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MG MGB Technical - electronic ignition
| Hi All I have just had an aftermarket electronic ignition module fail after 6 or 7 years, and when they fail, they fail bigtime ie the engine stops immediatly. It is an Aldon magnetic type and I wondered if anyone else has had this sort of problem with electronics or have I just been unlucky. I have now put the points & condenser back in and will probably keep them in as when they act up usually you can limp home without resorting to the big yellow transporter Ron |
| r algie |
| The advice that's usually given is to keep the old points in the glovebox just for that purpose. With mine being a '78, I don't have that option. But I do carry an extra Crane optical pickup and amplifier assembly. I just hope I'll never have to use them. Out of curiosity, did you ever have any other problems during the 6-7 years you were using it? The distinct advantage of electronic is timing and dwell don't change over time as mechanical points do. Mike |
| Mike Phillips |
| Hi Mike No I had no problems at all thats what made it all the more alarming I was driving along about 55 mph minding my own business when the engine just stopped Ron |
| r algie |
| Gee, 6-7 years of no problems doesn't sound unlucky to me! ;-) |
| Rob Edwards |
| I've got Magnetronic in my car, and it has let me down a couple of times. Both occasions the engine just stopped (electronic normally either works or doesn't, there's no in between like there is with points), but on both occassions it was simply the crimp spade connectors. I keep spare spades and a crimping tool in the toolbox, but a better solution would be to solder instead of crimp the connectors. Have you checked to see if this is all that's wrong with yours? Tim. |
| Tim Jenner |
| One thing that can break the connections to both the optical and magnetic pickup is the vacuum advance. I had this problem with the Crane -- the vacuum advance would cause the connection to the pickup to flex. The engine started to cut out when I let my foot off the accelerator (maximum manifold vacuum.) The fix is to route the wire to the pickup such that it is pushed out of the distributor body when the advance is actuated. If the advance pulls the wiring into the distributor, the connection may break. |
| Ronald |
| There are more flexible wires available than those that the current manufacturers (Crane, pertronix, etc) have chosen to use, and such wiring would aleviate a lot of the problems with worn/frayed/broken wiring. We used something called Litz wire for electronics applications that required a lot of flexing and that stuff would last quite a long time IF it was laid out correctly. By that, I mean that the wire had to be anchored such that there was just the right amount of play so that the device could move its full range of movement and yet the wire itself never really came into tension (yanked/pulled on). Oddly, an good example of what I am discussing is that short little black cloth covered wire that grounds the breaker plate to the dizzy body in most Lucas (and other) distributors. If you have one of these, you can see how limp this type of wire is, and yet it is fully capable of lasting a very long time when mounted correctly. FWIW |
| Bob Muenchausen |
| Heh Heh. That'll teach yer to stick ter points and condenser ... |
| Paul Hunt |
| Hi all.. I believe I have the best compromise on my BGT. I have the original points / condenser driving an old Sparkrite capacitive discharge unit. These were sold as an aftermarket add-on in the 70's and 80's, or thereabouts. This uses the original points to trigger the sparks, but only passes a small current through them, so they last indefinitely.. they only seem to need changing when when the heel of the cam follower wears down. If the electronics do misbehave, throwing a switch on the unit puts the system back to a conventional points / condnser / coil arrangement. I believe that some 80's cars were built with a TAC module (Transistor Assisted Contacts) that could be used on a B, but haven't investigated this. Don |
| Don |
| Don - I still have that Sparkrite system, built from a kit, but in a drawer not on a car. I *did* use it on a Mini many years ago but found no benefit so although I took it off when selling the Mini never bothered fitting it to anything else. Interestingly, many North Americans complain it is heel wear that is the bug-bear needing constant gap resetting, but I've never experienced that in 35 years. |
| Paul Hunt |
| Hi Paul. The Sparkrite units were produced in various versions, some of which were more sophisticated than others. The SX2000 capacitive discharge unit that I have offers the following benefits : 1) Switching an inductive load (eg a coil) with mechanical contacts usually results in the formation of the familiar 'pit' on one contact and 'pile' on the other as metal migrates from one contact to the other during the later part of the arc period. The points are only required to switch a small current with a non-inductive load with the Sparkrite in place, which (in my experience) makes them last a lot longer. 2) The Sparkrite unit eliminates the dwell factor, the duration of points contact is irrelevant. The ignition system doesn't 'run out of steam' at high revs. 3) The voltage delivered to the plugs is higher due to the higher coil primary voltage and cleaner waveform, so a larger plug gap can be used, providing your leads and distributor cap are in good shape. 4) The unit generates a good spark even when the battery voltage is a bit low, ie during cold cranking. Having said all that, I personally can't detect any performance improvement over a correctly set up standard system. Don |
| Don |
| Don, How well does it cope with worn shafts and the accompanying timing wander? It's my understanding the the magnetic-pickup arrangements are somewhat forgiving in this regard. Granted, that's masking a symptom, not fixing the problem, but still.... |
| Rob Edwards |
| I bought two Jacabs capacitive discharge units in 1975. One was installed on a Toyota and the other on a VW. Both units failed in about a year. I use a Crane XR700 on both my MGB's. The one on the 74 is five years and never caused a problem. But I don't like the stiff optical trigger leads coming into the breaker plate as Bob mentioned. Also the optical trigger mounting bracket looks like something from a $10 unit. Based on the number of threads I've seen citing electronic ignition failure it appears that some work needs to be done to assure reliability. I have a 23 year old Echo weed eater with electronic ignition, which must have cost at least $5 to produce, it has never missed a beat. We pay from $65 to over $100 for units to use in our MG's and carry a set of points and condensor to install when they fail. How many modern cars have electronic ignition failure? Do you carry a back up ignition? I've owned probably 30 cars with electronic ignition since 1979 and never had a failure. I don't recall anyone I know having a failure other than some early GM HEI units. Based on what I have said and my age I should like points but I don't like them any more than I like bias ply tires. But I do wish someone would come out with an after market unit as reliable as those found in newer cars. Off the soap box so I can check to see if my Crane system trigger leads are getting brittle. FWIW, Clifton |
| Clifton Gordon |
| Clifton, I have to disagree, the very expencive oem electronic ignition system do fail and fail on a regular basis ask a few Honda owners from the early to mid 90s . That said buy two Pertronix systems, put one in your best distributor and install it in your car, install the other Pertronix in your second best distributor, put it in a padded box with a 7/16ths wrench and throw it in the trunk, I use a padded box because it will be in the trunk for a lot of years before you dig it out of the trunk, at night,while its raining, loosen a bolt , pull out the distributor.splice two wires, slide in the replacement, get the advance unit as close to where the other one was, tighten the bolt, plug in five ignition wires,drive it home, Overkill maybe, but tell me that when when you drop the points screw at night, while its raining etc etc etc. RIC |
| Ric |
| Also check your spare points work, I changed out a set last weekend, and the car would not start, no spark nothing. The point contact material was faulty or looks like there is something missing, as instead of there being two flat faces the inner one is a ring of material, maybe something fell out. Anyway best to find out at home instead of on the road. Easy to check with a meter, wish I had done it before pulling the dizzy. Tatty ( Non-member since 2003 ) |
| Tatty |
| Hi All Dont really see the point [no pun intended] of the Sparkright system it seems to give you the worst of both worlds, anyway I'm sticking to the points for the time being. As a matter of interest I also have an ex USA TR6 which had electronic ignition by 'Allison' which might have been a pre Crane unit and it failed after 2 years of not using the car so you could say I am quite disillusioned with electronic ignition Ron |
| r algie |
| Ric, Your point about carrying a spare distributor could equally apply to a points system! Tim. |
| Tim Jenner |
| Ric, I carry a spare distributor with points in each car. I wouldn't try changing MG points without removing the distributor. I had a 79 Accord and 79 Civic HB and had no ignition problems with either. Lucky, maybe. I still think on a precentage bases there are far more electronic ignition failures with MG after market units than with oem units in other cars. Clifton |
| Clifton Gordon |
| Clifton: my Honda referance was from the late 80s and mid to late 90s it was so bad that they did a secret extended warranty on the ignitors way past the normal period.I guess haveing a points distributor in the trunk might work as long as it gets used before oxidation forms on the contacts, of course you could carry multi-meter and a flashlight etc etc etc-RIC |
| Ric |
| I am looking for installaiton insturctions for a crane XR700 electronic ignition into a 79 MGB. I installed it up in 94 when I purchased the car. Subsequently removed EVERYTHING from the engine compartment to restore it and cannot find the instructions to re-install the ignition. Don;t know if I ever really understood what was going on with the ballast resistor. Any help will be appreciated. |
| Peteh |
| Hi all... Rob... I don't understand how any alternative ignition system can compensate for a worn distributor, unless the benefit is gained by eliminating dwell... does anyone else have any ideas ?. Peteh... later models used what is basically a 6V coil with a ballast resistor, which aids starting when the battery voltage is a bit low, as when cold-cranking the engine. The ballast resistor is connected in series with the coil to 'soak up' the extra 6V during running, but is bypassed when the starter is operated so the coil gets the full battery voltage at this time, and so produces stronger sparks. HTH... Don |
| Don |
| Don, I'm told (and haven't verified) that the benefit comes from not having the mechanical loading on the shaft created by the points return spring... |
| Rob Edwards |
| Don, Scratch that. I think what makes more sense is that as the shaft moves, it changes the point gap and thus both the timing and dwell for a particular firing event. A magnetic trigger would probably be less susceptible to that effect. Again, this second-hand supposition, so take it for what it's worth... |
| Rob Edwards |
| Hi Rob... Just thinking aloud here... I wonder if the points spring could actually HELP the timing stability by applying a loading to a worn shaft, hence stopping the shaft from wobbling about ?.... Would a new distributor with an electronic trigger not wear as it dosen't have the pressure from the spring ?. I don't know, but I do find it interesting to toss ideas around.... I suppose the answer is to take a look with a strobe. Don |
| Don |
| If the loading were uniform, it seems like it might increase stability. But I wonder if the "bouncing" type load from the points alternately touching a cam lobe and "floating" over the interstices would tend to make the shaft chatter or otherwise dance... Interesting thought about the possibility of less wear with some form of non-contact triggering. I hadn't even considered that angle. |
| Rob Edwards |
| Ric, Right, we could load the car with all kinds of back up parts and tools. Of course when something does fail it will be a part we didn't think to carry or we will not have tools to install it. If we spend all our time worring about something breaking we'll miss out on the fun part of owning an MG. I did a search and did find some information about Honda ignitor problems in the mid 80's models. Clifton |
| Clifton Gordon |
| Hi Don, I also use the Sparkrite; the SX1000. Some messages before you said you can't detect an improvement over a well setup standard system. Basically when I bought my car it had Lumenition Optronic fitted. This gave up on me some months ago. So I converted it all back to points. I replaced all bits and pieces and had it checked by a competent garage (angle, dwell, spark plug gap, advance etc). However, the car never ran so smooth as with the electronic kit fitted. Besides that, it looks like the point-breaker system needs constant adjusting. So I feel it is never functioning at its optimum. With the sparkrite it all has improved. No glitches at 1500 rpm, or higher up the rev range. Accelerating beyond 3000-3500 rpm is no problem anymore. Continuous running at 3500 rpm is now possible. So for me the Sparkrite meant quite an improvement over the point-breaker system. Frank |
| Frank de Groot |
| I used a Sparkrite SX2000 system for years. It never gave me any problem and I always felt that the engine ran smoother and I didn't seem to have the adjustment needs which I had before I used the system. I just received an MSD from the USA and I shall fit it to my V8 to see what difference it makes. |
| Marc |
| Not quite 'the worst of both worlds', but it would certainly be subject to the same timing variations due to shaft wobble as conventional ignition. Whilst a shutter, and possibly a magnetic, system is not subject to the same variation as points when the spindle moves towards and away from the shutter, it still must affect timing if the spindle moves back and fore across the face of the pickup. The biggest cause of timing wander I have found is a worn timing chain or tensioner. Points pitting certainly does occur in conventional systems, and when checking the gap it was always a case of removing the points and flatting them down before I could do so. But as long as the dwell and timing are within limits (and you don't constantly try to keep them cock-on like the council slab-layer) any pitting that might be present is immaterial. |
| Paul Hunt |
| Peteh Check out the .pdf files on the Cranecams.com website for XR700 installation. http://64.90.9.168/cranecams/pdf/90002000a.pdf and http://64.90.9.168/cranecams/pdf/90000700.pdf Mike |
| Mike Phillips |
This thread was discussed between 11/05/2003 and 16/05/2003
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