Disco 3.5v8 loss of power

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Huntley-Smythe

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Evening all. Hoping someone might be able to help with an electrical issue...
Went out to give Debbie (my disco - MK1 3.5v8, k reg) a spin a week or so ago. Got in, turned the ignition and nothing, no dash lights, no signs of starting.
Took the battery off and charged since it was sitting around 11v.
Tried again, still nothing.
When I say nothing the following still work: side lights, interior lights, main beam flash, the hazards and central locking.
Have done some testing with my multi meter and I'm getting power all the way back to the ignition switch, ignition relay and starter solenoid. Have previously changed out the fusible links for a 300 fuse box. It's as if there is a fault onward of the ignition switch. Have tried a new "Lucas" ignition switch as it seemed as though that may be the issue but still no joy.

Is it a dash out job to trace the wires? Any assistance/pointers grateful received.
 
No its not a “dash out job” :)
But u need to check the 12v supply via the all fusible links to the rest of the vehicle, you will need a wiring diagram, also for starters a voltage at the coil would be good, plus as u will have an active immobiliser fitted, therefore the micro switch within the drivers door or the switches operating cam at the rear pf the lock could be iffy, 2the door lock controls the security ecu which carries out the immobiliser function.

Unfortunately it’s a crystal ball time… which I don’t have. :(
 
Thanks Discool
I swapped out the fusible links for a proper fuse box and the power is getting past that point so that's not the issue.

Will look at the immobiliser side as you mention, would that stop all the dash warning lights coming on, hand brake, oil pressure etc?

I have the Haynes diagrams but they're not great, also have an original workshop manual. Have worked through the "starting system" diagram and testing procedure but all seems fine...
 
You say the ign and batt lights don't come on? I've had similar either nothing or chattering relays but I think the dash warning lights did illuminate.

I'm getting power all the way back to the ignition switch, ignition relay and starter solenoid​

The exciter wire from the alternator to the starter solenoid had come off/was loose. It's only live when cranking.
Just a thought and worth a quick look.

PS Mine is a Disco 1 3.5 hotwire but in a 90 so no immobiliser etc in the circuit.
 
Huntley-Smythe said:
Thanks Discool
I swapped out the fusible links for a proper fuse box and the power is getting past that point so that's not the issue.

Will look at the immobiliser side as you mention, would that stop all the dash warning lights coming on, hand brake, oil pressure etc?

I have the Haynes diagrams but they're not great, also have an original workshop manual. Have worked through the "starting system" diagram and testing procedure but all seems fine...
Click to expand...
No the immobiliser won’t stop the dash lamps, but failing to illuminate could be a second issue.
In fault finding stick to one item at a time, so its ‘why the engine wont start’, then move on u may be lucky in your investigations to find the issue is also in the area related to the engine also not starting.
If the starter motor can crank the engine, then check the petrol is arriving at the fuel rail from the tank then spark plugs are sparking also.
 
Evening all. So, I've tried the suggestions and still nothing.☹️ It's like a broken ignition switch as there is voltage to it but nothing past it on any of the terminals when it's switch round. Have the existing and a new ignition switch and it's the same on both so I'd be surprised if both were faulty. Therefore, I think it's a fault preventing the circuits from completing past the ignition switch. Do the W, WO and WR wires go into a connector block somewhere or is there like a main relay or something or do they just feed into the fusebox does anybody know? All the fuses are fine btw.
 
Have you checked all the grounds ? If you have power, and nothing works, then what about the grounds?

I agree with you on the Haynes diags - What about the ETM for your age of D1 ?

If you have no warning lights, I'd suggest tracing the easiest one of those first - choose either the alternator or oil pressure circuit...
 
The electrical circuits are a bit simpler on the ‘200 series. Below is the Haynes wiring diagrams for engine starting, depending on the model year.
The 3.5 efi was between 1990 -1993 with wiring changing slightly between 93 and 94MY. 3.9 the 93 onwards diagram shows having fusible link also autos having a inhibit switch.
The diagram shows diesel but from the ignition switch the principal is the same.
 

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Thanks
An earth fault did cross my mind so I checked the main earth's between engine and chassis and body and chassis in the engine bay and they tested ok. Are there other grounding locations in and around the dash anywhere?
 
Huntley-Smythe said:
Thanks
An earth fault did cross my mind so I checked the main earth's between engine and chassis and body and chassis in the engine bay and they tested ok. Are there other grounding locations in and around the dash anywhere?
Click to expand...

How are you testing them ? IMO, needs to be under load - they can test fine with a DMM in terms of resistance, but if you try to draw some amps, they can just give up the ghost... Headlamp bulb is a good test of most circuits fused 10A or more ... and a wander lead from the battery -ve to provide an "extra", I.E. known good earth is an excellent trouble shooting tool IME .... if your problems go away when you "add" the "extra", then :)

Loads of multiple point grounds in the footwells of D1 300's and RRC's - don't know the D1 200 that well, but I can't imagine they're that different - RAVE should tell you....
 
Huntley-Smythe said:
Have only been testing with an Digi multi meter but will try your tip re a test lamp, cheers
Click to expand...

HTH. Have a nosy at South Main Auto's YT channel - excellent tutorials on on electrical trouble shooting from the ground up ;);):D - everything from "normal" grounds gone AWOL (etc) through to 'puters up to all sorts of shenanigans :rolleyes: ...

Also, presuming yours has a hand brake cable - watch out for it becoming the only earth, and getting hot, thus losing its strength .... thus no handbrake !!:eek: I've added extra earth straps on both our D1's, given the low cost of doing so :)
 
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