Non Starting Mark II with 123 Electronic Ignition.

[Garreth]

I have a problem with my 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.

[PJF]

My guess would be the rotor arm. I have Lumenition fitted to my 340 and although it has been fine for 12 years, I have twice experienced a dead engine due to failing rotor arms. There are still a number of duff rotors still in circulation.

You could pull off the HT lead feeding the dizzy and connect a plug to that, to check, but you'll need to keep the hot end away from ground.

In any event, let us know what the solution was, when found.

[smiffy]

Hi Garreth
You changed a lot in one go, so difficult to be sure where the problem is without some further investigation.
Is the coil OK? I know you replaced it, but you say you have a low tension circuit, but no spark - I had a new coil that failed after only 300 miles. Take off the low tension wire from the coil to the distributor and disconnect the HT lead between the coil and the distributor at the distributor end. Pull back the rubber boot on the free end of the HT lead to expose the connector. Attach a wire to the ground side of the coil (the one you removed the lead from earlier) and bare the free end. Switch on the ignition. Hold the free end of the HT lead with something non-conductive (thick rubber glove, folded rag, insulated pliers) a few mm away from a bare metal grounded surface (don't allow it to touch the metal though) and then briefly touch the bare end of the low tension wire to ground. This should produce a spark. If not, either the coil or the HT lead is duff; replace the HT lead with one of the plug leads and repeat. If you now have a spark it is the lead, not the coil, that is the problem but if there is still no spark then the coil is dud.
If you had a spark with the first test, then the rotor arm is a good bet for the culprit. Simple substitution is the best way to go with this.
Good luck, David

[Garreth]

Hi,

Just to update in case anyone else has a similar problem, I took advice from another forum and removed everything. I then checked the coil separately. It appears that this was suspect so I changed this. I then put the whole lot back and tried again. I then got a spark but not even the slightest glimmer of a fire. I did notice that when I took the leads out that even though the Jaguar manual is insistent that the Mark 2 XK engine has number 1 piston at the back mine had the leads in the other way. I moved the HT leads round put everything back and she fired up first time.

The running is stunning as she pulls really well now.

[stuarthardy]

Hi Garreth

What you have experienced is an all too common problem where people put their distributors in 180 degrees out and reverse the firing order. They do this by using the wrong compression stroke for TDC. Its probably more likely to happen when number 1 is at the rear of the engine as is the case with Jaguars. People generally just assume that number 1 is at the front.

You should really correct this as there is a valid reason for doing so (apart from making maintenance and troubleshooting easier) but I can't remember what it is. Something to do with advance curves I think, but I'm not sure.

Anyway, congratulations on sorting it out.

Regards
Stuart