Electronic Ignition options - Alfa Romeo Bulletin Board & Forums
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post #1 of 19 (permalink) Old 01-02-2018, 06:58 PM Thread Starter
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Electronic Ignition options

I really want my car to get back on the road. Can't seem to get it to run right, won't idle, and runs extremely rough to a point that it's totally undriveable....happened almost overnight.
Tried everything. Timing is right. Carbs have been rebuilt, and taken off and checked again. New plugs, new wires. Fresh gas, in the process of replacing fuel regulator (1750 engine with electric fuel pump.)

Car has Marelliplex electronic ignition and coil.

Thinking about replacing the distributor with a new electronic distributor, and replacing the coil as well. Not sure what else to do.

Was looking at a standard 123 electronic distributor, no need for fancy programming. How does the Centerline ID405 compare, anyone any experience?

What other parts do I need, condenser, ballast resistor? Or just 12V to the coil (thinking Bosch Blue) and coil wire to the electronic distributor? You can tell I don't really know what I'm doing and I need some guidance. Sorry for my ignorance

Thanks!

Peter

Currently: '65 Giulia TI

Previously:
'76 Alfasud Ti/'75 GT Junior/'87 Alfa 33
'91 Alfa 75/'95 Alfa 164/'79 Alfa Spider '69 Euro 1750 GTV, '67 Duetto, '84 Spider Veloce
'91 164L
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post #2 of 19 (permalink) Old 01-03-2018, 06:07 AM
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I have had an original type 123 distributor on my Spider for about 10 years when it replaced a Marelliplex. I first ran it with a Bosch Blue coil, then I connected to an MSD 6AL capacitive discharge unit and now with an MSD Blaster 2 coil with an MSD ballast resistor. This current arrangement is simple and makes very high energy sparks. I documented this in http://www.alfabb.com/bb/forums/engi...ml#post7771474
This is the ignition system that I would use if I were starting from scratch.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #3 of 19 (permalink) Old 01-03-2018, 09:23 AM
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Yo, Peter. As frustrating as things may seem, you are in fact doing everything right in what is a more involved fault-finding process than, perhaps, you expected. Been there and done that. These are, after all, old cars. In searching for a solution to your running problem you discovered that the carbs really needed seeing to so rebuilding them solved once source of problems in old Alfas. Webers are great . . . until they're not. Likewise replacing plug wires set aside another problem with old cars. I think you've also ascertained that fuel delivery is adequate so you don't need to worry about that. Check, check, and check.

Before you do anything else, however, you need to check the distributor itself. Is the advance mechanism working smoothly? If not that can be fixed. If you can feel slop when you move the shaft side to side, this means the distributor itself is worn out. If the advance mechanism moves smoothly and the distributor shaft feels solid, distributor mechanicals are good and we can move on.

That leaves us with ignition components. Here's what I recommend:

1. Before you proceed to anything else, you need to check and see if the distributor is in good

If your engine is running as bad as you describe and the problem appeared "overnight" . . . I presume after you installed the new plug wires . . . then you may have inadvertently installed the wires 180 degrees out (as me how I know this). The proper solution is to remove the cam cover, rotate the engine to top dead center---cam lobes point out---and then check to see if the distributor rotor point to #1 spark plug position. If it doesn't someone has installed the distributor the wrong way and the firing order is reversed. The fast and dirty "solution" to this is to re-install the plug wire make the #4 position #1 and so on.

If you don't want to pull the cam cover, you can go directly to the plug-wire swap. It's entirely possible that someone has installed the distributor the wrong way and compensated by just changing wires. Happens all the time. As I say these are old cars.

2. If the plug-wire swap doesn't work, then you can move on the 'Plex components. Replacing the coil is a good idea. (Robert Rogers, a noted Alfa race-mechanic in Dallas recommends using an MSD Blaster non-ballasted coil---'Plex ignitiions will run just fine without ballast resistors, btw).

You can also take it to an AutoZone and have them test it for you. If the coil is good, you can move on to the GM trigger which is mounted on the 'Plex heat-sink. A few years ago I had AutoZone test several of these that I had collected in my tool box: fully half were bad. Fortunately, there are excellent aftermarket triggers widely available.

I installed an Accell trigger (thanks RJ) which only costs a little more than the generic triggers of indifferent quality. If the plug wires are installed in the right firing order, the coil is good, and you've installed a new GM trigger, everything is in order and you car will start and run properly. (Please note that I haven't mentioined the 'Plex sensor installed in the distributor. These seldom fail, even after decades of use. However, if everythng check out and you still have rough running these sensors are not expensive and can be obtained from most Alfa parts vendors.)

3. Bob now has his cell-phone back (long story) so you might want to give him a call and ask him to check your distributor. Last that I checked he had a box of 'Plex parts in his shop.

Here's a link to a thread I posted several years ago that shows how the 'Plex distributor is put together.

http://www.alfabb.com/bb/forums/elec...lex-photo.html

Jim . . . '72 Super 1300, '70, 1750GTV, 2nd series,
'62, Lancia Flaminia Zagato3c, 2nd series

Last edited by 180OUT; 01-03-2018 at 09:35 AM.
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post #4 of 19 (permalink) Old 01-03-2018, 10:14 AM Thread Starter
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Thanks guys. Jim, I know it's not the wires/firing order.....it happened about 5 months after I changed the wires. I can certainly take the cam cover off and double check, but I doubts it's 180 degrees out. I like your approach of further trouble shooting, and you're making some good suggestions that I can work with. Having said that, it could be that the plex is fine, and there's an issue with the advance mechanism, or whatever.....I'm just thinking I might just as well start fresh, and work with brand new components as it'll improve overall reliability in the end....even if replacing my current ignition does not end up solving my issues.

Peter

Currently: '65 Giulia TI

Previously:
'76 Alfasud Ti/'75 GT Junior/'87 Alfa 33
'91 Alfa 75/'95 Alfa 164/'79 Alfa Spider '69 Euro 1750 GTV, '67 Duetto, '84 Spider Veloce
'91 164L
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post #5 of 19 (permalink) Old 01-03-2018, 11:21 AM
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Quote:
Originally Posted by Peter View Post
Thanks guys. Jim, I know it's not the wires/firing order.....it happened about 5 months after I changed the wires.
Agree that the wire position is not the issue - if it ran OK right after changing the wires, then the wire installation is OK. The wires wouldn't just re-install themselves 180 off 5 months later!

However, your symptoms are consistent with bad ignition wires: you might check that all ignition terminals are fully seated. How many miles are on the new wires? The last set on my 164 failed within a year/few thousand miles - no idea why - many new parts are simply junk.

Quote:
I'm just thinking I might just as well start fresh, and work with brand new components as it'll improve overall reliability in the end....even if replacing my current ignition does not end up solving my issues.
I personally don't agree with that approach. While 123 distributors are great, and probably what you'll install in the long term, I wouldn't do that until I had the car running properly. I'm still not convinced that your issue isn't carburation (since most "ignition problems" are caused by the carbs, and visa versa).

I like 180OUT's idea of testing the advance on the distributor, as well as testing the little circuit board on the Plex. Do you still have an old points-type distributor in your box-o-parts? Or can you borrow one? Whenever I have these problems, I just temporarily install an old-fashioned Kettering ignition to determine whether my fancy, modern, high-tech, impossible-to-diagnose, electronic ignition is the problem.

Jay Mackro
San Juan Capistrano, CA

'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 01-03-2018 at 11:28 AM.
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post #6 of 19 (permalink) Old 01-03-2018, 11:38 AM
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Ignition advance issues aren't gonna cause rough running-poor running but not rough.
I suggest you inspect the plug wires as mentioned, along with removing and inspecting the spark plugs and then doing a compression test.
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post #7 of 19 (permalink) Old 01-03-2018, 03:24 PM
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Marelliplex were good distributors in their day but they are all about 35 years old. I had two in different cars, both with modified advance curves because the stock curve gives poor throttle response. But they both had wear in the pivots that caused the timing to be all over the place. The signal from the pickup coil is small and if it is degraded you will have intermittent or poor sparks. The module usually fails completely but like any other electronic device it will have other failure modes that may be hard to diagnose.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #8 of 19 (permalink) Old 01-03-2018, 04:54 PM
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If you find yourself looking towards replacement something that has worked extremely well for me is the MSD StreetFire CD ignition box with a RML distributor. While the 123 is trick I still only need one curve and the RML works. I have three of them on my three Alfas and three Streetfires with Magnacor wires and MSD blaster coils, well the Berlina has a blue Bosh coil. I first tried the Centerline distributor and had to send it back as the motor would buck like crazy under load accelerating from low rpms. The top end was fine. I actually took it apart and found one of the weights was completely disconnected and just flopping around. I mentioned this to them and only got back silence so I don't know what was going on there but they took it back and I found one that would work. Hey Ed, that RML I bought from you works great!
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The passenger seat is 15 miles an hour faster than the drivers seat.

currently
2017 Giulia Q4
74 GTV restored daily driver
71 Berlina in 2L restored driver
the ones that got away:
1959 750 series Giulietta Spider Veloce
1962 Giulietta Spider normale
1965 Giulia Sprint normale
1972 GTV
1974 GTV
1974 GTV
1977 Spider
1974 Spider
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post #9 of 19 (permalink) Old 01-04-2018, 05:52 PM
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Quote:
Hey Ed, that RML I bought from you works great!
Do you think that I would sell you a lemon! The advance curve was unsuitable for my motor.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #10 of 19 (permalink) Old 01-04-2018, 08:03 PM
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Why would you even say that? You told me that when I bought it. I was trying to say something nice.

The passenger seat is 15 miles an hour faster than the drivers seat.

currently
2017 Giulia Q4
74 GTV restored daily driver
71 Berlina in 2L restored driver
the ones that got away:
1959 750 series Giulietta Spider Veloce
1962 Giulietta Spider normale
1965 Giulia Sprint normale
1972 GTV
1974 GTV
1974 GTV
1977 Spider
1974 Spider
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post #11 of 19 (permalink) Old 01-05-2018, 05:39 AM
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It was an attempt at humor. I clearly failed.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #12 of 19 (permalink) Old 01-05-2018, 06:01 AM
Richard Jemison
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RML Distributors

Ric has the capability of building you a distributor with any curve you think you need. Including the amount of total advance and rate of advance(ie:spring rates).

Don`t just buy one off the shelf, call him and tell him what you want. His phone # is 386-212-0450

Richard Jemison
RJR Racing

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post #13 of 19 (permalink) Old 01-05-2018, 06:09 AM
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I've had a couple of conversations with Ric. He knows his stuff and is a pleasure to work with.
Certain types of humor don't translate well to the written word, no harm, no foul.
Here we go again Ed, that 136 you sold me is working well with Richard's 785 although I can't tell exactly how well because I'm waiting on my HP pump to get back from Wes and I'm running a stock, original Spica pump. I been keeping the AFR's in the green so no WOTs yet and besides it's a new motor.

The passenger seat is 15 miles an hour faster than the drivers seat.

currently
2017 Giulia Q4
74 GTV restored daily driver
71 Berlina in 2L restored driver
the ones that got away:
1959 750 series Giulietta Spider Veloce
1962 Giulietta Spider normale
1965 Giulia Sprint normale
1972 GTV
1974 GTV
1974 GTV
1977 Spider
1974 Spider

Last edited by gigem75; 01-05-2018 at 07:47 AM.
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post #14 of 19 (permalink) Old 01-05-2018, 07:56 AM
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One of your fellow Texans wrote " I can substantiate the rumor that the English sense of humor is drier than the Texas sand". I guess that I need to keep that in mind.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #15 of 19 (permalink) Old 01-05-2018, 10:49 AM
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Quote:
Ric has the capability of building you a distributor with any curve you think you need. Including the amount of total advance and rate of advance(ie:spring rates).
I talked to Rick about the advance curve options before I decided to sell it and take a hit on what I paid for it.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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