Thread: 3.5lt 88RRC Won't produce spark?

You need to test the magnetic pickup coil, take the module off and place a multimeter in the two connectors. Stationary, you should get a stable resistance that then jumps wildly when you spin up the dissy, because the pickup coil is generating small AC voltages.

Once you have a working pickup, you could consider leaving out the Lucas amp module altogether and fit this Bosch conversion:

Lucas ignition amplifier replacement by Bosch 024

The pickup was my no start problem. Well the pickup coil itself was fine, just the wire had broken inside the insulation near the plug.....looked fine from the outside tho.

Miltimeter across the pins, should get about 3500 ohms.

Cheers Fella's. I'll check out both suggestions.

I worked out what the problem was. It is always the thing you over look. I knew it was simple. Anyway...

2 problems
1st the main high tension lead from the coil to the distributor was intermittently open circuit. probably the cause of all my issues.
2nd there is a little o-ring type insulator in the distributor above the gear (reluctor?) that drives past the pick up point. Anyway a washer goes on top of this and a circlip to hold it all onto the main shaft. The problem was this created effectively electro magnetic short circuit. The ignition coil never collapsed to generate the spark. In the process of discovering this i blew up my new amplifier module and it turns out the old one was fine anyway

After a lot of time, brain power and self education via stupidity. (thankfully i have the workshop manual) I figured it all out. The car now runs but still does not start. I think i've broken the vacuum advance in the process of all this. I might just get a reco distributor and be done with it.

1. A burnt out coil lead will definitely cause starting problems!
2. The o-ring on the shaft is just an anti-rattle spacer, it has nothing to do with the way the pickup works. Touching the point of the pickup against anything containing iron, eg a screwdriver, will cause a pulse that sets off the amplifier.
3. Starting on gas is a matter of getting a rich pulse of gas into the inlet manifold. Depending on your gas system you either add a manual primer or adjust the idle mixture a little richer. If you have an Impco system (commonest) there is a pressure plug between the water connections. You need to unscrew this, plumb in a gas solenoid to the manifold and wire it to a button under your dash off your gas power wire. When you crank the engine press the primer for 1/2 to 1 second and it should spring into life.

Cheers for the tip about how to prime the gas. You are spot on about the less than ideal Impco system that i do have.

Interesting what you mention about the o-ring. I guess it is possible my new amplifier module was buggered from the beginning. I agree that even a screwdriver shooting past the pick up will generate a spark. I find it interesting though that until i put that o-ring back in there was always power on the negative side of the coil. It behaved as if the points were short circuit. But with the o-ring in the coil field was able to collapse therein generate a spark. I looked at the manual and carefully inspected the distributor and realised the gear for the points mechanism is most certainly insulated from everything around it. This could be a coincidence but it does make electrical sense for it to be isolated.

Originally Posted by Jazzman

Cheers for the tip about how to prime the gas. You are spot on about the less than ideal Impco system that i do have.

Interesting what you mention about the o-ring. I guess it is possible my new amplifier module was buggered from the beginning. I agree that even a screwdriver shooting past the pick up will generate a spark. I find it interesting though that until i put that o-ring back in there was always power on the negative side of the coil. It behaved as if the points were short circuit. But with the o-ring in the coil field was able to collapse therein generate a spark. I looked at the manual and carefully inspected the distributor and realised the gear for the points mechanism is most certainly insulated from everything around it. This could be a coincidence but it does make electrical sense for it to be isolated.

That is perfectly normal. When the coil is not firing at all, there is no voltage drop between the positive and negative terminals, ie both positive and negative should read the same voltage. When the amplifier gets a signal from the pickup, it momentarily drops the negative terminal to a lower voltage then lets it go. That instant is the point at which the coil's magnetic field collapses, ie the current in the primary drops suddenly to zero and the energy of the magnetic field is transferred to the secondary winding. This time is analogous to "dwell angle" in a points system but is of constant length regardless of revs. It is why Land Rover call this a "constant energy" system.

With points, the coil negative is held at zero volts for a time that varies with revs, which is why output drops off with higher revs. At no time should an electronic ignition hold the voltage down for any time longer than a tiny moment just before the spark occurs. As most electronic coils have a very low primary resistance, shorting the negative terminal to ground deliberately will blow it up within a very few minutes.