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MG TD TF 1500 - Defective EI module?

Car is a 1950 TD, 12 volt negative ground with a newly installed (by me) pertronix EI unit. And a new rotor. Car came with a "Flamethrower" coil installed. Car has run for about 2-3 hours w/ the new EI w/ no problems whatsoever until yesterday when it would not start. Battery is fully charged. I have battery voltage to the coil. An adjustable gap plug checker opened 1/4" shows a nice white spark, but it's intermittent. Starter pulls about 100 amps; not knowing what it's supposed to pull, I used a 12v jumper directly to the starter to put the fully charged battery voltage into the EI. Still has an intermittent spark. And when it does spark, the engine tries to start. (I checked fuel first thing by putting the fuel line in a can & turning the key on; it has a good flow to the carb. It would not fire w/ starting fluid in the manifold). Other than a defective EI module, what else should I check before I call the Pertronix hotline tomorrow? Thanks
Bruce Haynes

I'd check the rotor and the base plate of the pertronix pick up. It might have come loose. Also check the wires to the pick up. Sometimes they get pinched between the distributor body and cap.

TW Burchfield

Tnx Tim. Rotor/cap look fine. In place, no shavings, etc. Module is firmly in place & wires not pinched. Grommet in place also. I did notice that the wire from the generator mounting bracket/block had been disconnected from (I assume) the distributor. So, I ran a jumper wire from the negative battery post to the distributor; no change in spark. Is that ground wire supposed to hook to the distributor timing bolt? I wouldn't think so, but I can't see anywhere else to attach it.
Bruce Haynes

What color is your rotor, the black ones are notorious for going bad. Use a red one from Advanced distributor, Jeff Schimmler has them maid and they work.
also try putting you points back in, if they work you know the Pertronix is the problem.
Good luck Steve
S E Bryan

Bruce, regarding the distributor ground strap: take a look at this picture on Dave Braun's site.

TW Burchfield

Tim, tnx; I'll put it back per the pic. Steve, I've got a new red rotor in it. And I wish it had points; I can make those work! It came w/ a 12v positive ground EI that I replaced w/ a 12v negative ground unit. It's been running fine now w/ the new EI in it for 2 or 3 hours or so. One thing I noticed is that when I let off the starter knob & as the starter stops spinning, it will spark & fire.
Bruce Haynes

The newer Pertronix units are susceptible to interference from the ignition wires. Sometimes switching to resistance carbon cored wires solve the problem, otherwise find an early model Pertronix or go back to points. You can almost always make points work, but if the Pertronix fails, you had better have a AAA card and a cell phone.

An update ......

Pulled the secondary coil wire & checked it out w/ the ohm meter & reinstalled. No luck.

Ran a jumper from the battery directly to the coil. Ran another jumper from the negative battery post to the distributor base. Result: the same, intermittent spark.

Found the Pertronix instructions for testing the ignitor. If the voltage fluctuates between battery voltage & 0 when the collar turns, it's supposed to be ok. Well, it fluctuated, but I never saw 0. So, maybe I'm on to something. Will call Pertronix tomorrow.

And it still will spark when I let off of the starter knob. A classic example of low ignition circuit voltage, but I eliminated that possibility w/ 2 separate tests.

I'm glad this is a hobby.........
Bruce Haynes

Lew is right. Search archives, Bud or someone did a great write up on this with the new vs old types and the plug wires. I recall the new type was useless without modern resister plug wires, and someone had a source for them. George
George Butz

Tnx Lew & George. I found a post describing the problem. (,1699738) Anyone got a source for the carbon core wires w/ screw in connectors? Moss? At $42 for 5 wires, they must be pretty special. I'm still planning on calling Pertronix to ask about the voltage reading & it sparking when I let off the switch, but the EFI problem sounds like the cause of the intermittent spark.
Bruce Haynes

Well, it gets more complicated.

Just found this thread in the archives:


The post below, from this thread, explains that the EFI issue is with the Ignitor II unit; I've got the Ignitor I unit, p/n LU146.

So, I should be able to use the OEM wires. Which have been on the car since I bought it 600 miles ago.

Bud Krueger , Massachusetts, USA,

What Jeff is talking about is a condition regarding the newer IgniterII series of Pertronix systems, those that do not use the magnet collar. The 'older' Igniters, those with the magnet collar, work fine with hard wires. A Pertronix LU-146 system should work fine with ordinary plug wires. The only issue that I know of regarding the LU-146 is the real estate battle between the rotor and the inside of the cap causing carbon dust. Bud
Bruce Haynes

What Bud is talking about is that the top flange on the magnet collar keeps the rotor from seating all the way. Check and make sure the rotor has not trashed the carbon brush in the cap center. Easy fix- just file/sand a bit off the rotor's collar, change cap if damaged.
George Butz

Tnx George.

I removed the cap, cleaned it out w/ electric parts cleaner (again) Replaced rotor. (again) No signs of dust or wear anywhere. No luck.

Pulled the 12v battery out of the tractor & directly wired it to the EI.

No luck.

Next steps are to pull the 12v coil off the tractor & see what that does and to call Pertronix.

Id say chances of a cold coil failure are slim to none.

Im thinking about taking up golf.
Bruce Haynes

Lots of people carry a points plate as a backup in case of a Pertronix failure, but I don't know of anyone who carries a Pertronix as a backup against points failure. I wonder why that is. Hmmmm. <grin>

Just talked to Pertronix.

EFI interference on the Ignitor II is a proven fact. (maybe thats why Moss Motors does not carry the Ignitior II for the TDs anymore) But, Pertronix said EFI problems MAY occur w/ the Ignitor I as well. So he said its a warranty issue; exchange it.

Which is fine, until the new EI burns out unless I get a set of carbon core wires.

So, anyone got a source for carbon core wires w/ the screw on ends? Or should I just plan on buying the ends & making my own?

Re EI in general......I've had Model A Fords & old Ford tractors around here for years. I have never & will never put EI on them. So, once I get this current problem solved, I'll buy a set of points & condenser & a plate for the TD & put them in the tool box.

Tnx to all for the help.

Bruce Haynes

This thread was discussed between 03/07/2016 and 05/07/2016

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