Thread: Lucas ignition amplifier replacement by Bosch 024

I'll put this here for future reference to stop me having to repeat myself.

1. Is 12V appearing at the #15 terminal of the module with the ignition on? This should be wired to the (+) terminal on the coil (#15 on the OEM coil). Also make sure ALL ELECTRICAL CONNECTIONS ARE CLEAN AND TIGHT!!!!!

2. Is the module #16 terminal wired to the #1 or (-) terminal of the coil? The voltage here should be the same as the positive unless there is a short circuit to ground on the negative side. This voltage can only drop when the coil is actually being fired and needs more than a volt meter to see the drop happening. A logic tester or an oscilloscope will see the pulse. A vehicle with an electronic LPG safety cut-out will also be able to see a pulse by switching on the gas solenoids. You can even just wire one up and look at the function LED on it. It will come on for around 1 second on switch on, and stay illuminated while coil pulsing is occuring.

3. Is the module securely earthed to the chassis/body? Use a multimeter to check for a low resistance if needed.

4. Is the pickup wired to the module terminals #3 and #7 as per the pics in the posts at the beginning of the thread? The direction of connection is very important.

5. Is the resistance of the pickup stable as you wriggle the wiring? Is this resistance exactly the same when measured across module terminals #3 and #7 and the wiring connected?

6. Turn the engine manually so the pickup is near one of the teeth of the star rotor inside of the dissy. Manually move the star wheel past the pickup by wriggling the rotor button. With the ignition off check the resistance across module terminals #3 and #7 while you are moving the star rotor point across the pickup. You should see the resistance swing around as small voltages are created by the pickup coil as the rotor moves. Stop and it should settle back to the stationary reading.

7. Take the coil lead out of the coil, bend up a piece of plain wire to go in the coil HT post and arrange a 6mm gap to a metal chassis/ body part. Turn on the ignition and wriggle the rotor as before and observe the strength or otherwise of the spark.

8. Now make sure the dissy cap can't foul the moving rotor and leave the test gap from the coil. Crank the starter and observe the spark. Still strong?

9. Now fit the coil lead to the coil and arrange a gap between the coil lead dissy end and a metal earth point. The spark should be a bit weaker but still present, due to the nature of the lead's internal construction.

10. Now using a pair of plastic pliers hold the coil lead near the rotor button metal strip and compare the spark you get with that from arcing to the dissy case. There should be only a tiny spark visible to the rotor but much much weaker than to the metal case. If the spark is equally strong your rotor button is burnt out and needs replacing.

11. Now refit everything and take off only one plug lead. Fit an old plug to the lead and clamp an earth lead (e.g. jumper lead) to the plug body. Observe the spark in the plug gap.

12. Now make sure that the vehicle ECU is still getting its pulse by checking the white/black stripe wire is fitted to the negative post of the coil. Without this wire you may have spark but will never have injection. Your fuel pump is your test function here: does it run when you first turn on the key to ignition? When you crank the engine a successful reading of the ignition will start the pump and you will hear it run on for around 1 second after you stop cranking. If your environment is too loud use a test light at the fuel pump wiring. Anywhere you find the fat white/purple wire in the loom to the fuel pump will do.

13. If all that fails see a LR doctor.

Just an addition to the thread since I learned so much from it. I did this conversion yesterday, not because I had any particular problems, but because when I was troubleshooting a non-starting new engine a while ago I replaced the existing amp, and just getting it out from underneath that box involved something like three different-sized sockets and quite a lot of time. Also, the new amp made the aftermarket tacho jump around. And I never did like the coil sitting on its side like that.

So I made some new brackets, steel for the coil and ally for the amp. Because I've changed the PAS reservoir there was just enough room for the coil. I might add a braided earth lead from the amp ground, (the RH mounting bolt on the amp), for later on, when corrosion starts giving trouble. I might also change the amp mounting bracket because it gets pretty hot after not very long.



Troubleshooting or just plain replacing this should be very easy.



Here's the wiring diagram I found somewhere online and used:



And what all this is inside the box next to the old amp, I have no idea. Certainly, it didn't suppress anything when I used the HF radio:



Timing hasn't changed, power seems about the same, but the tacho is behaving and now I've got a new genuine Bosch part instead of some Dodgey Brothers special.

Thanks, Bee Utey!

Question,


What should the voltage be at Terminal 7 and 3 to the coil, I am getting 1.2v is that correct ?

Originally Posted by Kevin B

Question,


What should the voltage be at Terminal 7 and 3 to the coil, I am getting 1.2v is that correct ?

I've never measured a voltage that way as its entirely irrelevant to the operation of the distributor. The voltage pulses from a rotating pickup (too fast for a regular multi meter to read accurately) are measured between 3 and 7. With the distributor stationary you can only use a multi meter to measure the resistance of the pickup coil connected between 3 and 7.

Ok well when I get home Bee ill post a full history, but yes the resistance at 3and 7 are stsble at both ends I now have no spark from coils but it was working this morning

ok ill start by saying I bought this 1994 D1 from a fellow forum member who was having problems getting it going, threads here


http://www.aulro.com/afvb/discovery-...to-breach.html


and


http://www.aulro.com/afvb/discovery-...er-2096-a.html


and


http://www.aulro.com/afvb/discovery-...chug-dead.html


during the course of the repairs in the above threads this Lucas ignition amplifier mod was done, after getting her here I needed to replace the starter motor and top radiator hose, that done I managed to resolve the problem, got the vehicle running very well, went for a spin up and down the road no issues, had it running for quite some time turning off and on again with no problems, then while it was idling in drive it kinda revved up then down and stalled, ok restarted no issue, then 10 mins later same again and again, so I went off to do some reading thinking that it could be a faulty coolant temp sensor.


armed with the ohm figures I needed I went to check them and they were fine, once again went to start the car, this time nothing no firing at all, pulled the coil lead off the dizzy and no spark, checked power to the coil, that was fine, checked power to the BIM, that was fine, checked resistance between 3 & 7 on the BIM and at the coil, that was strong and stable too, simply by having the vehicle running I have concluded that the mod was done correctly.


I have noted in this thread though that the coil used are mostly Bosch, the one that is on there is the Lucas DLB?? something or other, which I was assured was new, I have tested the resistance across + & - against spec I found on the net and it was fine, however when I test between either + or - and the centre I find the resistance much higher than the spec I found on the net,


Question,


Could this mod have killed the LUCAS coil after a short period of time?
Could the Lucas coil have killed the BIM?


Tomorrow I will,


Replace the HT lead and see if that is the problem also I have a second Lucas coil which tested to spec with the meter, I will try that as well.


one other question, does the ECU have and influence on the spark at all, when I first plugged the 14CUX reader into it just after it had arrived, when it got the tune screen it said


"TUNE - LIMP NO CATS"


when I had gotten the vehicle running again and turned it off and plugged the reader in same screen said


TUNE - RED NO CATS


I know this means the resistor colour,


Once again it says TUNE - LIMP NO CATS


I am a bit reluctant to blame the ECU at this stage as it has been running fine and the only problem it has now is no spark from the coil..


Ideas????

There is no input to the ignition from the 14cux, it's the other way round, the 14cux gets a signal from the coil negative connection.

Once you have double and triple checked the connections for cleanliness and tightness try another coil, then another module. Is the module securely mounted on an adequate heat sink? When either the coil or the module heat up they can have intermittent faults. In the case of the coil it will be internal insulation failure not connection failure, ie you won't be able to measure it with a multi meter.

So Bee should I get a bosch coil or would the lucas be ok providing that is the actual problem.