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MG MGA - Of subject 'Jaguar'

Hi,

You have helped in the past with questions with my MGA, but I have an issue with my Mark II Jaguar that is driving me insane and I wonder if you guys have any suggestions.

The car is a 1961 3.4 Mark 2.

A couple of months ago I had electronic ignition fitted as I was struggling with performance and was constantly changing points. The difference in performance was staggering she pulled away so well and went so fast it was like I had a new car. I came home one day and stalled her as I was reversing her onto the drive. After that she would not start. I asked the garage that fitted the electronic ignition to investigate. They came out and investigated. It appeared that there was a problem with the unit. After investigation and refitting the unit the car started again. A couple of weeks ago on my way back on an A road doing about 50 she just died. There was no power. I called the AA who looked and indicated that there was no low tension circuit. When I got home I investigated I could find no low voltage circuit. I took the decision to buy a 123 ignition system and fitted this. I have also replaced the coil and the leads. I must point out that the car has been converted to Alternator.

I still can not get the car to start. I have done the following:-

Proved that there is power to the 123 unit as I can get the green light to come on as part of the set up.

Proved that there is power to the coil through the white low voltage cable by putting a bulb in sequence

Proved that there is power when trying to start as the bulb stays alight.

Proved that there is no spark by putting a clean plug on lead 1 against the body

put a timing light in sequence showing no spark.

Checked the timing

Checked that the leads are in the correct order.

Proved that the rotor arm goes round

I have reviewed my manuals and can not think of anything that can be wrong. Can anyone advise what may be wrong. I suspect that the electronic ignition is not the problem, but that there is an odd electrical problem somewhere.

Can anyone offer any suggestions?

G T Smith

Im probably the last person who should be giving any advise on electrics,but if you have power to the coil but not from it then that could still be the problem you my have a faulty coil even given it is new, just a thought, vin
V Rafter

I thought that, but I tried the new unit on hte MGA and the MGA on the Jag, The A started with the Jag one, but it didn't make any difference on the Jag with either unit.
G T Smith

I have never used a 123 system, but all systems using a coil require the low voltage circuit to "make" and "break". That is how a coil works.
You say that a bulb in series with the coil is always lit.
Why doesn't the light go on and off as you turn the engine? A continuous low voltage current flow through the coil means that the high voltage circuit will not operate.


Mick
M F Anderson

How about going back to conventional point to prove whether or not the fault is in the 123 unit. If it works that way it would look as if the Jag's ignition circuit is "blowing up" the electronic ignition. You said in your first post that you were "constantly changing points", it sounds to me like you could have too much current flowing in the low tension side of the circuit due to a coil which should run with a ballast resistor. Have a look along those lines. Regards, Lindsay
Lindsay Sampford

The MGA has had a known problem with weak rotors. They short internally. This could be your problem. It meets your symptoms.

To test it, remove the rotor from the disty. Connect a sparkplug and its wire directly to the center post of the coil. Place the sparkplug against the engine block and give the engine a turn. see if you now get spark at the plug.

Alternatively, just put the timing light clipped around the high tension wire from the center of the coil to the center of the disty. If the rotor is bad, you should still get a trigger (6x) on the timing light.

Chuck Schaefer

Yes, I agree with Lindsay, sounds like the original problem was either condenser or ballast resistor related, and the latter could be causing the current problem. However, as Mick suggests it sounds like there is a problem with the breaker system in the distributor.

It would be useful to post some pictures of the installation to help the guys here to see any potential problems.

BTW, I also have a MK2 Jag with electronic ignition and FWIW the Mk2 Jag did not have a balast resistor as standard.

I don't know what the previous electronic system was, but I understand that the Luminition electronic ignition boxes have quite a reputation amongst local club members for failing suddenly. A colleague recently had to change his on his Daimler 250.

Finally, I also have been unable to find a good forum for the Mk2!

Neil
Neil McGurk

Check Alt output voltage, with system hot and stable. High voltage will cause all your symptoms and DOA ign systems.
As Neil says, no ballast resistor stock, but the need is determined by the coil fitted.

FRM
FR Millmore


In reply to the comments and suggestions (that are gratefully received), I put my timming light on the coil and got nothing. The 123 system is a complete replacement dizzy including cap and rotor. The leads are the latest silicon. This is a link to the 123 web site http://www.123ignition.nl/downloads/manuals/123JAG6.pdf as you can see it is very simple from an installation point of view. I fast approaching Linday’s idea and putting points back in just to prove that I do not have any other problems. I am interested in Mick’s point as it worried me that the bulb stayed alight. I have 2 new coils and they both work on the MGA.

Garreth
G T Smith

Garreth, do make sure that you are NOT using a coil that requires a ballast resistor; see Barney's note on the subject http://mgaguru.com/mgtech/ignition/ig109.htm
There are a lot of those types of coil around, as Barney's note says, late MGB. They will work very well but put a lot of strain on the low tension side.
Lindsay.
Lindsay Sampford

Gentlemen,

Thank you for your suggestions. As suggested I took it all out again and checked everything. I found that the coil was very suspect, after replacing the coil I got a good spark, I also found that even though the Mark 2 should have number 1 piston at the back if I put the leads on as though 1 were at the front she started first time.

So thanks again for your help.
G T Smith

This thread was discussed between 13/07/2009 and 19/07/2009

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