About a coke bottles worth. Just let the vacuum pull in enough to not stall the motor which isn't much. A little at a time.......your just creating a little of steam to pop the carbon off, not dumping a bucket of water into the cylinders.

 

• I put in new spark plugs as you suggested, gapped to .28".

• Replaced the one-week operational old OEM Prince of Darkness ignition amplifier with the previous no name unit (imported by InterPart).

• The distributor was set with the rotor arm at N0. 1 cylinder and the engine at 6 degrees BTDC.

• The throttle valve was opened while an assistant sprayed a three second sqeeze of ether into the plenum chamber.

• The starter turned over the engine briskly.

Not even the slightest indication that any sparking occurred. The smell of ether was evident over the engine as well as at the exhaust.

 

Ignition lead on coil + and amplifier lead on coil - correct? Distributor; rotor rotates in a clockwise position? Starting with #1 the next spark plug lead going clockwise is #8, 4, 3, 6, 5, 7 and 2? Do you have a spare coil to try in place of the one that is now installed? Have you changed the air gap inside the dizzy, it should be between .020 - .035mm (measured with a non-metallic gauge).

 

Good evening friend,

I have not done anything to the gap inside the distributor - will take it out and have good look tomorrow. Firing order is correct, yes.

I still have the old coil I removed when I had replaced it with the new one a week before the present lack of spark started. The symptoms then were exactly as now, and replacing the then week-old ignition amplifier and old coil it had started immediately. Was good for a week until the present issue presented itself.

I do have some worries about the coil connections - there are two leads from the amplifier unit and one is shaped for the negative terminal on the coil and the other for the positive. Same from the main ignition harness (one white with a green stripe and one white with a black stripe. Maybe I should try and swop them around, and see? - What harm can be done? They were this way previously when it started and ran normally for a week and then suddenly stopped sparking.

To make sure I also made a direct connection from the battery + to the coil + and tried a start but no spark.

Thanks for your prompts.

 

Noise suppression capacitor mounted to the + side of the coil?

 

Yep.

I am now where I do not think the immobilizer is an issue anymore, having read all I can about 1995 V8i. There is LT power to the coil when the ignition is turned on so it can not be the immobilizer. The battery is excellent and so is the starter motor.

I'll be out of circulation for a few days but on Monday I'll have the "new" OEM ignition amplifier module tested. I think the break in HT current to be either due to a rotor arm or distributor cap. Inspection does not show anything wrong, but I am going to invest in new ones of those.

The pick-up coil as I mentioned before tests 3.3 K Ohms and the air gap with the reluctor is correct.

What do you think?

 

The immobilizer is not the issue.

Lucas cap and rotor is the one brand that work 100% of the time. Aftermarket aren't reliable. Besides this I can only think of the pick-up coil inside the distributor or a bad connection to the amplifier or a failing ignition switch post to the coil or worn bearings for the dizzy shaft. These are not that complicated but when the distributors have high mileage they can be a bugger to wring out. Most skilled DIY folks go with GM HEI or Pertronix to make life easier. Distributors for British Engines

How many miles on the truck?

 

194,000 miles.

 

Both the ignition coil (Bosch - or so the sticker says) and ignition amplifier module (Lucas, ordered from London) tested dead, both had been in operation for one week.

The previous amplifier unit (Intermotor) had lasted two weeks before dying. The previous (before the previous!) Intermotor unit lasted three weeks.

The pick-up coil in the distributor tests OK. The air gap at the reluctor arms is very small but visible- I do not have a non-metallic feeler gauge.

The distributor cap terminals inside show bad mechanical wear on ONE side as if it is not perfectly concentric, but the rotor arm does not show any wear.

I have ordered new coil, IAM and distributor cap.

 

Now to find out why they are dying......

Does the dizzy shaft have play in it, cap not mounted squarely, rotor not sitting flat? With as many miles on the truck the distributor, if original, is sure to have wear.