My Fathers day (with questions...)

[maz_r]

Being Fathers Day, I was allowed to spend the day tinkering (as well as having an enormous fry-up brunch ).

Car is going to go for it's MOT soon, so I though I would check/set the base timing & check the CO level.

Having spent quite a while trying to find the timing marks (who the hell put them up there out of sight??!), I got the timing gun connected up and put the car in service mode. I was expecting the timing to be out (and I was right) but what I wasn't expecting was that every once in a while the gun seemed to fire when the timing was around 8 degrees BTDC; mostly it was firing at 16 degrees (with a little bit of a wobble) but every once in a while it fired at about 8 degrees AND sometimes the gun didn't fire at all; the question at the end of all this is "is this normal" or is everyone else seeing rock solid timing pulses?

Having got the timing as correct as I could, I moved on to the CO measurement; I'm guessing 9.8% isn't going to pass!! After several minutes (read "45 minutes of swearing") I managed to get to the CO pot and having fought long and hard with the tool got it down to 2.7% which I believe should be good enough to pass...

And just to rub salt into my already dipping enthusiasm, I'd been running the engine a little while (40 minutes maybe) at tick-over whilst fiddling with the CO pot and (the good news) the fans had cut in a few times and gone off again, just like you expect when suddenly there was a 'POP' and the expansion tank disappeared in a cloud of steam and boiling water; I wasn't able to see exactly where it was all coming from (I was busy making sure my lad was out of the way) but once the excitement was over, the entire coolant was liberally spread over most of the engine bay, the drive and my missus favourite flowers (which went down particularly well...not) - I know it was empty due to the amount of coolant I had to put back in it (after 45 minutes of cooling down before I dared remove the cap on the expansion tank).

So thank you for reading all this and I would welcome the collected wisdom as to:

1. Does the timing wobble slightly in service mode?
2. Spurious timing pulses - are they normal and/or should I ignore them?
3. Is 2.7% CO good enough?
4. What the heck and a half happened to the temperature/coolant?

I have more questions about why the car seems to run on 3 and a half cylinders, but they can wait.

[John_W]

Maz,
I've not read and digested your whole post, but wavering timing in service mode was cured on my car by replacing the HES.
John

[esprit888]

Maz,
I've not read and digested your whole post, but wavering timing in service mode was cured on my car by replacing the HES.
John

same here

[Brit-Car-Nut]

Hall Effect Sensor (HES) Kit: A100E0102S £18.28 + VAT from ANY Lotus Dealer

[maz_r]

Thanks all - as luck would have it, I ordered one off the aftersales list some time ago whilst having a 'just in case' moment....now, if only I could find it; I am now hoping that this might sort out my slight 'rough running' that disappears (or at least, isn't noticable) when giving it some beans but is evident whilst just pootling around.

Adding to the (never-ending) list.....

[theelanman]

IIRC.....3.5% is the upper limit requirement for MOT

[Enright]

We all feel your pain Maz - entertaining read when you can sitting there nodding in agreement and going "been there, done that!"

Dave Pinky gave a top tip elsewhere a while back - he made his own timing marks!
It's not as daft as it sounds: Seriously - he found the original, lined it up to 0 while the engine was switched off, and then transposed it to about 120 degrees round from that. I thought it was a really good idea as it cuts out the parallax viewing problem.

If you're worried about scatter, take the plastic cover off the CAS and see if there's any rotary play in the reluctor ring - there should be hardly any.

Spurious timing pulses could be caused by over-sensitivity of the pickup on your timing light. It could pick up the odd spark from neighbouring leads I guess...

According to my Gunsons Gastester manual 2.7% is almost ideal - 2.0% is apparently spot-on, but Gareth's right: the pass limit is 3.5%. If you really want to nail it you could always go closed loop with an S2 chip from Alan and an O2 sensor. The scariest bit is getting the old bung out of the pre-cat.

I've not experienced the exploding expansion tank yet, but after 20+ years for something that was originally designed for Novas, it's only a matter of time!