Rover V8 - starting issue

[Ranger 6]

Scenario:

Drove the car in and stopped - switched off and walked away - it was running completely normally

Came back to the car a few days later - won't start - turns over freely

The car is a factory built one - not a conversion, and all parts are standard

Symptoms:
There is only one spark (tested with a plug) at the start of turning the key and another spark when turning the key off
Otherwise the engine will not run

Tested/changed:
New Ignition module (tested and changed) - it's a two pin module fixed to the side of the distributor
Distributor - std fit electronic ignition - hall effect sensor checked
HT leads - resistance check
Ignition switch bypassed to coil
New coil
Earth checked (bypassed with HT lead)

Stumped a couple of experienced mechanics who have had a look

Next thing to change is the HT leads and try that - we have swapped them to see if the king lead has died, but no difference

So, what could be the 'fix' here?

[Ranger 6]

When you say ballast resistor - is that also known as a condenser?

Doesn't have one as it's electronic ignition.

Bypassed the ignition with a cable direct to the coil.

[Ranger 6]

OK - thanks - checked on the ballast resistor and it doesn't have one

He did a load of check on the coil - I'll have to check if he did the switching.

Land Rover 90

[Ranger 6]

richhead said:

littleredrooster said:

My money's on the Hall Effect sensor. The fact that it sparks when the circuit is energized/de-energized probably suggest that the Module and coil are both working.

I had one fail on a BMW bike some years back - it started being a bit awkward when hot, then stopped working altogether. I initially blamed coils, but it was the sensor.

I would agree, but the op does say this has been checked, Best way to check is as i said, an easy way can be a old fashioned test light across the coil termilals and see if it flashes on cranking, that rules out everything apart from coil/leads/plugs.
Also op you say you changed the coil, is it the same one, there are 12v coils and 6v coils, often not obvious which is which. But if there is no ballast then most likely a 12v one.
If its a 2 wire module and a hall sensor, there isnt really alot to go wrong tbh and easy to test.

How do you check a hall effect sensor – we took the dizzy apart enough to check the magnet on the sensor. I think it’s pulsing enough to trigger a spark.

Short of a new distributor – what would you buy to fix it?

Coil – yes – swapped with a new one – the same as was fitted – 12v

Yes the ignition amplifier is a two pin one that’s fitted on the side of the dizzy – new Intermoto one and pulses when checked

stevieturbo said:

Perhaps give us a clue as to what car ? what age ? And these checks....exactly what and how are you "checking" ?

You're only talking about a distributor, so is it a carburettor car ? fuel injection ? other ?

Car – as mentioned above, it’s a Land Rover 90
1988 CSW – 3.5 on SU carbs

Checks done using a multimeter and ‘module checking box’ – pulled out of the back of a cupboard as no one uses stuff this old any more

[Ranger 6]

Yes, the old module took him back too - I had to find a new battery to get the thing working properly.

Some of the wiring between the ignition amplifier and coil has been replaced as it was looking bad. the rest is ok and has been checked with a meter.

The coil is being switched

The shopping list is currently a new King lead and a new sensor for the dizzy

[Ranger 6]

Yes - we've done all that and are only getting the one spark at the turn of the key

[Ranger 6]

richhead said:

Ranger 6 said:

Yes - we've done all that and are only getting the one spark at the turn of the key

Done what?

This

richhead said:

try testing for a spark at the distributor end of the king lead,

Used the plug lead from No: 1 to check

Going to get a new king lead anyway as we've broken the connector pulling it and shoving it through all the testing.

richhead said:

If there is a spark at the end of the lead

Yes - again just the one spark at each turn of the key

richhead said:

Getragdogleg said:

Does it have an oil pressure sender unit that tells the ignition side of things all is well ?

I have had similar faults on other cars that turned out to be this system being broken, the pressure gauge still worked but the other circuit in the sender was goosed.

That , and all other safety systems would be rulled out it the coil is getting a voltage and the coil earth being switched, it sounds like the op has tested this

I've got a spare sender which we can try - but I doubt it. A 90 isn't that clever and it's run with the pressure warning light on in the past (cheap eBay senders!)

Belle427 said:

Is the rotor arm actually spinning around properly?
Not uncommon for the drive gears to strip teeth.

In a V8? They're all metal

But yes, everything is turning correctly and timed

[Ranger 6]

@richhead - where are you?

Fancy coming round and having a look

[Ranger 6]

richhead said:

Just to explain what i mean by testing the switching, disconect the low tension leads from the coil and connect a light up test lead instead of the coil, the old style ones with a bulb are best for this, and crank the engine, it the light flashes then the fault is as i said either plug leads/coil its self, or rotor arm/cap.
Sorry if this sounds patranizing, but this is the best way to check everything else, and cap/rotor/leads can easy be tested with a continuity tester.

No, not patronising at all - welcome your input

Not sure we did this - so will try

Thanks

[Ranger 6]

finlo said:

If my memory serves me right the RV8 oil pressure switch is in the fuel pump circuit but is bypassed while cranking.

I've had a load of issues with cheap senders and it's never stopped the engine running

The fuel pump can be heard running through all these tests - as well as the smell of fuel not being ignited

[Ranger 6]

littleredrooster said:

Do you have a different rotor arm you could try? I have recollections of a batch of counterfeit (i.e. crap) Lucas rotor arms coming from China. Looked the part, but sent the spark straight to earth through a hairline crack.

This one has been running fine for a while, and yes, it's been closely inspected

[Ranger 6]

richhead said:

Just to explain what i mean by testing the switching, disconect the low tension leads from the coil and connect a light up test lead instead of the coil, the old style ones with a bulb are best for this, and crank the engine, it the light flashes then the fault is as i said either plug leads/coil its self, or rotor arm/cap.
Sorry if this sounds patranizing, but this is the best way to check everything else, and cap/rotor/leads can easy be tested with a continuity tester.

If we try this and it's not switching - is it the dizzy?

[Ranger 6]

Fab - thanks

Will try these :-)

[Ranger 6]

I'd forgotten all about this - so apologies for being one of those 'who never came back...'

I sent the bus off for some work on the bulkhead corners and the new engine to be fitted. Dr Land Rover picked up a spare dizzy off the shelf (for his son's comp safari racer) and stuck that in - yes, it fired up straight away.

The old 3.5 is now being replaced by a rebuilt 3.9 - and it'll have a new dizzy so when it goes in he'll know that everything is working - well as much as everything on an old 90 does....