M.O.T emission results , ever seen worse?

thanks for the reply - i think we are on the same thought process.

For reference here is what i find -

With relays in place, igntion on -fuse ok try to start engine fuse blows.
With main relay out results same as above except engine doesnt start fuse stays ok.

With Maf unplugged , both relays in place , engine starts, fuse ok.
plug MAF in when engine running , fuseblows , engine dies.

Looking at the wiring diagram it suggest the feed the ECU gets power from the ST2 "battery connection" on the same wires as the main relay and the fuel pump relay. yet when the fuse blows i still get power to teh relays but not the ECU, suggesting the diagram is not correct for the year. looks like 1994 was a change year for the disco 1.

So looks like i have followed you logic through.

In theory the M.A.F could blow the fuse without causing damage to the wiring as the wiring can sustain high current for a short period of time without breakdown , the fuse is designed to protect the wire in that circumstance so will blow in a very fine time period.

I suppose i could power up the M.AF on the bench and see what current it draws .

Interesting! I don't see how the MAF can be causing a short to the 20amp fuse because the power supply cable is spliced before the fuse although it is off ECU pin 15. The other components on the same circuit as the MAF are the coolant temperature thermistor and fuel temperature thermistor which could tie in to the emissions being high. Try unplugging the thermistors and see what happens. I would also try unplugging the oxygen sensors as they definitely draw power through the fuse via the relay but I would have to agree that based on what you say the MAF could be causing a short.

Just exchanged my MAF so will plug back in tonight and everything will work just fine.

Pigs fed and ready to fly! winning lottery ticket purchased and just waiting for the call from cheryl cole about the date this weekend!

leclance said:

Just exchanged my MAF so will plug back in tonight and everything will work just fine.

Pigs fed and ready to fly! winning lottery ticket purchased and just waiting for the call from cheryl cole about the date this weekend!

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At that rate, i REALLY hope that MAF works for you!!!

10 seconds of success , then the fuse went .

Back to the drawing board.

So after a night laying awake thinking about this , the plan today is to get a full day on this problem.

Im planning on checking through the sensors individually , found a usefull sight for checking lambda sensor so ill pull them out and bench test them. will also go back through the check of other sensors after some of the basic checking is done.

as the fault only occurs when the m.a.f is plugged in im conserned i have knackered the ECU when testing the sensor inputs - failry easy to short to of the inputs together, 12v on the input sensor wouldnt do to much good . if the sensor inputs are protected by a diode as industrial instrumentation can be then i may have one of these shorted and that would take out the fuse. I will run a log of all the checks today and post them later fro info.

Good luck

well unbelievable

Lost hope after another morning tinkering, now its running worse than before

So looked for a landrover garage that could sort for me, book it in the garage so i could get them to sort it, booked in for an m.o.t so i coudl drive it there. They put it through the M.o.T on LPG and the it sailed through the emmisions test.

Failed on a light out on the number plate and i put the front bulb in upside down.

Hasn't resolved the issues with running on petrol but still at least ill have an m.o.t tommorow to get me moving.

Ecu swap?

Mr Noisy said:

Ecu swap?

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Like I said in post 10?

i hate to say you both probably right , but ...your both probably right.

One last thing that is nigling me is the strobe light, when i connect it to any of the ht leads the firing light is very in consistent. The engine clearly isnt running well even if it was in limp mode its still lacking power and when under load.

What does the pickup do in the dizzy ?

Just had a chat with the guy doing the m.o.t, it appears the petrol system has been neglected for some years. It looks like one of the lambda sensor feeds the gas system and isnt sending its signal to the ecu so the engine is struggling to control the engine.

Now its through the M.O.T huraah ! ill run it on gas and gentle rebuild the petrol system. Give's me more time to tinker on those lonely winter nights in warrington.

Thanks for all you help and advice on this thread , i will keep the thread going as i find the problems.

leclance said:

What does the pickup do in the dizzy ?

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Think of the pick up as the equivalent of points in a non-electronic ignition system. The pickup sends pulses through the ignition amplifier then to the coil to trigger the low tension field coil to switch on and off which then triggers the HT pulse from the coil.

the inconsistent strobe light seems to go hand in hand with poorly igntion system.

indeed mine was doing that when it was running like ****, basically it was a bit of a dirty dizzy cap and wanted a new set of plugs...

and sorry for stepping on your toes Kev

Mr Noisy said:

sorry for stepping on your toes Kev

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Don't be silly, you've not stepped on nuffink, I woz being sarcastic

classic kev said:

Don't be silly, you've not stepped on nuffink, I woz being sarcastic

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Just being polite

classic kev said:

Think of the pick up as the equivalent of points in a non-electronic ignition system. The pickup sends pulses through the ignition amplifier then to the coil to trigger the low tension field coil to switch on and off which then triggers the HT pulse from the coil.

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Ok i think this is the route cause of the poor running and lack of power.

I just need to work out how to get the rotor arm of without damaging the dizzy as it seems likes its been welded in place so i can get a visual look at the pickup and the star cog thingy that the pickup detects.

leclance said:

Ok i think this is the route cause of the poor running and lack of power.

I just need to work out how to get the rotor arm of without damaging the dizzy as it seems likes its been welded in place so i can get a visual look at the pickup and the star cog thingy that the pickup detects.

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Be careful if the rotor arm is stuck to the shaft. You can test the pickup with a multimeter. If you remove and disassemble the distributor make sure you mark where everything is before you start. Do some searches of the forum you will find info about ignition checks and also what happens if you end up breaking the distributor removing a stuck rotor arm. The fact the rotor arm is stuck suggests it has not been cared for in a while.

Mind you, don't forget your ignition timing is wrong for petrol because of the LPG, the engine will run at 10 degrees BTDC but it should be only 4 degrees +/-1 degree.

Get a large flatblade screwdriver and bear down on the metal washer that sits on top of the reluctor wheel.

Apply pressure, this will hold the dizzy centre shaft in place and not allow you to dislodge the balance weights.

And then pull the rotor arm off.

Unscrew the 3 screws securing the flash shield, and finally you can get a good look at the pickup unit.

I had no trouble setting the air gap with steel feeler gauges...

Cheers

By the way you will not 'break' the dizzy if you pull the centre shaft out, but you will have to rebuild it!!

Fiddly job but easy enough!!