Missing with advance connected ???

[lanciamad]

With the on-going saga still going with the running of my dads 1600 hpe, I've come across the latest possible cause. It's just had the Carb overhauled and is running not too dis-similar than before, but at least it's been checked over professionally, cleaned, new gaskets etc so it's definitely not the carb.
On trying a brand new coil that showed to spark, the car would just not start. Re-fitted the original and it fired up. Went back to the new and it wasn't having it. So back on with the original and let it run upto temperature. Through the whole time, auto-choke worked correctly but still giving the symptoms of missing and struggling to accelerate smoothly.
I dis-connected the vacuum pipe from distributor to (back? nearest engine) of the carb and it didn't miss and seemed to accelerate smoothly...

I presume this is some type of vacuum advance unit for the ignition? Has anyone experience one breaking down, and what to expect? Just seems odd that if it had failed would that not be similar to not being connected.
You guys may have a better idea
Marcus.

[lukasdeopalenica]

This is exactly a vacuum ignition advance unit and should be connected somewhere to the inlet manifold. When the vacuum in the inlet manifold increases, what is connected with engine loading, the ignition corrector advances the ignition. At iddle speed, the unit is at the zero angle. Not connected hose, or not operated correctly vacuum advance results in poor acceleration.

[gengis]

The vacuum advance can fail...diaphram split, or actuator rod binding.  But having the pipe disconnected would stop the ignition advancing, but also the free end of the tube would be drawing unmetered air into the inlet manifold...which would cause the mixture to lean out.  Couple of things to check...

Check static ignition timming with vacuum pipe disconnected and free end pluged (maybe too much advance at idle)
Check mixture with Gunsons colourtune, or at m.o.t. station.

[capriblu]

I would go with gengis suggestion and check static ignition timing.   If static timing is a touch too advanced at tickover then perhaps  this is partially counteracted/corrected by the lack of any additional advance as engine load and speed increase.   Have you tried making small adjustments to ignition timing?  i.e. simply undoing nut at base of dizzy and turning unit very slightly clockwise (retard) or anti-clockwise (advance) and feeling/hearing/sensing how car responds?

[lanciamad]

Thanks for the suggestions guys, forgot to block the pipe when I disconnected it to see if it had an effect disconnected (and blocked) or not. As it ran better not being connected and as you say drawing in un-metered air perhaps it's running too rich and needs leaning off. Will give it a go and report back, if I can get it running well then it can be finally setup at a garage but it's too bad for that at the moment. I'm pretty sure the timings been checked recently so that should be ok.
Thanks for now, Marcus.

[lanciamad]

Update
Finally some dry weather to get on with things, I removed the vacuum pipe from the distributor and plugged it...

and it seems to run and rev up ok, but as soon as it's connected up to the vacuum advance it plays up and splutters. The timing should be fine as it previously ran fine and it hasn't been adjusted, i've roughly adjusted the mixture on the carb to the best I can at home, so am putting it down to a failure of the vacuum advance unit on the distributor mucking up the ignition
Is there any recommendations of companies that could refurb the unit or anyone with one going spare? (it's for a 1600 if they differ from the 2000)
Thanks, Marcus.

[gengis]

I'll have a look tommorrow, I'm sure there's one in the garage.  It should run ok without the vacuum as it was used for low compression engines to help with low end torque before the main bob weights ramped up the ignition advance.

You could try...taking off the dizzy cap and connect up a tube to the advance unit and sucking it, you should see the actuator rod move (pull)  This will also tell you if the unit is holding a vacuum (diaphram split) or if there is binding on the rod.

[cheeky monkey]

Hi Marcus
regarding a refurbishment, H&H ignition solutions of Brierley Hill did mine.

regards
Graham

[lanciamad]

Thanks Graham, i'm probably going to get them to do this one as well

[capriblu]

Thanks Graham, i'm probably going to get them to do this one as well

Why not send H&H the whole ignition set-up, coil leads etc.. and they will test the lot for you.  This is what they recommended I did so sent them the lot in well packed shoebox!   My system (Bosch Electronic Ignition off 2litre Carb) checked out OK but I took their advice and swapped the original Bosch black box for an alternative trigger/amplifier unit that they built into the distributor (which they rebuilt) and a conventional (non ballasted) coil.  I'm convinced spark is much stronger than before and I've finally managed to eliminate the part throttle hesitation on my coupe that I had endured for too many years despite numerous carb swaps / rebuilds etc.   I think the design of the DAT/DATR carbs produces a slight mixture issue at the transition between 1st and 2nd choke openings and that this is exacerbated if spark strength is a bit weak.