Thread: Honeymoon's over

Originally Posted by Tins

I have wiring diags for the '95, but it would be a waste of time if they aren't for the one being discussed.

Tins, Is yours the "Electrical Troubleshooting Manual" version?

Originally Posted by gavinwibrow

Tins, Is yours the "Electrical Troubleshooting Manual" version?

Yes. It's a little impenetrable as it deals more in modules than actual wiring, but I'd have a go.

Originally Posted by DoubleChevron

Well you have found the problem. 0volts at the coil when cranking means it will never
start. Who wants to bet you have the identical issue to me .... SO if I just wait a bit, you will solve it for me

Seriously, we need to hit the wiring diagrams. There is obviously a 'start' and 'run' circuit. Possibly through the key.
We need to trace out the start circuit and see where the problem in it is. Even really early cars had a "start" circuit
to bypass the ballast resister and throw 12volts at the coil for easy starting.

Yes, and... maybe no.

I was talking to Ward (Graeme Coopers) before I realized what the actual issue was... Ward happens to know the car intimately before I purchased it via him in 2014.

We ran through the 0v at coil scenarios, what's been done electrically, what hasn't.

Based on what I knew (believed) at the time, he came to the same conclusion that I had, in which there's an issue in the harness. (nb: he was working from the information I gave him in our phone conversation, he had not formally diagnosed the vehicle personally).

So, rather than pull the entire dash out and look for the solder joins in the harness that runs along the firewall,
there's another white/green wire that pops out near the coil which apparently also has +12v on it when IGN on and
while cranking.

I tested that later - it was pouring down here since 9pm previous night - we're getting a proper
monsoon season up here for a change (i.e. it's a bit late starting but it is properly wet), and with the RRC in the lean
to (i.e. not on the concrete floor shed, but on a red dirt/soon to be mud floor) I was in no hurry to head out there the next day to bypass the main feed and go bezerk on wiring and testing.


EDIT: 8 hours later (other work had to be done)

It's running.

So the moral of the story is/was pretty simple. don't make assumptions based on an incomplete diagnosis (i.e. don't rush).

What did I forget? One small step... (one giant rooster-up)

With RRC pointless (pun intended) ignition, there are only 3 failure modes that have "replace-only" consequences. The
fourth is an unlikely and rare (but it happened to me in 2015) starter switch failure (age shall weary them) which typically manifests itself with no ign on or a stuck key or no-turn.... all these failure modes are well-known and obvious to an owner with half an idea of vehicle maintenance.

1. Failed HEI module (in my case- a relocated Bosch 021 - aka the BIM 024 module). Generically you can get a number of 4-connector GM HEI modules which all do the same thing, but the holden blue motor 6cyl module is actually the strongest- the bosch 021 - aka BIM024. Fuelmister do one, CM418, There's a bunch of other US-based ones, including pertronix and MSD, mallory etc... all do the curved GM hei version, Tridon make one - I think it's TR-024 from memory.

2. Coil - unlikely to have a coil fail, but the new stuff - i.e. transistorised ones - are not oil-filled like their
cylindrical ancestors. I believe they are just as reliable but perhaps decades of thermal cycling in a LR engine bay
might be a rougher life than in other vehicles.
My RRC under bonnet temps are ridiculous - and I have twin 3000cfm thermos pulling through the radiator and blowing the engine bay down... heaven knows how much worse it was with the visco fan before that.
I humbly suggest if you have a known good coil that's an oldie, keep it as a spare, and buy the new transistorized one (because that's all you're likely to get from the parts stores these days) or pillage one from anold Holden or ford v8 or 6cyl HEI (commodore/falcon) if you're in the sticks.
Yes, you will need to change the HT lead end because of the different connection, but if you're stuck in the middle of nowehere, you can use what you have and some electrical insulation tape, and you will be able to limp home. Again, bosch HEC/MEC coils are around, but harder to find. You need the older female connection type unless you plan on changing the coil HT lead to an HEI style connector on the coil end.

3. Reluctor coil (in distributor) Not a common failure mode, but it does happen. When it does happen, it's also likely
to take out the module - as the module will overheat, or module failure takes out the reluctor coil. BUT - the module may not fail in immediate sympathy - it may develop an odd or erratic behaviour - and this can be puzzling.

This is why the Bee-Utey relocation / BIM 024 mod is the best available option without ditching the setup completely.
Failure mode of the reluctor coil is an open circuit resistance measurement on the coil - it is the definitive indicator, however it is not always a 100% guarantee that a failed reluctor coil will go 100% open circuit. It's entirely possible for the coil to "self-heal" in thermal cycling or for the coil fracture to only occur when the thermal cycle allows the wire to break. AND... it doesn't have to be a break, it can be a short across windings, which simply reduces the resistance of the coil (so it appears to be within spec) but the coil output is not at it's correct peak - and this is where it can deceive. (and it's where I caught myself short by not taking my time to think it through while diagnosing and testing).

Most of the time the ignition issue presents itself as an intermittent start - and eventually no start. The most benign precursor to the failure mode will be a random stall or a stumble / misfire which self-corrects, with everything returning to normal immediately following. This scenario may occur more frequently over time or only occur a few times over a longer period before the reluctor coil goes open circuit fails completely.

It's so easy to confuse it with the Prince of Darkness Rotor/cap replacement regime... and it does give cause for any ignition issue diagnostic, to include summarily the resistance and voltage tests for the reluctor and the module and coil, before shotgunning parts in as replacements.


So, Where did I go wrong in my diagnostic process?

The old adage - To assume makes an ASS out of U and ME - that's what!

I made the assumption that my recently acquired cheapo DMM was following the reluctor output as quickly as my fluke and Agilent DMM's- and because I don't have my 'scope here- or any of my tools for that matter, I incorrectly assumed that the peak to peak cycle was accurate - I was seeing quite a decent swing on each pass of the triggers, but it was obviously not accurate. The DMM was so slow, that I was actually missing maybe 50% of the P2P readings at cranking.

Secondly, I discounted the fact that the reluctor coil was intermittently faulty, simply based on the previous evidence under test. I *should* have parked my results there and continued the process completely, by checking the resistance measurements AND the voltage / current measurements when I was cranking the motor over - but instead, I believed the DMM reading to be wholly infallible, when it wasn't following the output accurately.

Thirdly, I should have directly referenced the spare dizzy resistance before I put it in - because this is the point where I decided that the reluctor on the dizzy in the car was OK when it was failing intermittently. - IF I had paid more attention to that, I would have seen a decimal point on the readout that was in the wrong spot.

YES... I got caught out by the auto-ranging on the cheapo jaycar DMM.

Because of the inordinately short leads of the DMM, it was not possible to crank and read the meter in situ, without being a contortionist, and the angle I had it on (sitting on the top of the radiator, facing the drivers a pillar) was only enough to be able to see the numbers, but not the decimal place - and this is where I made the fatal mistake of ASSUMING that the reluctor coil was OK.

OK, how did that happen?

Yes, it was observing similar digits on the screen output- the readings on each reluctor were about 3.458 and 3.620 from my scribble notes. Except one was MΩ and the other was KΩ - and that's a massive difference.

Now, since I had discounted the reluctor coil, I moved to the module and HT coil - I tested them, got inconsistent readings on the two ignition modules so I swapped the existing module and coil out believing the module had failed or perhaps the coil had shorted internally or misbehaved and sent HT back to the module... I tested the new ones in circuit, and then found I had Zero volts on the coil when cranking.... and, yes, there WAS zero volts on crank - but again, I made an assumption that the module and coil were bad and the new ones I put in were OK.

So I pulled the steering colum cover and lower dash out, and started to chase the starter switch - which I had replaced back in 2015 after a similar issue where the car would not start (and I should have remembered) - which was (get this....) when I replaced the starter switch and at the same time ironically, did the Bosch ignition update and module relocation from the original distributor mounted unit.

Yes, I had been there before.... I had DONE THIS TESTING before... Properly, with tools that I was familiar with.

But the nuts and bolts of it are simple... I misread the DMM and because of that I went on an endless circle diagnosis loop.


Some context/pretext for the failure...

The car had been towing a boat up the highway in the abnormal torrential rain for 16 hours, and the thermal cycling on the trip up was not the norm for the vehicle to say the least. Those conditions created a scenario for a weak reluctor to only fail intermittently - despite testing OK and running like a normal vehicle without intervention. Not having a multimeter in the car, nor all my tools (due to moving house) I was a little short on 'backup' because I had a car choc full of stuff that the removalists couldn't/wouldn't ship in their precious containers....

I was running the gauntlet - and I got caught short. and it cost me a pretty penny to get 'home'.

So all that second guessing myself and then ignoring the logic in my testing observations, along with mistakes made in observation meant that I could have resolved this a lot sooner had I been a little less hasty with the 'get the damn car running' attitude.

Now, after all is said and done, the car's still not quite right. There is an idle stumble, and a leaking IACV, which I had previously sealed, but in my 'remove-clean-replace-test' I realized the threads going into the plenum are pretty well munted, I'll need to replace that (but it is not the cause of the stumble) as lokseal is not going to prevent the thread from complete separation.

It could do with new plugs and leads, I have not changed them since 2015, as they are 'known good'. and were until this events occurrence.

But, again - the vehicle was running just fine, even when it was intermittently going birko.

So I have not discounted another underlying issue.

This motor is tired, it's in need of a reco, but I really do want to see how long I can make it last. I don't abuse it, and it's got the best of care with fluids etc, so the conclusion is - it's not over yet. But it has had a good life and part of me still wants to keep it for farm truck use (bit too nice for that though) and maybe with all the spares I have I might see a disco or something else a little more "reliable" (yes I know that's a false reality) in the driveway in future.

Mistakes made. Lessons learned.

But the Honeymoon is over, for sure.

I had a similar issue with my VH commodore. Whenever it was a really hot day on a long trip, I would lose power until the engine bay cooled a little and everything was fine again. I put this down to fuel starvation, which I thought was confirmed when I found a badly contaminated gauze fuel filter in the carby. As this only occurred a couple of times a year, it took a few years to finally target the reluctor coil as the problem.

A couple of weeks ago I went to use the ****box here and it wouldn't start again ..... I thought "you bloody rippa, lets leave it broken so I can figure out what the damn problem is". Its taken me a couple of weeks to get to it ..... You see it could be anything... dizzie pickup, fuses, ignition switch.... the fact it runs perfectly once it starts is quite bizare.

Anyway, I finally got to it. I just whipped out there and checked for power at the coil ( ie: fuses and igntion are ok). Whipped a plug lead off to check for spark and reached through the door to turn the key ........ It turned about 1 revolution and started instantly sounding absolutely lovely rumbling away on 7 cylinders .... giving me the finger saying "up yours"

Damn it all, do you know how difficult it is to fix something that isn't broken

Originally Posted by DoubleChevron

A couple of weeks ago I went to use the ****box here and it wouldn't start again ..... I thought "you bloody rippa, lets leave it broken so I can figure out what the damn problem is". Its taken me a couple of weeks to get to it ..... You see it could be anything... dizzie pickup, fuses, ignition switch.... the fact it runs perfectly once it starts is quite bizare.

Anyway, I finally got to it. I just whipped out there and checked for power at the coil ( ie: fuses and igntion are ok). Whipped a plug lead off to check for spark and reached through the door to turn the key ........ It turned about 1 revolution and started instantly sounding absolutely lovely rumbling away on 7 cylinders .... giving me the finger saying "up yours"

Damn it all, do you know how difficult it is to fix something that isn't broken

Test your reluctor coil.
That is exactly the same scenario I had.
If it's failing, the reading will be high or intermittent. wiggle the two wires under the protective cap while you test for conductivity on the connector.

Originally Posted by Mercguy

So I did a bit of ham-fisted diagnostics yesterday after slashing... I was tired, but not making excuses. Following outcomes.

Coil has 13.2-13.8v with ign on
coil has 0v (yep ZERO) when cranking. as in zip, nada, zilch.

I tested coil+ and coil - direct from battery, and pulled the coil lead from dizzy, attached a spare sparkplug and let it earth out to the block for confirmation.

No spark.

Fuels fine, cranks beautifully.
Have had to disconnect the ecu sensor wire to do some tests, but it's obviously connected when trying to start the thing.

........................................

Lastly, I removed lower dash cowl and steering column cowl to check the ignition switch (which I replaced back in 2015) - it is fine physically, but I have not tested it electrically yet (ran out of daylight)

........................

I haven't been able to post due to log in issues, but today I can.

The symptoms above are exactly what I had some years ago, which was caused by worn dimples inside the actual ignition switch which sits on the end of the key barrel. Was somewhat temperature dependent.

From memory the feed to the coil when cranking comes from a separate wire (resistor wire in my case) then switches to a normal 12v wire to coil when you release the pressure on the key to normal 'ign on' position. (Could be be the other way round.......)

I had to figure it out in the middle nowhere when it got really bad..............temporarily solved by hot wiring the switch to supply power to coil when cranking (from memory).

Took the actual switch apart when I got home and remediated the dimples, which sorted it as a bodge till I got a whole new switch / barrel unit (they're only a hundred and something dollars).

cheers, David L

Thanks Guys,

I'll get back to it soon. Does anyone know what resistance the pickup should be ? The best bet is probably a new replacement, keeping the old one in the glovebox as a spare if it is ok.

seeya,
Shane L.