Ignition Mystery

Greets,

Just bought a '76.

I'm new to the site.

Enjoyed the articles on shocks conversion and Fiero seat swap. I'm looking forward to reading more from the library. Thanks for it.

Pulled the oil pan first thing and though there was alot of sludge, I didn't notice any of the "glitter" material which might signal metal wear. I dragged a magnet through the sludge and picked up nothing.

Compression tested at 150 on all four cylinders (cold) with and without oil squirted into the spark plug holes.

There's lots of body rust though, which tempers my joy.

I need a gasket and float needle set for the Zenith 175 CD before I attempt to start.

My reason for posting is that I can't seem to easily figure the ignition wiring. The three wires coming off the distributor are blue, red and black. The wiring color key in my Haynes repair manual makes no mention of these colors.

These three distributor wires go directly to a 2" square aluminium finned module mounted on the right side of the engine compartment aft of the fuse block, near a relay. Stamped on the module is the name "Lumenition". This then is an optically triggered distributor?

On one tab of the coil mount bracket is a round, blue plastic button (an identical one is located in the trunk... ballast resistors?). On the other tab is another finned aluminium module about 1/2" square and 2" long. This module has a steel mounting tab attached and two leads... one white, the other white w/ blue stripe.

Loomed into the positive and negative leads to the coil (Lucas 16C6) is a white plastic female connector with three wires... white, white w/ blue stripe and white w/ black stripe. The connector is shaped to accept only one male connector, but I can't find it.

The coil may be damaged (my ohmmeter shows a value of 2.3 ohms, rather than the specified range of 1.43 - 1.58).

I wonder... am I dealing with one or more aftermarket ignition products which may've been installed on this car?

I look forward to getting the engine started, and though I may be able to slug this one out on my own, I'd appreciate help.

yours, Len

Yep, aftermarket optical system. The plug once went to the unreliable OEM Lucas Opus system. If you can't get the thing to work ditch the Lumintion and install a Pertronix.

You could send the dist to Jeff and have him install a Pertronix and set the whole thing properly on his machines.

Jack

Suggest:

at first opportunity get yourself a Moss catalog (free--request at Mossmotors.com)...and the parts diagram and interchange info is priceless.

Then get a copy of "The Complete MGB" for the 74-80 cars (different edition from the early cars version). Amazon is back ordered for months. Try ebay or even a regular book store. This is the factory shop manual. All other service references are supplemental to this.

Sounds like you have stock ignition. (don't know what I should about the RB cars (RB=rubber bumper, 74-80, vs CB=Chrome Bumper, 63-73+). Hopefully our "resident" ignition expert, Jeff Schlemmer, will chime in about the ignition. Jeff rebuilds and recurves distributors...for less than getting a "new" "what spec is this" distributor.

You've got a guy in Tulsa, named Tom (mumble mumble...can't remeber his last name) who drove his bought-when-new 80 B to California for the MGB assn gathering in July then back home, and won the Concours! Someone with a copy of MGB Driver handy can find his name...I can't find the magazine!)

Jack

Thank you for your reply.

Being on a budget, I'll stick with what I've got. It sounds like it may be complete, so I'll try to make it work.

I forgot to mention... no spark.

I'll blame the coil for now while I do some more tracing.

I read somewhere about removing the ignition ballast and some of the wiring and thereby switch to a 12 volt coil.

yours, Len

Welcome to the party. We are always glad to have new people joining in. You soon won't be new.

This is a third vote to go ahead and send your distributor to Jeff. Here's a link to his website:

http://www.advanceddistributors.com/

You'll fill out a worksheet about your car, and Jeff will curve it appropriately.

While you're ordering stuff for your Zenith, order the diaphragm. If it has a pinhole in it, your car will run rough - if it has a slit, it probably won't run at all. If its old, it will develop a pinhole or slit fairly quickly. Better to just go ahead and replace it for $5. Notice that it's keyed with some tabs - be sure and put them in the correct slots to orient the piston correctly.

OJX Wrote:

It sounds like you definitely have the Lumenition aftermarket igniton installed into the original distributor. Make sure you have 12V into the reed wire and all the contacts are clean. If it doesn't work at that point, consider a repalcement!

Here is my 2 cents, keep the optical system if it is functioning well. I just trashed a Pertronix, and replace with the XR 700 Crane system that the PO had on an old Opus. The Pertronix was new, but left me on the side of the road twice when the thing got hot. The XR 700 is an optical system, when I made the swap, the engine fired quickly and ran smoother. Jeff had done the dizzy for me, he did not install the Pertronix, and I can now feel the benefits of his work.

Mike

Everyone is recommending that Len sends me his distributor, but he needs to solve the mystery FIRST! If its a wiring issue outside the distributor, no rebuilt distributor in the world will fix it! Wire by wire, you need to sort and clean everything. Take voltage measurements and trace wires. Find the voltage loss from resistance and figure out what's not right! Are you measuring coil resistance with all the wires disconnected? If not, it won't be accurate!

Follow the previous igniton/distributor threads from the last week and you'll find the wiring layout for the Lumenition! I believe red is 12V power at the coil +, blue is coil neg, black is ground.
Jeff

Thanks y'all!

For all your input. It's good to have and it helps lessen the damage I cause myself through ignorance. Having my laundry aired also helps to keep me on my toes and thinking...

Thanks to Jeff for suggesting to continue to trace wires and check connections in order to possibly locate a simply (and inexpensively) fixed problem. The car'd been sitting for a long time and I've already gotten some of the lighting to operate just by cycling switches and cleaning connectors.

Here I must let everyone know I live on a pension along with an occasional pickup carpentry job (I also have several years' experience in antique repair & refinishing and pull a job once in a while there as well) as supplement.

My "B" will be no concours winner, rather a daily driver, repaired under the restrictions of a very modest budget.

Fabrication is my strongest suit, electrical troubleshoot my weakest. My normal method of tracing electrical problems was to throw new parts into a problem and hope for a hit. I can't afford to do that anymore.

Thank Jeff again for some sage advice.

My brain is available for picking on the subjects of carpentry (I own a copy of the "International One- and Two- Family Dwelling Building Codes" book) and antique repair & refinishing.

I'm also a pilot (a little over 2,000 hours- mostly fright instruction and FAR 135 IFR night cargo), and musician (I'm a novice buff and a quite small collector of antique tube guitar amps). As a famous airline captain wrote, some of the best pilots are also involved in some kind of artistic sideline.

Of course, that's got nothing to do with me.

Maybe my little way of making an (off subject) contribution to repay all the help I've already gotten and look forward to getting.

By the way, should I still expect to get a start with the coil out of spec? I tested the coil while disconnected from the system.

yours, Len

p.s. ...the 1.8 liter weighs 400 pounds?? That's incredible!! I love that heavy iron.

Chances are good that the coil being out of spec won't harm performance. The Low resistance in the coil is much better than very high resistance (meaning a short.) As long as you can generate a spark from the HT coil lead (plug wire) to ground, your coil is working fine.

The specs for the Lucas 16C6 coil (according to the Haynes manual) are 1.43 - 1.58 ohms.

My coil tests at 2.3 ohms, so I'm assuming there is some damage (the coil's got a couple of dents in the case).

I'll do some more cleaning and testing and if I get no satisfaction, I'll buy a new coil. Will report back.

yours, Len

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