Thread: 96 Disco V8i - Possible Ignition Issue

You have misread the test. The voltage reading should be between the positive terminal of the coil and the negative terminal. Ignition off: zero volts is correct. Ignition on, engine not running, zero volts indicates the amp is not drawing any current through the coil. Any voltage measured here will indicate a failed amp that is drawing permanent current with the ignition on.

To repeat: the voltage should be measured from the positive terminal of the coil across to the negative terminal. Otherwise you are simply testing whether the ignition switch is on or off.

To check the coil out of the vehicle set your meter to ohms, check the resistance across the 2 terminals (primary resistance) somewhere around 0.5 to 1 ohm. Then check from the negative to the main hi voltage terminal (seconday resistance), should be in the Ks of ohms.

For upgrade/repair suggestions look in my thread here:

Lucas ignition amplifier replacement by Bosch 024

Thanks for the quick reply bee utey.

Here's the diagram from the RAVE manual for the specific test I'm querying.



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The test is between the two points marked as V, so as you can see I've tested as per the manual in this instance.

I've actually upgraded the ignition module to a BIM024 as part of the troubleshooting exercise with the same result for the test above.

Any further light you, or anyone else, can shed would be appreciated.

Originally Posted by TooQik

Thanks for the quick reply bee utey.

Here's the diagram from the RAVE manual for the specific test I'm querying.



Uploaded with ImageShack.us

The test is between the two points marked as V, so as you can see I've tested as per the manual in this instance.

I've actually upgraded the ignition module to a BIM024 as part of the troubleshooting exercise with the same result for the test above.

Any further light you, or anyone else, can shed would be appreciated.

How odd. The test makes no sense that way. Maybe no-one writing the manuals ever noticed? I've seen worse errors in instructions.

If you are already using the BIM024 try reversing the sensor wires. Terminal 3 on the module needs to be connected to the blue wire going to the original Lucas amp/module. Reversed connection will cause retarded and erratic ignition firing. You might have to readjust the timing afterwards.

The (+) of the coil and module terminal 15 both need to be securely wired to ignition positive. Are you getting 12V at the coil +ve with the ignition on? If not your alarm "spider" may be faulty. Try hot-wiring the +ve coil direct to the battery (with a switch in the wire) to see if it fires up.

With the distributor aligned to a firing point of any cylinder you should be able to check for spark at the coil by rapidly twitching the rotor button by hand past the pick-up point. If you have spark at the coil (insert a paper clip and arrange a 1/2 inch gap to body) then try another rotor button, cap, coil lead etc. N.B. Do not pull on your rotor button without making sure it is loose enough to come off without wrecking the plastic clip in the shaft assembly. You may need a small screwdriver to hold down the innards while you pull on the button.

Originally Posted by bee utey

How odd. The test makes no sense that way. Maybe no-one writing the manuals ever noticed? I've seen worse errors in instructions.

Interestingly the Haynes manual has the exact same test but written rather than done as a picture. Only thing that comes to my mind is maybe it's a check for a earth leak back through the wiring or in the immobiliser itself???

Originally Posted by bee utey

If you are already using the BIM024 try reversing the sensor wires.

I'll try this tomorrow. I've been working on this almost two days now and my head is about to burst.

Originally Posted by bee utey

Are you getting 12V at the coil +ve with the ignition on? If not your alarm "spider" may be faulty.

Yes, getting 12V at coil +ve with ignition on. I actually suspect that the issue might be immobiliser related and have already had the dash apart to check the "spider"....but it appears to have gone AWOL. It's not above the heater where it "should" be. Any ideas on where else I might find it? I found the Alarm ECU (green box in the passenger footwell) along with a few other modules which I'm trying to identify in the hopes that maybe someone moved it. Is it possible that it's been removed altogether?

I've already checked cap and button, but another look won't hurt.

Appreciate all the feedback.

Okay, finally have been able to do some more testing with the following results:

1. Reversing the amp module wires results in no change.
2. I have spark at coil.
3. I have spark at the number 2 spark-plug.

Car still does not fire though. Regarding spark at spark-plugs, how quickly should this spark when cranking? I ask because I'm getting a spark about once every one second which seems low to me.

Also, I have no immobiliser spider. Seems that some models came out with only the main alarm ECU which contains a primary immobiliser and no secondary immobilisr (spider). Lucky me.

Have you checked the fuel side of things? If you have good spark (correctly timed) and compression, then fuel is the third side of the running engine equation.

Thanks BigJon.

The first thing I did was change the fuel filter when I started troubleshooting. When trying to start the Disco you can hear the fuel pump relay triggering and the fuel pump prime. You can also smell petrol after a few attempts to start.

I haven't checked the fuel pressure specifically, but I would expect the engine to fire then stall again if the fuel pressure was too low.

One extra thing to add to the mix which I've noticed. My distributor does not contain the internal plastic cover to protect the base plate workings from the cap. Is it possible that prolonged exposure to the spark has damaged something internally within the distributor? I have checked the pick-up coil resistance which is within spec as per the RAVE manual. It's sitting just above 2k ohms.

Originally Posted by TooQik

Thanks BigJon.

The first thing I did was change the fuel filter when I started troubleshooting. When trying to start the Disco you can hear the fuel pump relay triggering and the fuel pump prime. You can also smell petrol after a few attempts to start.

I haven't checked the fuel pressure specifically, but I would expect the engine to fire then stall again if the fuel pressure was too low.

One extra thing to add to the mix which I've noticed. My distributor does not contain the internal plastic cover to protect the base plate workings from the cap. Is it possible that prolonged exposure to the spark has damaged something internally within the distributor? I have checked the pick-up coil resistance which is within spec as per the RAVE manual. It's sitting just above 2k ohms.

The loss of the cover shouldn't make a lot of difference. Some particles of corroded dissy cap contacts could possibly fall into the works. You should have spark every 2nd revolution of the motor, so 2 revs/sec means 120rpm cranking speed. This is a little low, so I would remove every plug and squirt a generous dose of CRC or similar down all the plug holes to increase the lube on the bores. Then spin up the motor without the plugs to spread the oil. You will get an increase of compression with improved cranking speed. Replace the plugs, check the timing on no. 1 cyl is correct with your timing light. Then load the intake with some start-ya-bastard or similar.

Re-reading your original post, it sounds a little like a stripped timing nylon cog/chain. I had a P76 engine that did that, step-wise it jumped 1 tooth making it run rough, then it jumped a second tooth and would hardly run at all. To check you will have to lift the RH rocker cover, turn the engine to fire no. 1, the valves at no. 6 should be rocking symmetrically at TDC. Major crank movement without valves moving is a dead give-away. Timing chains are relatively easy to replace.