 'starting phase' only.

The engine runs perfectly having started.

 

Roger

Only if The ground path was marginal when running. When cranking the volts will drop a fair bit, which might be the last straw for your electronic ignition which is relying on a good ground connection for it's own power, & to connect your coil to.

 

Bob.