Irritating Ignition Failure

[sweller]

Last night my '65 3.8 S-Type ground to a halt on the M27 with no sparks. It had stuttered a bit and then died on the junction slip road, coasted to halt and refused to start.

There was a very weak spark - to be fair it would be more accurate to describe it as no spark so feeble was it.

Changed the points and condensor for a new pair and still no go. It strated to rain so the ignominy of a ride on a big yellow lorry followed.

Today's efforts have made no progress either. The car has had in stages this morning, a new coil, new rotor arm and a known good used distributor cap (it was fine when it was taken off the car a year or so ago), the gap and timing is ok but there's still no spark.

There is 2v voltage drop between battery and coil +ve but even a direct fly lead between battery and coil and then a clear 12v has no improving effect.

The coil HT lead gives a nice blue spark that can jump a 4mm gap to the rocker box but there is no real spark at the plug end.

I'm loathe to spend £50 on a set of HT leads just to isolate them. However the ones on it are 3 years and 15,000 miles old. It seems unusual for them to just die mid-journey (it had done 170 miles that day and 50 miles that leg before expiring) - my experience of leads is they deterioate slowly or make an effort to pop and bang with this it's no spark whatsoever.

Opinions?

[Martec]

Hi Can I suggest you check the resistance of the leads, I've just looked for the ideal resistance but can't find it at present. I bought a new set of leads and had to take the ends off, clean them and refit to get the resistance down to acceptable limits.

There has been a lot written about the new black rotor arms being so poor they earth down very quickly, the orange ones from distributor doctor or rimmers (from the same source) are supposed to be good.

Seems a daft comment, but is the rotor arm turning as the engine turns, is the damper turning as the engine turns over, cranks have been known to fail.

Best wishes

Brian

[oldtimer]

Hi Simon,
What an absolute bummer, you have my commiserations.

Six HT leads don't suddenly break down all together - so I would forget that one

I think the answer is in your text.

You say that you get a good spark from the coil lead to earth. Are you making that spark by manually opening the points or cranking it over? Not that it really matters which way - the fact is you have a good spark from the coil lead to earth.

So sitting on my bar stool with a Gin & T to hand, what conclusions can we draw!

It appears to me that the system has the ability to make big fat sparks but fails to squirt them out to the plugs via the distributor cap. So are we homing in on your problem. The King lead seems OK and I reckon the six HT leads are OK, that only leaves the Rotor Arm and Distributor Cap.

First Check:-
Make sure the carbon brush and spring in the Dizzy is in good order, take the spring out and ensure in one piece and free from corrosion. When assembled ensure that it is free to move and long enough to make good contact with the rotor arm.

Second check:-
After market rotor arms have a history of failure, check for tracking to earth, this is a black burn line heading for the rotor spindle. This very often extremely difficult to see. Try and find an old Lucas rotor arm Good ole Joe Lucas.

Third check:-
Very careful check of cap for tracking.

Or Beg Borrow or Steal another Distributor Cap and Rotor Arm

I hope that helps a little ---- do let us know the result

Oldtimer

[sweller]

Not that I'd tested the crank or distributor drive are in order but when I've been turning the engine over to set the points gap the shaft moves as expected.

It's had a new Lucas rotor arm and an old known to work distributor cap. The carbon brush is intact and is free to move.

I tested the king lead to earth by ignition on and cranking the engine on the solenoid button.

A friend of mine suggested that the king lead may be at fault - it makes a spark when simply going to earth but breaks down when asked to do some work. I must have a something kicking about Ii can swap over to test this theory.

I think chief suspects are the rotor arm and cap but both have been changed but I will try another rotor arm when I can find one! I'll buy another cap as they're not that expensive.

I'm also tempted to get a distributor from a breakers (a local one to me used to specialise in Jaguars and has occasionally some buried treasure lurking) and do a straight swap and see how that goes - it all depends on the price though!

Ho hum - it's all a bit inconvenient as it's my only car.

[oldtimer]

Hey Up Martec.
You nipped in there a bit quick!

Brian, there Simon was driving on the M27 minding his own business, slowed down for the slip road, up the slip road , then hey presto DEAD. Why?

All six plug leads ain't going to fail together. Yes, the rotor arm could stop going around but that's pretty serious.

We must not forget that Simon has achieved a big fat spark from the king lead to earth. Was that achieved by cranking the engine or by opening the points? If that was by cranking the engine the distributor shaft must be in one piece.

Every way which way brings me back to the Dizzy cap or rotor arm.

Or is that big fat spark off the King lead putting us off the scent?

Oldtimer

[oldtimer]

Simon,
I want you to check something for me.

Now I've got to think about this. Yes, right, Remove the Distributor Cap, turn the engine slowly until the points are closed, so that the heel of the points is halfway between two of the lobes of the cam shaft and check the clearance between the heel of the points and the shaft.

The point of this task is to ensure that the points are able to close properly. If there is no gap then clearly the points are restricted from closing.

I trust the points are in good order. Points have a thin tungsten coating any attempt to clean them removes that coating and renders them useless.

I would resist the temptation to exchange the distributor at this stage

Oldtimer

[oldtimer]

PS
It may sound daft but are we being completely led astray here by any chance. Is it possible that
it is a fuel pump problem? Do they both work Ok

Oldtimer

[sweller]

It may sound daft but are we being completely led astray here by any chance. Is it possible that
it is a fuel pump problem? Do they both work Ok

Funnily enough that was my first thought when it ground to a halt. They work and fuel under pressure escapes the banjo at the fuel filter.

[sweller]

The point of this task is to ensure that the points are able to close properly. If there is no gap then clearly the points are restricted from closing.

I trust the points are in good order. Points have a thin tungsten coating any attempt to clean them removes that coating and renders them useless.

The points are new and close and shut ok - there's a nice spark at the coil lead. I will get a new distributor cap and replace the coil lead just to make sure I'm not being led up the garden path.

I would resist the temptation to exchange the distributor at this stage

Do you see that straw over there....

[PPV]

I agree with comments re distributor cap and rotor arm but can you smell petrol when turned over? If not would not rely on fuel being delivered to filter as proof it getting to the carbs but check by lifting top of a float chamber, but unlikely problems with both carbs but you never know. I once had vent from a carb blocked and it airlocked the carb and it would not start even though one carb operational. I found it by checking all items one by one and the rodding the vents as one of the last items. You should have seen the dried muck that came out.
Regards,
Paul

[oldtimer]

Hi Kim,
I have always been dubious with what I call "Bar Stool" diagnosis. In my experience it is a recipe for disaster and think this could be where we are at the moment.

What ever scenario I dream up I keep coming back to the Dizzy cap and Rotor Arm but you indicate that you are fairly confident that they are OK. Time will tell on that front!

Perhaps now is the time to broaden the background of this car to examine other possibilities, think outside the box as they say If you are happy to answer the following questions further help may be forth coming and help understand the situation

How long have you had the car
How many miles have you done-- not total mileage
Is it used on a regular basis
Is it normally used in an Urban area at very modest speeds
Have you recently been on the Motor Way prior to this event
What sort of speed were you doing on the M27 on the day of the incident
Has it started properly in recent days.
Do you do all your own servicing.
What jobs have you done recently

We are a bit stuck until it can be proved conclusively that the Dizzy Cap and Rotor Arm are Ok

That's all for the moment Doing our best to help

Oldtimer

[oldtimer]

Simon,
Apologies for the wrong name - forgive me - one of those senior moments (old geezer)

Also I was reading through another thread about rear lights off No6 Fuse in which you contributed. Now I am understanding!

Any developments today?

I've had some fairly outrageous thoughts on the subject but will keep them to myself for the moment

Once again sorry

Oldtimer

[sweller]

How long have you had the car

Five years

How many miles have you done-- not total mileage

28,000

Is it used on a regular basis

Yes, it's my only car - usually gets used once a week in all weathers.

Is it normally used in an Urban area at very modest speeds

No, both urban and motorway/dual carriageway

Have you recently been on the Motor Way prior to this event

Yes, that morning.

What sort of speed were you doing on the M27 on the day of the incident

70-80-90 (this is normal on M/ways) it had travelled down empty A roads before failing for about 50 miles - and a very pleasant drive it was too!

Has it started properly in recent days.

Yes

Do you do all your own servicing.

Yes

What jobs have you done recently

Oil/filter change and new battery (was the one that came with car and was no longer holding a charge - judging by the case it was about 6-8 years old)

We are a bit stuck until it can be proved conclusively that the Dizzy Cap and Rotor Arm are Ok

It's a new Lucas rotor (!) and I'll fit a new a cap this weekend (I'm away with work at the moment).

Cheers.

[peterdpps]

Nobody has mentioned Condenser. Is this ok?

[oldtimer]

Hi Peterddps & Simon,
I've just quickly re-read all the thread and I think you are right I can see no reference to the condenser. I'm sure Simon will tell soon enough!
BUT with a big fat blue spark that in it self tends to eliminate the condenser!!??

Simon, Thanks for answering the above questions. This clearly demonstrates a well maintained vehicle in regular use operating at a variety of speeds and conditions, that gives a clearer picture.

Simon, I am sure you know that with the CB Points closed, if you pull the points open with a small screw driver you will create a spark at the King lead to earth. This will save the battery a bit. Not only that the coil should get full voltage.

I've just been gazing at the exploded view of the distributor in the manual, there really is B... All in there to go wrong - unless it has totally disintegrated. Perhaps one thing worth a look at is the LT lead that links the connection at the side of the distributor to the points. Ensure insulating washers are correctly positioned as well. Scraping the bottom of the barrel now.

Do you think it is worth removing the distributor for a good check over. I found the easiest method is leave the clamp bolt alone but remove the single bolt that secures the clamp to the block. By doing this the timing is not disturbed. Use a half moon ring spanner.

We have had to ensure almost monsoon rain conditions for an age, can you think of any way water can get into the fuel system around the tank caps etc.? At some point we must extend the investigation into other areas. Do you still have the glass bowl sediment filter under the bonnet?

That will have to do for the moment

Oldtimer