Club 80-90 Forums

937carrera wrote:Hope that helps

It does help. Thanks.

Now we have established which fusebox this is the wiring diagram.
The coil connection should go onto the input side of fuse 12 the last on the right in your picture but it looks like somebody has been at the wiring already. The coil cable is the second thickest black cable the thicker one comes from the ignition switch.
Disconnect the coil cable at both ends, and with a multimeter check the resistance to earth it should be open circuit if there is resistance the cable has most likely shorted to earth (the body).

bigherb wrote:The coil connection should go onto the input side of fuse 12 the last on the right in your picture but it looks like somebody has been at the wiring already. The coil cable is the second thickest black cable the thicker one comes from the ignition switch.

Thanks bigherb. I have not seen that wiring diagram before. What manual is it from? It may be a good one to buy. Are you sure S12 is in the Engine Bay Junction box and not in the fuse box in the cab? The second page says that it's in the fuse box. Right now I have no fuse on the coil wire in the Engine Bay Junction box, just on the circuit that runs to through the reverse switch to the reversing lights.

bigherb wrote: The coil cable is the second thickest black cable the thicker one comes from the ignition switch.

I seem to only have one black wire coming from the ignition switch but it goes to the instrument display 14-pin connector. I'll chase the black wire back from the engine bay J-box and see where it goes...

bigherb wrote:Disconnect the coil cable at both ends, and with a multimeter check the resistance to earth it should be open circuit if there is resistance the cable has most likely shorted to earth (the body).

Great idea. I should have thought to do that. I'll have to find the end in the cab fuse box first. It may be Friday before I get to have a proper go at this.

Thanks again for your help & ideas.

S12 is fuse 12 in the fusebox

bigherb wrote:S12 is fuse 12 in the fusebox

Thanks, I thought you were talking about the other photo. That is a big help in tracing the coil wire.

Ive been posting in this thread quite a lot, viewtopic.php?p=8311353#p8311353but would like to segway over here now

(orignal SS replacemed with an MV, so with all electrics for SS) 1 year ago and suddenly again, I lose the priming of the fuel pump and idle stabiliser, with Key ON (no cranking)
relais are all good and now I figured out that the coil had no power 

I just bridged the cable from the engine bay junction box (black cable and yellow connector) to the Black coming out of the ignition, it seems this is broken.

now both the fuel pump and idle stabiliser, and I guess the crankcase breather heater all come on 

now the coil has spark when I ground the middle of the Hallsender connector

still doesnt start tho at the moment, but then there is more wrong than the cable from ignition to engine bay junction box? I thought that the ECU is on its way out, if hall sender grounding makes it spark, that means the ECU is working right?

next step is to replace the Hallsender?
 

I had the exact same problem and it turned out to be a 1980's Halfords type alarm immobiliser which was fitted behind the headlight grille. I didn't know it was there and neither did the previous owner! It immobilises the engine by cutting the 12V supply to the coil. The multi plug had totally corroded away over the years causing the problem. Not an immediately obvious issue and it did take a while to accidentally stumble across it!!

now it just started working again suddenly this morning 

all I did was take a spark plug out to have a look

so then not the ECU, Hall sender could be a intermittant, I got a new one in the post this morning too (havent exchanged it yet tho)

but that 1 cable from the ignition to the Ignition coil and also all of the circuits back there could could explain it, but then I fixed that 2 days ago and still wouldnt start??

I decided to replace the distributor to rule out the hall sender
took the distributor off and put a new one in then nothing worked again
but then after some research, I found out I didnt seat the bottom properly, so it wasnt turning the dizzy
I put in the used one I already had now and then the motor jolted around, so also realised that the timing was off, luckly took a photo before and turned it around and now its working again

the original dizzy does have quite a lot of play and the hall sender is quite wobbly, and also the plastic cap inside doesnt look too healthy, so good to remove anyway

also the 4th cable on the same Hall sender cable to engine earth, broke off, so had to be replaced

D15 connection to the coil 

I bridged that from the black Ignition cable directly and tested it for 12V to the engine bay, seems fine, so no need to lay a new cable

Yesterday I drove 150km and shortly before home, stopped for petrol, and then it wouldnt start, got towed home by a tow company, (240euros, but luckily was only around the corner).

Relais were switching, but pump was still not priming. Tried to bridge from the battery directly to the pump, while on side of road, but may have done it wrong (but thought I tested the ground) so it didnt work.


Got it working now by bridging the ground (green/brown) from the petrol pump to the engine bay. Even though I cleaned that up recently, the engine bay ground recently too, but guess cable is bad somewhere

 

I had to check then...
Had me puzzled saying Green/brown for earth, ground, or chassis.

I was always convinced that ground was brown unless it was a switched ground.
In which case it would be brown with coloured stripe.

Anyway - glad to say you were correct.
Brown with green stripe is indeed the ground for the fuel pump. And there is no switch in that circuit.

Obviously positive feed from the relay is red / white to the fuel pump.

checking resistance on the brown/green at pump and in engine bay, showed nothing

checking on the pump live and the bottom cable off the relais did show something

layed a new ground cable from pump to engine bay ground point (12)

I cant seem to find the T2a/1 & 2 connectors in the Engine bay left, tho?