Before you spend a lot of money, there are a couple of things you can test - the 2 pigtail components mounted to the coil bracket.... the rectangular one is an LC filter with 2 wires and the cylindrical one is a capacitor:

1) disconnect the capacitor lead, touch the connector terminal to ground to bleed any charge.... now read resistance from the connector to engine ground - it should be infinite (no continuity).

2) disconnect both leads from the LC filter and ground them briefly. read resistance from both leads to ground (individually). Both should read infinite (no continuity). Now read across both leads - there should be SOME continuity (don't know how much), but a capacitor and resistor are inside the filter and the resistor bridges the 2 leads internally.

If either component's capacitor is shorted, they will bleed coil voltage to ground.

Other possibilities are the distributor and ignition wiring, but try those tests first.

Frank

Thanks Frank. I put a new power transistor in and it made no difference. I forgot to check the power unit before installing it. However took it out to test. When 1.5v applied across term 1 and 2, the resistance between term 2 and 3 drops but by about half. I'm hoping that means it's OK.

Just saw your post above re: the capacitor and filter. Will check those tomorrow - I did wonder about the capacitor... they fail fairly often and is usually the first suspect when a spark disappears from an engine with points (contacts)

Am also tracing the power from the ignition switch to the coil (wire 3-BW in the circuit diag). I still only get 8 to 9v at the coil, with or without the ECU and power transistor which should not be. I have now checked the back of the ignition switch - 12v, next just after connector C-66 - 12v. After connector C-66, wire 3-BW branches off and changes colour to RL via a multi purpose fuse to power the instrument binnacle (speedo pod). the main BW wire carries on to B-67 which is the last connector before the coil..... Apparently B means it's in the engine bay somewhere but I cant see a connector, only wiring loom. I'll check behind the battery tomorrow. Surely that connector is causing the voltage drop although I don't quite see how it would suddenly happen. Thanks for your help so far. Rgds

Yes, B-67 is your last connector before the coil. I remember searching for it when I had a coil issue - IIRC, it's somewhere between the passenger headlamp and the battery - maybe fairly difficult to access..... but on the Japan spec truck it may be in a different location - maybe on the other side of the engine bay from ours.



That doesn't sound quite right - you should get continuity (zero ohms) between terminal 2 & 3 with power connected and those terminals should read completely open (infinite resistance) when power is removed. Maybe you're on a low resistance scale, but I'd be concerned about that and want to recheck it.

It sounds like some of your problem was in the ignition switch since voltage increased after replacement.

On these ignition systems, I've never heard of a capacitor failure - but anything's possible with electronic parts.... they can last for 1 second or forever. What DOES happen fairly often is the insulation and wires on the LC filter get very brittle and can break.

Frank

Hey Frank I've found it - connector B-67 nicely hidden under the airbox which had to be removed to access the connector. All gunged up inside but looks lovely and clean outside. Can I attach a pic? Will try and clean in the first instance, unless I can buy a new connector and it's not too difficult to connect the wires? - perhaps theres an alternative.

After cleaning will check for a spark again.

Good work! <img src="/forums/images/graemlins/kewl.gif" alt="" />

If you have a picture host, just insert it as an [image] file. If you don't have a picture host, use:

ImageShack

Re-size it to 600x800 or so (before the upload), then click on the produced thumbnail to get the re-sized picture - right click the picture and copy the URL address - paste that into the forum's [Image] link. I've found that to eliminate the porn that sometimes invades these free image sites on thumbnail links.

Any water-tight 2-wire connector should work - or you can direct splice the wires.

Frank

See if this works:

Any idea how to get the wires out of the back of the connector. Mitsubishi left no slack so I would be keen to retain as much wire length as possible. Is it as simple as a good tug to get them out?

Here's the picture - and it looks nasty, like salt corrosion, followed by arcing:



I forgot that B-67 has that many pins - you'll be better off going to a junk yard and finding another good connector pair - then you can cut and splice with plenty of wire length. I'd suggest that you crimp, solder AND shrink wrap the butt splices.

Frank

There are actually only 6 wires on either side so it looks more daunting than it is. I don't know how it continued to run - some of the pins seem to be are missing and the male pin for the wire to the coil was not connected any more...

Anyway will order a suitable connector and once received put everything back together to see if the old coil and power transistor are up to snuff... Will update as to the outcome.

In the meantime thanks much for your support with this - persistence is helped a lot when there are two trying to solve the prob. B/Rgds

Glad to help - let us know how it goes..... I think you've found the problem.... and yes, sometimes it takes an extra boot in the <img src="/forums/images/graemlins/butwiggle.gif" alt="" /> to not give up on diagnostic efforts. <img src="/forums/images/graemlins/lol.gif" alt="" />

The older I get, the more I have to remind myself that mechanical things usually aren't self-healing... and that nothing will improve until I pick up a tool and use it. <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

Frank

All done and running perfectly. I decided not to put in a connector in the belief connectors are only there to help meet different specs during factory assembly. A connector would also increase the potential for future failure as instead of just two splices that could go wrong you would have splice, wire to connector, connector to connector, connector to wire, then splice.

Pic attached of the result. I twisted the wires sort of in line and heavily soldered the connection. The heat shrink has adhesive inside to water proof the connections. At this point my only concern is that the wire I used may be a bit light for the coil connection. The description was 6amp max 10amp but upon checking the conductor diameter it might be 14 gauge which has a max of 6amps. I doubt the coil draws more than 6amps though and will keep an eye on it. Also if I get a misfire at high revs I'll know where to go.

B/Rgds, Matthew - car shown below