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MG TD TF 1500 - Looks like a I need a new coil, recommendations?

Well, my problem with the car dieing out when fully warm appears NOT to be related to the condensor. So it must be the coil. I believe I still have the original in there. Great big black thing. I see Moss has 2 different ones, the smaller sports coild and apparently they still offer the big original type. I kind of would like to stay with the big original type unless there are some major advantages of going with the smaller one.

Any feedback would be appreciated.
l rutt

Do you have anything else hooked up to that circuit? A buddy once had an old truck that someone had wired an added fuel pump to the coils hot wire. Somehow this would cause the coil to heat up and the truck would stop every few miles.
Richard Taylor

Nope, it's as per the original wiring diagrams of the car.
l rutt

I'm betting it probably isn't the coil... if it goes open, it is usually dead, cold or hot. Its not impossible to have a temp related intermittent failure,
but I oubt it.

For What Its Worth, I bought a cute chrome plated coil with bracket and ballast resistor for about $20 off ebay.
It is "rated" at 60,000 volts, but in reality, I expect the spark is identical.

The ballast resistor and coil each have 1/2 the resistance of the original coil alone, so the coil heat is cut in half and offers the option of hotter start with jumper wire from the starter.

You might try a pertronix instead of investing in a coil. I dug one up for less the a $91, including shipping. They claim a hotter spark with the same coil, which is understandable considering the solid state option likely offers a longer dwell.
Jim Northrup

The issue is finding the root cause of things quitting after 20 minutes or so when it gets thoroughly warm. A pertronix is not the solution to that as the points aren't overheating. I must source this problem out first otherwise it will do the same thing even with EI. Everything jumpered the only devices in the circuit are condensor or coil.

So it must be the coil. The fuel pump still pumps fine. Let it set for just a couple minutes and it will sputter back to life briefly until things heat up again. Let it cool completely and it starts and runs perfectly.

l rutt

I agree with your diagnosis of a bad coil. I had the same problem when I got my TD about 13 years ago. The car would run fine for about 15 minutes and would quit. It would show no life. I would push it back to my garage, and after a few hours it would run fine, and the cycle would repeat. I addressed just about every other fuel or ignition possibility, because everyone said that it couldn't be the coil! I finally ordered the Moss large origional type coil (not sport) and it has been fine ever since. During the course of 13 years, the manufacturing site could well have changed continents 2 or 3 times, but the coil that I rec'd has been fine!
Steven Tobias

I'll trade ya! If you want to try a good used one, I'll trade the one I swapped out for chrome coil/ballast resistor for yours.

In fact, if you want a new coil, I'll sell you one for half what Moss sells them.

I'll install yours on my wife's car and see if it strands her somewhere!

When a robot died at a customer's facility, we'd scrounge a set of boards out of demo robots, go out and swap them until it fired up, then come back and install the bad ones in the lab machines and they'd always work fine.
Jim Northrup

i rutt,

Again, if you'd like add some "dress up" there's the chrome plated coil and bracket with ballast resistor for $17 (plus $9.50 shipping) on ebay.

http://cgi.ebay.com/ebaymotors/60-000-VOLT-CHEVY-GM-CHROME-COIL-W-BRACKETS-59-VALUE-_W0QQcmdZViewItemQQhashZitem483b5d7c0dQQitemZ310233627661QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

I snapped the spot weld between ballast resistor and coil brackets and relocated the ballast resistor, so it looks much cleaner.

Again, the coil has 1/2 the resistance, thus 1/2 the heat, and offers the option for hotter start with jumper wire off the starter.

Even though they advertise 60,000 volts, that really doesn't impress me since the voltage is determined by the combined gaps between rotor/cap and the sparkplugs. Spark energy is pretty much equal for that generic coil construction.
Jim Northrup

Jim with reference to the robots, could it have simply been bad connections, and refreshing the boards refreshed the connections?

warmly,
dave
Dave Braun

(no Dave...its a robot conspiracy)
gblawson(gordon- TD27667)

Dave,
When one craps out, I usually start just pulling & reinstalling boards or ribbon cables into sockets. If that doesn't work, I might pry ROM & other chips loose and shove them back in. If that works, latch the door and get back to work. They are complicated & persnickety. One teeny open/bad connection can shut it down. Sort of like an MG.

At a demo for GM, every time the technicians closed the cabinet door, the robot died. They were going to cancel the demonstration until I stepped in and pointed out the loose ground wire swinging in the door.

Had to lay on my back for an hour, prior to a Dallas robot show, looking through a board to find a cold solder joint that created an intermittent open.

I once spent 200 hours working on one of my robots I refused to quit on. Finally discovered, when I set a board down, a superfine wire from a die grinder brush lodged in between solder joints- only visible with intense light and 2 pair magnifying glasses.

Reminds me of the one technician the customer ran out of the plant; he reinstalled their boards with a hammer! No lie! Another techie showed up late every morning on one job. He was exposing himself to the cleaning maids at the hotel.

Lots of knee slapping episodes, MANY I'D RATHER FORGET!

Domo arigato!
Mr. Roboto
Jim Northrup

Imagine your worst nightmare-
You're driving through Detroit at night and your coil burns out. You're stranded, cold, flat broke, and have to sleep in the car.
That happened to me with a buddy as teenagers. I wandered around the next day begging for a used coil. Went into a rundown car parts store, and the guy behind the counter said if he had a used coil, he'd give it to me. The old black janitor reminded him he threw a Ford coil in the wastebasket the day before. I have to believe the parts guy knew it all along, since he bent over, reached down and plunked it on the counter rather reluctantly.
If it wasn't for the janitor, I'd still be walking the streets of Detroit!
Jim Northrup

I run sports coil & Pertronix. Coil was per John Twist years ago. It had gone to his shop with a brand new "orginial replacement" that John said was bad. Painted mine black so it looks like the orginial and slapped a Lucas sticker on it. Been like this for 10+ years now.
David Sheward

Are we saying that the TFs original coil was black in color? I have an original coil, but there's no paint on it. PJ
P S Jennings

Mr Rutt's problem might be the rotor arm. Lot's of dodgy rotor arms out there - even the new ones and especially those with a brass rivet on the arm. I had an identical problem a few years ago. A hairline crack in the rotor opened up as the engine warmed up. Misfire started then it died. Allowed to cool down it would start and run until it heated up again....
D J Burgess

This thread was discussed between 19/07/2010 and 24/07/2010

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.