7 days and still a weak spark - inspiration required please

[dwhitaker]

Which nicely brings me back to the question. I would really appreciate someone doing a comparative test. This will only work on a 2.9.

I think my ignition earth path from the coil is poor, but I am "poking and hoping" a bit so need a comparison. I think the path for the ignition earth is from the ignition module, to the ecu, then out of the ECU to ground. This would make sense, as there is paste between the ignition module and the dizzy.

If a kind volunteer would
1) pull off the plug on the ignition module which is mounted on the side of the dizzy.
2) Put a small pin (I used a tiny watchmakers screwdriver) into the bottom (Blue/Black) hole of the plug
3) measure the resistance to the battery negative. This reads something over 2000 ohms.
4) Then switch the ignition to the run position. Mine drops to about 190 ohms.

I "believe" this should be close to zero and is my problem. However, the wire to the ECU, and the earths from the ECU are all good. Suspect is now the ECU, but need a comparison to be sure.

Next steps irrespective are to get an ECU, and then if that does not work, shell out for an auto electrician. Have had the lid off the ECU, and no obvious water ingress.

Many thanks in advance.

[Le TVR]

Sounds like a failing condenser or condenser earth? But IIRC the condenser is integral to the ingition amp and you've already swapped that out.
I think the ignition amp earth is from the dizzy? Might be worth checking that or even running a new wire direct.

[dwhitaker]

Le TVR said:

Sounds like a failing condenser or condenser earth? But IIRC the condenser is integral to the ingition amp and you've already swapped that out.
I think the ignition amp earth is from the dizzy? Might be worth checking that or even running a new wire direct.

The earth is on the Black/Blue towards the ECU from the ignition amp. Need someone to test this resistance to earth with ignition off and on so I can compare (Please :-) )

Cheers
Dave

[phillpot]

dwhitaker said:

Need someone to test this resistance to earth with ignition off and on so I can compare

Dave, don't know if this will help or confuse further...?


Bottom terminal ign. off = 1740 ohms

ign. on = open circuit

So I thought I'd check for volts...ign. on

bottom (blue/black) = 4.6
next = 12.9
next (black) = 12.9
next = 0
next = 12.2
next = 4.1

Started sorting out mt spares yesterday and found an ECU.....Pretty sure this will have come from an S2 or 3 and not a late catylist car. Condition unknown but in the five or six years I've been following this Forum I can't recall anyone definitely having a faulty one.

Edited by phillpot on Tuesday 21st October 21:19

[dwhitaker]

Hi All
Thanks for having the interest and taking the time to support this re-commissioning.

I ma delighted to tell you that its a runner!

Just to remind you, the symptom was originally no spark. Quickly found coil was a gonner. Then it was an extremely weak spark, so weak that it did not spark at all and could only be detected with a spark tester.

Going downstream, changed ignition module, then whole dizzy (thanks Phillpot), then ECU (is anyone interested in having one for a spare?). No change.

Yesterday, started working upstream, had obviously checked for 12V before, but this time checked resistance to battery with ignition on (but earth disconnected). Read about 80 ohm. Bad. So traced it back and found a twisted joint on the white wire into the taco, fixed that and it dropped to 26 ohm. Then realised the connections in the taco leads did not connect to the correct colours in the loom??? Something up. Took apart the connectors, put the black one to the measured earth in the loom, the red one to the measured battery, and the white on to the other. Really confident now..... No joy!

Pissed around for another 20 mins then FINALLY figured out that the taco and speedo connectors were reversed. My coil was being fed by the speedo!!! (FYI I only got the car 10 days ago). Swapped these over - spark to light up Blackpool.

Put the whole thing back together, crossed fingers and turned the key. It must have turned over about half a turn and burst into life - wow, its been standing for over 3 years that I know of, so I am pretty pleased in the end.

Total cost
Postage for START tester and Loan Dizzy - £12
Coil £50
Ignition module £24
ECU £40 (wasted)

So in total £126, of which only £50 was definitely required. However, a ton of wiring bodges removed and the yellow connector gone.

Phillpot, I am away with work now for a couple of weeks so cannot set the timing up until I get back - let me know if its a problem to hold onto the tester.

Thanks again to all

Regards
Dave

[phillpot]

dwhitaker said:

Phillpot, I am away with work now for a couple of weeks so cannot set the timing up until I get back - let me know if its a problem to hold onto the tester.

No problem at all, glad you're sorted



but 50 quid for a coil!!! and does it work with the coil not earthed

[v8s4me]

Brilliant bit of detective work!

dwhitaker said:

........ECU £40 (wasted)..So in total £126, of which only £50 was definitely required. However, a ton of wiring bodges removed and the yellow connector gone. ......

Not really wasted; you've now got a spare ECU, you've learned an awaful lot about your new car and saved a packet.If one of us lesser mortals had had to pay an auto-electrician to try and resolve the problem it would have cost a fortune Plus if course you've "met" us lot

[magpies]

well sorted - patience of a saint - most people would have resorted to

[glenrobbo]

Well done Dave
Just goes to show how perseverance pays off!

I've been having an intermittant electrical problem with my S1, it's always the worst thing to track down, when you think you've got it fixed, it decides to play up again

But last weekend after hours of flesh scraping fun behind the dash, with looms & wires everywhere & disconnecting every device fed by a green wire, the cause turned out to be the plug-in multi-socket power adapter that I use for my satnav h phone charger. DOH!
At least I think so, watch this space!
Never mind, at least my wiring is a bit tidier now. And I saved the expense of having an auto electrician coming round to my house to test the thickness of my wallet. ( It's actually very thin! )