Rev counter going nuts!

[BRoadGhost]

Pretty sure I've mentioned this before & no one else had come across it / knew the remedy and it's come back after replacing pretty much everything on the ignition front...

After sending the 3rd brand new small o.e type bosch ignition module [and dizzy] to H&H for analysis their response was the module was shorting out like a good 'un and needed replacing. The new one is physically much bigger and I took the time to relocate it so there's no possibility of the heat soak the last ones were subjected to.

Everything went fine for the 1500+ miles I ran it for, never missed a beat, so I gave it some advance; drove it for a bit, advanced it some more etc to the point where the mid range felt stronger & stronger. That's where it was left & then randomly not too long after it missed like the ignition just cut out, just holding medium revs under no load. I backed the advance off a few degrees, ran it for another 50+ miles with the same thing now happening only more frequently.

Got the full on stall at 4000 RPM tonight and it not wanting to start again for a good 25 minutes.

All the wiring should be spot on because this has been going on for such a long time now there's little that hasn't been put right. What I'm asking basically is, is it possible to fry the ignition module advancing the timing too much?

If so that would make sense as it seems to kill them slowly over about the next 500 miles along with random total cut outs and making the rev counter go nuts...

[Nova_Tek]

My bro had a crazy mental rev counter and it was a faulty crank sensor. The engine would cut out and would be difficult to start though.

[BRoadGhost]

Well it couldn't be that since it doesn't have one; it's just a basic C20XE on carbs with bosch electronic ignition.

[Benn]

It does get more power thru it cause of the advancing does it? (might sound stupid)

[BRoadGhost]

I'm no expert, but it would make sense that damage could come from too much advance because the system takes load into account; if the spark ignites the mix so soon that the piston is being pushed down before the rod is past the vertical then that would make the hall effect sensor think the engine was under huge load even under normal conditions, overloading the module.

If that is right then even backing the timing off after this [possible] damage, wouldn't make it perform correctly again.

[Benn]

No, i'd say it would still damage it.. Cant see how you could test this really tho.. Or prevent it..

[Jon_nova1]

although i can't see a way in it having to be used, would a ballast resistor be any use?

[BRoadGhost]

Hmm Benn? I think we're both saying damage could very much occur.

I guess having something you can adjust to alter the power / torque curve can be a bad thing unless you're measuring the changes on a dyno, taking things too far.

Prevention could only come from remembering how far I advanced it when the problems occurred, marking the distributor and never putting it round there once a new module has been fitted.

[mowgli]

please explain to me how advancing the electronic sensor in the dizzy will cause electrical component failure.

i'm assuming its got basically a 1.4sr ignition setup on an old style redtop? so the ignition is so basic that if you advanced it too much, simply retarding it will cure it.

the only thing i can think of is that if its running slightly lean & the plugs are getting hot, then advancing it could knacker the plugs.

it was so easy in the bad old days, it was always the coil. cos there was nothing else that could go wrong.

[Benn]

I took it would be a 1.6Cav dizzy.. But i did say it might be a stupid question, cause i wasn't sure if it would take more current as it advanced it..

[BRoadGhost]

It's a hall effect electronic setup from a MK1 1800 8V GTE Astra, but I think it's just the same as the 1600 cav type.

The loom, coil and ignition module has been sent to H&H to be tested when it was doing the exact same thing last year and the failure was the ignition module. I went through about 3 in as many weeks with the advance set far round. There's absolutely no doubt as to what's at fault again, I'm just trying to confirm the why.

There's not a chance the mixture is too weak as it's been jetted on a dyno and the plugs only ever have coke on them.