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MG MGA - Problem Starting

After a bit of advice please. Tried to start the MGA today with pout success, it normally starts really easy.
The engine is turning over slower than normal but the car has been on a trickle charger so don't think its flat. I have 12.7v on one side of the starter switch with ignition on. Which reduces to about 9.5v on the other side of the switch whilst its cranking. I have a battery isolator fitted, so I turned it off and connected the starter wires together (so by passing starter switch) Turned the isolator on and the engine turned over fast as normal. I didn't do this for long as not sure what damage, if any would happen if it started.
Thinking it may be the switch. Any help appreciated thanks Paul
p anderton

http://mgaguru.com/mgtech/electric/ss_104.htm
mog

Thanks Mog if I understand correct from below.When cranking it should be less than 1v measured across the two starter terminals?
Just been out and its started 1st time ??

Another way (maybe easier) to check on the health of the switch is to measure voltage drop across that switch while it is carrying the high current used to run the starter motor. To do this set the volt meter on the 0-20 volt scale and connect the test probes to the two studs on the starter switch. Here you should be reading available battery voltage as the starter motor has such little internal resistance as to serve as a ground connection for the volt meter. Then with ignition switch OFF (transmission in neutral and parking brake set), operate the starter switch to crank the engine while observing the volt meter. With about 200 amps flowing through the switch, if the switch resistance is indeed no more than 0.005 ohms, the volt meter reading should drop to no more than 1 volt maximum. If you see higher voltage, that means the switch has too much internal resistance and it will be dissipating too much of the voltage needed to run the starter motor.
p anderton

sounds right, quite a current isnt it !
mog

Thanks. I will have a look tomorrow and let you know how I get on.
p anderton

OK so today I checked the voltage across the starter switch when cranking and it was less than 1v its 13.5v when not cranking.
What I have noticed is that with the ignition off the engine spins really quickly. With the ignition on it cranks very slow almost from slow to a little quicker back to slow. If it fires the engine starts and runs great. What could cause it to run slower with the ignition switched on? Could it be the starter motor??
Thanks Paul
p anderton

Too much spark advance.
Barney Gaylord

barney is that the same as ignition timing advance? if so should I try to retard the ignition slightly? once running it is very smooth. Paul
p anderton

You will probably find that the plastic heel on your points is worn, and the points are closing earlier than before, which will advance your timing. New points and resetting the timing as before will solve your problem.
dominic clancy

Paul A

A bit of a long shot but are all 4 of the plug leads the right way around. Some winters I have swapped 2 leads around, for security, and then forgotten and even a cold engine will start and run rather weakly and roughly but it will start. A long shot as I say.

Paul D
Paul Dean

Thanks lads, the leads are OK and fairly new so don't think that is the problem.
No points there's a pertronix electronic ignition fitted. If I have time tomorrow I will retard the ignition slightly. Am I right that its anti-clockwise for the distributor. Paul
p anderton

do you have a timing light?
mog

yes I do a very old one but it works.
p anderton

super, not sure on the petronix, but I would do a quick check on current timing. somebody on here will know whats a good start point.
mog

Yes, anti-clockwise to retard.

Mog, with electronic ignition you cannot time with a light until it's running.
Neil MG

Yes Neil, but P's car does run, I should have made my comment clearer, sorry.
mog

Ok so just connected the strobe and at tickover (with vacuum removed)the notch on the pulley was at 4 O'clock with the timing marks at 6 O'clock. Ive moved the distributor anticlockwise and the notch is now at 5 O'clock. I would guess if the 2 little pointers are 5&10d btdc I'm now at about 15ish before it would have been nearer to 30d btdc. The tickover revs have now dropped.
I've left it to cool down to see if it starts any easier. Ive also left the distributor loose untill someone (cleaver than me) can confirm I'm now, hopefully moving in the right direction. Paul
p anderton

there should me more than 2 pointers I am sure, 1 large and a few smaller.
mog

Mog there are 3. 1 large which I guess is TDC and 2 smaller ones 5&10d BTDC ?
p anderton

I spent a lot of time adjusting my timing last year. Firstly at what revs are you taking these readings as anything from 8 to 32 btdc can be right depending on revs with vac advanced disconeccted. Personally I would start at a conservative 10 degrees btdc at tick over, say 600 rpm, and if it you still have starting problems there is some other problem as it really should start Ok at this setting. If it is OK at this conservative setting you can start advancing it playing around with it aiming for around 30 to 32 degrees btdc at around 3500rpm.

Paul D
Paul Dean

Paul D I took the readings at tickover. Just been out and there seems to be a vast improvement. Engine is cold and its trying to fire 1st turn. With the choke pulled it fires and starts 1st turn. As I say the tickover has now slowed down to about 500rpm but that's easy to adjust.
p anderton

Yes, you seem to be much closer.

Ideally you need a timing light with dial in advance so you are always checking at the TDC mark.

As Paul D says, you can then aim for around 32 degrees maximum advance with vacuum advance disconnected.

It sounds likely that your mechanical advance mechanism is sticking or not working properly. That is a common problem on old distributors. If so, that may be why the car has so much advance set, in order that it runs ok at higher revs. Certainly you should check the advance with the timing light at different revs to confirm. Same for vacuum advance.

Personally, if in any doubt I would stick a brand new distributor on. If you get an electronic one you can get rid of the Pertronix too. For £75 or so you get red a rotor arm and coil included too.

I have fitted several of these now, both Powerspark and Accuspark, cars all run great and have not had any issues to date.
Neil MG

I will try and give it a road test tomorrow. Maybe I should look out for a new light. How does the dial in part work? Im going to the restoration show at the weekend, so could be on my list of things to get. Paul
p anderton

Typically there is a knob on the side of the light/gun that you turn to set the advance figure, which is displayed on the back of the light/gun. That adjusts the timing of the light so that at say 32 degrees the timing mark on the pulley will line up with the TDC mark on the flywheel.

Either you turn the knob until the marks align and check what the reading is, or you preset the desired advance and turn the distributor until the marks align. Simples.
Neil MG

Yes that sounds better than mine, I will get one. So as Paul Dean says above, with the dial in type strobe, set it to 32 get it revving at 3500rpm and the tdc & pulley marks should line up? With the vacuum disconnected.
I'm getting there I hope..
p anderton

Here is a guide as to what to pay:

Budget:
http://www.ebay.co.uk/itm/Adjustable-advance-Strobe-Light-Ignition-Timing-Lamp-Powerspark-TL200-/360513112288?pt=LH_DefaultDomain_3&hash=item53f04188e0

Quality:
http://www.ebay.co.uk/itm/BERGEN-Xenon-Inductive-Digital-Timing-Light-with-LED-Tacho-Readout-/301540670109?pt=LH_DefaultDomain_3&hash=item4635397a9d

Pro:
http://www.ebay.co.uk/itm/gunson-G4123-Supastrobe-Professional-Timing-Light-/251741238330?pt=LH_DefaultDomain_3&hash=item3a9cf2743a
Neil MG

It's the way I always tune mine. So easy. I got a very good Chinese replica distributor from Bob West for £50 about 6 years ago and fitted the flamethrower (Petronix). Never had to touch it since.

Steve
Steve Gyles

Steve, my guess would be that the Accuspark and Powerspark kits use the same distributor. They have been selling for a similar price to Bob, for about the same length of time. The deals have gradually got better though and in my view the quality too. Distributor, red rotor arm, electronic ignition, cap, leads, spark plugs and coil all delivered for about £85!
Neil MG

Took the car out this morning, it started nice and easy and drove very well. I only did a few miles but all seems well.
I have ordered a timing light so will check timing when it arrives, but as its running OK I'm not going to fiddle any more. Thanks for all the good advice.

Im off to the NEC restoration show on Sunday anyone else going?
Paul
p anderton

Paul, off topic but, where do you live? I am near Malvern.
Nigel Munford

Hi Nigel, I'm in Bromyard. I have sent you an email. Paul
p anderton

Timing light arrived today. Checked timing and I'm running at 12d BTDC at 500rpm and it gradually moves to 30d BTDC at 3500rpm so I'm hoping all's well. It is certainly driving better.
Thanks for the help. Paul
p anderton

Excellent!

That confirms the mechanical advance is working and that you are nicely timed! You have another couple of degrees to play with too!

Which timing light did you get?
Neil MG

I got the Accuspark P8000 £29.00. Seems Ok for what I will use it for.
Next job is to get the speedo recalibrated, its reading way to high.
p anderton

Paul

Well done. Like Neil says you could take it another couple of degrees to 32. Bit of trial and error and what works best for your set up and fuel type (I always use super unleaded).

I have any number of good quality tools in the workshop that sit idle for sometimes years on end. However, when that particular job comes around the investment is so worth while. What would often be a few hours work can sometimes be done in minutes.

The guys will tell you of plenty of recalibration specialists if you do not already have one. I use Speedy Cables. They did a good job for me. http://www.speedycables.com/calibration.html

Steve

Steve Gyles

This thread was discussed between 22/03/2015 and 28/03/2015

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