V8 disco 1 has no spark

Hey,

Got a v8 disco 1 which isn't getting spark to the plugs.

What would be the next steps in fault finding?

Welcome

Do you have power to the coil?

J

Cheers

How can I test the coil?

What engine do you have?

let’s get the basics first.

J

3.9 V8

Jack Ryall said:

3.9 V8

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Is it still in the disco?(only asking incase you put the engine in something else)

Have you got an immobiliser fitted?
Have you heard/seen the motor running?

Yes it's still in the disco
It's cranking but won't fire up
The immobiliser has been bypassed

What motor do you mean sorry?

I have tested the spark plugs bit nothing doing

Do you have wiring diagrams (workshop manual)? and a multimeter?

You need to check power to the coil with ignition on it may go through a relay/fuse.
I dont know that engine but its pretty basic stuff to check first. So I would have to have it in front of me, I mean talking you through it is difficult.
Distributor/rotor arm/ amplifier/coil would be my first ports of call, staring at the first thing in line, I.E power to the coil.

Think @discool knows a bit about them so may be able to point you right.

J

As @marjon states above diagrams and meter are required.

The battery voltage to the coil is via the ignition switch when in position two.
So if the spark plugs are wet then fuel pump is running, so power is as far the coil is ok as the coil supply links to the EFI ECU which then controls the fuel pump.

So the usual suspects are dirty coil top terminations, iffy coil, king lead (is there a spark at the end removed from the distributor ?) or ignition amplifier… I can think of for starters at the moment.

We don‘t know the model year of your vehicle, but if you say the immobiliser has been bypassed and hopefully it hasn’t been touch and there’s no need to go there, and the 300 series 1995 onwards doesn’t have any relays or fuses directly with the circuit to the coil… when it left the factory




Sent from my iPad on a train.

I have been having a similar problem with a mates Discovery 1 3.9 V8.

We can do not seem to have a 12v supply to the ignition coil.
The car runs fine if you run a wire from the positive battery terminal to the coil.

where does the coil gain its 12v from and from what cables, where should we be able to trace these cables back to.
The spider has been removed. 2 button key fob is still needed to turn the immobilizer off.

Any help would be appreciated.

Aidan

AMAILES98 said:

I have been having a similar problem with a mates Discovery 1 3.9 V8.

We can do not seem to have a 12v supply to the ignition coil.
The car runs fine if you run a wire from the positive battery terminal to the coil.

where does the coil gain its 12v from and from what cables, where should we be able to trace these cables back to.
The spider has been removed. 2 button key fob is still needed to turn the immobilizer off.

Any help would be appreciated.

Aidan

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If it was me I'd start at the ignition when the key is in position 2, if you get it turning on, then the feed to it from the batt is good, then follow that cable through all cables, connections and relays if there aren't any. A simple Haynes manual wiring diagram should help. Sorry I don't have one.
But @discool will.

Hi Stanley, thanks for the reply.
we turn the key to position 2 and do not receive any voltage to the ignition coil.
Turning the key to position 3 then using a jumper lead from the +battery to the ignition coil starts the car.
The car stays running and runs great.
does this confirm the ignition barrel wiring is okay but there is a break that goes to the coil.

Electrics are not my strong point. be nice to see a wiring diagram to the coil to see where it should get 12v from and i can try trace it.

As you didnt mention the year of your D1 nor your location i can presume that you are in UK and it's post '94 RHD and if it is the feed for coil is from fuse F3 sattelite fusebox 1(on top of interior fusebox) but if this was blown the engine would not run as well cos it feeds the pump too so for simplicity you better run a wire from that fuse directly to the coil, you can pick up that feed from HJ7/S292 white/green wire, see attachments (if it's earlyer modell or LHD next time make a better introduction)

Thank you for the support, yes the vehicle is a 1997 discovery 1 V8.
I will try these steps and see if this resolves the issue.
I shall update you.
Thanks again

AMAILES98 said:

Hi Stanley, thanks for the reply.
we turn the key to position 2 and do not receive any voltage to the ignition coil.
Turning the key to position 3 then using a jumper lead from the +battery to the ignition coil starts the car.
The car stays running and runs great.
does this confirm the ignition barrel wiring is okay but there is a break that goes to the coil.

Electrics are not my strong point. be nice to see a wiring diagram to the coil to see where it should get 12v from and i can try trace it.

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If the starter tunrs when you turn the key to position 3 then you have got +ive to the ignition switch. But as you have no further +ive to the coil then there is a break somewhere either in the switch or from the switch position 2 to the coil. You'll need to use a test lead or a multi meter to find the break. Once you have checked all fuses are intact, and test them with a MM, battery and wire or by substitution, they can look OK when they aren't. Personally I'd start first at the4 ignition switch checking there is juice at position 2 outlet. If not the switch is fubar.
Next at the nearest point it comes through the bulkead in the engine compartment, testing from there to the coil. If that is OK then you know the break is inside the vehicle.
It's a process of elimination.
At least you can jury rig a wire from batt +ive to a switch in the cab and from that to the coil as a temporary measure to make it easier to drive the car.
Best of luck, total pain!

Total Pain is certainly how i feel about this!
I have a feeling it is down to a broken cable somewhere, I have been through fuses multiple times all looked okay.
I shall let you know how I get on

AMAILES98 said:

Hi Stanley, thanks for the reply.
we turn the key to position 2 and do not receive any voltage to the ignition coil.
Turning the key to position 3 then using a jumper lead from the +battery to the ignition coil starts the car.
The car stays running and runs great.
does this confirm the ignition barrel wiring is okay but there is a break that goes to the coil.

Electrics are not my strong point. be nice to see a wiring diagram to the coil to see where it should get 12v from and i can try trace it.

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To answer your question.. Yes. As I take it u have a 1995MY 3.9 or onwards.

Ok if u have, it seems to be a simple issue with the spider immobiliser thats fitted in the factory. But if u don’t have one then the link to bypass has the issue, and as your test proves… with the wire link from battery + to coil +.
If so then remove the connector with a black wire on the coil + as that is now redundant, and install a new wire from the + terminal, and take this wire following the engine loom that runs across the engine under the Plenum chamber and through via the bulkhead grommet into the fuse box area.

At fuse board, locate it at the ignition switch 3wire loom at it termination on the fuse board, and terminate the new wire with the yellow wire… irc the other two wire, are red/ white and white which u don't need to touch.

Or it may be simples for you to just ‘piggy back the new wire with fuse no.3 as stated in #13 by sierrafery

Stanleysteamer said:

If the starter tunrs when you turn the key to position 3 then you have got +ive to the ignition switch. But as you have no further +ive to the coil then there is a break somewhere either in the switch or from the switch position 2 to the coil. You'll need to use a test lead or a multi meter to find the break. Once you have checked all fuses are intact, and test them with a MM, battery and wire or by substitution, they can look OK when they aren't. Personally I'd start first at the4 ignition switch checking there is juice at position 2 outlet. If not the switch is fubar.
Next at the nearest point it comes through the bulkead in the engine compartment, testing from there to the coil. If that is OK then you know the break is inside the vehicle.
It's a process of elimination.
At least you can jury rig a wire from batt +ive to a switch in the cab and from that to the coil as a temporary measure to make it easier to drive the car.
Best of luck, total pain!

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As the OP states the engine is starts and is running then there’s not an issue with ignition switch and “all the fuses “

discool said:

As the OP states the engine is starts and is running then there’s not an issue with ignition switch and “all the fuses “

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AMAILES98 said:

Hi Stanley, thanks for the reply.
we turn the key to position 2 and do not receive any voltage to the ignition coil.

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discool said:

So if the spark plugs are wet then fuel pump is running, so power is as far the coil is ok as the coil supply links to the EFI ECU which then controls the fuel pump.

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So OP says there is no voltage to the coil, yet you say "power is as far as the coil is OK" How can both be true? Power could still be getting to the EfiECU but still not to the coil. But this may be a good point to start looking.

OP jumps from Batt positive to the coil and hey presto it starts and runs, which very clearly implies that, no, he doesn't have power to the coil via the ignition switch and its subsequent wiring. .

The OP did not make it clear whether it keeps on running with the jumper wire disconnected or not. you seem to be assuming that he disconnects the jumper wire and it still runs, which makes little sense to me.

As for "all the fuses" I have no idea if it has any or where they area as, although I have 3.9 Disco sitting on my drive, it is under tarps and I have better things to do at the moment than start crawling over it, under it or inside it.
I also have no Haynes for it as I bought it on a whim cos it is lpg and I have yet to get stuck into it

Parts of, or even all of, the ignition switch may well be OK, which I said he'd simply have to eliminate, but I am not convinced that the connection between +ive to the switch and the wire to the coil is still there, although it ought to be.

Why not try to be more positive and less patronising.?
I notice that @marjon said more or less the same as I did in post#8 yet you didn't take the p!ss out of him.

Stanleysteamer said:

I notice that @marjon said more or less the same as I did in post#8 yet you didn't take the p!ss out of him.

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Because by the time I posted that it had been established the immobliser had been removed bypassed.

I think you reading a bit too much into the smileys.


J