17 replies to this topic

[Paul@Frimley Green]

All my local Mini contacts can't answer this one, so maybe some of you folks have an answer. 

The car is an '87 Mayfair, but with a pre- A+ 1275 installed. It has the Verto/pre-engage starter and still runs a ballasted coil. I've been using an old 23D (41372) from a Marina with a Lumenition magnetronic (fed with 12 volts) set to about 10 degrees btdc @ 1000 rpm. It starts easily and has been running well for several years, but it's a bit on the thirsty side.

So I thought it was time to modernise it with a 12G4180MS (http://www.minispare.../12G4180MS.aspx) from MiniSpares, with it's advance curve to suit modern fuel and a vacuum advance to save fuel... It fitted all well and good and ran well when I timed it in at 13 degrees @ 1000 rpm (vacuum plugged). Once it's warmed up, the problem arises that it then struggles to start again. It's just like the battery has gone flat (it's not!); at first I thought that the starter motor was shot, but when I re-fitted the original dizzy it was fine again. It seems to me that the electronic module in the new one is somehow draining power away from the starter. If I disconnect the red lead from the 12 volt feed the motor spins over fine (but won't start, of course...).  All I can think of is that maybe the electronic module doesn't like the ballasted coil for some reason, but what coil would it want, if this were the case? I'd be quite happy to do away with the ballasted coil system, if it cures the problem, but I don't want to buy a new coil and find it still won't start. It's very annoying, particularly in stop-start motoring like queuing, which was never a problem before. MiniSpares Technical help desk can't think of anything, so I'm hoping one of you folks might have an idea. Thanks in anticipation...

[ACDodd]

Reduce the static ignition advance.
Try it at 8 degrees.


Ac

Edited by ACDodd, 13 August 2016 - 12:30 PM.

[Dusky]

I guess you Have too much advance. Try turning the Dizzy a bit counterclockwise and see what it does.
A std coil is what I use with these modules.

Edit: AC was quicker

Edited by Dusky, 13 August 2016 - 12:26 PM.

[dyshipfakta]

As above for sure really tough to turn a motor over if it's too far advanced.

[Paul@Frimley Green]

Thanks for the suggestions, guys. I'll try that. One of my concerns was that this new one didn't seem to have much total centrifugal advance. With it at 13 degrees, I couldn't get it to show much more than 20 degrees when revved hard. Of course the vacuum gave it a lot more advance, but again, I couldn't see that reducing with the throttle wide open (for a second or two...). The carb's an HIF44, by the way, the cam is a "256" of uncertain heritage and the head is a standard (but "unleaded") Mk lll S 12G940. I had settled on 13 degrees because that's apparently what late 1275GTs needed (but with their standard distributor of course).

 

AC, you said try 8 degrees static. But how can I set that with no points? It seems to drop to about that if I let the idle speed drop as low as possible.

 

I'll have a play and report back. :)

Edited by Paul@Frimley Green, 13 August 2016 - 01:22 PM.

[Paul@Frimley Green]

Well, setting it at 8 degrees at the lowest idle I could get (about 500 rpm) gave me 16 degrees @ 1000 rpm. so that wasn't going to work. In the end I tried 8 degrees @ 1000, which gave me 2-4 @ slowest idle. With vacuum, air filter etc reconnected and idle set at about 800, I tried it over a couple of miles of the range roads near us. Initially, it started strongly. It felt quite flat from mid revs up but pulled reasonably well low down. I stopped and let it sit at the far side of the ranges for a minute. Then, it would barely turn over and it took several goes to get it to catch. Does anyone think it's worth me trying a 12 volt coil? I might try to measure the current draw of the module tomorrow. Can't think of anything else at the moment, other than saving up for an Aldon Amethyst and a mapping session on the rollers... 

 

Might have to put the old 23D back in for the SevenOaks Solo at Brands Hatch on 4th September...  :)

[ACDodd]

Are your valve clearances correct?

Ac

[Paul@Frimley Green]

Umm, I think so, as I only reassembled the engine very carefully a couple of months ago. I think I see where you're coming from in that wrong clearances affect the cam timing. If the clearances were too big, the valve would stay shut longer, creating a higher compression ratio. Am I on the right lines? However, I've already established that the motor starts fine with the old 23D with Lumenition, and runs very well, even with the new 45D when I can get it running, such that I've been fastest sub 1400 saloon by miles in 3 Solos so far this year (had a late start to the season). As I said in my OP, if I disconnect the red lead of the new dizzy from the 12 volt feed the motor spins over fine (but won't start, of course...). Not been able to measure the current draw yet...

[Shifty]

Put a new 12v feed from the fuse box to the dizzy instead of piggy backing the one off the coil.

 

Chances are you're running a ballasted system and the electronic dizzy doesn't like the voltage drop.

[Paul@Frimley Green]

Thanks Shifty, but that's what I've done from the start.

[Spider]

Sounds to me that the new dissy has the wrong advance curve for your engine.

 

What's it's specs? (the engine).

[lrostoke]

Pull the plug leads off, if it still spins slow, you know its the advance thats causing the issue.

[Paul@Frimley Green]

There's definitely something odd about this dizzy, Moke Spider! Nothing special about the spec of the motor (see thread above ~ 8th post up from this one).

 

Thanks Lrostoke, just tried that (with the coil HT lead off) and no problem turning over at normal speed, same as with the 12V feed disconnected. But then, with no spark in the cylinder, excessive advance wouldn't slow the pistons down, would it?  I guess that means that either the module is faulty (this is the second dizzy, as Mini Spares changed the first one...) or it's incompatible with '87 Mayfair wiring for some reason. There seem to be several components in the loom that don't feature in the Haynes wiring diagramme! I think I've figured out what they all do, but having had a play with a multimeter and renewed a few joints this afternoon, I can't figure out why there seems to be a random 0.3 ish volts at the white (ignition on) fuse lead with the ignition right off (but not all the time). This voltage feeds through to the module supply lead and even to the far end of the ballast lead. And the rev counter signal lead occasionally shows about 4 volts from time to time, with everything turned off. I'm now wondering whether the diode (rectifier) in the alternator is playing up, but I can't see a connection between any of this and the starting problem. I'm very sorry that this whole issue is now probably too big for me to expect someone to come up with the solution, but thanks again for all your suggestions so far. Maybe it's time to talk to Mini Spares again...

[lrostoke]

If with the HT lead off it spins normal its the advance.

 

You've removed the spark at the plugs. If the spark is firing to soon basically the piston is on the way up and the firing is trying force the piston down while the starter is trying make it go up...So it turns over slow.

 

Sounds like the dizzy just as wrong curve for your engine...

[Paul@Frimley Green]

Not here for a few days now, so I'll post an update after I see what Mini Spares have to say next week.