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tom kilner

ignition circuit replacement

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On my 911 2.2 engine I have a weak and intermittent spark  - worse in damp weather.20181125_110921.thumb.jpg.6a115b624fb527d20c5d974e3a63282d.jpg

Coil with 4 wires (ballasted?) (That loose yellow with the blue spade comes off the starter) Hall effect distributor, ignition amplifier on the wheel arch.20181125_110929.thumb.jpg.a103bd31d3348e29cc9cf5d8ae1735b0.jpg

The connections on the starter motor are wobbly, the test of the wiring needs ripping out anyway.20181125_111055.thumb.jpg.1826b7cc6125671cd47fc9332a89efe2.jpg

Is there a simple test to identify the problem?  the spark from the coil lead is weak on cranking.

Should I just fit a replacement distributor with simpler wiring - and if so what's best - simple and inexpensive if possible.

Edited by tom kilner
accuracy

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Quote

 

Hi Tom ,could not quite make it out from photo but is there a wire running from a small terminal on the starter motor

to the pos.+ on the coil, that is to compensate for voltage drop during cranking , also it looked like some liquid on top of the coil

which is not a help 

cheers   Ian

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Hi Tom, agree with Ian, + 

The white wire on the left with the blue then the red connector looks like it could have been spliced at some point. May have been an original blue end then a red one added to a little bit of cable.  If it has I would replace. 

Also the white cable on the top left of the coil looks like the cable has got too hot at some point as cable has a brown patch.  Could of course just be a bit of muck, but worth a look.

The white/black cable that sticks out from the top right of the coil has a very sharp 90 deg turn in it, looks like it's hanging on by just a few strands, worth looking at.  The same is happining with a brown? wire towards the bottom of the coil photo.

Cheers Roland

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http://www.mossmotoring.com/wp-content/uploads/2012/07/Lucas-Test-Card-6.pdf

Here's a flow chart for diagnostics

I'd Start by re-making the connections to the coil . That's probably the culprit. The Lucas constant energy  system is pretty reliable ( despite what people say about the AB14).

Sometimes the Rev limiter can be a problem (black box with a 3 wire multi-plug usually a bit lower down the inner wing). You can just unplug it to remove it from the equation, plug it back in when you are running ok.

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Tom, forgive me if I am teaching my granny to suck eggs:

A couple of things need to be determined first:

Your car has obviously had an engine and ignition system grafted in from elsewhere. Check the type of coil you have fitted. A ballasted voltage coil in a non-ballast system (and vice versa) can cause problems.

A missing wire to the coil from the starter suggests its not a ballasted system and may have a 12v coil. I'm not sure what ignition system you have fitted - it was usually lumenition on series 1's, but your picture suggest your car 503 has a Lucas AB14 ignition amplifier? (which was introduced with the eclat excel; these can break down with age and be a proper pain in the ass...)

I can't recall off the top of my head if the AB14 ignition system was balasted - I have a feeling it was not and used a 12v coil. If this is the case - is your coil receiving 12v from the ignition switch rather than the 8-10v the wiring of your car would provide as standard? Grafting in a 2.2 and non ballast ignition would require a replacement feed from the ignition switch without ballast ressistance - easy to overlook when the engine was dropped in. If its not being done, your car will have a weak spark as the primary windings of the transformer (coil) won't be getting fed enough voltage.

If it is a ballasted system with a ballast spec coil and uses a resistance feed from the ignition switch - the missing wire to the coil from the starter would only manifest itself with a car being difficult to start as the link wire from the starter solenoid to the coil only has function when cranking. When you release the key to the run position, the feed from the starter link wire becomes redundant, and the coil is fed a lower voltage through the balast resistor (or resistor wire).

I'd also check your ignition switch and clean all the poles behind it - its a common problem on elites and eclats that dont see much use and can give the symptoms described.

I'd approach your problem like this:

 Step 1: clean up all contacts- starting with the earth points.

Step 2: determine what spec of coil you have and check that its being fed correctly (12v for non ballast) (6-10V for ballast)

Step 3: If it is a ballasted coil, buy a balast resistor from ebay (couple of quid) and run an independent feed to the coil through the resistor.

or: Step 4: If its a 12v coil - run another feed to the coil and disconnect the one from the ignition switch.

If you still have an issue:

Step 5:  borrow another AB14 from someone and try it.

 

Good luck

 

Dunc

 

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Thanks for those replies - ignition problems are my blind spot! Having these suggestions on hand shines a light into the filthy engine bay of the problem.

I think that dunc's point that it's a mix and match (or just mix) is probably the issue. Add to that poor condition wires and connectors. .. The car never started well and ran OK only once warmed up. I think this implies a wrongly connected and specified starting circuit and an ongoing weak spark rather than any faulty component.

You know how it is - some jobs have been done right in the car's history,  and sometimes a PO has just lashed things together. The engine's been in the car at least 20 years though,  so you think the starter circuit would be wired right. ..

As I was trying to start it to move it into my freshly repaired shed for chassis replacement,  it doesn't seem worth major dismantling - so on this advice I will stick with the original distributor,  identify the components,  rewire completely, test the existing and then see what happens.

As I was planning to get the carbs properly cleaned, it would have been helpful to have the ignition working correctly so I could concentrate on the carb setup on reassembly, but owners of 40 year old high performance cars can't be choosers. I will probably need professional help by then.

And a proper mechanic😉

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3 hours ago, Dunc said:

Was always a Fordson man myself.....

Why the "was"?

You could use a fordson to pull the lotuses around the garden. Acceleration isn't great but the torque is all there right from low revs

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Spent far too many hours as a teenager harrowing and seeding in a super major to want to ever drive one again. I do have a lawn tractor as an emergency tow vehicle though.... 🚜

Moved to the big smoke 20 years ago so grandads farm in Aberdeenshire (and the fully equipped workshop) is now but a memory.

Occasionally... if I was good... Grandad would let me drive something with power steering which didnt try to break my wrists.... :driving:

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